Doc:ME 14 (0916)c For Comments Only
Draft Indian Standard Code of practice for heavy duty electric overhead travelling cranes including special service machines for use in steel work (Second Revision of IS 4137 ) ICS: 53.020.20 ___________________________________________________________________
Not to be reproduced without the permission of BIS or used as a STANDARD
Last date for receipt of comments : 16 March 2009
___________________________________________________________________
FOREWORD
(Formal clause will be added later on). This standard was first published in 1967and revised in1985. The necessity for the revision has arisen in view of the experience gained by the industry during the course of the implementation implementation of the standard. In this revision the material of components has been upgraded, stress relieving of material included, mechanical design parameters and electrical equipments requirements, manufacturing manufacturing and erectioning have been modified in line with revised version of IS 807:2006 Design, Erection and testing (Structural Portion) of Cranes and Hoists - Code of Practice and IS 3177:1999 Code of practice for of overload traveling cranes and gantry cranes other than steel work cranes ( Second Revision )The components are designed and selected on more rational basis. This code covers design, manufacture and erection of heavy duty electric over head traveling cranes for use in steel works. Steel plant cranes and special service machines covered in this standard are listed in Appendix A. Also covers mechanical, electrical, inspection and testing aspects as related to design, manufacture and erection of electric overhead traveling cranes for use in steel works in order to secure safe, efficient and reliable working of these heavy duty cranes during service. Structural design aspects of all types of cranes and hoists are covered in IS807:2006 Design, Erection and testing (Structural Portion) of Cranes and Hoists - Code of Practice, Mechanical, electrical, inspection and testing aspects of overhead traveling cranes -and gantry cranes other than steel work cranes are covered separately in IS : 3177:1999. Cranes are broadly classified into four classes in IS: 807-1976” depending on duty and number of hours in service per year. In IS : 3177-1977 the different motions of a crane and the design of component parts are required to be treated on the basis of mechanism classification defined in terms of the severity of duties to be performed or average life of mechanism or the component part. All the necessary information regarding the conditions under which the crane is to be used together with the particulars laid down in Annex A shall be supplied with the enquiry or order. The manufacturer shall shall supply with the tender tender the information information in accordance with the proforma laid down in Annex B.
1
Doc:ME 14 (0916)c
A list of Indian Standards relevant to this standard is given in Annex F. This standard is the first in the series of standards relating to cranes and covers the structural design. The other standards in the series covering the mechanical and electrical portion are as follows: IS 3177:1999 Code of practice for of overload traveling cranes and gantry cranes other than steel work cranes cranes ( Second Revision ) IS 807 : 2006 Design, Erection and testing (Structural Portion) of Cranes and Hoists Code of Practice The committee kept in view the manufacturing and trade practices prevailing in the country while formulating the standard. Assistance has also been derived from the following publications:
For the purpose of deciding whether whethe r a particular requirements of this standard is complied with the final value, observed or calculated expressing the result of a test or analysis, shall be rounded off in accordance with IS 2:1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.—[In case of code of practice, this clause will not be applicable.]
2
Doc:ME 14 (0916)c
Page
1.1. 1.1.
SCOPE… SCOPE………… ……………… ……………… ……………… ……………… ……………… ………………… ………………… ……………… ……………… ……………… ……………… ……………… ………..… ..…….0 ….09 9
1.1.1 TERMINOLOG……………………………………………………………………………………………....…..09 1.1.2 CAPACITYID CAPACITYIDENTIF ENTIFICATIO ICATION…………… N…………………………… ……………………………… ……………………………… ……………………... …….....09 ..09 1.1.3 INFORMATIO INFORMATIONTOB NTOBESUPP ESUPPLIEDWI LIEDWITHENQ THENQUIRYO UIRYORORDE RORDER.10 R.10
1.1.4 WORKMANSHIP WORKMANSHIP,MATE ,MATERIALA RIALANDINS NDINSPECTI PECTION……… ON……………………… ………………………10 ………10
2.1.0 CALCULATION CALCULATIONPROCE PROCEDURE…… DURE………………… ……………………………… ………………………………… …………………………. ………….……12 ……12 2.1.1 CHECKINGFOR CHECKINGFORULTIM ULTIMATESTR ATESTRENGTH… ENGTH………………… …………………………… …………………………. …………….12 12 2.1.2 VALUEOFTHE VALUEOFTHEPERMIS PERMISSIBLE SIBLESTRESS STRESS…………… …………………………… …………………………. …………..……12 .……12 2.1.3 VALUEOFTHE VALUEOFTHECOEFFI COEFFICIENT CIENTV VR……………………………………………………..……13 2.1.4 RELATIONSB RELATIONSBETWEEN ETWEENTHECA THECALCULAT LCULATED ED STRE STRESS SSES ESA AND NDT THE HEP PER ERMI MISS SSIB IBLE LES STR TRES ESSE SES… S……… ………… ………… …….. ..…… …….. ..13 13 2.1.5 CHECKINGFOR CHECKINGFORFATIG FATIGUE………… UE………………………… ……………………………… ……………………………… ……………………….. ………..……..1 ……..14 4 2.1.6 STRESSES……………………………………………………………………………………………….…..………14 2.1.7 PERMISSIBLEFATIGUESTRESS…………………………………………………..……….15 2.1.8 CHECKINGFOR CHECKINGFORCRIPP CRIPPLING… LING………………… ……………………………… ……………………………… ……………………….… ……….………... ……...16 16 2.1.9 CHECKINGFOR CHECKINGFORWEAR…… WEAR…………………… ……………………………… …………………………… …………………………… ……………………..… ……..……….16 …….16 2.1.10HOOKS……………………………………………………………………………………………………….………..16 S……………………………………………………………………………………………………….………..16 2.1.11ROPEDRUMS……………………………………………………………………………………………………..19 2.1.11ROPEDRUMS……………………………………………………………………………………………………. .19 2.1.12ROPES………………………………………………………………………………………………………….…………20 2.1.13SHEAVES………………………………………………………………………………………………………….21
3
Doc:ME 14 (0916)c
2.1.14EQUALIZERBARORSHEAVES……………………………………………………………23 2.1.15TRACKWHEELS……………………………………………………………………………………………23 2.1.16BUMPERS…………………………………………………………………………………………………………26 2.1.17SHAFTING……………………………………………………………………………………………………….28 2.1.18 PRESSFITSANDKEYS………………………………………………………………………………29 2.1.19BEARINGS………………………………………………………………………………………………………….30 2.1.20GEARING……………………………………………………………………………………………..............31 2.1.21MACHININGSPECIFICATIONS……………………………………………………………....34 2.1.22GEARBOXES…………………………………………………………………………………………………….34 2.1.23LUBRICATION………………………………………………………………………………………………....36 2.1.24LINESHAFTINGANDCOUPLINGS………………………………………………………..37 2.1.25RAILS……………………………………………………………………………………………………………………..38 2.1.26OPERATORSCABIN……………………………………………………………………………………..38 2.1.27MEANSOFACCESS……………………………………………………………………………………….40 2.1.28GUARDING…………………………………………………………………………………………………………..40 2.1.29WEATHERPROTECTION………………………………………………………………..40 2.1.30PAINTING……………………………………………………………………………………………………………41 2.1.31HANDLINGFACILITIES…………………………………………………………………………………41 2.1.32BRIDGEANDTROLLEYDRIVES…………………………………………………………….41 2.1.33TORSIONALDEFLECTIONANDVIBRATION………………………………....43 2.1.34MOTIONLIMITINGDEVICE……………………………………………………………………....43 2.1.35 CROSSTRAVELANDLONGTRAVELLIMITINGDEVICES……….44
4
Doc:ME 14 (0916)c
2.1.36LOADINDICATIONANDLOADLIMITINGDEVICES………………....44 2.1.37DRAWINGSANDDOCUMENTS…………………………………………………………...44
3.0ELECTRICALEQUIPMENT…………………………………………………………………………...45 3.1POWERSUPPLY…………………………………………………………………………………………………45 3.1.1GENERAL…………………………………………………………………………………………………………...45 3.1.2DSLSYSTEMSANDACCESSORIESFORCRANES……………………46 3.1.2.1GENERAL……………………………………………………………………………………………………....46 3.1.2.2CONDUCTORS……………………………………………………………………………………………..46 3.1.2.3CURRENTCOLLECTORS……………………………………………………………………….46 3.1.3CROSSTRAVELCURRENTCOLLECTINGSYSTEM…………………..47 3.1.3.1GENERAL………………………………………………………………………………………………………..47 3.1.3.2CONDUCTORS…………………………………………………………………………………………....47 3.1.3.3COLLECTORASSEMBLY……………………………………………………………………....47 3.1.4EARTHING………………………………………………………………………………………………………....47 3.1.4.1GENERAL…………………………………………………………………………………………………………47 3.1.4.2CONTROLCIRCUITEARTHING………………………………………………………...48 3.1.4.3MAGNETEARTHING………………………………………………………………………………..48 3.1.5CONDUCTORBARS,CABLEREELSANDFLEXIBLECABLES.48 3.1.6CALCULATIONOFCROSS-SECTIONOFCONDUCTORS………..50 3.1.6.1GENERALOPERATINGCONDITIONS……………………………………………...50 3.1.6.2INTERMITTENTDUTYAPPLICATIONS…………………………………………….50
3.1.6.3CO-ORDINATIONBETWEENCONDUCTORSANDPROTECTIVE
5
Doc:ME 14 (0916)c
DEVICES………………………………………………………………………………………………..…..…50 3.1.6.4SHORTCIRCUITPROTECTIONOFCONDUCTORS………………..51 3.1.6.5CALCULATIONOFTHECROSS-SECTIONINRELATIONTOTHE ADMISSIBLEVOLTAGEDROP……………………………………………………….....52 3.1.6.6CALCULATIONOFTHEMINIMUMCROSS-SECTIONINRELATION TOTHETHERMALCAPACITYOFTHECONDUCTORS…..56 3.1.6.7INSTALLATIONOFCABLES………………………………………………………………....57 3.2ELECTRICALPROTECTIVEANDSAFETYEQUIPMENT…………….…59 3.2.1PROTECTIVEEQUIPMENT…………………………………………………………………….….59 3.2.1.1GENERAL…………………………………………………………………………………………………….....59 3.2.1.2ELECTRICALPROTECTIVEDEVICE……………………………………………....62 3.2.1.2.1GENERAL……………………………………………………………………………………………………..62 3.2.1.2.2PROTECTIVEDEVICECOMMONTOALLMOTIONS…………..63 3.2.1.2.3SCHEMEA–PROTECTIVEDEVICEFOR INDIVIDUALMOTIONS………………………………………………………………………..64 3.2.1.2.4ACINSTANTANEOUSRELEASESINGLEPOLEOVERLOAD……64 PROTECTIVEDEVICEFORINDIVIDUALMOTIONS:.. 3.2.1.3PROTECTIVEDEVICESFORMOTORCIRCUITS……………………….65 3.2.1.4CONTACTORS………………………………………………………………………………………………..66 3.2.1.5CONTROLSWITCHFUSE………………………………………………………………………..66 3.2.1.6EMERGENCYSWITCHES………………………………………………………………………..66 3.2.1.7OFF-POSITIONINTERLOCKING………………………………………………………....67 3.2.1.8PILOTLAMP……………………………………………………………………………………………………..67 3.2.1.9MAINFEATUREOFBUILT-INCRANEWEIGHINGSYSTEM (LOADCELL)………………………………………………………………………………………………..67 3.2.1.10AUXILIARYISOLATINGSWITCHESANDFUSES…………………...68
6
Doc:ME 14 (0916)c
B)MOVINGCABCRANES……………………………………………………………………………………….69 3.2.1.11DISTRIBUTIONBOARD…………………………………………………………………………..70 3.2.1.12AUXILIARYSWITCHESOTHERTHANISOLATIONSWITCHES…..71 3.2.1.13IDENTIFICATIONOFCIRCUITS………………………………………………………….72 3.2.1.14DISPOSITIONANDHOUSINGOFELECTRICALEQUIPMENT……..72 3.2.2SAFETYFEATURES……………………………………………………………………………………....74 3.2.2.1MOTOROVERSPEEDPROTECTION………………………………………………..74 3.2.2.2DEVICESFORSWITCHINGOFFFORPREVENTIONOFUN- EXPECTEDSTARTUP……………………………………………………………………………………………..74 3.2.2.3LIMITSWITCH…………………………………………………………………………………………………..75 3.2.2.3.1LIMITSWITCHESINHOISTMOTION……………………………………………….75 3.2.2.3.2TRACKLIMITSWITCHES……………………………………………………………………...76 3.2.2.3.3PROXIMITYSENSING/ANTI-COLLISIONDEVICES……………….76 3.2.2.4SAFEGUARDINGMOTORSAGAINSTOVERHEATING……………….77 3.2.2.5OVER-CURRENTPROTECTIONOFCONDUCTORS…………………..78 3.2.2.6SAFEGUARDINGAGAINSTABSENCEOR INVERSIONOFPHASES……………………………………………………………………………..78 3.2.2.7ACTIONOFSAFETYDEVICES…………………………………………………………………79 3.2.2.8PROTECTIONAGAINSTTHEEFFECTSOFLIGHTNING…………..79 3.3DESIGNANDSELECTIONOFMOTORS…………………………………………………...80 3.3.1GENERAL…………………………………………………………………………………………………………….....80 3.3.2SELECTIONOFMOTORSFORHOISTMOTION………………………………..83 3.3.3MOTORFORCRANETRAVELORTROLLEYTRAVERSE…………….86
3.3.3.1GENERAL…………………………………………………………………………………………………......86
7
Doc:ME 14 (0916)c
3.3.3.2SELECTIONOFMOTORSFORCRANETRAVELOR TROLLEYTRAVERSE……………………………………………………………………………....86 3.4DESIGNINGTHECRANECONTROLS…………………………………………………...93 3.4.1CRANECONTROLLINGARRANGEMENTS………………………………………93 3.4.1.1GENERAL……………………………………………………………………………………………………....93 3.4.1.2CONTROLLERS…………………………………………………………………………………………..94 3.4.1.3CONTROLLERSPROVIDEDINTHECABIN…………………………………95 3.4.1.4PENDANTCONTROLLERS………………………………………………………………...97 3.4.1.5REMOTECONTROL…………………………………………………………………………….....98 3.4.1.6RESISTORS………………………………………………………………………………………………...102 3.4.1.6.1GENERAL…………………………………………………………………………………………………..102 3.4.1.6.2FITTINGS…………………………………………………………………………………………………..102 3.4.2CRANECONTROLS…………………………………………………………………………………...103 3.4.2.1THYRISTORCONTROL–MAINFEATURES………………………………..103 3.4.2.2SPECIALPROTECTIONFORDIRECTCURRENT DRIVESYSTEM…………………………………………………………………………………………….105 3.4.2.3THYRISTORCONTROLLERSFORSLIPRINGMOTORS…...106 3.4.2.4VARIABLEFREQUENCYDRIVES…………………………………………………....107 3.4.2.4.1GENERAL…………………………………………………………………………………………………….107 3.4.2.4.2VFDSELECTION……………………………………………………………………………………..108 3.4.2.4.3DYNAMICBRAKINGSELECTIONFORVFDS……………………...110 3.5BRAKING………………………………………………………………………………………………………………….111 3.5.1ELECTROMECHANICALBRAKING……………………………………………………...111
3.5.1.1GENERAL……………………………………………………………………………………………….…...111
8
Doc:ME 14 (0916)c
3.5.1.2HOISTMOTION…………………………………………………………………………………………...112 3.5.1.2.1GENERAL…………………………………………………………………………………………………….112 3.5.1.2.2BRAKINGPATH………………………………………………………………………………………..112 3.5.1.3LONGTRAVELANDCROSSTRAVELMOTIONS………………….....113 3.5.2ELECTRICALBRAKING……………………………………………………………………………....114 2.5.3BRAKEMAGNETCOILS……………………………………………………………………………...114 TABLEBRAKEMAGNETCOILRATINGS……………………………………………………....114 TABLE2.BRAKEMAGNEETOPERATINGVOLTAGESANDCURRENTS.115 3.6AUXILIARYELECTRICALEQUIPMENT……………………………………………….....118 3.6.1LIGHTING…………………………………………………………………………………………………………....118 3.6.1.1CABIN………………………………………………………………………………………………………………...118 3.6.1.2WORKINGAREALIGHTING……………………………………………………………….....118 3.6.1.3ACCESSANDMACHINERYLIGHTING…………………………………………....119 3.6.1.4EMERGENCYLIGHTING………………………………………………………………………....119 3.6.2HEATINGANDAIR-CONDITIONING……………………………………………………….119 3.6.2.1MACHINERYHOUSE………………………………………………………………………………...119 3.6.2.2OPERATORCABIN……………………………………………………………………………………..119 3.6.3AUXILIARYCIRCUIT……………………………………………………………………………………….120 3.6.4LIFTINGMAGNETS&LOADHOLDINGDEVICES………………………….120 3.6.4.1GENERAL…………………………………………………………………………………………………….....120 3.6.4.2MAGNET…………………………………………………………………………………………………………...121 3.6.4.3MAGNETLEADANDCABLE……………………………………………………………………122 3.6.4.4MAGNETCOUPLINGS……………………………………………………………………………....122
9
Doc:ME 14 (0916)c
3.6.4.5CABLEDRUM……………………………………………………………………………………………..122 3.6.4.6MAGNETCONTROLANDPROTECTIVEEQUIPMENT…………123 3.6.4.7BATTERYBACKUPSYSTEM……………………………………………………….....123
4.1.10 CRANEINSPECTIONANDTESTING………………………………………………125 4.1.13 INSPECTIONPROCEDURE………………………………………………………………..127 4.1.14 GENERALREMARKS…………………………………………………………………………....130 4.1.34 TESTING……………………………………………………………………………………………………....133
A
Listofsteelplantcranesandspecialservicemachine…………138
B
Informationtobesuppliedwiththeenquiryororder…………………..139
C
Selectionofmotors…………………………………………………………………………………...147
D
RatingofResistors…………………………………………………………………………………....150
E
Preferredparameters……………………………………………………………………………....150
F
ReferenceStandards……………………………………………………………………………....151
10
Doc:ME 14 (0916)c
Draft Indian Standard Code of practice for heavy duty electric overhead travelling cranes including special service machines for use in steel work (Second Revision of IS 4573) SECTION I - GENERAL
1
SCOPE
This code covers design, manufacture and erection of heavy duty electric over 1.1 head traveling cranes for use in steel works. Its provisions where applicable, shall also apply to special service machines, such as those listed in Annex A. 1.2 This crane service classification system applies specifically to fatigue strength analysis of Mechanical components. The maximum rated load will also be used to check the crane for static strength, buckling, deflection and stability. 1.3 The concept of classification may also enter into the rating and selection of electrical equipment and provide guidance for the selection of components which have a metal life between replacement. 1.4 This code is not intended for application to cranes for use in areas where sparks from cranes could lead to explosions. Which are covered IS 3177. 2
REFERENCES
The standards given in Annex A contain provisions, which through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated at Annex G. 3
TERMINOLOGY
For the purpose of this standard the definitions given IS 13472 (Part 1)1992/ ISO 4306-1: 2007 shall apply. 4
IDENTIFICATION
4.1 A small plaque shall be located in a prominent position in the cab bearing the following inscription:
a) b)
Manufacturer’s name; Manufacturer’s serial number; and
11
Doc:ME 14 (0916)c
c) d)
Year of manufacture Capacity of each hoist shall be shown on each side of crane in such a manner as to be easily legible from the floor.
4.2 Information to be supplied with Enquiry or Order
Information regarding the conditions under which the crane is to be used, together with the information required in Annex B, shall be supplied with the enquiry or order.
4.3 Information to be supplied by the Manufacturer
The manufacturer shall supply all tender documents including drawings giving the over all sizes, clearance, end approaches, structural features, travel wheel loads, end carriage buffers, impact forces, wheel spacing, etc., 5
WORKMANSHIP, MATERIAL AND INSPECTION:
Workmanship and material shall be subject to the inspection of the owner or his representative at all times. Weldments of carbon steel (except bridge girders) shall be stress relieved by uniformly heating in a furnace. Field welds shall likewise be stress relieved unless other means agreeable to the owner as specified in the information sheet. The temperature of the furnace when the weldment is placed in it shall not be over 150°C at the start and increased to 650°C at a rate not exceeding 95°C/hour, and then held at the temperature for 1 h/25mm of thickness of material. It shall then be cooled in the furnace at a rate (not exceeding 95°C/hour) to 260°C, before being removed from the furnace. Weldments of alloy material shall be welded and stress relieved using a procedure specified by the owner.
12
Doc:ME 14 (0916)c
SECTION 2 MECHANICAL COMPONENTS 5. 5.1
5.2
5.3
5.4
5.5
CALCULATION PROCEDURE Mechanism components shall be designed by checking that they offer required safety against failure due to fracture, crippling, fatigue or excessive wear. Other factors shall also be taken into consideration and it is particularly important to avoid over heating or deflection which may interfere with correct functioning of the mechanism. CHECKING FOR ULTIMATE STRENGTH Mechanism components shall be checked for ultimate strength by verifying that the calculated stress shall not exceed a permissible stress dependent on the braking strength of the material used. VALUE OF THE PERMISSIBLE STRESS The value of the permissible stress σa is given by the following formula: σa = σR /VR , Where: σa is the ultimate stress of the material VR is a safety coefficient corresponding to each case of loading. VALUE OF THE COEFFICIENT VR The values to be adopted for VR are given in table I below: Table I
Case of lading
IV exceptional loading condition
Value of VR
1.8
Relations between the calculated stresses and the permissible stresses. According to the types of loading considered, the following relations shall be verified in which: σt is the calculated tensile stress σC is the calculated compressive stress σf is the calculated bending stress σs is the calculated Shear stress (a) Pure tension : 1.25 σt ≤ σa (b) Pure compression : σc ≤ σa (c) Pure bending :
σf ≤ σa
(d) Combined bending and tension: 1.25 σt + σf ≤ σa (e) Combined bending and compression: σc + σf ≤ σa (f) Pure Shear : √3 σs ≤ σa (g) Combined tension, bending and shear: 2 2 o.5 ≤ σa [(1.25 σt + σf ) + 3 σs ] (h) Combined compression, bending and shear: 2 2 o.5 ≤ σa [( σc + σf ) + 3 σs ] 5.6 CHECKING FOR FATIGUE General method -The fatigue strength of a given component is mainly determined by the following factors a) The material from which the component is constructed.
13
Doc:ME 14 (0916)c
b)
The shape, surface condition, state of corrosion, size (scale effect) and other factors producing stress concentration. c) The ratio between the minimum and maximum stresses which occur during the various stress cycles. d) The stress spectrum e) The number of stress cycle 5.7 STRESSES The following characteristics shall be determined for each type of fluctuating stress, tension, compression, bending or shear, occurring during an appropriate stress cycle in the component details having regard to the loading that it will experience. ƒmax, ƒmin = extreme values of stress occurring in the stress cycle. ƒmin = considered as negative if it is of opposite sense to ƒmax Pfb = permissible fatigue stress in bending Pts = permissible fatigue stress in shear Pfb = fatigue reference stress at which a component details has a 90 percent probability of survival ƒomax, ƒamin = extreme values of axial tensile stress. ƒ bmax, ƒ bmin = extreme values of stress in bending ƒsmax, ƒsmin = extreme values of torsional shear stress ƒmax, ƒmin = Max degree of stress fluctuation. 5.8 PERMISSIBLE FATIGUE STRESS The permissible fatigue stress ‘Pfs’ for each type of stress, tension, bending or shear is given by: Pfs = 0.8 Pfr for hoisting mechanisms = 0.85 Pfr for all other mechanisms. Where the component detail is subjected to a single type of fluctuating stress, that is ƒmax shall not exceed Pf the permissible fatigue stress. The stress combination occurring most frequently in practce in a component detail is that of bending and torsion. The details subjected to this combination shall be designed so that 2 2 ( ƒ b Max ) + ( ƒs Max ) < 1.0 Pfb Pfs 5.9 CHECKING FOR CRIPPLING Component subjected to crippling that in overall flexural buckling due to axial compression shall be checked so that the calculated stress does not exceed a limit stress determined as a function of critical stress above which there is a risk of crippling occurring. For this check co-efficient Cdf of IS 3177 (Table 2). 5.10 CHECKING FOR WEAR In the case of parts subjected to wear, the specific physical quantities such as surface pressure or the circumferential velocity shall be determined. NOTE: Annex B of IS 3177shall be referred for calculating the fatigue stress Pfr. 5.11 HOOKS 5.11.1 Generally hooks shall be designed material clause as per IS 3664 for infinite life based on the rated load except where the owner specifies finite life design. The design shall be established by analysis or testing.
14
Doc:ME 14 (0916)c
5.11.2 Hooks shall be forged from fine grain material. Any welding on the hook shall be with the approval of a qualified welding engineer and performed prior to initial heat treatment. The capacity of the hook may be stamped on the hook nose. The hook shall not be painted. 5.11.3 Hook shank The calculated maximum stress at the root of the thread of the shank section, including a fatigue stress concentration factor for the type of thread used, shall not exceed 0.33 of minimum ultimate tensile strength at mid-radium. 5.11.4 Considerations: Due consideration shall be given to impact, service and to the possibility of bending forces on the hook shank. These bending forces will be partially dependent upon the geometry of the hook saddle and the coefficient of friction between the hook saddle and the loading element. The shank shall be undercut below the last threads for a length of at least two pitches to allow for a uniform stress flow. The undercut shall have a radius at each change in diameter. 5.11.5 Hook Body Hook bodies shall be as per IS 3664 where the line of the resultant load on the hook passes through the center of curvature of the inside edge of the hook and coincides with the centreline of the shank. The lifting Hooks shall comply with IS 3815 and IS 5749. The maximum combined stress at the inner surface of curvature of the critical section 90 degrees from the vertical load shall not exceed 0.33 time of minimum ultimate strength. This applies to hook bodies of trapezoidal section. Where square or rectangular sections are used, these stresses shall be reduced by at least 10 %. 5.11.6 Testing Where hook capacity has been established by testing, the static load required to straighten out the hook body shall not be less than 5.0 times the rated load. A certificate of compliance showing both fatigue and static load testing covering both the configuration of the hook body and the hook shank shall be provided. Approval by the owner shall be obtained for hooks selected on this basis. 5.11.7 Sections Proportions of hook sections other than the critical section shall be such that the stress does not exceed the stress in the critical sections. 5.11.8 Threads The hook nut and shank threads shall provide required strength for the hook capacity. Due consideration shall be given to the weakening effect of the nut locking arrangement. 5.11.9 Latches Hook latches and swivel lock plates shall be provided when specified. 5.11.10 Laminated Point hooks Laminated hooks shall be made for steel works and foundries for lifting and carrying molten masses in spigot ladles. The material, dimensions, design, components and assembly for laminated point hooks are covered IS 5749 and part and technical delivery conditions for laminated hooks are covered IS 5749. 5.12 ROPE DRUMS
15
Doc:ME 14 (0916)c
5.12.1 Drum shall be rolled or centrifugally cast steel as per IS 2328 Flanged ends, if required, shall not be less than 2.5 mm in thickness and project not less than 65 mm. beyond the pitch diameter of the drum. 5.12.2 Drums shall have wrapped grooves of a depth equal to 12 mm of the diameter of the hoisting rope and a pitch of not less than 1.2 times this diameter. The groove radius shall be 0.8 mm in. larger than the radius of the rope. Drums shall be designed so that not less than two complete wraps of hoisting rope will remain in the grooves ahead of the first rope clamp when the hook is at the lowest position. In addition, it shall be possible to lay the hook block on the floor for maintenance with one full wrap remaining on the drum. 5.12.3 One empty groove for each rope shall be left on the hoist drum when the hook is in the highest position. This provision is to insure that overlapping of the rope will not occur when the hook is in the highest drifted position.The pitch diameter of the drum for 6 x 36 wire rope shall not be less than 30 times the diameter of the hoisting rope used for Classes M7 and M8 cranes. 5.12.4 Radius of the bottom of the groove The useful life of the rope depends not only on the dia of the pulleys and drums, but also on the pressure exerted between the rope and the groove supporting the rope. The winding ratios are given as the radius of supporting groover where r = 0.53 d, d being the nominal dia of the rope.The drum gear shall be keyed and pressed on to the periphery of the hub or shell of the drum, or shall be bolted with fitted bolts to a flange on the drum or by other attachment means as approved by the owner. The o lead angle of the rope shall not exceed 5 on either side of helix angle of the groove in the drum. The contour at the bottom of the grooves shall be circular over a o minimum angle of 120 . 5.13 ROPES 5.13.1 The hoisting ropes shall be of the grade and type specified in IS 2266. Based on the static breaking strength, a design factor of 8 shall be used for hot metal handling hoists and 5 for hoists other than hot metal handling.The sheave arrangement should be reeved so as to eliminate reverse bends except at the drum. 5.13.2 The maximum allowable fleet angle for frequent working positions shall be 2½ degrees for Classes M7 and M8 cranes. The maximum allowable fleet angle for seldom reached positions shall be 3½ degrees for Classes M7 and M8 cranes.When special reeving, such as a stabilised reeving arrangement is used, consideration must be given to geometry and dynamics to maintain the appropriate safety factors. Provisions should be made to prevent the twisting of the hook block. 5.13.3 Where load swinging can occur due to the crane service, rope lead angles shall be set, or other provisions made, to minimize or eliminate the possibility of the rope skipping grooves on the hoist drums. When designing hoist drums the following should be taken into consideration. On high duty cycle cranes, drum grooves should be flame hardened to a minimum of 400 BHN. 5.13.4 The minimum breaking load Fo of the intended for a particular duty shall be determined from the formula given below, however impact factor shall not be considered while calculating the rope tension Fo = S x Zp x Cdf
16
Doc:ME 14 (0916)c
S – Maximum rope tension considering inclination of the rope in the upper most position. Zp – Minimum practical co-efficient of utilisation. For M7 and M8 duty, Zp shall be taken equal to 6.0 Cdf – duty factor for hoisting as defined in 7.4.3 of 3177 5.14 SHEAVES 5.14.1 The pitch diameter of all sheaves, except equalizer sheaves for 6 x 36 wire rope shall not be less than 30 times the diameter of the hoisting rope used for Classes M7 and M8 cranes. Use the next larger size diameter for lead sheave. Sheaves shall be enclosed by guards which fit close to the flanges to prevent the ropes from coming out of the groves. The material of the sheaves shall be as per IS 1030 Gr B 1989.The bearing assembly in each sheaves shall be individually lubricated. The fittings and grease lines shall be located so that they will be protected from damage. Where possible, upper sheave block mountings shall be above the trolley deck. The upper sheaves block shall be removable as a unit from the above. 5.14.2 Grooving Sheaves shall have machined groove. The contour at the bottom of the groove o shall be circular over a minimum angle of 120 and shall have an included angle o of 45 . The depth of the groove shall not be less than 1.5 times the dia of the rope. The radius of the groove shall be between 0.53 to 0.59 times the dia of the wire rope rounded of upwards to the nearest 0.5 mm on higher side. 5.14.3 Diameter of the Sheave The diameter of the bottom of the groove at an equalizing sheave shall not be less than 65 percent at the minimum sheave diameter. The value shall be calculated as per clause 8.5.2 of 3177. The minimum winding diameter shall be calculated as per the formula, D≥ H.d. Where: D – the winding dia meter on pulley or compensating pulleys H – a coefficient depending upon the mechanism group d – the nominal dia of the rope. The value of H for main pulley shall be 28 The value of H for compensating pulley shall be 18, 5.15 EQUALIZER BARS OR SHEAVES 5.15.1Where required, either an equalizer bar or sheave will be acceptable. In either case the bar or sheaves shall be positioned to be accessible from the floor of the trolley and made in such manner that it can turn or swivel to align itself with the pull of the ropes. Equalizer sheaves shall have a pitch diameter not less than 18 times the diameter of the rope. Cranes having hoists which handle hot metal or critical loads should utilize equalizer bars to provide two independent rope systems, not equalizer sheaves. For increased rope life, consideration shall be given to using equalizer sheaves with the same diameter as the running sheave. 5.16 TRACK WHEELS 5.16.1 All track wheels shall be double flanged. The blanks shall be made by roll forming, forging or casting from grades of steel appropriate to the forming process. Bridge track wheels shall have either straight or tapered treads. The
17
Doc:ME 14 (0916)c
material of the wheels shall be grade C 55 Mn 75 of IS 1570(Pt I & II) Bridge wheel loads shall be determined with the maximum lifted load on the trolley, which shall be positioned at the closest working approach that produces the maximum wheel load. Trolley wheel loads shall be determined with the maximum lifted loads, Max lift load = (Wt + W L + W A) , where: WT - Weightofthetrolley WL–WeightoftheliftedloadW A - Weightofthecolums
5.16.2 Material for wheel The material for the track wheel shall be grade C55 Mn 75 of IS: 1570 and also may be of steel. The steel shall not contain more than 0.06 percent either of sulphur or phosphorus. 5.16.3 Dia of the wheels The Thread diameter of wheels shall be standardised to sizes 160, 200, 250, 315, 400, 500, 630, 710, 800, 900, 1000 and 1250 mm. The minimum tread diameter of the wheel may be calculated from the formula given below: W x Cdf x Csf D= 1.5 a x Cbh x Csp Where: D – Tread dia of the wheel in mm W – Maximum wheel load in newtons a – useful width of rail Cdf – duty factor undefined in 7.4.3 of IS 3177 Cbh – hardness factor for the wheel. For values refer Table 9 of IS 3177 Bhw – as calculated in 7.4.3 of IS 3177 Csf – safety factor depending on the material used as defined in 7.4.3 of IS 3177 Csp – Co-efficient depending on the speed of rotation of the wheel defined in Table 10 of IS 3177. 5.16.4 Determining the mean load In order to determine the mean loads, the procedure is to consider the maximum and minimum loads with stood by the wheel in the loading cases considered, i.e. with the crane in normal duty but omitting the dynamic factor. The values of P mean shall be determined by the formula for loading case I and II, III P mean = (P min I, II, III + 2 P max I, II, III) / 3 5.16.5 Determining the wheel width a) Flat bearing surface : a = B – 2r b) Convex bearing surface : a = B – 4r/3 where: B – width of the rail, and R – radius of the rounded corners of the side 5.16.6 Flanges The dimensions of flanges for guiding trade wheels at the base shall not be less than the values given in Table 11 of IS 3177/1999.
18
Doc:ME 14 (0916)c
5.16.7 Determining the limiting pressure P1 Table Values of PL 2 Ultimate strength for metal used PL in N/mm for rail wheel 2 500 N/mm 5.0 2 600 N/mm 5.6 2 700 N/mm 6.5 2 800 N/mm 7.2 5.17 BUMPERS 5.17.1 Provisions in the design of the runway and the design of the runway stops shall consider the energy absorbing or storage device used in the crane bumper. The device may be nonlinear (e.g hydraulic bumpers) or a linear device such as a coil spring. 2 5.17.2 The maximum deceleration rate for both bridge and trolley shall not exceed 5 m/s at l50% of the full load rated speed (full load rated speed shall be used unless adequate information is supplied by owner to determine the actual attainable maximum speed.) Additionally, bumpers shall be capable of absorbing the total energy at 100% full load rated speed. 5.17.3 Between cranes or trolleys (if two trolleys are located on one bridge) bumpers shall be capable of absorbing the energy from 70% of full load rated speed of both cranes or trolleys travelling in opposite directions, or the energy from 100% of full load rated speed of either crane or trolley, whichever is the greatest.
5.17.4 The design of all bumpers shall include safety cables to prevent parts from dropping to the floor. For computing bridge bumper energy, the trolley shall be placed in the end approach which will produce the maximum end reaction from both bridge and trolley. This end reaction shall be used as the maximum weight portion of the crane that can act on each bridge bumper. The energy absorbing capacity of the bumper shall be based on power-off and shall not include the lifted load if free to swing. Bridge bumpers shall have a contact surface of not less than 125 mm in diameter, be located on the rail centreline and mounted to provide proper clearance when bumpers of two cranes come together and both are fully compressed. Where practical, they shall be mounted to provide for easy removal of bridge track wheels. 5.17.5 Buffers shall have sufficient energy absorbing capacity to bring the loaded cranes or crab to rest from a speed 50 percent of the rated speed at a deceleration rate not 2 exceeding 5 m/s . 5.18 SHAFTING 5.18.1 Hoist shafting design torque shall be based on the torque required to lift the rated load plus hook block and/or lifting beam and shall take account of mechanical efficiencies. Design torque for all travel drives shall be based on 2 times the 60 minute motor rating for series wound, constant potential D.C drives, and 1.7 times the 60-minute motor rating for A.C motors and adjustable voltage D.C drives
19
Doc:ME 14 (0916)c
without motor field weakening, or wheel slip at maximum wheel load (0.20 friction factor) whichever is lower. Due consideration shall be given to the maximum brake torque which can be applied to the drive. Axles or shafts which are provided with sleeve bearings are to be surface or casehardened and ground. 5.18.2 Shafts All shafts shall be made of low alloy steel of C 45 and axles shall have strength, rigidity and required the bearing surfaces. All shafts shall be supported on minimum two bearing. Angular deflection of the line shaft at torque corresponding to 1.5 times the motor torque during the acceleration period shall o not be more than 0.25 per meter of shaft length. The drive for line shaft shall be mounted as close as practicable to the centre of the span. 5.18.3 Stress calculations - All shafting shall be designed to meet the stresses encounted in actual operation. Due consideration shall be given to the maximum Torque which may be applied to the shaft. When significant stresses are produced by the other forces, these forces shall be postioned to provide the maximum stresses at the section under consideration. Impact shall not be included. 5.18.4 Fatigue stress check for normal operating conditions - Any shafting subjected to fluctuating stresses such as the bending or rotating shafts or the torsion in reversing drives must be checked for fatigue. The bearing stress must not exceed 50% of the minimum yield strength for non - rotating shafting. 5.19 PRESS FITS AND KEYS 5.19.1 Keys shall be provided for all connections subject to torsion. All gears, pinions and couplings shall be pressed or shrunk onto shafts in addition to being keyed. All press fits shall be made in accordance with IS: 2048/1983 Preferred Limits and Fits for Cylindrical Parts. All keys and keyways shall be radiused and/or chamfered according relevant Indian Standard. 5.20 BEARINGS 5.20.1 Antifriction bearings shall be spherical, tapered, straight. Antifriction bearings shall be selected on the basis of B-10 life, to give a minimum life expectancy of ten years or 5,000 to 40,000 hours under the service conditions for which the crane is intended. Bearing selection in this specification is based on the total number of cycles which it is expected the bearing will undergo during the number of hours service the crane will be used in a 10 year period. 5.20.2 All bearings selected shall meet the required life at 75% of the maximum bearing load (at rated speed) based on the recent catalogue rating of the bearing manufacturer. Bearings are selected for 75% of the maximum load (at rated speed) on the assumption that this gives a practical average value for fatigue life purposes. If the load on the bearing is essentially constant, the bearings must meet a required life of 100% of the maximum load at rated speed. In some cases axle sizes establish bearing sizes.With wheel bearings of the antifriction type, one bearing on each wheel axle shall be of the fixed type. The other bearing shall be arranged to allow for expansion or float of the axle. 5.20.3 Lubrications-Provisions shall be made for the service Lubrication of all the bearings unless sealed and lubricated for life. Ball and roller bearings shall be lubricated before assembly.Gear housings shall be split or designed to permit easy
20
Doc:ME 14 (0916)c
removal of the shaft.Gear reduction units should be designed so that gears, shafts and bearings, as well as bearing cartridges and end pieces, can be pre-assembled as a spare.Drum bearings and supports for the upper sheave block shall be located so as to equalize the load on track wheels as near as possible. 5.20.4 Bearing Brackets and Housing Bearing brackets, if not integral with the frame, shall be mounted on a machined surface and be kept in alignment by fitted bolts or other equally effective methods. When shafting is geared together the support structure for all bearing cartridges should, where practical, be integral and located as close as possible to the gears and pinions. Heavy caps shall be provided with a means for lifting. 5.21 GEARING: 5.21.1 Gearing types Gearing shall be spur, herringbone, helical as specified in the IS 4460, 7504. No split gears or overhung gears shall be used without specific approval of the owner. 5.21.2 Gearing Design: Horsepower ratings for all spur and helical involute gearing shall be based upon American Gear Manufacturers Association or IS 4460 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth. 5.21.3 Allowable Stress (Sac) and (Sat ) The allowable stress for contact stress (Sac) and for bending stress (Sat ) and material used shall be as listed for Grade I material as per IS 4460. 5.21.4 Dynamic Factors (Cu) and (K u) The dynamic factors for pitting resistance (Cu) and for bending strength (K u) shall be as per Paragraph 8.3.2 and 8.3.3 of AGMA 2001 B-88 based on the lowest quality member in the mesh. 5.21.5 Elastic coefficient, (CP) The elastic coefficient (CP) shall be as per IS 4460. 5.21.6 Hardness Ratio Factor (C H ) The hardness ratio factor (C H ) shall be as per IS 4460. 5.21.7 Service Factors The service factors (CSF ) and (K SF ) shall be used as per IS 4460. 5.21.8 Maximum and Minimum Gearing Face width: The gearing face width shall be a maximum of 1.4 times the pinion pitch diameter and a minimum of 3 times the circular pitch. 5.21.9 Gear Design Loading Hoist gear loading for bending strength and pitting resistance shall be based on the torque required to lift the rated load plus hook block and/or lifting beam.Travel drive gear ratings for bending strength and pitting resistance shall be based on 2 times the 60 minute motor rating for series wound constant potential D.C drives, and 1.7 times the 60 minute motor rating for A.C motors and adjustable voltage D.C drives without motor field weakening, or wheel slip at maximum wheel load (0.20 friction factor) whichever is lower. Due consideration shall be given to the maximum brake torque which can be applied to the drive. 5.21.10Dynamic Response
21
Doc:ME 14 (0916)c
Where unusual drive arrangements are employed the dynamic response of the system should be analysed to ensure that any a dditional loadings are identified.
5.21.11Drum Gear Alignment-The effects of trolley frame and rope drum deflections on the alignment of the hoist drum gear and pinion shall be considered. 5.22 MACHINING REQUIREMENTS 5.22.1 Machining and Inspection-All gears shall be 20º pressure angle full depth tooth form and shall have a full root radius unless this compromises other design considerations. The wall thickness over the keyway of pinions shall be atleast equal to the tooth depth and the rim thickness of gears shall be atleast 1.2 times the tooth depth. Gears shall not have a shoulder or step left in the fillet area. 5.22.2 Bores - Bores for gears requiring heat treatment shall be finish-machined or ground to size after heat treatment and shall be no harder than 345 BHN for Class G-1; 300 BHN for Class G-2; and 269 BHN for Classes G-3 and G-4. 5.22.3 Keyway Tolerances - Keyway tolerances to be in accordance with relevant Indian Standards. 5.22.4 Effective Case Depth - The effective case depth for carburised and hardened gears is defined as the depth below the surface at which the Rockwell “C” hardness has dropped to HRC 50. 5.23 GEAR BOXES – 5.23.1 All gears shall be completely enclosed in gear boxes which shall be attached to rigid supports. All gear boxes except for drum ring gears shall be oil-tight and sealed with compound or gaskets.The bottom of the gear boxes shall be split horizontally above the oil level. Easily accessible drain plugs and breathers shall be provided. Oil level dipsticks shall go directly into the main body of gear box. 5.23.2 Openings shall be provided in the top section for the inspection of gearing at mesh lines. Gear box inspection cover plates should provide reliable sealing, and be easily opened and resealed. 5.23.3 In Classes M7 and M8, bearings shall be mounted in cartridges. Cartridges shall be held in place by tapped bolts and flanges. Splash oil lubrication of bearings may be used unless otherwise specified. Oil pumps shall be used if vertical gearing exceeds two reductions. On horizontal gearing, the oil level shall be above the smallest gear. Oil seals shall be sized to allow replacement with split seals. Through bolts should be used to hold the gear cases together and to mount the gear box to its base.All gear cases shall be mounted on machined surfaces. Shims shall not be used. 5.23.4 Gear box seats shall be of sufficient size to allow the installation of shear blocks to locate the gear box positively. Gear boxes shall be provided with lifting lugs that are suitable for use in lifting the whole gear case assembly without tilting. 5.23.5 The gear box mounting shall be machine cut, hardened and profile ground to relevant Indian Standards and shall be seated and positively located on machined surface. The fabricated gear boxes shall be stress relieved before machining. The internal surfaces of the gear box shall be painted with oil resisting point. All gearing not enclosed in Gear boxes which may constitute a hazard under normal
22
Doc:ME 14 (0916)c
operating conditions shall be guarded with provision for lubrication and inspection.Guards shall be securely fastened. 5.24 LUBRICATION 5.24.1 All lines shall be located so as to provide the maximum natural protection, and at the same times lines should be positioned so that ordinary repairs can be made without complete removal of the lines. All lines shall be fastened to the crane’s structure. 5.24.2 Centralised automatic grease systems should be considered on trolleys. Manual pumps should be considered for bridge drive assemblies. Flexible hoses should be utilised at components end for easy removal. 5.24.3 Provisions shall be made for lubricating all bearings unless sealed or lubricated for life, matting gears and chain and sprockets arrangements, where necessary easy access shall be provided. 5.24.4 A lubricating chart shall be provided indicating all the lubricating points with ‘Red colour’ paint, the type of lubricant and recommended frequency of lubrication. 5.25 LINE SHAFTING AND COUPLINGS: 5.25.1 Floating shaft Where possible, the flexible halves of half flexible couplings shall be mounted on the floating shaft. Couplings shall be located close to the bearings and be provided with substantial removable guards which shall extend beyond the ends of the hubs and overlap with the coupling hub OD. Where half-flexible couplings are used, the couplings shall be located close to the bearing on the end truck and the adjacent line shaft bearing shall not be closed than 1250 mm. 5.25.2 The load shall be transmitted between couplings half by means of fitted bolts. For shaft speed below 400 rpm, the following maximum bearing spacing shall be permitted. a) 3.5 m for 75 mm dia b) 4.25 M for 90 mm dia c) 4.5 M for 100 mm dia d) 4.85 m for 115 mm dia 5.25.3 For shaft speed in excess of 400 rpm, the above spacing shall be reduced as necessary to avoid harmonic vibrations. Supports for motor and gear reduction units shall be welded structural steel, rigidly connected to the crane girder. Bolts for fastening bearing brackets, motors and gear reduction unit shall be accessible from above the foot walk. Angular deflection of bridge line shafts at torque shall not exceed 0.3 degree/m of shaft length. 5.26 RAILS 5.26.1 Joints on trolley rail shall be welded or made by using standard joint bars. There shall be no bolt holes adjacent to the welded joint. Where joint bars are used, the joined ends of the rails shall be laid without openings between the ends.The rails shall be as per CR rail. 5.26.2 For box girders, rails shall be fastened in place by suitable clamps. The rail clamping shall be of soft mounting system, consist of pad and clips. The pad shall be reinforced with galvanised steel vulcanised to and totally encapsulated by the elastomer. The clips should provide positive lateral rail and pad restraint and vertical restraint. The clips shall be of spring clips presses the rail against the pad.
23
Doc:ME 14 (0916)c
The clamps shall be spaced at not more than 900 mm centres. Heat treated rail shall be used for increased rail life. The rails shall be welded together by flash butt welding or thermit welding. 5.27 OPERATOR’S CABIN 5.27.1 Type and location - The operator’s cabin may be of the fixed/moving type as required by the purchaser. 5.27.2 Structure - The cabin shall be rigidly built of structural steel and fire proof material and shall be braced to prevent movement between cabin and supporting members. It shall be supported by rivets or bolts in shear. The head room of the cabin shall not be less than 2 M. 5.27.3 In ladle cranes, other cranes handling hot materials and outdoor cranes, cabins shall be totally enclosed, unless otherwise specified. 5.27.4 The cabin of outdoor shall be weatherproof. 5.27.5 Cabin Access - The entrance to the cabin shall be fitted with a door located for safe access. The cabin floor shall be extended outside the cabin on the side containing the door, and if necessary, sideways also to form a platform unless otherwise required. Suitable hand railing should be provided on the platform. 5.27.6 Accessibility to the bridge platform shall be through the stairs. 5.27.7 Visibility and Field of vision - Cabins shall be so designed that under all operating conditions the field of vision of the driver is ad equate. 5.27.8 Lighting, heating, ventilation and air-conditioning: Fixed service lighting shall be installed to provide glare free illumination in the crane cabin. 5.27.9 All cabins shall be provided with an air circulating fan of minimum sweep 400 mm. 5.27.10 All air-conditioned cabins shall be fitted with a suitable hydraulic door closer and temp in the cabin shall be around 25ºC. 5.27.11 A suitable Co2 type fire extinguisher shall also be provided. 5.27.12 The cabin shall have a robust seat with a fixed or hinged base and a durable upholstered squab. The seat shall be capable of withstanding severe braking force. 5.28 MEANS OF ACCESS 5.28.1 General requirements - Safe means of access shall be provided to the driver’s cabin and adequate hand-holds and foot-holds shall be provided, where necessary. 5.28.2 Platform - Every platform shall be securely fenced with double tiered guard rails having a minimum height of 1.1 metre. 5.28.3 Ladders - Sides of ladders shall extend to a reasonable distance above the platforms. Vertical ladders exceeding 3 metre in length shall be provided with back safety guards. 5.29 GUARDING 5.29.1 All gear wheels, pinions and chain drives shall be totally enclosed. Effective guards shall be provided for revolving shafts and couplings. Long travel crossshafts and couplings above the top platform shall be guarded wherever necessary. The sheaves of hook blocks shall be guarded to prevent the trapping of a hand between a sheave and the in-running rope and shall be enclosed except for rope opening. 5.30 WEATHER PROTECTION
24
Doc:ME 14 (0916)c
5.30.1 For outdoor cranes all electrical and mechanical equipment shall be adequately protected from weather. All weather proof covers shall be easily removable. 5.31 PAINTING 5.31.1 Before the despatch of cranes, the complete crane covering structural, mechanical and electrical parts shall be thoroughly cleaned of all dirt, grease, scales, rust and given a single coat of primer. All components shall be given two finishing coat of paint of colour as per customer’s choice. 5.32 HANDLING FACILITIES: 5.32.1 Suitable structures at all four corners for handling the track wheels, should be provided. However for all outdoor goliath and semi-goliath cranes, this facility shall be provided. 5.32.2 All cranes shall be provided with jack pad on both end carriages and trolley structures in such a way so as to facilitate removal of wheels, wheel bogie and compensating bogie. 5.33 BRIDGE AND TROLLEY DRIVES5.33.1 Bridge and trolley drives arrangements may cover most types of crane drives regardless of the number of wheels. 5..33.2 Bridge drives- Bridge drive shall consists of one of the following arrangements, and these arrangements cover most four or eight wheel crane drives. 5.33.3 DRIVE I-The motor is located near the centre of the bridge and connected to a self-contained gear reduction unit located near the centre of the bridge. Output of the Gear reduction shall be connected directly to the truck wheel axle by means of suitable shafts and couplings. 5.33.4 DRIVE II The motor is connected to a self contained gear reduction unit located near the centre of the bridge. The Truck wheels shall be driven through gears pressed and keyed on their axles or by gears fastened to, or integral with, the Truck wheels and with pinions mounted on the end section of the cross-shaft. The end sections of the cross-shaft shall be connected by suitable couplings. 5.33.5 DRIVE III-The motor is located at the centre of the bridge and is connected to the cross-shaft and gear reduction units with suitable coupling. Self-contained gear reduction units located near each and of the bridge shall be either directly connected to the wheel axle extension or connected to wheel axles by means of shafts in the suitable couplings. 5.33.6 DRIVE IV-The motors are located near each end of the bridge without torque shafts. The motors shall be connected to self-contained gear reduction units. The gear reduction unit shall be applied to the truck wheels by means of both suitable shafts and couplings or directly mounted to the wheel axle shaft extension. Another variation of this drive would separate the high speed and final reductions by locating the motors near each end of the bridge without torque shafts. 5.33.7 DRIVE V-The motor is located near the centre of the bridge and in connected to a self-contained gear reduction unit located near centre of the bridge This reduction unit shall be connected by sections of cross-shaft having suitable couplings to self-contained gear reduction units located near each end of the crane, and these in turn connected to truck wheel axle by means of shafts with suitable coupling. 5.33.8 DRIVE VI-The motors are located near each end of the bridge and connected with a torque shaft. On the drive end, the motors shall be connected to self-contained
25
Doc:ME 14 (0916)c
gear reduction units by suitable couplings. The output of the gear reduction units shall be connected directly to the truck wheel axle by means of suitable shafts and couplings. 5.34 TORSIONAL DEFLECTION AND VIBRATION Natural frequency and amplitude of total torsional deflection of the drive system should be determined. determined. Low frequencies and large total torsional deflections are undesirable for crane operation. 5.35 MOTION LIMITING DEVICE Positive by operated hoisting motion limiting devices shall be provided that stops the upward and downward motion when predetermined level is reached to prevent over winding or over unwinding. NOTE:-The limiting device shall be regarded as a safety feature and not as a routine operational means of stopping. Where normal normal operation of the crane necessitates frequent approach to the upward limit, an additional motion limiting device shall be provided that operates independently and require manual settings. 5.36 CROSS TRAVEL AND LONG TRAVEL LIMITING DEVICES: The limiting devices shall prevent the following conditions: (a) Over traversing and over travelling, and (b) Collision where two or more crane/Trolleys operating on the same track. 5.37 LOAD INDICATION AND LOAD LIMITING DEVICES Load indication and limiting devices are recommended it weights of objects to be lifted are not not known accurately. When fitted, they shall sense the load on the crane by means other than the current consumed by the hoist motor. motor. If the load lifted is more than SWL load limiting devices shall stop further hoisting operation till the load is removed or reduced. 5.38 DRAWINGS AND DOCUMENTS Following drawings and documents shall be submitted for approval of the purchase before manufacturing of the crane: (a) GA drawings of the crane (b) GA drawings of crab/Trolley (c) GA drawings of individual mechanisms (d) Drawings of bridge, end girder and their connection (e) Sub-assembly drawing for wheels, hook blocks and hoist drums. (f) Calculation for selection of motor, reducer brake, couplings, etc.
26
Doc:ME 14 (0916)c SECTION – 3 ELECTRICAL EQUIPMENT 6.1 POWER SUPPLY 6.1 GENERAL-This document deals with a.c. low-voltage systems upto 1000 V. The power supply system should comply with relevant Indian Standards. Voltage variation at the point of supply to crane DSL system be limited to – 5% … +5% of the rated voltage under normal operating conditions. The End User should ensure this with respect to number of cranes in the bay with dedicated feeder, etc., In applications with very long cabling distances it may be necessary to limit the voltage variation further. The allowed per cent voltage drop in the different parts of the power supply need to be considered case by case. The type of the power supply grounding may have significant effects on the requirements of the crane electrification. The type should always be agreed between the purchaser and supplier. For Cranes with incoming power requirement higher than 1000 kVA , the system voltage should preferably be 690 V a.c in order to design with optimum sizes of conductor , cables , motors and controls. Typical example is Ladle Cranes. 6.2 DSL SYSTEMS AND ACCESSORIES FOR CRANES 6.2.1 General Down shop lead arrangement using copper, aluminium or steel sections with or without shrouding or by using flexible trailing cable arrangement may be used. Use of shrouded conductors, where ever possible is recommended. 6.2.2 Conductors Current collecting system shall be provided either by the purchaser or by the crane manufacturer as agreed by them. Cranes operating on bare conductors shall be equipped with suitable guards to prevent ropes or suspended load coming in contact with the live conductors due to swing of the hook block. Down-shop conductors also shall be screened to prevent contact while handling long lengths of conducting materials from floor. 6.2.3 Current collectors Unless otherwise agreed to, all collector assembly shall be supplied by the crane manufacturer. The purchaser shall furnish relevant details depending upon the manufacturer’s scope of work. Collector rollers or shoes shall be so designed as to avoid sparking and shall be easily replaceable. Collector assembly shall be mounted on a rigid structure on the crane bridge. Necessary safe and convenient access shall be provided for maintenance or replacement of the collectors. 6.3 CROSS TRAVEL CURRENT COLLECTING SYSTEM 6.3.1 General-Cross travel current collecting system shall be with bare conductors or with shrouded conductors or with trailing cable arrangement. The collection system shall be provided by the manufacturer. 6.3.2 Conductors-Cross travel conductors for the main crab shall be mounted on the main bridge platform and not inside the main girders. Conductors for auxiliary crabs shall be mounted suitably above the level of auxiliary crab rails. Cross travel conductors shall be arranged so that they are all accessible for maintenance from atleast one side along the whole length. Bare conductors mounted on the bridge adjacent to a walk way along the bridge shall be completely screened from the walkway. 6.3.3 Collector assembly-Collector assembly shall be rigidly mounted on the crab and shall be provided with reasonable accessibility to all parts for maintenance purpose.
27
Doc:ME 14 (0916)c 6.4 EARTHING 6.4.1 General-The crane structure, motor frames, and metal cases of all electrical equipment including metal conduit or cable guards shall be effectively connected to earth complying with Indian Electricity Rules (See IS 3043). A flexible metallic tube or duct may not form an effective earth connection. The crane wheels shall not be used as means of earthing.Where the crane is connected to the supply by flexible cord or flexible cable, the crane shall be connected to earth by means of a separate earthing conductor enclosed with the current carrying conductors.Travelling cranes connected to the supply through collectors shall be effectively earthed through a fourth lead or through a set of collectors sliding on the gantry rail with reference to IS 3043.The purchaser shall arrange for the earthing of the gantry and/or the long travel earth conductor. 6.4.2 Control Circuit Earthing One end of the secondary winding of control circuit transformer shall be earthed. One end of the coil of all relays and contactors shall be connected to earth side of the control circuit supply and this connection shall not be interrupted by any fuse or contact.In the case of dc control circuits one pole of the rectifier shall be earthed. 6.4.3 Magnet Earthing The magnet frame shall be bonded to the crab by the earth connection via the magnet lead, the magnet coupling, the magnet cable and an extra slip-ring on the cable drum. 6.5 CONDUCTOR BARS, CABLE REELS AND FLEXIBLE CABLES The following three important considerations must be taken into account in dimensioning insulated wires or cables: - The temperature rise in normal condition. - The temperature rise in faulty operation and on short-circuit. - The voltage drop The following clauses in IEC 60204-32 defines the basic requirements. Clause 13.7 – Flexible Cable Clause 13.8 – Collector wires, collector bars and slip ring assemblies Clause 14.4.3 Connections to cranes and between moving parts of the crane. According to 13.8.2 of IEC 60204-32, where ever collector wires, conductor bars and slip-ring assemblies are installed as part of the protective bonding circuit, they shall not carry current in normal operation. Therefore, the protective conductor (PE) and the neutral conductor (N) shall each use a separate collector wire, collector bar or slip-ring. The continuity of the protective conductor circuit using sliding contacts shall be ensured by taking appropriate measures (e.g. duplication of the current collector, continuity monitoring). The continuity of any protective bonding connection with sliding contacts shall be ensured e.g by duplication of the current collector (one set). Additionally, when sliding contacts are used to supply power to electronic drives, double collectors should be used also in phase collectors to avoid noise and hardware failures which may occur if a contact cuts off momentarily (2 sets of current collectors). 6.6 CALCULATION OF CROSS-SECTION OF CONDUCTORS These requirements apply both to the power supply to the crane and also to cabling within the crane.In general the selection of cable / conductors depend on the following : a) General operating conditions b) Ambient air temperature
28
Doc:ME 14 (0916)c
c) Methods of installation d) Grouping e) Intermittent duty applications 6.6.2 Co-ordination between conductors and protective devices a) In all cases, the following relationships shall exist: I b < = In I b < = Iz Where In = is the nominal current or current setting, in amperes, of the over current protective device Iz = is the effective current carrying capacity, in amperes, of a cable for continuous Service under the particular installation conditions concerned. b) Where the over current protective device is intended to provide overload protection, the following relationships shall exist: I b < = In < = Iz I2 < = 1.45 x Iz where I2 is the minimum current, in amperes, that when maintained for 1 hour will cause the protective device to open the circuit c) Where the over current protective device is intended only to provide short circuit protection: In may be greater than Iz and I2 may be greater than 1,45 Iz However, it should be remembered that the higher In is in relation to I z , the greater is the possibility of exceeding the ultimate short-circuit conductor temperature in the event of a short circuit. That is particularly true in the case of the smaller conductors ranging in size 2 up to 16 mm . 6.6.3 Short circuit protection of conductors The conditions to be met for short circuit protection is: s=
t xI
, where: k 2 s = conductor cross section in mm t = switch off time for protection against hazardous shock currents – max 0.2 to 5 s, as applicable. I = effective short circuit current in amperes exp ressed for a.c as the rms. 2 K = factor for conductor [As / mm ] when insulated with the following material, = 76 for PVC insulated Al conductors = 115 for PVC insulated copper conductors = 141 for Rubber insulated copper conductors = 132 for SiR insulated copper conductors = 143 for XLPE insulated copper conductors = 143 for EPR insulated copper conductors 6.6.4 Calculation of the cross-section in relation to the admissible voltage drop The voltage drop must be considered, paying attention to the fluctuation and the voltage drop within the power supply. For very long supply lines, not only the resistive but also
29
Doc:ME 14 (0916)c
the inductive part of the supply impedance need to be taken into account. Drop due to reactance should also be checked.The cross-section of the conductors should be determined by taking into account the mechanical strength required and the electrical load to be carried. Looping cable may be provided in parallel after checking the limit of voltage drop.When calculating the voltage drop, the most unfavourable position of the hoisting appliance in relation to the supply point must be considered.When calculating the admissible voltage drop on a supply line used by several hoisting appliances, the startup (ID) and rated (IN) currents of the motors operating simultaneously must be taken into account. Table No: 2.1 For all lifting appliances as a whole Number of hoisting Motion-1 Motion-2 Motion-3 Motion-4 appliances on one Motions in decreasing order of main contact line (highest rating in kW) power.(kW) 1 X X 2 X X X 3 X X X 4 X X X X 5 X X X X Two hoisting appliances working X X X X together Table No: 2.2 Number of For all the hoisting appliances as a whole appliances on one Motion-1 Motion-2 Motion-3 Motion-4 main contact line ID I N ID I N ID I N ID I N 1 X X 2 X X X 3 X X 4 X X X 5 X X X X 2 appliances X X X X Working together Notes for the calculation: a) In this clause, the rated current (In) should be considered not necessarily to mean the name plate current of the motor but the current drawn by the motor at full rated load. (ie. FLC corresponding to mechanical KW) for slip ring motors. b) In case of squirrel cage motor to be controlled by an electronic drive (softstarter, frequency converter, etc.,) the maximum current during any phase of operation should be considered as start-up current, although the highest current does not necessarily occur when starting the motion. With direct starting the ID (starting current) is typically 5 to 10 times In. With electronic drives the start-up current depends on the converter type and on its adjustments; with frequency converters the ID is typically below 2 times IN (nominal current).
30
Doc:ME 14 (0916)c
c) d) e)
For slip-ring rotor motors, consider ID to be approx. 1.8 x In. For drive with n motors in parallel, apply n x ID or n x IN. In case two or more hoisting appliances are working together, they should be considered as one appliance by using the sum current (ID or IN) of each joint motion. f) In case the power supply also feeds other (continuous) loads such as lighting, hydraulic pumps, lifting magnets or other cranes, the current drawn by these devices need to be taken into account. For a three phase power supply, the required minimum cross-section (S) of copper conductors can be calculated with the formula:
S1 =
ϕ 3 X 1XI tot X cos
∆uXK
mm 2 , where
l = Effective length of the line (m) Itot = Sum of the above calculated (ID and IN) currents (A) ∆u = Admissible voltage drop (V) k = Electric conductivity [Ω x mm2 x 2-1]-1 cos φ = Power factor. Calculation for voltage drop: (for reference purpose) ∆u= √ 3 x Itot x l x Z where Itot = Net current load on DSL l = effective length ( l/2 for mid point feed ) Z = Impedance (Ω/km) 6.6.5 Calculation of the minimum cross-section in relation to the thermal capacity of the conductors When calculating the cross-section for the conductor bar, which supplies several hoisting appliances, the actual simultaneous operation of the drive motors must be taken into account. Notes for the calculation: a) In this clause, the rated current (I n) should be considered not necessarily to mean the nameplate current of the motor but the current drawn by the motor at full rated load. b) In case n>1 motors are driven in parallel, consider: In = n x In (In = nominal current for one motor) c) In case two or more hoisting appliances are working together, they should be handled as one by using the sum current of each joint motion. d) In case the power supply also feeds other (continuous) loads such as lighting, hydraulic pumps, lifting magnets or other cranes, the current drawn by these devices need to be taken into account. The maximum allowed conductor temperature shall not be exceeded during normal operation. Conductor cross-section should be selected according to manufacturers’ specifications. 6.6.6 Installation of Cables a) While selecting cables consideration shall be given to factors like ambient temperature, grouping and disposition of cables, and the limitation of the voltage
31
Doc:ME 14 (0916)c
drop. The cables selection, testing shall be as per IS: 694, IS 554 and IS 9968 part 1 and Part 2. b) Protection: All cables shall be adequately protected against mechanical damage and metal trunking may be used if desired. If electric conduit is used it shall be welded conduit complying with the to relevant Indian Standard. c) Where cables are drawn into a steel tubes, the steel tube shall be heavy gauge, welded or solid-drawn, screw-jointed and drained. d) For outdoor cranes, except where flexible unarmoured cables are essential, cables shall be either armoured or enclosed throughout their length in galvanized trunking or conduit either flexible or rigid. A flexible metallic tube or duct shall not be used as an earth connection. Taped and braided varnished cambic insulated cables shall not be used for out-door cranes. e) Installation; The cable and wiring systems for each motion shall be independent and common returns shall be avoided. Main cables and controlled wiring shall be effectively separated. Where there is incidence of direct radiation of heat, the cable shall be protected by a shield of sheet metal. f) Cables shall be adequately secured to the main structure of the crane having due regard for the weight of the cable and the possibility of vibration. Where mineral insulated metal cables are subject to the effects of high transient voltage they shall be suitably protected by the use of surge limiting devices. g) Cables remaining alive when a main isolator is opened shall have metallic protection and shall be separately installed. h) Cable runs shall not be installed in any place where they will impede the crane driver’s field of view. i) Due consideration shall be given during the design of the crane to make suitable provision for cable runs and to avoid cable runs in locations where high temperatures and mechanical damage are likely to be experienced under service conditions. The cables should be easily accessible and should not hamper the movement of persons on the crane. j) Suitable precaution shall be taken to prevent the ingress or collection of water or oil in any part of a conduit or trunking system. k) Termination: Where trunking is used it shall extend into the electrical compartment or enclosed units. It shall be terminated as close as practicable to motors, collector gear and master controllers. Where junction boxes are necessary, as at motors equipped with flexible tails, these boxes shall be rigidly fixed to the crane structure close to the end of the trunking. Flexible or rigid conduit may be used to protect the cables between the trunking and the connected apparatus. l) Conduit systems shall be continuous to switch boxes and conduit outlets. m) Cable tails shall be suitably insulated and mechanically protected, and shall be suitably supported with insulated cleats, where necessary, to ensure rigidity. n) Identification: Cores of multicore cables shall bear a distinguishing mark or tape. p) Cable ends and terminals shall be ferruled at both ends and permanently marked with numbers or letters to correspond with the diagrams or connections to be supplied. 6.7 ELECTRICAL PROTECTIVE AND SAFETY EQUIPMENT
32
Doc:ME 14 (0916)c 6.7.1 PROTECTIVE EQUIPMENT 6.7.1.1 General-Suitably located efficient means shall be provided to protect every part of a system from excess current and voltage to prevent danger or damage. Enclosures having minimum degree of protection IP 41 shall be provided for all electrical equipments except for motors and resistors. Main Isolating switches: Main switches used for isolating shall comply as per IS 2516 part 1 and 2. The main metal-clad isolating switch shall be provided on the crane bridge in an accessible position and connected directly to the long-travel collectors or terminal box in case flexible cables are used. The switch shall be located as close as possible to the long-travel collectors or terminal box, unless its position be otherwise specified. On fixed cab cranes (See Fig. 1) it shall isolate all circuits, except the crane lighting circuits, warning lighting circuits, communication circuits; and in ac cranes, the circuit of the transformer supplying the portable lighting socket outlets. On moving cab cranes, it shall isolate all circuits except bridge lighting circuits, warning lighting circuits and in ac cranes the circuit of the transformer supplying the portable lighting outlets. This isolating switch shall be unfused, unless high betaking capacity fuse protection is specified.
FIG. 1 DIAGRAM OF MAIN ISOLATING SWITCHES AND FUSES REQUIRED FOR FIXED – CAB CRANES On moving cab cranes (See Fig. 2) an additional main unfused metal-clad isolating switch shall be provided on the cab structure in an accessible position outside the crane cab and connected directly to the cross travel collectors or terminal box in case flexible cables are used. The switch shall be located as close as possible to the cross-travel collectors, unless its position be otherwise specified. It shall isolate all circuits, except the crab lighting circuits, circuits arranged to operate warning devices and on ac cranes the circuit to the transformer for the portable lighting socket outlets on the crab. The selection, maintenance and installation shall be as per IS 10118, part 1 to 4.Each of the above main isolating switches shall be rated to carry atleast the combined full-loads currents of the two motions of the crane using the largest power (kW) working together with auxiliary loads such as lifting magnets and shall be provided with a means for locking it in the ‘OFF’ position of the switch. The switch cover shall be interlocked with the operating handle, so that it may not be removed or opened when the switch is closed. Live terminals inside the switch shall be shielded to prevent accidental contact. A pair of neon type pilot lamps or other device in duplicate, indicating when the supply to the
33
Doc:ME 14 (0916)c
crane control circuits is live, shall be provided in a position visible to the driver from his normal working position. If specified, the main isolating switch on the bridge shall be fitted with a pair of auxiliary contacts which will be closed when the main switch is open and vice-versa , to operate the crane warning lights
Fig. 2 DIAGRAM OF MAIN ISOLATING SWITCHES AND FUSES REQUIRED FOR MOVING-CAB CRANES 6.7.2 Electrical Protective Device 6.7.2.1 General If electrically operated contactor equipment is used for control of all crane motions, the protective equipment shall be in accordance either with Scheme A, in which each motion has separate protection, or with Scheme B, in which an overload of any motion trips off the crane supply. If drum controllers or master controllers are used for the control of all motions, the protective equipment shall comply with Scheme B. Also it is more often required that in master controller operated crane, overload of any motion should not trip the complete crane circuit, but should trip the individual circuit. In general, overload protection shall be of electromagnetic type with time delay. Thermal overload relays in conjunction with high rupturing capacity fuses or manual reset type overload relays may be provided if agreed by the purchaser. Where a motion is ward-Leonard controlled, provisions shall be made for: a) Protection in case of motor field failure; Protection against the motor creeping when the controller is in the ‘off’ b) position; and Tripping of the generator field circuit with suppression of generator voltages c) instantaneously when there is an over current of 250 percent in the generatormotor loop; or after a time-lag when there is a sustained over current of lower value. Operation of any of the above protective devices shall automatically apply the electromechanical brakes on the relevant motion. If other systems of control or mixed systems are specified, the protective equipment shall be in accordance with the recommendations of the control gear manufacturer. An indelible circuit diagram of the protective equipment shall be provided in the electrical equipment compartment. 6.7.2.2 Protective device common to all motions As minimum equipments of protection, electromagnetically operated contactors or manually operated circuit breakers fitted with no volt release capable of cutting off the
34
Doc:ME 14 (0916)c
power supply to the motion drives with under voltage protection shall be provided. Suitable protection against short circuit shall be provided at each of the isolator positions. The circuit breaker of the main contactor shall be rated to carry at least the combined full load currents of motors for any two motions having largest powers and auxiliary loads such as magnet, etc., if specified by the purchaser that more than two motions may be operated simultaneously, circuit breaker/main contactor shall be rated to suit the requirement. In appropriate cases, high rupturing capacity fuse may be provided. The circuit-breaker shall incorporate thermal and electro-magnetic overload protection device for protection against sustained overload and short circuit condition. If adequate protection against short circuit is to be provided at each isolating positions, there will be either HRC fuses or MCCB/ACB in each isolating position. As HRC fuses may lead single phasing only MCCB should be provided in each isolating position. The circuit breaker or main line contactor should not be rated to carry magnet full load current as magnet supply is taken before the circuit breaker/main line contactor. The breaker shall have adequate rupturing capacity to withstand and clear fault current of the system. If specified a suitable control circuit may be provided for this circuit-breaker to prevent it from being closed when the main contactor of a particular motion has failed to open, although the corresponding controller has been brought to its ‘zero’ position. 6.7.2.3 Scheme A – Protective Device for Individual Motions The provision of overload protection with adjustable inverse time log overload release shall be under-voltage release and with overload. The minimum provision of overload protection shall be such that all supply lines except one to each motion shall be provided with adjustable inverse time-lag overload releases. These shall be connected as close as possible to the contractors they control and shall be set to trip the circuit of the motion controlled when carrying 200 percent of the full load current of the motor, after a timelag of not more than 10 s. It shall not be possible to reinstate the current supply to the contactor closing coils of a motion until the master controller for that motion is returned back to the ‘off’ position. 6.7.2.4 Ac Instantaneous Release Single Pole over Load: Protective Device for Individual Motions: Any motor having its power less than one-third that of the largest motor and served by the same common overload release, shall be protected by a separate overload release. However, normally instantaneous release of overload relays are not used for individual motion and circuit breaker is tripped by its own overload. In crane with circuit breaker overload protection is provided by circuit breaker. In cranes with line contactor one triple pole magnetic overload relay rated for total crane power may be provided to trip the main contactor. Adjustable overload releases shall be provided to trip the main contactors or circuit-breakers and shall be connected as close to them as possible. The minimum provision for over current protection shall be as given below: a) one instantaneous release in a common line feeding all motions set to trip the main contactors or circuit breakers instantaneously when the current rises to 250 percent of the value specified above; and b) One inverse time-lag release in each other line feeding each motion, set to trip the respective motion when carrying 200 percent of the full load current of the line, after a time-lag of approximately 10 s.
35
Doc:ME 14 (0916)c
It shall not be possible to reinstate the current supply to the common main contactor closing coils, or complete the under voltage circuit of the circuit breakers until the master controllers for all motions are returned to the ‘off’ position. 6.7.2.5 Protective Devices for Motor circuits The number of overload devices and their position shall normally be in accordance with the arrangements shown in Table 14. If specified by the purchaser, other arrangements giving protection not less than any of these shall be considered as complying with the specification. Table 14 Normal Requirements for Number of Protective Devices for Circuit Dc Supply 3-phase ac supply No line earthed One line earthed 2 per motion in separate lines 1 per motion 3 per motion in connected in the nonseparate lines earthed line. 6.8 Contactors Reversing contactors shall be interlocked, preferably mechanically as well as electrically so that only one directional contactor can be in the closed position. 6.9 Control Switch Fuse Operating coil circuit of the main contactor or control contactor in case of cranes with circuit breaker. A double pole control switch fuse shall be connected in the operating coil circuit of the contactor. Miniature circuit breaker as an alternative to control switch fuse may also be used. 6.10 Emergency Switches A mushroom head push button or a prominent switch for emergency stop shall be provided at each control facility to switch ‘off’ the total crane supply or to de-energize the main contactor common to all the motion drives. In the case of dc cranes, rheostat braking shall be applied to the hoist motions. When any circuit breaking device is open no main pole on the nominally dead side shall be made alive by a parallel circuit in emergency.The emergency switch shall be so located as to be readily available for prompt use by the operator in case of emergency. If specified by the purchaser or when the crane span is larger than 20 m, the number of emergency stops shall be more than one. A reset button shall be provided if required by the purchaser. The emergency stop push-buttons or switches shall be connected in the operating coil circuit in the case of a contactor and in the under voltage release circuit in the case of a circuit breaker. 6.11 Off-Position Interlocking Electrical interlocking shall be provided to prevent inadvertent starting of the motions, in the case when power is lost, without the controller being brought to the ‘off’ position on restoration of the supply. 6.12 Pilot Lamp A red pilot lamp shall be connected to indicate that the crane is ready for operations and it shall be so located that it is visible to the operator. The pilot lamp shall be connected so that it indicates whether the control supply is ON or OFF or the contactor is CLOSED or OPEN. 6.13 Main feature of built-in crane weighing system (Load Cell)
36
Doc:ME 14 (0916)c
-
The load cell shall be of compression type and IP 68 protection. The power supply shall be 230 V ac or 110 V ac 50 Hz single phase. The load cell shall be placed in such a way that the load which is inert on the equalizing pulley/bar is transferred to this load cell by a pivot assembly. The built-in crane weighing system should have local indicator, processor based type, LED displa y, IP 55 protection, shall be located on the control cabin of the crane. The built-in crane weighing system should have remote indicator, LED display type, minimum visibility range of 50 m, shall be located on the crane girder. The resolution shall be in the order of 5 kg. The system shall have the provision of tripping the circuit in case of overloading the cranes and should serve on an additional overload safety device. 6.14 Auxiliary Isolating Switches and Fuses Auxiliary switches used for isolating shall comply with the relevant Indian Standards. If specified, an isolating switch shall be provided to isolate all supply lines to the main circuits of each motion. Double-pole high breaking capacity fuses shall be provided on each motion control panel. If specified a double-pole isolating switch shall be provided on each motion control panel to isolate the control circuits. Miniature circuit-breaker as an alternate to control switch fuse is also permissible.Metal-clad isolating switches with cartridge fuse protection in all lines shall be provided to isolate all supply lines to each of the following distribution boards or circuits where they exist. The cartridge fuses shall comply with the relevant Indian Standards. a) Fixed cab cranes: Distribution board for all crane lighting circuits including warning lighting circuits. Distribution board for auxiliary circuits other than lighting circuits. Magnet circuits. b) Moving cab cranes Distribution board for bridge lighting circuits including warning lighting circuits. Distribution board for all crab lighting circuits. Distribution board of boards for auxiliary circuits other than lighting circuits. Magnet circuits. In fixed cab cranes, the crane lighting circuit isolating switch shall be connected directly to the long travel collectors and located in the immediate vicinity of the main isolating switch on the bridge.In moving cab cranes, the bridge lighting circuit isolating switch shall be connected directly to the live side of the main isolating switch with cables as short as possible. The switch shall be located on the bridge in the immediate vicinity of the main isolating switch. The crab lighting circuit isolating switch shall be connected directly to the cross-travel collectors and located in the immediate vicinity of the main isolating switch on the crab. 6.15 Distribution Board Metal clad distribution boards incorporating adequate protection in all lines, except those directly connected to earth, shall be provided as detailed below to
37
Doc:ME 14 (0916)c
feed the following auxiliary circuits where they exist. Distribution boards shall comply with relevant Indian Standards, except that semi-enclosed fuses shall not be used. a) fixed Cab Cranes: - One distribution board for crane lighting circuits as follows: - Cab service and maintenance lighting: cab and bridge approaches and electrical equipment compartment lighting; warning lights; in ac crane, the step down transformer supplying the socket outlets and walkway, and bridge lighting for illuminating the floor area. - One distribution board for cab heating circuits, fan and air conditioning circuits, if provided. b) Moving Cab Cranes: One distribution board for bridge lighting circuits, as follows: Warning or signal lights; in ac cranes, the step down transformer supplying the bridge socket outlets, and walkways and bridge lighting. One distribution board for crab lighting circuits, as follows: Cab service and maintenance lighting; cab and bridge approaches and electrical equipment lighting and in ac cranes, the step-down transformer supplying the crab socket outlets. One distribution board for cab heating circuits, fan and air-conditioning circuits. 6.16 Auxiliary switches other than Isolation switches 6.16.1Each auxiliary circuit shall be provided with a totally enclosed lighting switch component complying with relevant Indian Standard (See Appendix C). These auxiliary switches shall be located as follows: i. For the equipment in the cab, such as fans and air-conditioners; ii. For the electrical compartment lighting, at the door of the compartment; iii. For the cab approaches, bridge approaches, and bridge walkway lighting such that an operator can illuminate the approaches or walkways without traversing them iv. For the bridge lights on the crane bridge, at the crane entrance platform in fixedcab cranes and on the bridge in moving cab cranes; and v. Non-fusible double pole emergency switches should be connected in series for opening the circuit breaker or main contactors on the protective panel. 6.16.2These switches when ‘OFF’ will open both the main lines of the protective panel control circuit and will be located at the following places one in driver’s cab within the easy reach of the driver and one on each of the landing corners of the end carriages to be easily accessible to a person when boarding the crane or getting down from it. Additional switches shall be provided if found necessary and when asked for. 6.17 Identification of Circuits All switches and fuses shall be adequately labeled to facilitate the identification of the circuits. All panels, controller and resistors are to be properly marked for each motion. All main and control wires shall be ferruled at both ends, as per drawing for quick identification. All elements of the controller and panels are to be clearly marked by furnishing functional nomenclature at the devices. All equipment terminals shall be numbered and tagged.
38
Doc:ME 14 (0916)c 6.18 a
Disposition and Housing of Electrical equipment Electrical equipment other than resistor assemblies: If electrical equipment is mounted in the open, it shall be of the enclosed type in weatherproof enclosure with provision for easy access to the parts inside. b Control panels and other electrical equipment should be so located that there is no change for oil from the gear boxes, to drip on them. c The compartment or units shall neither impede the maintenance of the long-travel drives, nor be mounted on the bridge platform occupied by the cross-travel collector gear. The thoroughfare between the different parts of the crane or between any portion of the crane and the exit platform shall not entail passage through the compartment or be impeded by any control unit. d Control panels or units shall be so spaced that efficient maintenance may be performed, and shall withstand the mechanical forces imposed by the crane under service conditions. e The compartment shall be constructed of steel sections and plates, or other fireproof material of adequate mechanical strength. It shall be drip proof, adequately ventilated and lit, and in addition for outdoor cranes, weatherproof. If windows are provided, wired or toughened glass shall be used and it shall be possible to clean all glass surfaces without danger. f Resistor Assemblies: Resistor assemblies shall be so mounted as to ensure an adequate flow of cooling air and shall be mounted outside the main contactor compartment. g Resistor assemblies shall not impede the maintenance of the long-travel drives or access to the platforms of the crane, and shall be arranged so that efficient maintenance may be performed on each unit. h Resistor assemblies for each motion shall be stacked separately for the facility of inspection, maintenance and safety. 6.19 SAFETY FEATURES 6.19.1 Motor over speed protection All electronically controlled hoisting motions shall be equipped with over-speed protection. The over-speed protection shall prevent a) uncontrolled and unintentional motions and b) all parts of the mechanism from reaching its mechanical limit speed. The trigger limit of the over-speed protection shall be set so that the mechanical brake is capable to stop the motion safety in all conditions. In general, the trigger limit should not exceed 1.15 to 1, 2 times the specified speed at nominal load.This protection can consist, for example of a centrifugal switch or speed limit monitor. The speed switch c an either be attached to the encoder (mounted on the motor) or at the Hoisting drum. Speed encoder for over-speed sensing is to be provided to avoid free fall of the load specifically for hot metal handling cranes.The emergency stopping with any possible speed and load combination shall not cause any hazard including the cases where the drive is intended to operate above the nominal speed. 6.19.2 Devices for switching off for prevention of un-expected start up. Devices for switching off for the prevention of un-expected start up shall be provided. The Main Incoming switch (crane-disconnector) fulfils that function for the complete crane.Where it is necessary to work on individual parts of a crane motion, additional disconnecting device shall be provided for each part requiring separate disconnection.
39
Doc:ME 14 (0916)c
Disconnectors, withdrawable fuse links, contactors can be used as hardware. Alternatively this protection can be provided by VFDs, in accordance with IEC 6020432, sec 5.4. If the discharge of stored energy would significantly restrict the availability of a machine, additional devices must be installed to reliably buffer the remaining energy“. For instance, this involves a multi-motor drive with inverters connected to a common DC link. In this case, suitable resources must ensure that the “stored energy“, i.e. the energy stored in the DC link capacitors of the individual inverters, is reliably buffered with the DC link voltage still available. 6.19.3 Limit Switch 6.19.3.1 Limit Switches in Hoist Motion a) Cranes with dc-series motors: The final switches to be provided in the power circuit shall be of self-resetting type and shall initiate dynamic braking when tripped. If specified by the user, provisions shall be made in the control circuit to have an audio-visual annunciation to indicate that the final limit switch has operated. b) Cranes with ac-Motors: The final limit switch, which shall trip the main incoming breaker/contactor, shall be of manual reset type, if used in the control circuit. Provision shall be made to by-pass the limit switch temporarily for emergency lowering of hot metal. While by-passing only lowering motion shall be possible. c) In case where final limit switch is used in the power circuit the same may be of manual or self-resetting type. If self-resetting type is used, there shall be a provision for audio-visual annunciation to indicate its operation, if specified by the user. d) If the ultimate limit switch is shunt-connected it shall control the protective panel circuit breaking device. No two-shunt limit switches shall control the same circuit-breaking device. e) If occasional abnormally high lifts are required, arrangements may be made (if specified in B-6.5 (f)) for by-passing the first limit switch. Under such condition, hoisting should be possible at slow speed only when by-passing button is kept pressed. 6.19.3.2Track Limit Switches:
If specified, one or more track switches shall be fitted to the bridge to give warning of approach to a danger area. They shall be operated by suitable devices to be fixed to the crane gantry as required and shall either operate an audible warning signal or trip the main circuit-breaker on the crane, as specified in Appendix B. Track switches shall be so arranged that they can be readily tested. Strikers shall be so arranged as to prevent damage of the limit switch on over travel due to impact. 6.19.3.3 Proximity sensing / Anti-Collision devices If specified, one or more devices shall be fitted to the bridge of the crane to give warning of the approach to danger, or another crane. Anti-collision devices are relevant to safety. Their failure will result in high impact forces, which may cause damage to the loads
40
Doc:ME 14 (0916)c
transported or to system components, or personal injuries. Strict requirements are to be met with respect to reliability and safe functioning of anti-collision devices. They shall be failsafe under the specified environmental conditions (such as temperature limits, dust, alternating electromagnetic fields). Note that “emergency stop functions” of electrical limit switches can be realized using mechanically actuated switches which function according to the positive-opening principle. Non-contact or proximity limit switch systems only afford the desired operational reliability if combined with a safe circuit including self-monitoring and plausibility check. Where the “emergency stop function” is undesirable, monitoring devices will be required for clear and unambiguous indication of any fault. 6.19.4 Safeguarding motors against overheating Motor overload protection shall fulfill the requirements of relevant Indian Standards. Protection methods based on actual temperature measurement of the motor are preferred. The overload protection can also be implemented b y electronic devices, which may be either separate devices or integrated in the control or drive unit. 6.19.5 Over-current protection of conductors All conductors are required to be protected against over-current by protective devices inserted in all live conductors so that any short-circuit current flowing in the cable is interrupted before the conductor has reached the maximum allowable temperature as per the relevant Indian standards . For example for PVC insulated conductors with a working o o o temperature of 70 C, the conductor is heated from 70 C to 160 C with the short circuit current duration not exceeding 5 Sec.For selection of the correct protective device for switching off in case of a short circuit, refer sec 2.1.6.1 The cross-section of a conductor should be determined according to the current intensity to which it is subject during both normal running of the motor and starting-up or electrical braking. Whether the loads (motors) are overload protected or not, all wires should be safeguarded against any over current, which could result from a short circuit or faulty insulation. The protective device shall be rated for the anticipated short-circuit currents. 6.19.6 Safeguarding against absence or inversion of phases Where an incorrect phase sequence of the supply voltage can cause a hazardous condition or damage to the hoisting machine, protection should be provided. If the absence of phases may occasion a danger, the appropriate safety measures must be taken. 6.19.7 Action of safety devices When several motors drive the same motion, the action of a safety device should stop all of the motors for this movement. After a safety device has been activated, it should be possible for the equipment to be started up again only manually. 6.19.8 Protection against the effects of lightning: For very tall pieces of hoisting equipment which are erected in particularly exposed locations, the effects of lightning must be considered. on pieces of vulnerable structure (for example: jib support cable)
41
Doc:ME 14 (0916)c
-
on anti-friction bearings or runners which form a link between large parts of the frame (for example: slewing rings, travel runner) When necessary, safeguarding against the effects of lightning should be carried out e.g by following IEC 61024-1. For the safety of personnel, it is recommended that the runner rails for the lifting equipment are earthed. 6.20 DESIGN AND SELECTION OF MOTORS 6.20.1 GENERAL The following details needs to be checked by the Crane designer while selecting the motors for the corresponding motions. The selection and testing of the motors shall be as per IS 325. Required power (thermal rating of the motor) Required maximum rated torque and maximum acceleration torque. (considering motor & load GD 2 values) Cyclic duration factor Number of cycles per hour Type of control (includes type of electrical braking also) Speed regulation Type of power system Ambient temperature Altitude In order to carry out the thermal calculation, the R.M.S (mean equivalent) torque must be calculated as a function of the required torque during the working cycles, by using the following method:
M RMS =
M 12 * t1 + M 22 * t 2 + ......... + M N2 * t n
Where: t1, t2 … t n
M1, M2 ….Mn
t1 + t 2 + ............ + t n are the durations of the time periods during which the motor develops the different torque values as required by the load. The periods of rest are not taken into account. are the calculated required torque taking into consideration the effect of load and motor rotor inertia.
The Cyclic Duty Factor (CDF) is defined by :
CDF =
Operatingtime operatingtime + Idletime
X 100[%]
The operating time and the number of operations per hour of the motors as well as the number of working cycles for the crane are important factors while designing the motor thermally. The number of operations per hour is defined by the User and agreed by the Crane Manufacturer. This is not same as the “Number of starts per hour” which by Definition takes into account the heating caused inside the motor or the temperature rise due to the Starts, Inching and Braking (plugging).
42
Doc:ME 14 (0916)c
Typically with a convention crane using Slip ring motors, one Inching is considered as 25% thermal equivalent of a start and one plugging braking is considered as 80% thermal equivalent of a start. With VFD fed motors, the motor manufacturers should define intermittent S3 ratings for 25%, 40% and 60% CDF. The number of operations per hour (or starts per hour) factor can be neglected due to the soft start feature of the electronic controller, thereby restricting the starting current and the starting losses. However it is left to the motor manufacturer to define these ratings according to their own design. If the required torque diagrams are not available to define the mean equivalent torque (RMS), the values mentioned in table 5.8.3.2 a can be assumed to carry out the calculations. In any case the mechanical computed kW must be the minimum motor rated kW. When the motor is fed from electronic based power control, the motor selection has to be made in consultation with the motor manufacturer taking into account the following factors:-
Motors fed from VFDs can deliver higher power compared to the S1- rating when operated on intermittent S3 duties. It is recommended that the motor manufacturers should publish the motor ratings at the various different CDF factors, i.e 25%, 40% and 60%. These should be considered for the optimum selection of the motor. Special insulation system for high dv/dt (typically available from VFDs) Insulated bearings for frame size > 280 / 315 is recommended for protection of the motor against bearing currents arising due to the shaft induced voltage due to high frequency waveform. The following shall be considered when two or more mechanism drive the same motion. The static and dynamic synchronisation of the motions according to the needs of the application. Necessary interlocks between the mechanisms to ensure safe operation. Both the static and dynamic asymmetrical loading of the mechanisms needs to be carefully considered and the adequate dimensioning of the motors and other drive components. 6.20.2 SELECTION OF MOTORS FOR HOIST MOTION For hoisting motor the power required shall not be less than that computed from the following:
kW
=
M X VXC
V
C d f
6.12 X E
X
1 C
am b
Where dc rating factor will be taken as 12 percent. kW = one hour power rating for dc motors and power rating M = mass of the rated load on the hook plus weight of the hook block and the wire ropes in tones. V = specified hoisting speed in M/min or actual gear box output speed which ever is higher. E = combined efficiency of gears and sheaves = (0.93)n x (0.98)m for sleeve bearings = (0.95)n x (0.99)m for anti-friction bearings (for spur and 43
Doc:ME 14 (0916)c
helical gears. Efficiency to be taken as 0.95 per reduction) = (0.985)n x (0.99)m for hardened profile ground and oil splashed lubricator. where n m
= number of pairs of gears = total number of rotating sheaves passed over by each part of the moving rope attached to the drum, Cv = service factor for vertical motion depending on type of motors, = 0.67 for ac motors = 0.5 for dc motors Cdf = duty factor as defined in 7.4.3 and Camb = derating factor for ambient temperature as given in the Table 20 A Note: 1 Selection of motors should also be cross checked with respect to load GD2 of the selected frame, average starting torque and accelerating time of motion mechanism. c) Mechanical computed kW must be the minimum motor rated kW. Table 20A Ambient temperature for Derating Factor Ambient Temperature Derating Factor, Camb 1.0 45° 0.95 50° 0.9 55° 0.82 60° Table 20 B – Values of Co-efficient, (Clause 7.4.3)
Group Classification of Mechanism
For Mechanism used for horizontal motion
For mechanism used for vertical motion
For mechanism used for vertical motion with people or while handling dangerous for example, molten metals, highly radioactive or corrosive products
M1 M2 M3 M4 M5 M6 M7 M8
1.00 1.06 1.12 1.18 1.25 1.32 1.40 1.50
1.18 1.25 1.32 1.40 1.50 1.60 1.60 1.70
1.32 1.40 1.50 1.60 1.70 1.80 1.90 2.00
Table 20 B Recommended Cyclic Duration Factor and Starting Class (Clause C.1) Duty cycle Recommended Starting class Mechanism number cyclic duration © class of cyclic class © factor percent equivalent cycles/hour starts/hour
44
Doc:ME 14 (0916)c
percent
M1 M2 M3 M4 M5 M6 M7 M8
6.20.3 6.20.3.1
Upto 5 Cycles 25 Upto 5 Cycles 25 10 Upto 15 Cycles 40 16 Upto 20 Cycles 40 21 Upto 30 Cycles 60 31 Upto 40 Cycles 60 41 Upto 50 Cycles 100 51 Upto 60 Cycles 100
25
90
25
90
25
150
25
150
40
300
40
300
60
300
60
300/600
MOTOR FOR CRANE TRAVEL OR TROLLEY TRAVERSE General
It is assumed that the drive mechanism from the motor to the track wheels will used enclosed gearings mounted on anti-friction bearings. The actual efficiency of the drive will be adopted in making calculations. Where actual efficiency values are not available the efficiency of the drive shall be taken in the range of 0.85 to 0.9. For the track wheel with anti-friction bearings the rolling friction at these bearings plus the friction between the track wheels with an average drive efficiency of 0.875 will give an overall friction factor of 8.0 kgf per tonne of the mass moved for calculation of the motor horse power or torque. In the case of wheels with the plain bearings an overall friction factor of 13.0 kgf per Tonne of the mass moved may be used. 6.20.3.2
Selection of motors for crane travel or trolley traverse
For bridge travel or trolley traverse the power of the motor required shall not be less than that computed from the following:
kW = kW =
M X V X S X C d f ⎡ 1 1 0 0 X a ⎤ + F for indoor cranes ⎢⎣ 6117 XT 9 8 1 X N ⎥⎦ M X V X S X C d f ⎡ Rw XV 1 1 0 0 X a ⎤ + + F for outdoor cranes. ⎢⎣ 6117 XT 9 8 1 X N ⎥⎦ 6117 XT
45
Doc:ME 14 (0916)c
Where kW = one hour power rating for d.c motors and power rating at 40 percent cyclic duration factor for a.c motors. M = mass of crane or trolley plus mass of max rated load in tones; V = specified free running speed M/min or actual gear box output speed which ever is higher. N = mechanical efficiency of gearing. For spur and helical gears it can be taken as 0.95 per reduction. T = factor introduced by the permissible motor torque during acceleration exceeding the motor-rated torque. = 1.7 for a.c Slip Ring Induction motors = 1.3 for d.c motors = 1.6 for a.c motors , fed from DOL = 1.5 for a.c motors when operated from VFDs F = over all friction factor = 8 kgf per tonne for wheels on anti-friction bearings = 13 kgf per tonne for wheels on plain bearings C df = duty factor as defined in 7.4.3 RW
=
load due to service wind acting horizontally as defined in 7.3.1 which can be obtained by multiplying the horizontal exposed area by the service wind by taking drag co-efficient into consideration. a = average linear acceleration of the crane or the trolley in cm/s2 till the mechanism reaches 90 percent of free running speed. For the values of average linear acceleration refer as given in Table 21A; and S = service factor aimed at providing adequate motor heat dissipation capacity as given in Table 21B. Table 21 A – Acceleration Values (Clause C-2.2) Acceleration in Speed to be reached Condition cm/s2 for High M/min speed with High acceleration 240 -50 67 190 -44 58 150 -39 52 120 22 35 47 100 19 32 43 60 15 25 33 40 12 19 -25 10 16 -15 8 --10 7 --Table 21 B Values of Service Factors Bridge Service Factor
46
Doc:ME 14 (0916)c
Troley Service Factor Without plugging 0.95 NOTES 1 2 3
4
5
6
7 8
With plugging 1.00
1.06
Duty cycle, recommended cyclic duration factors and recommended starting Class for the mechanism class can be taken from Table 20B. At free running speed the acceleration becomes zero. The gear reduction ratio actually used should be reasonably close to the ideal reduction ratio: Motor rev/min at free running = Track wheen rev/give specified running speed In order to limit the acceleration to the specified value and also to take full advantage of the service factor the electrical control should be designed to suit the values of ‘S’ and ‘T’ actually adopted or values of ‘S’ and ‘T’ should be selected based on electrical controls to be provided. Since the wheels must transmit all acceleration forces to the crane, to prevent wheel skidding due consideration should be given on percent driven wheels after acceleration rate has been fixed. The wheel skidding should be checked at no-load conditions considering 20 percent adhesion between wheel and rail. The skewing force arising during the running of the crane needs to be considered by the designer while designing / configuring the electronics controls. This is usually a function of the ratio of span to the wheel base. The gradients of the track and the necessary forces for CRD fed cranes has to be taken into consideration when designing the Travel motor. The horizontal forces arising due to the swaying of the load also needs to be considered for designing of the motor motor especially for a high load inertia.
5.8.22 CYCLIC DURATION FACTOR AND NUMBER OF CYCLES PER HOUR Table Indications for the number of cycles per hour and the cyclic duration factor for the vertical motions.
Type of appliance RefeRence
Particulars Concerning nature of use (1)
Designation
Number of cycles per hour
Type of mechanism ED% Lifting
47
Derricking Derric hinged king boom boom
Doc:ME 14 (0916)c
1
Hand-operated (=not motonsed) appliances Erection cranes Eraction and dismantling cranes for power stations, machine shops, etc. Stocking and reclaiming transporters Stocking and reclaiming transporters Workshop cranes
2 3
4
5
6 7
8 9 10
11 12
13
14
Hook duty
2-25 2-15
25-40 15-40
20-60
40
Grab magnet
or 25-80
60-100
Grab magnet
or 10-50
25-40
Overhead traveling cranes, pigbraking cranes Scrapyard cranes Landle cranes Soaking pit cranes Stripper cranes, open-health fumace-charging cranes Forge cranes a) Bridge cranes a-Hook or for unloading, spreat duty bridge cranes for containers. b-Hook duty b) other bridge cranes (will crab and/or slewing Bridge cranes for Grab or unloading, bridge magnet (with crab and /or slewing jib crane) Drydock cranes, Hook duty shipyed jib cranes, jib crarens for dismanting.
Table
48
S2 (2) 15-30 min S (2) 15-30 min
40-120
40-100 60
3-10 30-60 30 10
40-60 40-60 60 60
6 20-60
40 40-60
20-60
40-60
S (2) 15-30 min
20-80
40-100
S (2) 15-30 min
60 20-50
40
S (2) 15-30 min
40
Doc:ME 14 (0916)c Indications for the number of cycles per hour and the cyclic duration factor for the vertical motions.
Type of appliance RefeRence 1
2 3
4
5
6 7
8 9 10
11 12
Particulars Number Concerning of nature of cycles use per hour (1)
Designation Hand-operated (=not motonsed) appliances Erection cranes
2-25
Eraction and dismantling cranes for power stations, machine shops, etc. Stocking and Hook duty reclaiming transporters Stocking and Grab or reclaiming magnet transporters Workshop cranes Overhead Grab traveling cranes, magnet pigbraking cranes Scrapyard cranes Landle cranes
Type of mechanism ED% Rotation
Crab
Travel
25
2540 25
25-40
2-15
20-60
15-40
4060
25-40
25-60
40
60
15-40
2540 4060
25-40
4060 4060 40 40
40-60
25 4060
25 15-40
10-50
or 40-120
3-10
Soaking pit 30-60 cranes Stripper cranes, 30 open-health 10 fumace-charging cranes Forge cranes 6 c) Bridge a-Hook or 20-60 cranes for spreat duty unloading, bridge cranes b-Hook duty for 20-60
49
25
40
100 15-40
25-40
60-100
40-60 60 40
25-40
Doc:ME 14 (0916)c
13
14
15
16
17
18 19 20 21 22
containers. d) other bridge cranes (will crab and/or slewing Bridge cranes for unloading, bridge (with crab and /or slewing jib crane) Drydock cranes, shipyed jib cranes, jib crarens for dismanting. Dockside cranes (slewing, on gantry, etc.), floating cranes and pontoon derricks Dockside cranes (slewing, on gantry, etc.), floating cranes and pontoon derricks Floating cranes and pontoon derricks for very heavy loads (usually greater than 100) Deck cranes Deck cranes
4060
Grab magnet
or 20-80
40
40100
15-60
Hook duty
20-50
25
40
25-40
Hook duty
40
25-40
40
15-25
20
Grab magnet
or 25-60
2-10
Hook duty 30-60 Grab or 30-80 magnet Tower cranes 20 Derricks 10 Railway cranes 10 allowed to run in train
40-60
25-40
15-40
40 60 40-60 25 25
25
15-40
1) This column comprises only some indicatory typical cases of utilization. 6.21 DESIGNING THE CRANE CONTROLS The following Crane control schemes are used in the Steel Mill depending on the type of motor:
50
Doc:ME 14 (0916)c
a) b) c) d)
DC motor with Thyristor based controls. AC Slip ring motors with conventional controls using Rotor resistances and Plugging braking. AC Slip ring motors with Thyristor based controls. AC squirrel cage motors with VFDs.
6.21.1 CRANE CONTROLLING ARRANGEMENTS 6.21.1.1 General The type of controls to be used shall be as agreed between the manufacturer and the purchaser. Cranes having alterative control or brake circuit facilities shall be provided with means to prevent operation from more than one facility at any one time. Note: Main circuits are those which carry main motor or magnet current. Control circuits with brake circuit mechanism are those which are used for control equipment for main motor or magnet. Table 13 Brake Magnet operating currents and voltages (Clause 13.2)
Series
Shunt
Windings
Dc Magnets
Ac magnets
For series resistor control
Lift at 60 percent rated current.
--
Potentiometer control
Hold at 15 percent rated current Lift at 40 percent rated current. Hold at 15 percent rated current *Lift at 85 percent rated voltage. *Hold at 50 percent rated voltage
---
-*Lift at 85 percent rated voltage *Hold at 50 percent rated voltage
*This list intended to apply with hot coils corresponding to the duty cycle at rated voltages. The temperature rise of the brake magnet shall not exceed that allowed for the control equipment fitted. 6.21.1.2 Controllers Controllers shall be rated to comply with IS 8544 (Part 1 to 4). Controllers shall be suitably protected to prevent accidental contacts with the live parts. Controllers in ‘off’ position shall open all supply lines of the respective motors, unless otherwise agreed to, in which case a warning notice shall be fixed to the controllers. On or adjacent to each control device, there shall be a clear marking identifying the motion controlled and the direction of movement.
51
Doc:ME 14 (0916)c
a) Control equipment for dc Motors Contactors, switches and allied electrical components shall be selected on the basis of calculated power in (kW) of the motor. b) Control Equipment for ac Motors The selection of contactors shall be made on the basis of S 3-40 percent rating arrived after applying appropriate service factor to the computed power of the motor. The rating of the control gears such as switches, overloads, etc., shall be selected according to the computed motor power without the service factor of the motion served and not on the motor power computed by the thermal requirements.The contactors selected under 14.2.1 and 14.2.2 shall have the stipulated contact life as may be specified by the user. 6.21.1.3 Controllers provided in the cabin All control handles and pedals shall be placed in convenient position to allow the driver ample room for operation and permit an unrestricted view of the load. They shall be so disposed that the contacts and terminal arrangements are readily accessible for inspection and maintenance purposes. The controls should be so arranged that the operator has an adequate view of the crane’s working area. The control for hoisting appliances shall preferably be arranged on the right-hand side of the operator’s seat. - Marking Direction of operation of controllers Where practicable controller handles shall move in the direction of resultant load movement. Each controller shall be marked in a permanent manner to show the motion controlled and direction of movement. For vertical lever, handle operating hoist controllers, movement towards operator shall indicate hoisting and movement away from operator shall indicate lowering. - Notching The notching for the controller handle in the ‘off’ position shall be more positive than the notching in other positions. The handle may be provided with a lock, latch, dead man or spring return feature if specifically requested by the customer. The control lelver shall be provided with stops and/or catches to ensure safety and facility of operation. A controller drum fitted with a star wheel shall be regarded as complying with the requirement. - Master Controller Master controller operated cranes shall be provided with automatic control of acceleration. Accelerating torque/current peak shall be limited during controller handle movement from one notch to the other with due consideration to the pullout torque of the motor and number of rotor accelerating contactors shall be selected accordingly. For master control operated cranes the control voltage preferably 110 ac and shall not exceed 240 for ac or dc supply. 6.21.1.4 Pendant controllers Cranes with pendant controls shall not have long travel speed in excess of 40 m/min. Pendant control may directly descend from the crab or from the independently traveling trolley or from a convenient position on the crane bridge. Push-buttons or other switching devices, which automatically return to their “off” position as soon as they are released, should be provided for the control of all motions by pendant control units. Housings of pendant control units should preferably be of fully insulating material or of material with protective insulation. Metal parts accessible from the outside, which pass through the
52
Doc:ME 14 (0916)c
insulation, should be separately earthed. The surface of the housing must be a vivid color. For indoor operation, the degree of protection should be at least IP43, and for outdoor operation at least IP55. Pendant control units shall be suspended with a strain relief arrangement. - Pendent switches The pendant switches shall be capable of withstanding rough handling without being damaged and the cover shall be effectively secured. If control is from the floor, the electrical control circuit to the pendant shall be energized at not more than 110V dc or ac supply. - Pendant control On all pendant controlled cranes means shall be provided to prevent inadvertent operation from the floor while maintenance work is being carried out on the crane. An isolator fitted on the crane bridge, which can not be operated from the floor will comply with this requirement. - Pendant control station If the control is by push buttons or switches, they shall automatically return to the ‘off’ position immediately after they are released. One lockable type push button shall be provided to switch off control power when the crane is not in use and if other means of switching off is not available. - Suspension of pendant switch The weight of the pendant shall be supported independently of the electric cables by means of chain or wire rope. If the pendant enclosure is of metal it shall be effectively earthed. A chain or hook does not provide effective earth connection. 6.21.1.5 Remote Control a) Main features of radio control system consist of: - A portable transmitter, - An antenna and receiver on the bridge, and - An intermediate relay panel on the bridge to amplify the signals for the crane contactors. b) Radio controls should be designed so that if the control signal for any crane motion becomes ineffective, that crane motion will stop, and conversely signals received any source other than the transmitter will not result in operation of any motion of the crane. The crane must not take off on its own or respond to or generate false commands. In case electricity failure occurs, the crane must stop. - A key switch or equivalent security device on the transmitter that can be used to prevent unauthorized use of the transmitter. - The sending of a continuous or continuously repeating secure signal when transmitter is in use, which the crane receiver can identify. A secure signal includes atleast three characteristics separately recognizable by the receiver. - An emergency stop device shall be used for emergency stop. - A carrying harness, belt, shoulder straip or lanyard on the transmitter. c) The arrangement of the operating levers on the radio transmitter should conform to Fig 2A. The manufacturers should supply motion switches with different shaped knobs so
53
Doc:ME 14 (0916)c
that the motion can be selected by feel and the operator’s vision remain on the load. Modular construction shall be preferable for easy replacement. d) Typical frequencies used for radio controls are in between 450-470 MH for which license is required. The recommended crane controls for operating are of maximum 250 metre range. Radio crane control transmitter lever arrangement are of four motions, namely, are given below: Bridge X O W
Trolley Y O Z
Main Hoist Down O Up
Aux. Hoist Down O Up
Radio crane control transmitter lever arrangements are of three motions, namely, are given below: Hoist X O W
Bridge Y O Z
Trolley Down O Up
Notes: 1. Markings on the crane visible from the floor, shall indicate the direction of bridge and trolley travel corresponding to the W, X, Y and Z designations on transmitter. 2. The maximum working range of radio control shall be limited to 40 – 50 m from the transmitter. This limitation reduces the likelihood of an accident caused by the crane operating beyond the operator’s visibility. 3. It is recommended that a device is fitted to the crane to give warning that the crane is under non-conductive control. 4. Incorporate a limited range feature, present by means not available to the operator so that the crane will stop when the extent of that range is reached. 5. If more than one crane are provided with this type of controls, only the intended crane and its motion is operated at one time. The transmitter shall be constructed so that it is capable of withstanding rough handling. Remote control may be by means of radio or infrared transmission or an off-crane control station connected to the crane through wiring. The control station may consist of pushbuttons, master switches, computer keyboards or combination thereof. For definition of remote control, see the applicable ASME standards. The selection and application of the remote control system shall be done to assure compatibility between the remote control and the crane control system and eliminate interference. When more than one control station is provided, electrical interlocks shall be included in the system to permit operation from only one station at a time. Electrical interlock is defined as effective isolation of the control circuits with the use of rotary switch contacts, relay contacts or with the use of a programmable logic controller and its input/output modules. Due
54
Doc:ME 14 (0916)c
consideration should be given to elimination of interference between electronic signals and power circuits. This includes physical and electrical separation, shielding, etc., Due consideration should also be given to the following: - Operating range of the remote control equipment - Operating speeds of the crane. - Application of end travel limit switches. - Wiring of magnet and vacuum circuits to the line side of the disconnecting means and use of latching controls. 6.21.6 Resistors 6.21.6.1 General Resistors shall be adequately protected to prevent accidental contact with live parts. Resistors shall be rated such that the temperature does not exceed the limits specified in the relevant Indian Standard specification, during the operation of the crane under service condition. The resistance and the current capacity of the resistors shall be computed according to the actual torque requirements of the motion served and not on motor size which may be set by thermal requirement. The effect of using plugging as a service brake shall be taken into account in determining the size of resistors.Resistor shall be rated according to the service conditions and the class of crane as specified by customer. 6.21.6.2 Fittings Resistors shall be enclosed in well-ventilated housings and, wherever necessary, be fitted with suitable covers. Resistors shall be mounted on frames and protected and arranged in such a way that the boxes can be easily replaced. Frames shall be of steel and shall be built to withstand mechanical forces imposed by the crane under service conditions. The connections to resistor terminals should be accessible and should have provisions for adjustment. Resistor elements shall resist corrosion and shock. 6.22.2 CRANE CONTROLS 6.22.2.1 Thyristor control – Main features are as under: a) The Thyristor shall be protected by fast acting semiconductor fuses having 12 x t value considerably lower than that of the Thyristor. These fuses shall be continuously of any fuse shall result in tripping of the power circuits. b) The thyristor shall be suitable to carry at least 200 percent of the drive motor current rated 53-4- percent. The PIV of the thyristor shall by 2.5 times the system peak voltage appearing across the thyristors. The factor 2.5 ;has been selected taking into account the line voltage variations.
c) Each thyristor shall be protected by RC snubber circuits so as to absorb the surges generated out of external line surges in consultation with the user. d) The drive system shall be protected against overload by means of thermal overload or oil dash pot of magnetic overload type with inverse characteristics having adjustable setting range. It shall also be protected against over current by means of instantaneous acting over current relays having a setting range of 200 to
55
Doc:ME 14 (0916)c
e)
f) g)
h)
400 percent of the drive rated current. Solid state overload protection may be used subject to the agreement of the purchaser. Preferably thermal overload protection to be used instead of magnetic overload relays as the thermal overloads have a reset time which would prevent the drive from restarting back immediately. Switching-off of reversing contactors shall be done at near zero current. This is to be done by ensuring that the stop/tripping command first inhibits the thyristor controller and then switches ‘off’ the reversing contactors. This requirement will not be applicable if the reversing is through thyristors. In the case of overloading or the single phasing of the synchronizing supply, the circuits shall be tripped immediately. Whenever armature reversal (in case of the dc drive) or stator reversal (in case of the ac drive) is to be done through the reversing contactors, the drive shall be protected against the free fall conditions at the time of switching on and reversals by having the preferred switching state of the reversing contactor. The drive controller shall have suitable provisions for preventing load drifts at the time of start and stop. For achieving smooth acceleration of the drive mechanism suitable ramp generator circuit shall be available with the controller.
i) Wherever necessary, suitable de-ration would be considered for a.c / d.c motors in consultation with the thyristor controller manufacturer and the motor manufacturer. j) The control circuits shall be so designed that the brakes are applied at around the zero speed. k) Test points shall be available in the cards. l) In case of wide deviation of the speed in actual value from the set value, the circuit shall trip the mechanism immediately. During acceleration or deceleration period such tripping shall be prevented by adjustable time setting. m) Thyristor control shall be suitable for operation at vibration levels and environments encountered in the crane operation. n) If specially required by the purchaser, the drive motor shall be protected against overheating by means of thermistors embedded in the motor winding. Matching thermistor for trip relay shall be provided by in the control panel. The embedded thermistors are best for preventing overloads and subsequent overheating of the motor as these thermistors give the correct thermal image of the motor irrespective of the current carried. o) Wherever a.c phase controllers are to be paralleled for load sharing, the converter outputs shall be paralleled only at the load end and not at the converter end. 6.22.2.2 Special Protection for Direct Current Drive System a) To minimize excessive rate of rise of armature current and radio frequency interference, commutating chokes with sufficient inductance shall be provided on the ac side so that PU (inductive drop) across the choke lies between 2 to 4 percent. Where isolating transformer is used, commutating chokes are not necessary.
56
Doc:ME 14 (0916)c
b) To prevent excessive wear and tear of the commutator, the ripple content of the dc output shall be minimized by providing smoothening chokes of sufficient inductance depending upon motor design. c) In case of the quadrant drives, to protect against inverter commutation failure during regenerating mode, branch thyristor fuses shall be used. However, where it is not possible to use branch thyristor fuses, there shall be at least one fast acting semiconductor fuse on the dc side of the converter in addition to the semiconductor fuses on the ac side. d) While switching on the system, the following sequence shall be adhered to: - Synchronizing supply is switched ‘ON’ - Field circuits are established, and - ac/dc contactors are switched ‘ON’. e) The drive shall be protected against field failure with suitable circuits. f) The field current shall be reduced to a safe value during the crane idling time to reduce the heating of the motor. The normal field current shall resume at the start of the drive operation. 6.22.2.3 Thyristor controllers for Slip ring motors The thyristor controller should be a dedicated controller for crane application. It should be with Microprocessor based closed loop, thyristor controlled adjustable AC voltage control. The current rating of thyristor drive shall be selected corresponding to F.L. current at electrical kW. Rating of each thyristor (ie. Itan ) shall be minimum 0.45 times Irms. The current rating of Rotor contactors and Resistance grids shall preferably be about 125 % to 150% of rated current (depending upon minimum speed required to achieve) which may be confirmed by thyristor drive manufacturer. The thyristor controller should be rated at maximum of (+) 65º C and should be operational for a supply voltage variation of –15% to (+)10%.The commissioning and trouble shooting should preferably be done through the in-built key pad on the drive for ease of operation and maintenance in Steel plant cranes. If possible the Key Pad should be detachable type with provision to store the drive data sets and parameters, allowing User flexibility to upload / download data. However provision for programming / trouble shooting from LAPTOP / PC should also be available. 6.22.2.4 Variable Frequency Drives 6.22.2.4.1
57
Doc:ME 14 (0916)c
When asynchronous motors are fed from VFDs , the speed can be changed by changing the frequency of the supply (to the motor) . Up to, the base speed / frequency of the motor (50 Hz) , the constant flux is maintained - thereby allowing the motor to deliver constant torque through out the range from 0-50 Hz. The complete Pull Out Torque of the motor is available at the time of starting. The normal Torque speed characteristics of the motor (at 50 Hz) shifts towards the origin with the lowering of frequency. In the field weakening region above the nominal motor speed / frequency , the motor’s rated torque decreases proportional to the increase of frequency and the maximum torque (Pull Out Torque) decreases inversely proportional to the square of the speed. Note: If the motor is loaded up to the Pull Out Torque or too close to it , there is a risk of getting into an unstable situation. It is recommended to use 30% margin on the P.O.T when selecting the motor for the maximum torque requirements. 6.22.2.4.2 VFD selection a) The VFDs selected for crane application should be IGBT based, PWM vector controlled drives.
b) Inverter selection shall be based on inverter manufacturers recommendation given due consideration of the following: - Application. - Power factor and efficiency of the motor at the load point . - Power supply - Actual current at mechanical load - Operating ambient temperature c) VFDs should always be selected based on the current rating (rated current) mentioned in the manufacturer’s catalogue. In case of dual rating of current mentioned in the catalogue, the current rating corresponding to “Constant Torque” or “Heavy duty” should be selected for Crane applications. d) The continuous current rating of the VFD shall be at least equal to the motor current at the highest speed maintaining torque. The current required by the motor at any foreseen loading, including dynamic situations shall not exceed the short time rating of the VFDs. e) The squirrel cage motors shall be of inverter duty. These motors may not be suitable for DOL starting, hence same shall not be used for direct online starting with bypassing VFDs. f) VFDs shall be provided with dynamic braking function or fully regenerative capability.
58
Doc:ME 14 (0916)c
g) VFDs shall be provided with proper branch circuit protection on the line side. h) Distorted waveforms on the line and/or short circuit current may require the use of Line Reactors, isolation transformers or filters. i) Line contactor shall be used with VFDs for hoisting applications to disconnect power from drive in case of overspend or fault. j) A minimum of two collectors for each runway conductor shall be furnished with inverter use. k) The cranes using VFD controls shall adhere to the crane safety standards mentioned by IEC 60204-32 6.22.2.4.3 Dynamic Braking selection for VFDs.
For the Hoisting motion, the braking occurs when the load is lowered . The braking resistor of a hoisting drive shall be selected considering the possible lowering height of the load being lowered at the maximum speed. The calculated regenerative energy and the lowering time can be used for designing the Braking resistor.The Hoisting drive should preferably have the flexibility of connecting external Braking units (IGBT based) along with the resistors.For horizontal motions, the braking resistor shall be capable of absorbing the regenerative energy during deceleration of the motion also taking into account the possibility of a swinging load and the wind push (the load and load attachment included)The braking resistor shall be thermally capable to absorb the generative energy during successive drive cycles of the application. NOTE: The braking resistor is usually connected to the DC-bus of the inverter and due to this it becomes live always when electric power is supplied to the inverter – also during not running the motor. 6.23 BRAKING 6.23.1 ELECTRO MECHANICAL BRAKING 6.23.1.1 General Brakes shall be provided for each drive. At least one brake shall be mounted on the input pinion shaft of the gear train.Cranes, which require particular safety, e.g. in steel works or with dangerous or melted loads, should be provided with a second brake.The operation of the second brake shall be arranged according to the design of the drive. It is recommended that under normal operating conditions, the second brake is always be applied on stopping, after the motion has been brought to a halt by the main brake. In some applications –for example if waiting for the releasing of the second brake would cause unacceptable time delay at each starting – it may be necessary to apply the second brake only when the crane switch (main contactor) is de-energized.In the event of an emergency stop, the second brake should be applied immediately. 6.23.1.2 Hoist Motion
59
Doc:ME 14 (0916)c
Electro-mechanical brake/brakes used for hoist motion shall apply automatically when the power supply fails or when the circuit brake is opened or when the controller handle is brought to the ‘off’ position. For hoists not handling molten metal and having single drive only the minimum braking torque shall be 150 percent of computed full load torque when the brake is fitted. When two brakes are fitted each shall have braking torque not less than 100 percent of the computed full load torque. Hoists handling molten metal shall have two brakes on each drive and each brake shall have minimum braking torque of 125 percent of computed full load torque.For dc-cranes having series motors when two brakes per motor are used, brakes will also be series brakes and connected in series. For accranes when two brakes per motor are used, the second brake may be fitted with a time lag in which case the braking torque shall not be less than 125 percent of the computed full load torque for each brake. 6.23.1.3 Braking path The braking path of the hoist motion should be within the distance given below with all the brakes applied simultaneously, except the effect o f brakes with time lag:
Speed of Hoist - v [ metre/minute] v<6 6 < v < 12 v > 12
Braking Path Max [metre] v/100 v/120 v/150
6.23.1.4 Long Travel and Cross Travel Motions Each drive shall be fitted with an electro-mechanical brake having braking torque not less than 100 percent of computed full load torque. Braking torque shall be checked so that it is capable of arresting the motion within a distance in metres equal to 10 percent of speed in metres/minute when traveling with rated load at rated speed, provided there is no skidding. Long travel motions of outdoor cranes shall be provided with an additional storm brake. The combined braking torque of the service brake shall not be less than the skidding torque assuming a coefficient of friction (µ) = 0.2.For long travel drives anchoring device shall also be provided for outdoor cranes in addition to storm brakes. All other motions such as slewing shall be provided with effective braking system which can be applied in an emergency or would be applied automatically in the event of failure of power supply. 6.23.2 ELECTRICAL BRAKING In addition to specific requirements of this code in regard to the provision of electromechanical brakes, and irrespective of the supply current system, electrical braking is permissible and recommended on all motions of electrically operated cranes. When electrical braking is used, provision shall be made to limit the current on reversal to a safe value. Effective means shall be provided for stopping the motion in the event of power failure and in the case of emergency. 6.23.3 BRAKE MAGNET COILS All magnet coils shall be fed from dc supplies, and the rating of brake magnet coils shall be as given in Table.
60
Doc:ME 14 (0916)c
Table BRAKE MAGNET COIL RATINGS Winding Brake Duty Rating Conditions (with economy resistance Shunt Emergency inserted where necessary Intermittent operation, Shunt One hour any motion Series Hoist Half an hour
The brake shall operate at the voltage and current values specified in Table2. Shunt magnets shall meet the requirements when the coils are at a temperature which corresponds to energization under rated conditions. Table 2. BRAKE MAGNEET OPERATING VOLTAGES AND CURRENTS WINDING DC MAGNETS AC MAGNETS Lift at 80 % rated voltage. Hold at Lift at 80 % rated voltage. Hold Shunt 50 % rated voltage at 50 % rated voltage For series Lift at 40 % rated current resistor Series or Hold at 15 % rated current potentiometer control
The temperature rise of coils shall not exceed that permitted by relevant Indian Standard for the class of insulation employed. Note: Brake Surfaces: The rubbing surfaces of brakes shall be smooth and free from defects. The temperature attained by the rubbing surfaces under service conditions shall be such that their operation is not impaired. C FLOOR CONTROL: C. Within Control features: C 1 Control circuits: If the mains supply is ac and the control circuits are supplied at reduced voltage, the supply to these circuits shall be from the secon dary winding of an isolating transformer or an isolating transformer and rectifier. The transformer frame and one pole of this supply shall be earthed and the contactor and relay coils shall be connected to this pole. An earthed screen shall be provided between the primary and secondary winding. The primary winding and unearthed pole of secondary winding of the transformer shall be protected by fuse in line connection. Effective means shall be provided to prevent maloperation owing to short circuits or earth faults. C 2 Rectifiers: On ac cranes, if dc supply is required, rectifiers shall be provided for supplying the control circuit, brakes and magnets. These rectifier units shall be of adequate capacity to supply the full dc loads required continuously. They shall be of suitable construction and mounting to withstand heat, dust, shock and vibration. Silicon type rectifier units shall be
61
Doc:ME 14 (0916)c
preferred. Adequate fuse protection shall be provided for the rectifiers. Rectifiers/thyristors used for magnets shall be protected against switch surges. C 3 Control for dc supply: When a dc supply circuit is used, motor acts as a generator in the lowering direction, the control shall be such that: a) Motor shall not exceed a predetermined maximum revolutions per minute. b) Progressive degrees of braking is provided, c) Adequate light hook lowering speed is provided, d) Brake is prevented from being released by back emf of the motor when power supply is interrupted, and e)Electro-mechanical brake is automatically applied when circuit breaker or contactor is opened. C4 Braking controls: When an electro-mechanical brake is used as an emergency or parking brake or when such an emergency or parking brake is used with hand or foot operated travel service brakes, the brake actuating device shall remain in the circuit when the main ckircuit breaker is closed. The brake shall apply automatically when the power supply fails or when the circuit breaker is opened or on operating an emergency stop push button or switch; but not when the controller handle is brought to the ‘off’ position. The brake shall lift off when voltage at the coils is a minimum of 85 percent of rated voltage. Provision shall be made for emergency application of this brake by means of the emergency stop push button or switch. In the arrangement of connections to the hoisting motion brake coils, means shall be provided to ensure that when associated drive motors are deenergized, the stores electrical energy in these motors will not delay the application of the brake. C 5 Acceleration control: Automatic control of acceleratxion shall be provided for all crane motions, unless for any motion another control system is specified. The hoist motion circuits shall enable any load to be lowered with safety and the hoist motors shall remainunder effective control with the controller in all positions. While calculating the number of rotor contactors, peak accelerating/decelerating torques and pull out torque of the motor should be taken into account. For creep lowering speed on hoisting motion, relatively flat speed control shall be provided. Peak accelerating/decelerating torque shall be considered as minimum 180% of full load torque for crxanes under M6-8 mechanism class. 6.24 AUXILIARY ELECTRICAL EQUIPMENT 6.24.1 LIGHTING 6.24.1.1 Cabin A fixed non-dazzling service lighting should be provided, so arranged that only the necessary illumination for the lighting of the control equipment is provided. When the general area lighting equipment is not sufficient to permit access and exit out of the cabin in safety, supplementary portable lighting should be provided. This equipment must be abele to work, even if the principal electrical circuits of the crane are isolated.
62
Doc:ME 14 (0916)c 6.24.1.2 Working Area Lighting When the working area lighting is provided by the appliance, projectors should be suitably placed on the crane, so that a minimum illumination of 30 lux at ground level is guaranteed. This lighting circuit should be independent of the principal circuits of the hoisting appliance. Precautions must be taken to avoid voltage drops produced by starting the motors cutting out the gas discharge lamps. 6.24.1.3 Access and Machinery Lighting When the general area lighting does not permit sufficient illumination, supplementary lighting independent of the principal circuits of the hoisting appliance should be provided. The minimum illumination should be 30 lux. 6.24.1.4 Emergency Lighting When the lighting of the area does not permit exit out of the appliance in safety, a portable lamp, equipped with batteries should be provided. A battery charger must be provided in the cabin. 6.24.2 HEATING AND AIR-CONDITIONING 6.24.2.1 Machinery House Natural or forced ventilation should be provided to disperse thermal power generated by the machinery and its equipment. Where electronic equipment is used and working conditions do not guarantee an ambient temperature for proper functioning of the electronic equipment, an air conditioning unit should be provided. 6.24.2.2 Operator Cabin If necessary, heating appliances should be provided in the cabin. This apparatus of black heat/non radiant type shall be securely fixed. It must be provided with a thermostat and must have such a power to assure a minimum temperature of 15 °C, taking into account the environment in which the equipment is installed. This apparatus must be fed independently of the principal circuits of the hoisting appliance. If required by the environment an air conditioning unit should be installed in the cabin to maintain a maximum acceptable temperature. This apparatus must be fed by a circuit independent of the principal circuits of the hoisting appliance. 6.24.3 AUXILIARY CIRCUIT If there is no possibility of supply in the proximity, auxiliary circuits should be provided for maintenance purposes, as follows:
a) A circuit for portable lighting, if the ambient lighting is not sufficient to carry out maintenance. b) A circuit for portable tools according to agreement between customer and supplier. c) These circuits should be protected by a differential circuit breaker of high sensitivity and them shall be independent of the principal circuits of the hoisting appliance. 6.24.4 LIFTING MAGNETS & LOAD HOLDING DEVICES 6.24.4.1 General The requirements given in this clause apply to all load holding devices such as lifting magnets and vacuum lifters. Load holding devices are normally designed for a cyclic
63
Doc:ME 14 (0916)c
duration factor of 50 %. Other cyclic duration factors should be agreed between the manufacturer and user. The tear-off force should be at least twice the lifting capacity. If there is a stand-by power supply from batteries, the holding time should be atleast 20 minutes. In this case, an automatic charging unit and a charge level indicator should be provided. Use of the stand-by supply should be indicated visually and audibly for general warning. If the battery voltage level is not adequate, a device preventing the installation from being used should come into effect. If required by the purchaser, the crane shall be fitted or provision shall be made to permit in the future fitting of lifting magnets, magnet control and protective gear. 6.24.4.2 Magnet The type and size of magnet shall be decided based on the details given by the purchaser. The type and size of magnets shall preferably be in accordance with details specified in Appendix B. Each magnet will be water tight and shall be provided with a water tight terminal box having the under mentioned features, however rectangular magnets are normally of fabricated construction type also can be used as follows: a) Integral construction with magnet casing, b) A gland through which the magnet load is brought to the magnet terminals c) A cover which shall be easily removable without interfering with the magnet lead inlet. d) Adequate thickness of box and cover, and e) Non-linear type discharge resistor of adequate rating and the rectangular magnets are fabricated constructions and nice fabricated type of magnets. 6.24.4.3 Magnet Lead and Cable The magnet lead and cable shall be flexible three core cables. If specified by the purchaser, the magnet lead shall be protected by rubber hose complying with the relevant Indian Standard. The magnet lead shall be so arranged that it does not become unduly slack or taut during normal operation of the crane. It should be so located that magnet cable does not foul with the rope. The use of sheaves and rollers for the cable should be avoided as far as possible. The magnet cable shall be rigidly attached to the bottom block by a suitable cable clamp at a point above magnet coupling. 6.24.4.4 Magnet couplings The type of magnet coupling shall be as agreed between the purchaser and the cane supplier. The coupling shall comply with the following requirements: a) The couplings shall be of rugged construction, b) At the moment of breaking, the contacts shall be enclosed by insulating material and earth connection shall break last, c) Provision shall be made to fasten the coupling in the closed position. d) The socket shall be connected to the supply and plug to the magnet or magnet lead. 6.24.4.5 Cable Drum The magnet cable drum shall be as follows: a) Arranged so that magnet cable does not foul with the hoisting ropes, b) Such that the cable will become neither unduly taut, nor slack enough to touch the hoist ropes or get entangled, and
64
Doc:ME 14 (0916)c
c) Capable of accommodating and paying out the length of cable necessary for the magnet to reach its lowest position. Cable drum when attached to the hoist drive, a disengagement device shall be provided. Where power is fed to the magnet by a brush and slip ring arrangement on the magnet cable drum, two brushes per slip-ring shall be provided and the rings shall have adequate clearance. The slip ring insulation shall bed of non tracking material and the assembly shall be enclosed by an easily removable cover, oil-proof for indoor cranes and weather proof for out door cranes. A spare slip ring complete with brush gear arrangement shall be provided if required by the purchaser. 6.24.4.6 Magnet Control and Protective Equipment The magnet shall be controlled either by direct-online control or potentiometer control as required by the purchaser. In both methods of control the magnet shall be demagnetized by current reversal. In direct-on-line control, the magnet shall be energized by switching it across full mains voltage and discharge resistance shall be connected on switching ‘OFF’. The control shall be affected by means of a master controller and magnetic contactor panel. 6.24.4.7 Battery Back up System If required by the purchaser, necessary and adequate battery back up system shall be provided by the supplier. The rechargeable battery shall keep the magnet energized till the time the lifted load is brought to a safe location, in the case of power failure. If there is a stand-by power supply from batteries, the holding time should be atleast 20 minutes. In this case, an automatic charging unit and a charge level indicator should be provided. Use of the stand-by supply should be indicated visually and audibly for general warning. If the battery voltage level is not adequate, a device preventing the installation from being used should come into effect.
65
Doc:ME 14 (0916)c
Section–IV
7.1
66
Doc:ME 14 (0916)c
67
Doc:ME 14 (0916)c
7.2
7.2.1
7.2.3
7.2.4 7.2.2
68
Doc:ME 14 (0916)c
7.2.5
7.2.7
7.2.6.
7.2.8. 7.2.9.. 7.2.10
7.2.11
7.2.12
7.2.13
69
Doc:ME 14 (0916)c
7.2.16
7.2.17
7.2.14
7.12.18
7.2.15
7.12.19
70
Doc:ME 14 (0916)c
7.2.26
7.2.20
7.2.21
7.2.22 7.2.23
7.2.24
7.2.25
71
Doc:ME 14 (0916)c
7.2.27
7.2.28
72
Doc:ME 14 (0916)c
73
Doc:ME 14 (0916)c
7.2.30
7.2.31
7.2.32 7.2.29
4.1.33
74
Doc:ME 14 (0916)c
Reverse pha.sing, if necessary. c) Allow trolley to move entire length of bridge span, are fully watching alignment of trolley collector pole and bridge conductors and also watching for any interference with building and building equipment. Do not run trolley into end stops.
7.2.38 If Crane is Equipped with a Lower Limit Switch. Proceed as follows a) Lower the empty block until one wrap of rope remains on each end of the drum. b) Set lower limit switch to trip at this point (or any higher elevation).
d) Adjust end limit switch trip.
7.2.39 Never lower block beyond the point at
e) Reverse master switch and repeat (a) to (d).
which one wrap remains at each end of the drum. 7.2.40 Load Test After the no-load running test has been completed, the crane should be tested with loads in the following manner:
t) Reset trolley timers, if needed. 7.2.34 Bridge Motion (Long Travel) a) Place master switch in 1st point 'Trolley travel' position. b) Observe contactor sequence and direction of travel through full range of master switch. Reverse phasing, if necessary. c) Allow trolley to move entire length of bridge span, are fully watching alignment of trolley collector pole and bridge conductors and also watching for any interference with building and building equipment. Do not run trolley into end stops. d) Adjust end limit switch trip. e) Reverse master switch and repeat (a) to (d). f) Reset trolley timers, if needed. 7.2.35 Check all Accessoriesfor Proper Function 7.2.36 No-Load Test 7.2.37 After Reeving the Hoist. Test the Operation of the Hoist Limit Switches asfollows a) Raise empty blocks to within about 500 mm . of its upper position and stop. b) Raise the empty block at the lowest control speed until the limit switch trips and stops the hoisting motion. During this operation watch for proper alignment between load block and limit switch trip. c) Check that block stops at correct height as shown on drawings. Adjust limit switch, if necessary. d) Lower block to 1.5 m. e) Raise block at about half speed. f) Check for adequate clearance between block and trolley frame (or upper sheaves) g) Repeat points (d), (e) and (1) with block being raised at full speed.
75
a) Raise a load equal to about 5 percent of the rated load not higher than required to clear its supports and stop adjust brake, if necessary. Raise load about I m above its supports and stop. Lower the load about 300 mm and stop. Check drift of load during stopping. If load drifts, brakes are not in proper adjustment and should be corrected. Repeat this operation until proper adjustment of brakes is obtained. Lower load carefully back to its supports. b) Load the hoist motion with 125 percent of rated capacity and follow the same procedure as mentioned in (a). i) Then hoist the load high enough to clear all obstructions but not higher than necessary. Move trolley across the entire span of bridge. Transport the test load by means of the bridge for full length of the runway in one direction with the trolley at the extreme right hand end of the crane, and in the other direction with the trolley at the extreme left hand end of the crane. ii) Measure the deflection when the trolley with test load is at the middle of the girder and at extreme end of the girder. Check whether the deflection is within the allowable limit. iii) Measure the 'No-Load' and 'Full Load' current of the motor and verify whether it is as per.the recommendations of motor manufacturers. Check the resistors in the circuit whether any over-heating of the element occurs. iv) If separate creep speed control is provided it should be run for check-out over a distance of about 500 mm v) Check overload relays for proper function
Doc:ME 14 (0916)c
76
Doc:ME 14 (0916)c
77
Doc:ME 14 (0916)c
78
Doc:ME 14 (0916)c APPENDIX A (Clause 1.2) LIST OF THE STEEL PLANT CRANES AND SPECIAL SERVICES MACHINES COVERED BY THE CODE
A-I. This specification applies to the following types of cranes and special service machines. ( The list is not exhaustive ): a) Coke ovens charging. b) Coke ovens drawing ( coke pushers ). c)
Blast furnace cast house.
d) Pig machine. e) Ladle cranes used in the charging and/or tapping of hot metal mixer vessels, Bessemer converters of LD vessels, open hearth and electric furnaces, etc. f)
All cranes and machines (either floor mounted or running on over-head gantries) used to cold charge open hearth or electric furnace, etc, or used to charge and draw all types of reheating furnaces.
g) Bucket handling cranes at various raw and scrap material stock yards, crab cranes and bridges handling, coal, ore, limestone, etc, or by-product or waste materials, such as slag, cinder and mill scale. h) Magnet cranes used for skull cracking, and for handling and preparing steel scrap. i)
Magnet and cradle cranes for handling semi-finished steel (such as slabs, blooms and billets) and for stocking and shipping finished products (such as structurals, rails, plates and sheets) in the various mills and departments.
k) Ingot and ingot mould handling cranes at stripper yards, ingot stock yards and soaking pit buildings, etc. m) MiIl building cranes for changing stands and rolls in the various mills.
NOTE -- This code is not intended for application to those cranes within the confines of a steel plant which are ancillary to the plant production processes. It is recommended that these cranes should be designed and manufactured in accordance with the appropriate classificaticn in IS 3177/1999.
n) Cranes and repair trolleys on fixed high level gantries for the servicing and repair of furnaces or of ladle cranes or s:ripper cranes, etc.
79
Doc:ME 14 (0916)c
APPENDIX B INFORMATION TO BE SUPPLIED WITH THE ENQUIRY OR ORDER
B-O. The purchaser shall specify his requirements by tilling in certain portions of the following proforma as indicated under each section heading. The other portions refer only to additional requirements and need only be completed where these are specifically requil ed, and should be crossed if not deemed necessary.
Where the purchaser is unable to fill in any particular portion, the requirement should be made the subject of agreement between the purchaser and the manufacturer, and the purchaser should state this in the relevant paragraph.
B-1. B-1.1 B-1.2
GENERAl, Number of cranes:................................. Duty or class of crane: .......................... ,... a) Crane structure ( see 5 of IS : 807-2006 ) b) Main hoist c)' Auxiliary hoist d) Cross-traverse e) Long-travel
B-1.3
Safe working load in tonnes: a) Main hoist .............................. tonnes b) Auxiliary hoist............., ..........tonnes c) Second auxiliary hoist............tonnes d) Stripping and extracting capacity in case of stripper cranes ... ...... ... ... ... ... ... .... ... ... ... tonnes NOTE - In case of magnet and grabbing cranes, the specification and physicals condition of the material to be handled shall be given.
B-1.4
Gantry or track rail ( see Fig. 3 ): a) Size and weight .....................tonnes b) Width of head (B) ...................mm c) Allowable gantry loadings ......tonnes
o e o prac ce or es gn o over ea steelworks cranes ( first revision ).
rave ng cranes ar. gan ry cranes o er
t
an
Code of practice for design, manufacture, erection ar:d testing structural portion) of cranes and hoists (first revision ).
80
Doc:ME 14 (0916)c
Fig.12
B-l.5 Any abnormal atmospheric conditions (to be specified ).............. a) Ambient temperature in °C ( Max and Mill ). b) Relative humidity ( Max ). B-l.6 Number of tender documents, including drawings and relevant technical literature required ……. ..…………………………………………………………………………. B.1.6.1 Any requirement for: a) Detailed drawings for approval by purchaser........................……. b) As made in drawings ................................................................…. B-2. CRANE PERFORMANCE B-2.1 a) With magnet (where supplied) in plate. the crane sbaH perform the following duty cycle in ................................ seconds, rest for... ........….. ........ ... ... …………………………….seconds, then repeat cycle for a period of ..................." ....................hours, and rest for .................................................................... "... hours b) Alternate information..............................………………………….. ……………………………………………………. c) Duty cycle..................................................................... 1) Lift weight of ..................... tonnes to a height of............... metres 2) Cross-traverse.................................................... … .......... metres 3) Long-travel......................................................................... metres 4) Longer load to ground and release load, raise hoist... ....………… ……………………………………………………………………… metres 5) Cross-traverse back ........................................…………….metres 6) Long-travel back .............................................................. ..metres
B-2.2 Operating Speeds ( Loaded ), not Less than a) Main hoist... ... ... ... ... ……………………………………….. m/ min b) First auxiliary hoist ............................................... ................m/min c) Second auxiliary hoist .......................................... ... ... .........m/min d) Cross-traverse ( main ) .........................................................m/min e) Cross-traverse ( auxiliary).................................... ................m/min f) Long-travel ................................................……………………m/min
81
Doc:ME 14 (0916)c B-3. STRUCTURAL DETAILS (See Fig. 12) B-3.1 Distance Between Centre Lines of Gantry or Track Rails (S) .. . .. . .. . .. . .. . .. . .. . .. . .. . .. ….. .. .. . .. . .. . .. . .. . .. . .. . . .. . .. .. . .. . .. . .. . .. . metres ( span) NOTE - It is recommended that the span of the track shall not vary by more than ±12 mm. When the track span does not satisfy this requirement the maximum and minimum span for which the crane has to be designed shall be specified by the purchaser. B-3.2 a) Side clearance - Distance from centres of gantry or track rails to nearest side: 1)…………………………………………………………(Al) metres 2) (A2 ) metres b) Distance from top of gantry rail to: 1) Lowest overhead obstruction (C)....................…….. .metres 2) Floor level (D) .......................................................... ..metres 8,3.3 End Clearances: ( P 1 )... .. . ... . . . .. . . .. . .. . . . . .. ... ... ... .. . .. . .. . ... ... .., ... ... metres ( P 2 ).. . . .. . .. ... ... ... .. . .. . . . . . . . ... ... .. . . . . . .. ... ... .. . . . metres ( T 1 ). .. . .. . .. ... ... . . . . . . . . . . .. . .. ... ... ... ... ... . .. .. . .. . . .. .. metres ( T 2 ).......……………………………………………… metres ( R 1 )... . .. .. . . .. . .. ... ... .. . .. . . .. . .. .. . .. . .. . . .. . .. .. . .. . .. . .. . ..metres ( R 2 )... ...... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . metres B-3.4 Vertical Clearance to Underside of Bridge: ( K ) .. . .. . .. . .. . .. . .. . . .. .. . .. . .. . . .. . .. . .. .. . .. . .. . .. . . .. .. . . .. metres B-3.5 Operator's Cabin: a) Clearance height to under side of cab (L)................. metres b) Length of cab ( N ) ............................................................ ..metres c) Distance from back of cab to nearest gantry rail (for fixed cabs) ( M)... .. . . .. . .. . .. .. . . .. . ... .. ... .. . . . . . .. ... . .. ... ... metres B-3.6 Lift of Hook Above Floor Level: a) Main hook (HI ).................................................................... metres b) First auxiliary hook ........................................................... ...metres c) Second auxiliary hook ....................................................... ..metres B.3.7 Drop of Hook Below Floor Level: a) Main hook (H2).................................................................... metres b) First auxiliary hook ........................................................... ...metres c) Second auxiliary hook ....................................................... ..metres B-3.8 Nearest Position of Hook to Centre of Gantry Rail: a) Main hoist: 1) Ca bi n end ( E)... ............. ... ... ..... .. .. ... ..... .......... .metres 2) Cabin end ( F)............................................................ .metres b) First auxiliary hoist: 1) Cabin end ( E) ............................................................ metres 2) Cabin end (F)...............................................,.. ........... metres c) Second auxiliary hoist: 1) Cabin end ( E )... ..".. .................................................. metres 2) Cabin end (F).............................................................. metres B-3.9 Any Other Site Restrictions........... ... .......... ... ............. ... """"".'" B-4. OPERATOR'S CABIN DETAILS B-4.1 a) Type of cabin (fixed or moving)......................................... b) Location on bridge, if fixed................................................ '8-4.2 Open or closed type............................................................... ... ............ ... ...
82
Doc:ME 14 (0916)c B.4.3
Any Requirement for: a) Steel plate of thicknesses other than 3 '15 mm........................ b) Insulated cab walls.......................................................... c)
Insulated floors...............................................................
d) Window opening on hinges.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... e) Dispensing with platform outside cab door.......................... f)
An extraction fan ( door should open inwards where platform is not provid ed ).. . ... ... .. . .. . .. . . .. . .. .. . .. . ... .. . .. ... .. . ... g) A circulating fan............................................................. h) Air-conditioning for totally enclosed cabs....... ... ... ... "" ... j) Fire extinguishers............................................................ k) Seating arrangement for crane operator .................. ........
B-5.1 General
a) Type of long travel drive................................................... b) Make and type of flexible couplings ............,................ c) Type of any overload slip device (fluid coupling, plate-clutch, or cone clutch)...............................................................
B.5.2 Type of Hooks: a)
Main hoist... ... ... ... ... ... ... ... ... ... ... ... …………………………….
b) First auxiliary ........................................................................ .'…… c) Second auxiliary... ... ... .. . ... . .. ... .. . . .. . .. .. . ... .. . .. . ... ... ... ... B-S.3 Any Requirement for: a) A lifting beam on outdoor cranes.....................................……….. b) Built in jacks on end carriages.........................................……….. c) Built in jacks on crabs ............................................................ '..... d) Special rail wheel tyres .......... ... ... ..........……………………….. e) Special gearing arrangements or details................................ f) Bearing other than ball or roller type g) Bearings having full ring cartridge housings h) Centralized lubricating system i) Locking device on swiveling hooks j) Closing fingers on the hooks
83
Doc:ME 14 (0916)c
B-6. ELECTRICAL DETAILS B-6.1 Electric Supply a) dc-supply Volts ..............................., ...... , ...No. of wires... ........... ... ... ..,......... ...
Supply ( rectifiers or not )... ............... ... ....... ......................……. b) ac-supply Volts ....... ............ ,... ..............No. of wires .................................. Frequency ............................... No. of phases.................. ……….. Neutral (earthed or Dot)..................................................
B-6.2 Braking Any requirements for: a) electromechanical shunt brake(s) on hoist motion(s)............ b) emergency brake(s) on hoist motion(s) of moving cab cranes. ( electromechanical shunt, mechanical or hydraulic ).............. c) emergency electro-mechanical shunt brake(s) on:
1) the .......hoist ... .. ... ..motions . .. . ..cab . .. cranes.............................. . .. . . .. . .. .. . .. . .. . . . .......... .... ...of .....fixed
2). ..the cross-travel motion(s) of moving cab cranes............... 3) the long travel motion of fixed cab cranes................. …….. d)emergency lowering of load by hand operation of brakes........ e)a mechanical drag brake on crab......................................……. f) brake magnet coils to be fed from ac...............................…….. g)alternative brake magnet coil ratings................................... …. h)additional brakes for other motions or purposes.................……
B-6.3 Motors a) Manufacturer of main motors: ........………………………………. c) Class of insulation of main motors......................................... d) dc-mill motor details (if not selected from any standard specification)
Table - 20
84
Doc:ME 14 (0916)c
d) Any special motor lead or terminal requirements.".................... B-6.4 Main Control Gear B-6.4.1 Type of control panels (open or separate closed units)............ B-6.4.2 Short time rating or duty cycle ratings of resistors: a) Ifoist moti on s... ... ... .., ... ... .. . ... ... .. . ... .., ... ... ... .,. .. . ... ... b) Cross-travel motions................. ...'"'''''' """",''''''... ......"..............". c) Long-travel motions............................................................ B-6.4.3 Scheme of protection for main control l:ircuits: a) Protection of each motion, or................................................ b) Tripping out crane supply if overload on any motion ..............'" B-6.4.4 Any requirement for: a) a special control system, or a control system other than automatic control of acceleration for any motion (for example, drum or mechanically operated contactor controller) c) an electrically operated main circuit-breaker...........................….. b) emergency rheostatic braking on travel motions: 1) cross-travel ..................................................... ………………….. 2) long-travel... ...,.. …………………………………………………… d) special clearances of creepages...…………………………………. B-6.5 Auxiliary Switching B-6.5.1 Any requirement for: a) special position of: 1) main isolating switch.......………………………………………….. 2) additional main isolating switch... h. ........... .., ............……… b) HBC fuse protection for main isolators................................... c) auxiliary contacts on the main isolating switch to operate the crane warning hights...............
85
Doc:ME 14 (0916)c
d) e) f) g)
an isolating switch on the main circuit of each motion............ an isolating switch on the control circuit of each motion. ……. special creeping button to by-pass lower hoist limit switches...... track switches (number, details and whether to operate a warning signal, or trip the main circuit- breaker) ' """'" h) proximity warning devices (number, location and duty)............
B-6.6 Disposition and Housing of Electrical Equipment B-6.6.1 Location of electrical equipment compartment for: a) fixed cab cranes (below or above the bridge platform, or above the cab) .. .. .. . .. . .. .. . .. . .. . .. . . .. . .. .. . . .. .. . . .. .. . ... .. . . .. ... . .. ... .. . ... .. . .. .. . b) moving cab cranes (above the bridge platform level, or above the cab), ..............................................................'... ... ... ... ... ... B-6.7 Long-travel System: B-6.7.1 Provision of long-travel collectors (purchaser or manufacturer )... , , .... B-6.7.2 Details of mountings on bridge structure for long-travel collectors, if these are to be provided by the purchaser... '. B-6.7.3 Details of long-travel conductors if long-travel collectors are to be provided by the manufacturer.....................--............................ B-6.7.4 Type of long-travel coIlectors if these are to be provided by the manufacturer ,......... B-6.8 Cross-travel System: B-6.8.1 Any requirement for flexible cable type of cross-travel system... ... ... ... ... ... ... ... ... ... ... '"
... ... ... ... ... ... ... ...
B-6.8.2 Type of cross-travel conductors (roIled steel section or wires ) B-6.8.3 Maximum current densitv for cross-travel conductors (if higher than that recommended in thi's specification )............................. B-6.8.4 Provision of cross-travel coIlectors (purchaser or manufacturer) B-6.8.5 Deta;ls of mountings on the troIley for cross-travel coIlectors, if these are to be provided by the purchaser ... ... .......... B-6.8.6 Type of cross-travel collectors, if these are to be provided by the manufacturer .……………………………….. B-6.9 Lifting Magnet and Equipment: B-6.9.1 If lifting magnets and magnet control and protective gear are to be provided a) Type and size of magnets... ... ... ... ... ... ... ... ... ... ... ... ... ... .... ... ...
86
Doc:ME 14 (0916)c
b) Type of magnet control ( direcet-on-line or potentiometer )... ...... c) Type of master controller for direct-on-line control (hand or foot operated)... . .. .. . ... ……………………………………………..... ... ... ... .., ... ..,. d) Type of potentiome~er control (master drum or mecbanicalIy operated contactor controller )
B-6.9.2 Any requirement for: a) provision for future fitting of a lifting magnet ( number of extra cross-travel conductors ) b) rubber hose protection of magnet lead..................................... c) special type of magnet coupling ........................................................ B-6.10 Crane Illumination and Warning Lights: Any requirement for: a) lighting of the bridge walkway and the cab and bridge............ approaches ..........................................................................……….. b) underslung lighting ( number, type and location of lamps and'lamp fittings) , .............………………………. c) 1) warning lights..............................................................……………. 2) if so, give details of their function ................................................. B-6.11 Earthing Any requirement for: a) earthing other than through crane gantry................................. b) the magnet to be earthed by a connection via the magnet ]ead,.coupling and cable and an extra slip-rirg on the magnet cable drum... ... ... ... ... ... ... ... ... ... ... ... '''... ... ... B.7. PROTECTION OF CRANE STRUCTURE AND MACHINERY
B-7.1 Any Requirement for Special Painting Schemes ............................... B-8. ADDITIONAL REQUIREMENTS B-8.1 Any Additional Requirements................................................
87
Doc:ME 14 (0916)c
ANNEX C (Clause – 44)
NOTES ON DESIGN AND SELECTION OF MOTORS
C-l SELECTION OF MOTORS FOR HOIST MOTIONS
For hoisting motor the power required shall not be less than that computed from the following: where
dc rating factor will be taken as 12 percent, kW = one 'hour power rating for dc motors and power rating at (S - 40 percent) cyclic
duration factor for a.c. motors, M = mass of the rated load on the hook plus weight ofthe hook block and the wire ropes in tonnes,
v= E=
specified hoisting speed in M/min, combined efficiency of gears and sheaves
= (0.93n x (0. 98)m for sleeve bearings, = (0.95n x (0. 99)m for anti-friction bearings, = (0.985) N x (0.99)m for hardened profile ground and oil splashed lubricator
88
Doc:ME 14 (0916)c
Table 24 - Recommended Cyclic Duration Factor and Starting Class (Clause C.l)
where n = number of pairs of gears, m = total number of rotating sheaves pass~d over by each part of the moving rope attached to the drum,
C v = service factor for vertical motion depending on type of motors, = 0.67 for ac motors = 0.5 for dc motors Cdf = duty factor as defined in 6.4.3, and C amb = derating factor for ambient temparature as given in the Table 20A. Table 23 - Ambient Temperature for Derating Factor
Ambient Temperature
Derating Factor, Camb
40°
1.00
45°
0.95
50°
0.88
55° 60°
0.83 0.75
For an ac hoist motor, the specified full load hoist speed must be obtained at not more than rated torque, therefore, the calculated full load kW must be multiplied by : ( 100 ~ rated slip percent) ( 100 - total ohms at full speed percent) Where sufficient information is not available values given in Table 20B for duty cycles, cyclic duration factor and starting class corresponding to mechanism class shall be used. The values given are based on the following formula: "
Operating time x 100
CyclIc duration factor = 0perating time x 100 Operating time + Idle time The starting class (C) assumes numbers of complete starts (S), jogging operations (J) and electrical braking operations (B) as follows: where
C= S+ K)J + K2B
Mechanism Duty Cycle Recommended Starting Class Number of Cyclic Class (C) Cyclic Duration Equivalent Class (C) Factor Startslhour Cycles/hour percent percent M1 Up to 5 25 90 cycles 25 M2 Up to 5 25 90 cycles 25 _/ 150 M3 10 to 15 40 cycles 40 M4 16 to 20 40 150 cycles 40 M5 21 to 30 60 300 cycles 60 M6 31 to 40 60 300 cycles 60 M7 41 to 50 100 600 cycles 100 M8 51 to 60 100 600 cycles 100
C-2 Motor for crane travel or Trolley Traverse C-2.1 Genral It is assumed that the drive mechanism from the motor to the track wheels will use enclosed gearings mounted on anti-friction bearings. The actual efficiency of the drive will be adopted in making calculations. Where actual efficiency values are not available the efficiency of the drive shall be taken in the range of 0.85 to 0.9.
For the track wheel with anti-friction bearings the rolling friction at these bearings plus the friction between the track wheels with an average drive efficiency of 0.875 will give an overall friction factor of 8.0 kgf per tonne ofthe mass moved for calculation of the motor horse power or torque. In the case of wheels with the plain bearings an overall friction factor of 13.0 kgf per tonne of the mass moved may be used. C-2.2 Selection of Motors for Crane Travel or Trolley Traverse
K) = 0.25 for slip ring motors
= 0.5 for squirrel cage motors
For bridge travel or trolley traverse the power of the
K2 = 0.8 for slip ring motors
= 3.0 for squirrel cage motors
89
Doc:ME 14 (0916)c
IS 3177: 1999 kW=
, F+ MVSCdf'
6117T
( out door cranes
1 100a ,, 98IN'
}
w +-- for 6117T
Table 25 Acceleration Values
Speed,
where
to be
kW = one hour power rating for d,c. motors and power rating at 40 perent cyclic duration factor for a,c. motors;
Acceleration Acceleration
Reached M/min
N
T
Long Travel
= specified free running speed M/min; = mechanical efficiency of gearing. For spur and helical gears it can be taken as 0.95 per reduction; = factor introduced by the permissible motor torque during acceleration exceeding the motor-rated torque. As a general guidance value of T may be taken as 1.7 for motors having pull out torque of 275 percent full load torque. Lower values of T should be taken for corresponding lower values of pull out torque.
= 1.6 for a.c. motors 160 x fuli load torque
(Normal Application) 50
-
67
190
-
44
150
-
39
120
22
35
47
100
19
32
43
60
15
25
33
40
12
19
-
25
10
16
-
15 10
8 7
-
-
I J
58 52
Table 26 Values of Service Factors
1.00
Trolley Service Factor 1.06
= overall friction factor
= 13 kgf per tonne for wheels on plain bearings
RwI=
1 Duty cycle, recommended cyclic duration factors and recommended starting Class for the mechanism class can be taken from Table 20B. 2 At free running speed the acceleration becomes zero.
Cdf = duty factor as defined in 6.4.3;
s
Speed
Acceleratio n in cm/s2 for High Speed with High Acceleratio n
240
0.95
= 8 kgf per tonne for wheels on anti -friction bearings
a
in cm/s2 for Moderate and High
Bridge Service Factor
= 1.3 for d.c. motors pullouttorque x 100
F
in cm/s2 Low and Moderate Speed with
M = mass of crane or trolley plus mass of max rated load in tonnes; v
Condition
load due to service wind acting horizontally as defined in 6.3.1 which can be obtained by multiplying the horizontal exposed area by the service wind by taking drag co-efficient into consideration;
= average linear acceleration ofthe crane or the trolley in Cm/S2 till the mechanism reaches 90 percent offree running speed. For the values of average linear acceleration refer as given in Table 2IA; and = service factor aimed at providing adequate motor heat dissipation capacity as given in Table 2IB.
90
3 The gear reduction ratio actually used should be reasonably close to the ideal reduction ratio: Motor rev/min at free running Track wheel rev/give specified running speed 4 In order to limit the acceleration to the specified value and also to take full advantage of the service factor the electrical control should be designed to suit the values of 'S' and 'T actually adopted or values of'S' and 'T should be selected based on electrical controls"to be provided. 5 Since the wheels must transmit all acceleration forces to the crane, to prevent wheel skidding due consideration should be given on percent driven wheels after acceleration rate has ben fixed. The wheel skidding should be checked at no-load conditions considering 20 percent adhesion betwen wheel and rail.
Doc:ME 14 (0916)c
ANNEX D (Clause-51) INTERMITTENT RATINGS FOR RESISTORS
To aid economic manufacture that the crane parameters given in be D-1 GENERAL The basis of the rating shall be the ratio of the running time to a total time of 15 min and the resistors are rated to carry the rated full load motor current in any section or sections except where current is restricted to lower value by the amount of resistance in the circuit in which case the resistor shall be rated to carry the current passed with the motor at stand still. D-2 DEFlNmON OF DIFFERENT RATINGS
it is recommended selected from a D-2.2 Five Minute Rating A resistor having a five minute rating shall be capable of being left in circuit for a period not exceeding 2 min on the first section and for a further period of 3 min equally divided between the remaining sections ofthe resistor, followed by a period of rest of 10 min, this cycle being repeated until a stable temperature is reached. progression based D-2.3 Ten Minute Rating
D-2.1 Two Minute Rating
A resistor having a ten minute rating shall be capable A resistor having a two minute rating shall be capable of being left in circuit for a period not exceeding 4 min on the first section and for a further period of 6 min of being left in the circuit for a period not exceeding equally divided between the remaining sections of the 30 s on the first section and for a further period of 90 s resistor, followed by a period of rest of 5 min, this divided between the remaining sections of the resistor, cycle being repeated until a stable temperature is followed by a period of rest of 13 min, this cycle reached. being repeated until a stable temperature is reached. upon the preferred number series.
ANNEX E CRANE-RECOMMENDED/PREFERRED PARAMETERS
E-1 GENERAL
E-3 PREFERRED LIFTING HEIGHT Preferred series R5 shall be used for lifting heights up to and including 16m and RIO for heights above 16m. The preferred lifting heights (in metres) are as follows:
E-2 PREFERRED LIFTING CAPACITIES Preferred series RIO shall be used for capacities up to and including 125 tonnes and R20 for capacities above 125 tonnes. The preferred lifting capacities ( in tonnes ) are as follows: 1.0
3.2
10
32
100
225
400
1.25
4.0
12.5
40
125
250
450
1.6
5.0
16
50
140
280
500
2.0
6.3
20
63
160
320
560
2.5
8.0
25
80
200
360
etc.
91
2.5
10
25
50
4.0
16
32
6.3
20
40
63 etc.
E4 PREFERRED SPEED OF OPERATION (FULL SPEEDS) Preferred series R5 and R1O shall be used for full speed of operation respectively. The preferred speeds of operation (in metres per minute) are as follows: 0.63 0.8
1.6 2.0
4.0 5.0
10 12.5
25 32
63 8)
1.0 1.25
2.5 3.2
6.3 8.0
16 20
40 50
100 125
160 200
Doc:ME 14 (0916)c IS 3177: 1999 ANNEX F (Section II and III) LIST OF INDIAN STANDARDS IS No.
F-l MATERIALS
1367
F-l.l Steels and Castings and Tubes Title
IS No.
210: 1993 1030 : 1989
1239
(Part 1): 1990 (Part2): 1992
1387 : 1993
1570 : 1961 2062: 1992
( Part 6 ) : 1994
Title
Specification for grey iron castings (fourth revision) Specification for carbon steel castings for general engineering purposes (fourth revision) Mild steel tubes, tubular and other wrought steel fittings:
General requirements for the supply of metallurgical materials ( second revision) Schedule for wrought steel for general engineering purposes Specification for steel for general structural purposes (fourth revision)
F-l.2 Threaded Fasteners
1364
( Part 7 ) : 1980
Mechanical properties and test methods for nuts without specified proof loads (second revision)
(Part9/Sec2) : 1979
Surface discontinuities, Section 2 Bolts, screws and studs for special application ( second revision)
Mild steel tubes ( fifth revision) Mild steel tubular and other wrought steel pipe fittings (fourth revision)
Specification for hexagon head bolts, screws and nuts of product grades A and B:
(Part 1): 1992
Hexagon head bolts ( size range M1.6 to M64) (third revision)
(Part2): 1992
Hexagon head screws (size range M1.6 to M64) (third revision)
( Part 3 ) : 1992
Hexagon head nuts ( size range Ml.6 to M64 ) ( third revision)
(Part 10) : 1979 (Part 12) : 1981
Surface discontinuities on nuts ( second revision) Phosphate coating on threaded fasteners ( second revision)
(Part 13): 1983
Hot-dip galvanized coatings on threaded fasteners ( second revision) \
(Part 14): 1984
Stainless steel threaded fasteners ( second revision)
(Part 16): 1979
Designation system and symbols (first revision)
(Part 18) : 1979
Marking and mode of delivery ( second revision)
3640: 1982 3757: 1985 6639: 1972
Hexagon fit bolts (first revision) High strength structural bolts ( second revision) Hexagonal structures
bolts for
steel
F-l.3 Wire Rope
( Part 4 ) : 1992
Hexagon thin nuts ( chamfered) (size range M1.6 to M64 ) ( third revision)
1856: 1977
( Part 5 ) : 1992
Hexagon thin nuts ( unchamfered) (size range M1.6 to MIO ) (third revision)
2266 : 1989
92
Tecchnical supply conditions for threaded fasteners: Mechanical properties and test methods for nuts with specified proof loads ( third revision)
Specification for steel wire ropes for haulage purposes ( second revision) Specification for steel wire ropes for general engineering purpose ( third revision)
Doc:ME 14 (0916)c IS 3177 : 1999 IS No. Recommendations for Title metal arc welding of IS No. carbon and carbon
2365 : 1977 manganese steels
Specification for steel wire ropes for lifts, elevators and hoists (first revision)
2762: 1982
Specification for wire rope slings and sling legs (first revision)
3973: 1984
Code of practice for selection, installation and maintenance of wire ropes (first revision)
6594: 1977
Technical supply conditions for steel wire ropes and strands (first revision)
F-2MECHANICAL DETAILS
AND
1323: 1982
F-2.3 Gears
2467 : 1963 2535: 1978
3734: 1983
F-2.1 Key and Key-ways
Specification of parallel keys and key-ways (second revision)
2291:1981
Specification for tangential keys and key-ways ( second revision)
2292: 1974
Specification for taper keys and key-ways (first revision)
2294: 1986
6166: 1971 6167: 1971
4460: 1967 5037: 1969
Notation for toothed gearing Basic rack and modules of cylindrical gears for general engineering and heavy engineering (second revision) Dimensions for worm gearing (first revision) Method for rating of machine cut spur and helical gears Basic rack and modules of straight bevel gears for general engineering and heavy engineering
6535: 1979
Data for procurement of straigh bevel gears (first revision)
7403: 1974
Specification for thin taper key and key-ways
Code of practice for selectiOl of standard worm and he1ica gear boxes
7504: 1974
Specification for parallel keys and key-ways
Methods of inspection of spur and helical gear
10911 : 1984
Method of inspection fo straight bevel gears
Specification' for woodruff keys and key-ways (second revision)
F-2.2 Welding
816: 1969
Code of practice for oxyacetylene welding for structural work in mild steel ( second revision)
9595 : 1980
FABRICATION
2048: 1983
Title
Code of practice for use of metal arc welding for general construction in mild steel (first revision)
F-3 ELECTRICAL DETAILS
F-3.1 Motors 325 : 1978
;' Specification for three-phase Ui (}, induction motors ( fourth ~'. revision) 900: 1992 Code o{practice for installation and maintenance of inductior motors ( revised)
818: 1968
Code of practice for safety and health requirements in electric and gas welding and cutting operation (first revision)
822: 1970
Code of procedure inspection for of welds
1231: 1974
1024 : 1979
Code of practice for use of welding in bridges and structures subject to dynamic loading (first revision)
Dimensions of three-phase foo mounted induction motor! ( third revision)
2223 : 1983
Dimensions of flange' mounted ac~induction motors (second revision)
93
Doc:ME 14 (0916)c
IS 3177 : 1999 Title
IS No.
2253 : 1974
4691: 1985
4722: 1968
Designation for construction and arrangement of electrical ~achines revision)
types of mounting rotating ( first
Degrees of protection provided by enclosure for rotating electrical machinery ( first revision) Specification for electrical machines
Title
IS No.
rotating
4728: 1975
Teminal marking and direction of rotation for rotating electrical machinery (first revision)
12065: 1987
Pemissible lirits of noise level for rotating electrical machines
3427: 1969
Specification for metalenclosed switchgear and control gear for voltages above 1000 V but not exceeding 11000 V
8544
Specification for motor starters for voltages not exceeding 1000 V:
( Part 1 ) : 1977 (Part2): 1977 ( Part 3/Sec 2 ) : 1977
( Part 4 ) : 1979
F-3.2 Cables and Conductors 9968 (Part 1) : 1988
(Part 2 ): 1981 694: 1977
1554
(Part 1): 1988 (Part2): 1981
8130: 1984
F-3.3 Switch Gear
2516: ( Parts 1 & 2/ Sec 1) : 1985
For working voltages up to and including 1100 V (first revision) For working voltages from 33 kVuptoandincluding 11 k V
(Part 1): 1982 (Part 2 ) : 1982
Specifjcation for PVC insulated cables for working voltages up to and including 1 100 V ( second revision)
(Part3):
For working voltages up to and including 1 100 V (third revision) For working voltages from 3.3 kV up to and including 11 k V ( second revision) Specification for conductors for insulated electric cables and flexible cords (first revision) Specification for circuit breakers: Parts 1 & 2 Requirements and tests, Section 1 Voltages not exceeding 1000 V ac or 1 200 dc ( second revision)
94
1982
(Part4): 1982 13 947 (Part 1): 1993
Specification for PVC insulated ( heavy duty) electric cables:
Star-delta starters Rheostatic motor starters, Section 2 Additional require~ents for ac rheostatic motor controllers Reduced voltages AC-starters, two-step auto transformer starters Code of practice for selection, installation and maintenance of switchgear and controlgear:
10118
Specification for elastometers insulated cables: .
Direct-on-line ac starters
13118: 1991
General Selection Installation Maintenance Low-voltage swicthgear and controlgear : Part 1 General rules High voltage alternating current circuit breakers
F-3.4 Earthing
3043: 1987 F-3.5 Conduits 9537
Code of practice for earthing
Conduits installations:
and
.electrical
(Part 1): 1980
General requirements
(Part2):
Rigid steel conduits
1980
(Part 3 ): 1981 (Part4): 1983
Rigid plain conduits insulating 0f materials Pliable self-recovering conduitsof insulating materials
