Seminar report On
“MANUFACTURE OF PRE STRESSED TUBULAR SPUN
CONCRETE POLE OF 11 METRE LONG” SUBMITTED TO VIVESWARAIAH TECHNOLOGICAL UNIVERSITY BELGAUM FOR THE PARTIAL FULFILLMENT OF M-TECH (STRUCTURAL ENGINEERING)
BY ASLAM KHAN Reg. No: st 1 Semester M-Tech Structures Under The Guidance of: G.A.SATISH Senior lecturer Department of Civil Engineering
BANGALORE INSTITUTE OF TECHNOLOGY (Affiliated To Visveswaraiah Technological University) Bangalore-560004
BANGALORE INSTITUTE OF TECHNOLOGY TECHNOLOGY BANGALORE -560004
CERTIFICATE
This is to certify that Mr. ASLAM KHAN bearing university USN has submitted the seminar report on “MANUFACTURE OF PRE STRESSED TUBULAR SPUN CONCRETE POLE OF 11 METRE LONG ” in partial fulfillment of the 1 st semester M-Tech course in structural engineering as prescribed by the Visveswaraiah Technological University during the academic year 2006-2007, under the guidance of senior lecturer senior lecturer G.A.SATISH
Prof.K.JAYRAM H.O.D civil engg department.
G.A.SATISH Senior lecturer Department of Civil Engineering
ACKNOWLEDGEMENT
senior lecturer lecturer G.A.SAT G.A.SATISH ISH, I expr expres esss my deep deep sens sensee of grat gratiitude ude to senior Department of Civil Engineering, BIT, for his guidance and help through out this seminar work. I will will rema remain in than thankf kful ul to all all the the facul faculty ty memb member erss of Depa Depart rtme ment nt of Civi Civill Engineering, BIT for their support during the course of this work. Finally I express gratitude to my parents, fellow students and friends.
ASLAM KHAN M-TECH STRUCTURES BANGALORE INSTITUTE OF TECHNOLOGY
CONTENTS
Page No ACKNOWLEDGEMENT ABSTRACT 1. About Industry
1
2. Man Manuf ufac actu ture re of Pres Prestr tres esse sed d Spu Spun n Conc Concre rete te Pole Pole Of 11 Mete Meterr leng length th
2
3. Technical specifications for Poles
4
4. Manufacturing process of Poles 11 5. Time study
15
6. Conclusions
16
7. Time Study report
17
8. Annexure
ABSTRACT The report contains detail information of manufacturing of pre stress tubular spun concrete pole. The manufacturing industry namely FERRO CEMENT PRE FAB LTD situated at 14-c Attibele industrial area Bangalore. The product manufactured in the industry involved chain line production with movement of crane all safety measures were incorporated and employees were thoroughly briefed about the safety aspect to be followed during manufacturing process.
Special emphasis was given to time study of manufacture of the pre stressed tubular pole.
1. ABOUT THE INDUSTRY Ferro cements Pre Fab Ltd is situated at 14-C Attibele Industrial Area Bangalore.
The company manufactures the following 1.
Pre Pre stre stress ssed ed Tubu Tubula larr spun spun conc concre rete te pole poless of 11 11 mete meterr long long..
2.
Ferr Ferro o cem cemen entt sum sump p tan tanks ks and and sep septi ticc tank tankss
3.
Pre Pre fabr fabric icat ated ed Ferr Ferro o ceme cement nt com commu muni nity ty Toi Toile lett Bloc Blocks ks..
4.
Pre Pre ten tensi sion oned ed und undul ulat ated ed tro troug ugh h sec secti tion on
5.
Ferr Ferro o cem cemen entt sla slabs bs of orde ordere red d siz sizes es..
The company possess in house fabrication workshop to prepare state of art molds and other fabrication work. The following machinery are available in the factory 1.
A mov movin ing g over overhe head ad cra crane ne of of 10to 10ton n capa capaci city ty..
2.
A con concr cret etee bat batch ch mixi ixing plan plant. t.
3.
Smal Smalll capa capaci citty conc concrrete ete mixe mixers rs..
4.
Mol Molds of diff differ eren entt cap capac aciities ties
5.
A boil boiler er for for steam eam prod produc ucin ing g
6.
A wi wire-cutt utting ma machin hine.
7.
A ba bar be bending ma machine.
8.
A comp compre ress ssio ionn-te test stin ing g machi machine ne of of 200t 200ton on cap capac acit ity. y.
9.
Sieve Sieve shake shaker, r, drying drying oven, oven, siev sieves es and other other testin testing g equip equipmen ment. t.
10. 10.
Mot Motor for for spi spinn nniing. ng.
The company’s organization consists of managing director at the top management production engineers at the middle management and skilled labour with supervisors. The manpower capacity of the company including casual labour is is 58. The company works in day and night shifts. shifts.
2.
MANUFACTU MANUFACTURE RE OF PRE STRESSE STRESSED D TUBULAR TUBULAR SPUN CONCRETE CONCRETE POLE POLE OF 11 METER METER LONG. LONG.
INTRODUCTION: Wooden, steel and concrete poles were used for power distribution lines since 19th century. The first poles used were wooden poles. When demand for poles increase and as the power lines under construction required longer poles suitable for resisting larger horizontal forces, steel poles were introduced in substitution towood. Though both materials are still in use through out the world, with wood primarily used for short length small forces country lines the general trend is to substitute both the materials with concrete and Use reinforced and prestressed concrete poles instead. Wooden have limited life and steel poles have a longer life compared to wooden poles requires continuous maintenance for protection against corrosion concrete and particularly prestressed concrete poles can be considered as having an unlimited life without maintenance cost for their corrosion protection. Poles supporting power lines are subjected to relatively small vertical forces and Primarily to large horizontal forces at bottom. The horizontal forces at their top are smaller along the axis of the power line and much larger on direction perpendicular to it. As in the perpendicular direction the pole must resist the horizontal forces cau sed from wind loads against the poles and the wires carried by them. In view of the difference in the horizontal forces to which a pole is subjected, the original solution given and, still adopted by authorities is to give the pole a cross section with larger moment in one direction and smaller one in the direction perpendicular to it like example a rectangular or double T cross section. Experience however has shown that concrete poles with a circular cross section are preferable to poles with rectangular or T section as they resist better impact loads and little extra cost give the added advantage that they have an equal resistance to horizontal forces in all direction. The circular cross section besides the advantage mentioned earlier lends it self to very well to use for the manufacture of poles of the spinning process. As w ell known the spinning process is one of the best methods of casting freshly cast concrete, as the centrifugal forces applied to concrete, secure a dense, excellent quality concrete at relatively less manufacturing costs. The pre stressed hollow or tubular pole have proved to be more economical, easily transported and erected due to lightweight.
Prestressed Tubular Spun Concrete Poles of 11 meter long were manufactured to BESCOM against their order.
3. TECHINACAL TECHINACAL SPECIFICATION FOR SPUN CONCRETE
POLES
3.1 SCOPE: This specification covers design, manufacture, testing and supply of pre stressed
concrete tubular spun poles designed for a working load of 500Kg. 3.2 APPLICABLE STANDARDS: The poles shall comply the provisions made in the following
IS specification except when the conflict con flict with specific requirements in this specification a)
IS 1678 1678-1 -197 978 8 Spec Specif ific icat atio ion n for for stre stress ssed ed conc concre rete te pole poless over overhe head ad powe power, r, trac tracti tion on and and
telecommunication lines. b)
IS 2905-1966-Methods of test for concrete poles for overhead power and telecommunication
lines c)
IS 7321-19 7321-1974 74 –Code –Code of prac practic ticee for select selection ion hand handlin ling g and errect errection ion of concr concrete ete pole poless for for
overhead power and telecommunication lines. d)
IS- 13158 13158-19 -1991 91 –Prest –Prestres ressed sed concr concrete ete circu circular lar spun spun poles poles for over overhea head d power power lines. lines.
3.3 TERMINOLOGY: For the purpose of this specification specification the definitions of average, permanent load, load factor, transverse load at first crack, ultimate failure, ultimate transverse load and working load shall be as per IS 1678 or any other equivalent International standards. 3.4 DIMENSIONS AND SHAPE: The poles shall be of hollow and circular in shape with an outside taper of 1:75. The diameter and thickness shall be as per design requirements. The tolerances shall be as follows: Outer diameter
+4mm
-2mm
Length
+50mm
-10mm
3.5 CEMENT: 3.5.1. High strength strength ordinary ordinary Portland Portland cement confirming confirming to IS 269-1976 or Rapid hardening hardening cement confirming to IS 804-1978 or any other cement of equivalent to International Standard shall be used which shall have the following additional requirements: Initial Setting Time: Not less than 30minutes Final Setting Time: Not more than 600minutes
3.5.2. The minimum compressive strength of standard mortar cube with standard sand as per IS650 at 7 days shall be 375kgs/cmsqare. 37 5kgs/cmsqare. A minimum 3 trail cubes shall be made with aggregate grading to be used for the approved mix and the average compressive results at 7 days shall be determined to asses the suitability of the cement for each and every batch of cement. 3.6 AGGREGATES:
Coarse aggregates and fine aggregates for ca sting of pole shall confirm to IS 383 or any other equivalent equivalent International International standard. standard. The normal maximum size of aggregates shall in no case more than 20mm or 1/4 th the minimum thickness of the pole whichever is less than the spacing between the prestressing wires. Each size of the graded aggregate shall be stocked in different storage bins or stock piles and shall be mixed only after the quantity required for each size has been separately weighed .The storage bins or stock piles shall be under cover to protect from weather. 3.7 WATER:
Water should be free from chlorides, sulphates other salts and organic matter. Potable water will be generally suitable. 3.8 ADMIXTURES :
Admixtures should not contain calcium chloride or other chlorides and salts which are likely to promote corrosion in steel.
3.9 REINFORCEMENT:
3.9.1. Reinforcing steel bars and wires wires used for the manufacture of prestressed pole shall confirm to the following Indian Standards or any other equivalent International Standards. a. IS: 1785(Pa 1785(Partrt-I) I) Specific Specificati ation on for plain plain hard hard drawn drawn steel wire for prestre prestresse ssed d concrete Part-I cold drawn stress relieved wire (second revision) b. IS: 1785(Part-II)-1983 Specification for plain hard drawn steel wire for prestressed concrete Part –II as drawn wire (First (First revision). c. IS: 2090-1983 2090-1983 Specificati Specification on for high high tensile tensile steel steel bars used in in PSC. d. IS-6003: IS-6003: 1983 Specifi Specification cation for for indented indented wire for for PSC(First PSC(First revision). revision).
3.9.2. The surface of all reinforcement shall shall be free from loose scale, oil grease, grease, clay or any other material that may have deterioting effect on the bond between the reinforcement and concrete. c oncrete. 3.10 CONCRETE: The concrete mix shall be designed to the requirement laid down for controlled concrete (also called design mix concrete) in IS 1343 and IS-456or any other equivalent International Standards subjected to the following conditions: a)
Mini Minimu mum m cub cubee str stren engt gth h at at 28 28 day dayss sho shoul uld d be be at at lea least st 50N/ 50N/mm mm2.
b)
The concrete strength at least half the 28day strength ensured in the design strength.
3.11 MOULDS:
Moulds shall be of steel and or rigid construction to prevent distortion and so arranged as to provide smooth surface. The moulds shall not allow any leakage of cement grout during casting. The The hole holess in the the end end pate patess for for HT wire wire shal shalll be accu accura rate tely ly dril drille led d by jigs jigs to ensu ensure re interchangeability. The end plate is designed to withstand forces arising out of the change in direction of prestressing wires during tensioning. 3.12 TENSIONING OF WIRES:
3.12.1. The HT wires shall be placed axially at regular spacing along the circumference. The spacing shall as per IS-1678 or any other equivalent International Standard. While cutting of HT wires automatic machines is be used. Button heading and forming reinforcement cages shall be done manually. 3.12.2. Helical steel shall be of 2.7mm dia MS wires pitch shall be of 150mm. 3.12.3. The clear cover shall be of 20mm. 3.12.4. Pre tensioning tensioning shall be by automatic automatic machines. machines. Force shall be applied applied for the entire group of HT wires to ensure all wires are equally stressed. 3.12.5. The pre stressing stressing wires wires shall be stretched stretched by an approved method. The anchoring anchoring of the stretched wires shall be such that during manufacture and until the wires are released, no slippage occurs. The force at the time of initial stretching shall addition to imparting of designed prestress also be sufficient to over come the friction on account of any change in the inclination of wires and slippage might occur during the anchoring anch oring process which will have to be suitably co mpensated 3.12.6. The tensioning of the prestressing wires shall be carried out in a manner that will induce a smooth and even rate increase of stress in the wires.
3.12.7. The force induced in the pre stressing wires shall be determined by means of gauges attached to the pretensioning apparatus and cross checked by extension to be achieved shall be determined well in advance, based on trails conducted on representative samples of wires as used in the pole. The accuracy of the devices for measuring of the tension force shall be within plus or minus 5%. 3.13 MIXING AND CONSOLIDATION OF CONCRETE:
3.13.1. Provision shall be made to measure the quantities of cement and fine and coarse aggregate by weight only. The accuracy of the measuring equipment shall be plus or minus 3%. All the measuring equipment shall maintained in clean and serviceable condition and accuracy regurly. Modern highspeed mixers, preferably pan or turbine type shall be used for mixing concrete. 3.13.2. The manufacture of poles shall be done under suitable cover and not in open. 3.13.3. The concrete shall be thoroughly mixed and consolidated. 3.13.4. Freshly cast poles shall protected during the first stage of hardening from harmful sunshine, dry winds, cold and rain. 3.14 DETENSIONING OF WIRES:
3.14.1. Anchoring system shall provide a device for gradual detensioning of the wires. No back pulling of the wires shall be permitted in gradual de tensioning device. Flame cutting of wires before release of full tension shall be strictly strictly prohibited. 3.14.2. The transfer of prestress shall not beeffected until the concrete in the poles has attained specified strength as established of the cube tests. 3.15 CURING:
3.15.1 The curing shall be done on a saturated steam at 65degrees centigrade. Ensure that 80% of strength is reached in 6 hours. There after wires will be cut demoulded and transferred to water for 14 days curing. 3.15.2 During manufacture periodical tests on concrete cubes of hallow cylindrical specimen measuring 200mm dia and 300mm height shall carried out till the concrete achieves the require strength at transfer. There after test on concrete shall be carried out as per IS 1343. 3.16 EARTHING: 3.16.1. Earthing shall be provided by having a length of 8SWG GI wire embedded in concrete during manufacture and ends of the wires left projecting from the pole to a length of 100mm at 250mm from top and 150mm below ground level.
3.16.2 Earth wire shall shall not be allowed allowed to come in contact with the pre stressing wire.
3.17. FINISH:
3.17.1. Poles shall be free from surface defects including hair cracks. The surface of the pole in contact with the steel mould shall be smooth and regular in shape and shall as for as possible be free from pores. Water retaining pockets and honeycombing formation shall not be admissible. 25mm thick 1:2 cement mortar cover shall be provided on the full area of the top of pole. 3.17.2. The ends of the pre stressing wires wires shall be cut as close to surface of the the pole as possible and in any case shall not project more than 3mm. 3.17.3. The ends of pre stressing wires shall be given two coats of suitable anti corrosive paints approved by BESCOM. 3.17.4. No touching up or finishing by cement grout grout shall be done on the poles after it is removed removed from the mould. 3.17.5. Metallic base plate is to be provided at the bottom of the pole. 3.18.WELDING AND LAPPING OF STEEL: The high tensile steel wire shall shall be continuous over the entire length of the tendon. Welding shall not be allowed in any case. 3. 19.PROVISION OF HOOKS AND HOLES:
3.19.1.Though holes shall be provided for fixing cross arms and clamp as specified by BESCOM. 3.19.2.A set of step up bolts shall be supplied along with each lot of 100 poles. 3.20.TESTS: 3.20.1 During manufacture tests tests on concrete shall shall be carried out as detailed detailed in this specification. 3.20.2 3.20.2 Transv Transvers ersee strengt strength h test: test: Poles Poles made made of ordina ordinary ry Portla Portland nd cement cement shall shall be tested tested on completion of 28 days and poles made of rapid hardening cement only on completion of 14 days after the day of manufacture. 3.20.3 The pole may be tested in either horizontal or vertical position. If tested on horizontal position provision may be made to compensate for hanging weight of the pole. For this purpose the over hanging portion of the pole p ole may be supported on a movable trolley or similar device.
3.20.4 The pole is rigidly supported at the buttoned for a distance equal to the agreed depth of planting. 3.20.5. Load shall be applied at a point 600mm from top of the pole and be steadily and gradually increased to the designed value of transverse load at first crack. The deflection at this load shall be measured. A pre stressed concrete pole shall be deemed not to have passed the test if visible cracks appear at a stage prior to the application of design transverse load for the first crack. The load shall then be reduced to zero and increased gradually to a load equal to the first crack load plus 10% of the minimum ultimate transverse load and held up for 2 minutes. This procedure shall be repeated until load reaches the value of 80% of the minimum ultimate transverse load and there after increased by 5% of the minimum ultimate transverse load until failure occurs. Each time load is applied applied it is held for 2 minutes. minutes. The load applied applied to PSC poles at the point of failure and shall be measured to the nearest 5Kgs. The pole shall be deemed not to have passed the test if the observed ultimate traverse load is less than the designed ultimate transverse load. 3.21. SAMPLING AND TESTING: 3.21.1. Lot-in a consignment of 500 poles or part thereof the same mounting height same dimension and belonging to the same batch of manufacture shall be grouped together to constitute a lot. 3.21.2 3.21.2 Sub-lot Sub-lot:: If the number number of poles poles in the lot exceed exceedss 500 the lot shall shall be divided divided into into suitable number of sub-lots such that the number poles in sub-lot shall not exceed 500. The acceptance or otherwise of a sub-lot shall be determined on the basis of performance of the samples selected from it. Size of lot
Permissible defective samples for dimension
Permissible defective sample for strength
0-100
2
4
100-200
4
6
200-300
6
8
300-500
8
12
4.MANUFACTURING 4.MANUFACTURING PROCESS OF TUBULAR PRESTRESSED CONCRETE POLE OF 11 METER LONG
The manufacture of Tubular PSC poles consists of the following operation: 1. Cleani Cleaning ng the moulds moulds and oiling oiling 2. Prepar Preparing ing the reinfo reinforce rcemen mentt cage cage 3. Placing Placing of PVC insert insertss and through through holes holes in the mould mould 4. Placin Placing g of the reinf reinforc orceme ement nt cage in in the mould mould.. 5. Mixi Mixing ng of of Con Concr cret ete. e. 6. Placin Placing g the the concret concretee in in moul mould. d. 7. Placin Placing g other other half half of the the mould mould and fixi fixing. ng. 8. Pre Pre tens tensio ioni ning ng the the wir wires es.. 9. Spin Spinni ning ng the the mou mould ld.. 10. Curing Curing with with steam steam 11. Demoulding Demoulding the pole. 12. Finished Finished dimension dimension of the pole. pole. 4.1.Cleaning the Mould: About the mould: Mould is made up of MS sheet. Mould of 11M length is made in two halves. Each half is made of 4 pieces and joined to gather. Mould is stiffened with circular MS flats. Enclosed drawing shows the detail. One half of the mould will be placed on rollers and the other half on ground. Cleaning: The mould halves are cleaned thoroughly with wire brush and oiled using REBOL oil. Oil is applied to the moulds with a painting brush. Dimension of the mould: Length-11000 mm +or-15mm OD (Big End)-392.5+4or-2mm OD (Small End)-227.5+4mmor-2mm
The mould when placed on the rollers the bigger rest on rollers powered by motor and remaining mould rests on support support rollers. rollers. Spacing between drive roller and the support roller is 3000mm. Number of rolling points is 5.
4.2 Preparing Preparing the Reinforcemen Reinforcementt Cage:
The reinforcement cage consists of the following: a) 7 mm dia HT indented wire of 13.5 meter length-11nos. b) 3 ply 3mm strands 5meter length –5nos c) 6 mm dia 8.2meter length earthing rod-1no. d) 2.7 dia coil 54meter long. The coil is fabricated to helical shape in a machine. machine. The pitch is 100mm.and 100mm.and 13.5meter long. and the bigger end dia of 342.5mm the smaller end dia of177.7mm.The helical coil is placed on the concrete mould having the shape of the pole placed on the ground. 3ply 3mm rods of 5meter are inserted into the helical coil and binded to it by binding wire. 11nos HT indented wires of 7mm dia are placed at equal spacing on the circumference of the coil the length of the wires being 13.5 meter the HT wires are tied to the coil by binding wire. These operations are made manually. End plates are inserted to the cage. 4.3. Placing PVC inserts, Nuts and through holes in the mould:
The following are inserted into the mould at designated places: PVC inserts-29nos. M16 Nuts –2nos. Through holes with nuts for fixing I-Bolts-5nos. 4.4 Placing of the cage in the mould:
The cage is lifted from the concrete mould by tower crane and placed on the MS mould for casting of the pole. The end plates are fixed to the mould by bolts. Earthing rod is inserted into the cage and placed at the designated place and welded to the MS 16 nuts placed in the mould 4. 5 Mixing of concrete
Cement of Birla 52 grade is used all required test are conducted at a reputed testing house and results approved for the use of this cement. The tests are conducted for every batch of o f 200 bags.
Sand: Locally available sand is used. The sand is stored in shade. The tests conducted on the sand in the factory laboratory are: a) Bul Bulking king of sand and b) Specific gravity c) Siev Sievee anal analys ysiis d) Wa Wate terr cont conten entt The above tests are conducted conducted for every load of cement. cement. Water content content of sand is estimated estimated daily and correction for water for mix is made. Coarse Aggregate: Coarse aggregate of 12.5mm down size are procured locally and stored in shade. The following test are conducted: a) Siev Sievee anal analys ysiis b) Surface dry By trial method a mix of 1:1:2.5 with water cement ratio of 0.35 and a plastiziser Conplast SP430 300ml per bag of cement is used gives concrete of strength of M52.5 Concrete is mixed in a batch mixer .3 loads of concrete is required for casting the pole. Each load consists of 85kg cement, 85kgs and 212.5kg coarse aggregate, 28.6litres of water, and 416Mlof SP430 are mixed for 10mnutes in the mixer. The concrete is transported in trolley ov er the railing. 4.6 Placing the concrete in the mould: Concrete transported is placed in the which is already with the mould.Concrete is placed manually by the masons and compacted lightly with tamping rod. Care is taken so that quantity qu antity of concrete mixed is uniformly placed throughout the mould starting from the bigger end. HT wires are button headed at the bigger end securely. 9 cubes of 15 cms cubes are prepared for compression test. 4.7 Placing the other half of the mould: mould: The other half of the mould already oiled is lifted using a truss with chains Using overhead crane. Care should be taken that the truss is properly fixed to the mould half by shackles. This half mould is placed on the already concreted mould properly. For proper seating of this mould is ensured through guide projections. After placing the mould the two halves are thoroughly tightened using bolts and nuts
4.8 Pre tensioning the wires: The HT indented 11nos wires w ires are pre tensioned at the smaller end of the already casted pole having fresh concrete. Pre tensioning is done using 2 hydraulic jacks. Diametrically opposite pairs of Ht wire are pre tensioned at a time using two hydraulic hydraulic jacks. The wires to be tensioned tensioned are buttoned securely to the anchoring plate. The hydraulic jacks are inserted to the wires and buttoned headed and load is applied to the wire manually. An extension of 115mm is obtained by applying pressure through the jack. Normally 330 to 340kgper sq.cm pressure is recorded in the pressure gauge attached to the jack. The extension required is obtained by Tension test results conducted on every supply of wires. After tensioning of the wire the excess wire is cut. Care should be taken that no movement of persons is allowed in front of the mould in the direction of tension. Some times if the wires are not properly buttoned the wires may come shoot out of the mould with great force. 4.9 Spinning the mould: After tensioning the wires all bolts are checked to its tightness. The mould at the bigger end is connected to a motor for spinning the mould at required speed. Both the ends are covered with covering plates and tightened with bolts. Spinning is done as per the following speed and time. TIME
MOTOR SPEED RPM
MOULD SPEED RPM
2 Minutes
550
72
3 Minutes
750
108
4 Minutes
950
136
9 Minutes
1100
156
The above speeds and time is arrived by trials.
4.10 Curing with steam: After spinning cover plates at the bigger end is removed and the cubes already casted in moulds are placed in the casted mould. Another cover plate which is having a hole for passing of the steam is fixed. Steam is produced through a boiler. Steam of temperature 100 degree centigrade is passed through already casted pole after 8 hours from mixing of concrete. Steam curing is done for 10 hours. The pole after demoulding is lifted and placed in curing water tanks for 14 days.
4.11 Demolding:
After cooling of the steam cover plates are removed. The cubes placed in mould are removed and compressive strength found out. Tension is realsed by cutting the HT wires. The top half of the mould is removed using truss and crane. I-Bolts are tightened to already existing through holes in the casted pole. The casted pole is lifted by using the truss connected crane by fixing hooks to the I-Bolt 4.12The Dimensions of the finished pole:
Bigger End Outer diameter: 392.5 mm Inner diameter: 292.5 mm Smaller End: Outer diameter: 227.7 mm Inner diameter: 12 7.7mm Thickness of the pole wall: 100 mm. Length of the pole: 11000 mm. 4.13 Testing of Pole: Test bench is established in the factory on ground with rigid support at the
bigger end 1.5meter from the bigger end. Intermediate rollers are provided at 4 meter from as required by BESCOM. Load is applied as pull from a dynamometer at the smaller end and load at first crack is noted. This load should not be less than 500Kg. Test is also carried out to destruction of pole and the load at destruction is noted.
5. TIME STUDY : I was asked by the company to monitor the manufacture time of the pole and
to make work study report. A sample work study format is enclosed. Work study was done and after 20 days of monitoring and making changes in work allotment to employees time for casting pole was reduced by 70 minutes.
7.CONCLUSION : 1.The pre stressed have a longer life compared to wooden or steel pole without maintenance cost for corrosion protection.
2.Because of its circular tapering section it has more stability and has ability to resist shear force and bending moment. 3.Since manufacturing process involve spinning process which is one of the best method of casting freshly cast concrete,has the centrifugal forces applied to concrete,secure a dense,excellent quality concrete at relatively less manufacturing cost. 4.Because it is pre fabricated the production p roduction of pole is consistant. 5.The pre stressed hallow or tubular pole have proved to be more economical,easily transported and erected due to light weight.
8. TIME STUDY FOR POLE CASTING.
Sl.No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Description Inserts Releasing H.T Wire cutting Bolts and nuts removing Demoulding Pole releasing Pole shifting Cleaning of mould Cage fixing & end plates Inserts fixing for first half Mixing first load of concrete Pouring of 1st load Mixing and pouring of 2 nd load Mixing and pouring of 3 rd load Mould assembling Pre tension Spinning TOTAL
Time in minutes 20 30 30 20 15 15 40 15 15 15 15 15 15 30 30 20 245
