ex inspaction

Pt

Ltd

Government Appointed ATL

CERTEX Appointed Ex Laboratory Laboratory

T0104

Reg No: 1999/027771/07 PO Box 467 Olifantsfontein Olifantsf ontein 1665

Tel: +27 (11) 316 4601 Fax: +27 (11) 316 5670 E- mail: [email protected] [email protected]

Inspection of in-service Explosion Protected Equipment - Unsafe Conditions and Cures

Presented by

Johannes Auret, Explolabs and CERTEX SAFA SYMPOSIUM 2011 CTICC

C CO ON NS SU UL LT TIIN NG G – Testing Testing and Certification – Certification Certification Mark for Explosion Protected (Ex) Equipment – – Area Area Classification / Explosion Risk Assessment – Inspection Inspection of New or In-service Ex Equipment & Installations – Management Management System for Ex Installations – Consultation Consultation – Presentations Presentations & Workshops – – Training Training Courses –

INSPECTION OF IN-SERVICE EXPLOSION PROTECTED EQUIPMENT Page 2 of 29

INDEX

TOPICS

Page

1. Introduct Introduction ion ................. .................................. .................................. .................................. ................................. ................................. ................................. .................. 3 2. Questions to be answered .................. ........ ................... ................... ................... ................... ................... .................. ................... ................... ........... .. 3 3. Definition of “Inspection” “Inspection” ............................... ............................................... ................................. .................................. .................................. ................. 3 4. Standards / Info Basis.............. ................... ......... ................... ................... ................... .................. ................... ................... .................. ............. .... 3 5. GRADES of inspection .................. ......... ................... ................... .................. ................... ................... ................... ................... .................. ................ ....... 4 6. TYPES of inspection.................. ........ ................... .................. ................... ................... .................. ................... ................... ................... ................... ........... .. 5 7. Generic Inspection Sheets.................. ........ ................... ................... ................... ................... ................... .................. ................... ................... ........... .. 6 8. Conclusi Conclusions ons ........................... ............................................ .................................. .................................. ................................. ................................. ..................... .... 25 Annex A Equipment selection.......................................................................................... 26

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C TIIN G CO ON NS SU ULLT NG


1. Introduction The inspection of Explosion Protected (Ex) Equipment, together with appropriate maintenance and repair, is critical for safety. This paper highlights the differences between electrical and Ex inspections and presents some solutions based on standards covering the subject and best practice from experience.

2. Questions to be answered 1 . Q : W h a t i s t h e P UR P OS E o f a n E x i n s p e c t i o n ? 2 . Q : W e k n o w w e n e e d to i n s p e c t i n -s e r v i c e Ex e q u i p m e n t at l ea s t o n c e i n 2 years (periodic ins pection ). - W h a t G r a d e o f i n s p e c t i o n m u s t b e u s e d (V /C /D ). 3 . Q : W h e n m u s t a d d i t io n a l i n s p e c ti o n s b e d o n e ? 4 . Q : W h o i s c o m p e t e n t t o d o i n s p e c t io n s ?

3. Definition of “Inspection” Action comprising careful scrutiny of an item carried out either without dismantling, or with the addition of partial dismantling as required, supplemented by means such as measurement, in order to arrive at a reliable conclusion as to the (suitability and) condition of an item.

4. Standards / Info Basis Legal Compliance Standard SANS 10086-1

SANS 10086-2

Based on Old version (Edition 2) of IEC 60079-17 SANS 10086-1, adapted for underground mining

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Application (technically) All surface installations in hazardous areas (under both the OHS Act and the MHS Act) All underground mining installations in hazardous areas



NOTE that information taken from SANS 60079-17 Edition 4 (IEC 60079-17 Edition 4) is used on the next pages (updated versions of the examples listed in SANS 10086-1). NOTE that this presentation is based on the above national standards. Individual companies may have stricter requirements.

5. GRADES of inspection SANS 60079-17 defines visual, close, and detailed inspections. visual inspection (V): An inspection that identifies, without the use of access equipment or tools, those defects, for example, missing bolts, which will be apparent to the unaided eye. Visual inspections do not require the enclosure to be opened, or the equipment to be de-energized. close inspection (C): An inspection that encompasses those aspects covered by a visual inspection and, in addition, identifies those defects, for example, loose bolts, which will be apparent only by the use of access equipment, for example, steps (where necessary) and tools. Close inspections do not require the enclosure to be opened, or the equipment to be de-energized. detailed inspection (D): An inspection that encompasses those aspects covered by a close inspection and, in addition, identifies those defects, for example, loose terminations, which will only be apparent by de-energizing the equipment and opening up the enclosure, or using, where necessary, tools or test equipment (or both).




6. TYPES of inspection TYPES of inspection are as follows.

Inspection Type Initial

Explanation

Purpose

Inspection of all electrical equipment, systems and installations before they are brought into service.

Periodic

Inspection of all electrical equipment, systems and installations carried out on routine basis. At least once in 2 years.

Sample

Inspection of a proportion of the electrical equipment, systems and installations

To check that selected type of protection and installation is correct. If supplier has quality control, only explosion protection features affected by installation need to be checked, e.g. flameproof joints on Ex d terminal box. To establish if the V or C. explosion protection of A visual or close periodic the item and installation is inspection might reveal the still intact. need for a detailed inspection. Example: Equipment in service and operates normally (fault free). V, C or D. To monitor the effect of environmental conditions, Example 1: Check 10% of motor stop-starts for vibrations , inherent cracks on insulators, design weaknesses, etc. Interpretation: To damaged seals. complement Periodic Example 2: Check the earth inspections by detecting high-quality for safety accelerated wear or impedance barriers on PT loops. damage that may only be detectable by a Detailed inspection.


Inspection Grades (V/C/D) applicable D (full or partial). Example 1: New installation. Example 2: Replacement motor.



7. Generic Inspection Sheets 7.1 Introduction Using the preceding definitions, generic inspection sheets from SANS 60079-17 Edition 4 (IEC 60079-17 Edition 4) may be used for practical inspection. (Reminder: These are updated versions of the examples listed i n SANS 10086-1). Depending on the sophistication of the inspection staff, these can be used, or specific checklists (suitable for specific equipment, e.g. fluorescent luminaries of a particular make and model, or Ex nA motors) can be compiled. The inspections sheets address three areas of compliance, i.e. the equipment, its installation and its environment. Equipment inspection requires the explosion protection rating and suitability to be first evaluated, then its condition. The inspection sheets make provision for the three grades of inspection, i.e. Visual (V), Close (C), Detailed (D).




7.2 APPLICATION – Ex ed indicator stop-start station (D)




Inspection schedule for Ex d, Ex e and T ype “n” installation (D = detailed, C = close, V = visual) Equipment description _____________ Tag no ________ Ex rating __________ 1

Check that:

2 Ex d D

C

3 4 Ex e Type “n” Grade of inspection V D C V D C V

1A 1 2 3 4 5 6

EQUIPMENT Equipment is appropriate to EPL/Zone requirement of the location ..... X X X X X X X X X Equipment group is correct ................................ ................................ .. X X X X X X Equipment temperature class is correct ............................. .................. X X X X X X Equipment circuit identification is correct ................................ ............. X X X Equipment circuit identification is available ............................. ............. X X X X X X X X X Enclosure, glasses and glass-to-metal sealing gaskets and/or compounds are X X X X X X X X X satisfactory 7 There are no uncertified modifications ............................... .................. X X X 8 There are no visible uncertified modifications ............................... ....... X X X X X X 9 Bolts, cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight X X X X X X  physical check ...................................................................................  visual check ....................................................................................... X X X X 10 Flange faces are clean and undamaged and gaskets, if any, are satisfactory ............................................................................................................. 11 Flange gap dimensions are within permitted maxima .......................... X X 12 Lamp rating, type and position are correct .............................. ............. X X X 13 Electrical connections are tight ............................... ............................. X X 14 Condition of enclosure gaskets is satisfactory .............................. ....... X X 15 Enclosed-break and hermetically sealed devices are undamaged ....... X 16 Restricted breathing enclosure is satisfactory ............................... ....... X 17 Motor fans have sufficient clearance to enclosure or covers (or both) .. X X X 18 Breathing and draining devices are satisfactory ............................. ....... X X X X X X 1B INSTALLATION 1 Type of cable is appropriate ................................ ............................... .. X X X 2 There is no obvious damage to cables .............................. .................. X X X X X X X X X 3 Sealing of trunking, ducts, pipes or conduits (or both) is satisfactory ... X X X X X X X X X 4 Stopping boxes and cable boxes are correctly filled ............................ X X X X 5 Integrity of conduit system and interface with mixed system is maintained ............................................................................................................. 6 Earthing connections, including any supplementary earthing bonding, are of sufficient cross-section X X  physical check ................................................................................... X  visual check ....................................................................................... X X X X X X X X X 7 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory .......................................................................................... 8 Insulation resistance is satisfactory .............................. ........................ X X X 9 Automatic electrical protective devices operate within permitted limits . X X X 10 Automatic electrical protective devices set correctly (no auto-reset) .... X X X 11 Specific conditions of use (if applicable) are complied with .................. X X X 12 Cables not in use are correctly terminated .............................. ............. X X X X X X 13 Obstructions adjacent to flameproof flanged joints are in accordance with IEC 60079-14 ............................................................................................. 14 Variable voltage/frequency installations are as per documentation ...... X X X X X X 1C ENVIRONMENT X X X X X X X X X 1 Equipment is adequately protected against corrosion, weather, vibration and other adverse factors ........................................................................... 2 No undue accumulation of dust and dirt ............................. .................. X X X X X X X X X 3 Electrical insulation is clean and dry ............................ ........................ X X NOTE 1 – General: The inspection for equipment that use types of protection "e" and "d " shall be a combination of columns 2 and 3. NOTE 2 – Account shall be taken of the possibility of an explosive atmosphere in the vicinity of the equipment, when electrical test equipment is used.




1A

EQUIPMENT

1*

Equipment is appropriate to EPL/Zone requirement of the location

EPL/Zone is provided from the area classification process. EPLs are determined by explosion risk and are mostly directly related to the allocated zones. Group

Zone

I

In underground mines, within 180m from working faces, return airways etc.

II

0

Minimum Equipment Protection Level (EPL) Ma Equipment remains functioning when explosive atmosphere present Mb Equipment isolated when explosive atmosphere present Ga

1

Gb

2

Gc

20

Da

21

Db

22

Dc

III

If more than one EPL, all must comply.




2*

Equipment group is correct Selected to suit the explosive atmosphere group (related to spark ignition properties i.e. minimum ignition energy). Normally determined during area classification.

3*

Equipment temperature class is correct Based on explosive atmosphere temperature class (related to heat ignition properties i.e. auto-ignition temperature) or minimum ignition temperature. Normally determined during area classification.

4,5

Equipment circuit identification is available (correct if detailed inspection) The purpose of this requirement is to facilitate the correct isolation of equipment whenever work is to be carried out. This can be achieved in a variety of ways, for example: a) Equipment is fitted with a permanent label which specifies the source of supply. b) Equipment is fitted with a tag number or the cable is fi tted with a cable number adjacent to the equipment.

6*

Enclosure, glasses and glass-to-metal sealing gaskets and/or compounds are satisfactory All enclosures must be able to handle reasonable impact, to prevent creation of ignition sources. Ex d equipment Enclosure must withstand internal explosion, including window glass/polymer parts.

Ex e and Type “n” equipment Enclosure must provide IP54 rating if containing bare live parts.




7, 8

There are no (visible) uncertified modifications Modifications = The explosion protection is affected! If not, the certified state of the equipment remains valid (painting).

9*

Bolts, cable entry devices (direct and indirect entry) and blanking elements are of the correct type and are complete and tight  physical check  visual check

Cable glands, adaptors and plugs must have the same explosion protection as the enclosure to which connected. The check-tightening of cable glands under close inspection can be effected by hand without t he need to remove weather proofing tape or shrouds. Detailed inspections may necessitate that the cable glands are dismantled only where the integrity of the glands cannot be ascertained by close Inspection.




10

Ex d Flange faces are clean and undamaged and gaskets, if any, are satisfactory

Faces must be rust-free and without deep pits, scratches or marks, e.g. caused by screwdriver to remove lid. A thin layer of grease (not silicone rubber) after removing loose rust is ideal protection. 11

Ex d Flange gap dimensions are within permitted maxima Generally speaking, the biggest flange gap that will be permitted is 0,4mm. A feeler gauge can be carried along. It should be possible to confirm a completely tight fit visually on smaller enclosures. N O T E 1 - It i s n o r m a l l y c o n s i d e r e d n o t n e c e s s a r y t o c h e c k t h e d i a m e t r i c c l e a r an c e o f s p i g o t , s h a f t , s p i n d l e a n d t h r e a d e d j o i n t s , u n l e s s t h e r e i s evidence of wear, distortion , corro sion o r other damage.

NOTE 2 - When reassembling flameproof enclosures, all (inspected) joints shall be thoroughly cleaned and may be lightly smeared with a suitable grease to prevent corrosion and to assist weather-proofing. Blind bolt-holes shall be kept clear of grease. Only non-metallic scrapers and non-corrosive cleaning fluids shall be used to clean flanges. Fasteners on Ex d external flanges must not protrude.

12

Lamp rating, type and position are correct




Lamps with higher power ratings or other types of lamps may get hotter than the approved lamp type. Some lamps will have a specific condition of use in terms of position/orientation, for example the lens of a highbay light fitting normally pointing downwards will get hotter if the light is pointed up. 13

Ex e, Type “n” Electrical connections are tight

Loose connections can cause sparks or hot spots. 14*

Ex e, Type “n” Condition of enclosure gaskets is satisfactory.

IP54 rating of enclosures containing live bare parts must be ensured. 15

Type “n” Enclosed-break and hermetically sealed devices are undamaged Enclosed-break and hermetically sealed devices are part of Ex nC equipment and must respectively contain an internal explosion and provide a gas-tight seal.

16

Type “n” Restricted breathing enclosure is satisfactory Restricted breathing devices are part of Ex nC equipment and must only allow a low exchange rate between internal and external atmosphere.

17

Motor fans have sufficient clearance to enclosure or covers (or both) To prevent frictional heat.




18

Breathing and draining devices are satisfactory Ex d equipment B&D devices contains at least one flameproof joint. Ex e and Type “n” equipment B&D devices must provide IP54 rating if enclosure contains bare live parts.

1B

INSTALLATION

1

Type of cable is appropriate Cables used for f i x ed w i r i n g in hazardous areas shall be appropriate for the ambient conditions in service. Cables shall be: a) sheathed with thermoplastic, thermosetting, or elastomeric material. They shall be circular, compact, have extruded bedding and f illers, if any, shall be non hygroscopic, or b) mineral insulated metal sheathed, or c) special, e.g. flat cables with appropriate cable glands. Such cables must be flame retardant. F l e x i b l e cables in hazardous areas shall be selected from the following:

• • • • •

ordinary tough rubber sheathed; ordinary polychloroprene sheathed; heavy tough rubber sheathed; heavy polychloroprene sheathed; plastic insulated and of equally robust construction to heavy tough rubber sheathed flexible cables.

Cables shall preferably be substantially compact ( round and filled). If not so for Ex d connections, then use barrier gland.

2

There is no obvious damage to cables

3

Sealing of trunking, ducts, pipes or conduits (or both) is satisfactory Openings in walls for cables and conduits between different hazardous areas and between hazardous and non-hazardous areas shall be adequately sealed, for example by means of sand seals or mortar sealing to maintain the area classification where relevant. Trunking, ducts or pipes connecting differently zoned areas must be sealed, for example by a sealing compound or sealing devices. For trenches, adequate venting or sand-filling may be used.




4

Stopping boxes and cable boxes are correctly filled

5

Integrity of conduit system and interface with mixed system is maintained

6

Earthing connections, including any supplementary earthing bonding, are of sufficient cross-section  physical check  visual check

Bonding connections must prevent self loosening and corrosion which may reduce the effectiveness of connection. Metallic enclosures of intrinsically safe or energy-limited apparatus generally need not be connected to the equipotential bonding system. 7

Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory Intrinsically safe resistance measuring equipment may be used, or the measurement may be carried out under a hot work permit if absence of explosive atmospheres in the areas affected can be guaranteed.

8*

Insulation resistance is satisfactory The insulation resistance for equipment and associated cabling up to 500 V (excluding safety extra-low voltage, SELV, electrical systems) shall be measured at 500 V d.c. The insulation resistance shall generally be at least 1,0 MΩ.

9*

Automatic electrical protective devices operate within permitted limits The following electrical protection is compulsory and must therefore comply with the above: Wiring Protection against overload and from the harmful effects of short-circuits and earth faults. All electrical equipment Protection against the harmful effects of short-circuits and earth faults.




Multi-phase electrical equipment (e.g. three-phase motors) Protection against loss of one or more phases where this can cause overheating to occur. Motors and transformers must be protected against overload. Resistance heating devices must be protected against overcurrent and earthleakage or earth-fault currents. In circumstances where automatic disconnection of the electrical equipment may introduce a safety risk which is more dangerous than that arising from the risk of ignition alone, a warning device (or devices) may be used as an alternative to automatic disconnection provided that operation of the warning device (or devices) is immediately apparent so that prompt remedial action will be taken. 10

Automatic electrical protective devices set correctly (no auto-reset) Short-circuit and earth-fault protection devices shall prevent auto -reclosing under fault conditions.

11*

Specific conditions of use (if applicable) are complied with Specific conditions of use are determined by the ATL as part of explosion prevention and stipulated in the equipment certificate. They address the user as they comprise essential information for the installation, use, and maintenance of the equipment must be complied with by the user. They can either be shown in full on the equipment lable or if there is a lack of space, be referenced by including an “X” suffix after the certificate number.

12*

Cables not in use are correctly terminated

If unused cable are not removed, the cores of the hazardous area end of such unused cables shall either be connected to earth or be adequately insulated by means of terminations suitable for the type of protection, for example isolating and capping both ends. Insulation by tape alone is not permitted.




13

Obstructions adjacent to flameproof flanged joints are in accordance with SANS 60079-14

Minimum distance are as follows: Gas group IIA IIB IIC

14

Minimum distance (mm) 10 30 40

Variable voltage/frequency installations are as per documentation Ex motors must be type-tested together with the VSD. Ex d, Ex p, Type “n” and Ex tD motors can alternatively be installed with a temperature sensing system. The maximum temperature of Type “n” motors operating with VSDs can alternatively be calculated.

1C

ENVIRONMENT

1*

Equipment is adequately protected against corrosion, weather, vibration and other adverse factors

2

No undue accumulation of dust and dirt

3

Electrical insulation is clean and dry




7.3 APPLICATION – Ex i level gauge (D)




Inspection schedule for Ex i, Ex iD and Ex nL installations Equipment description _______________ Tag no ___________

Ex rating __________

1

2

3

4

Grade of inspection Check that:

Detailed

Close

Visual

X

2A EQUIPMENT 1

Circuit or equipment (or both) documentation is appropriate to area classification

X

X

2

Equipment installed is that specified in the documentation  Fixed equipment only

X

X

3

Circuit or equipment (or both) category and group are correct ............. .......

X

X

4

Equipment temperature class is correct ............................... .......................

X

X

5

Installation is clearly labelled ................................ ................................ .......

X

X

6

X

7

Enclosures, glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory There are no unauthorized modifications ....................................................

8

There are no visible unauthorized modifications ............................. ............

X

X

X

9

X

X

X

10

Safety barrier units, relays and other energy limiting devices are of the approved type, installed in accordance with the certification requirements and securely earthed, where required Electrical connections are tight ............................ ................................. .......

11

Visible printed circuit boards are clean and undamaged ...... .......................

X

X

X

2B INSTALLATION 1

Cables are installed in accordance with the documentation ........................

X

2

Cable screens are earthed in accordance with the documentation .............

X

3

There is no obvious damage to cables ................................. .......................

X

X

X

4

Sealing of trunking, ducts, pipes or conduits (or both) is satisfactory ..........

X

X

X

5

Point-to-point connections are all correct ............................. .......................

X

6

Earth continuity is satisfactory (for example, connections are tight and conductors are of sufficient cross-sectional area) ....................................................................

X

7

Earth connections maintain the integrity of the type of protection ................

X

X

X

8

X

11

The intrinsically safe circuit is isolated from earth or earthed at one point (see the documentation) ........................................................................................... Separation is maintained between intrinsically safe and non-intrinsically safe circuits in common distribution boxes or relay cubicles ............................................... As applicable, short-circuit protection of the power supply is in accordance with the documentation ............................................................................................ Special conditions of use (if applicable ) are complied with ........................ .

12

Cables not in use are correctly terminated ................................ ..................

X

X

X

X

X

X

X

9 10

X X X

2C ENVIRONMENT 1 2

Equipment is adequately protected against corrosion, weather, vibration and other adverse factors ......................................................................................................... There is no undue accumulation of dust and dirt .........................................




2A

EQUIPMENT

1*

Circuit and/or equipment documentation is appropriate to the EPL/zone requirements of the location

The essential documents are the ATL-certified installation ( loop) drawing and the ATL certificates for individual equipment used in the loop. EPL/Zone is provided from the area classification process. EPLs are determined by risk and are mostly directly related to the allocated zones 2*

Equipment installed is that specified in the documentation  Fixed equipment only

3*

Circuit or equipment (or both) category and group are correct Levels of protection (EPLs) available for intrinsic safety equipment are ia, ib and ic. EPL/Zone is provided from the area classification process. EPLs are determined by risk and are mostly directly related to the allocated zones. Equipment group is selected to suit the explosive atmosphere group (related to spark ignition properties i.e. minimum ignition energy). Normally determined during area classification.

4*

Equipment temperature class is correct Only the instrument (equipment exposed to explosive atmosphere) has a temperature rating.

5

Installation is clearly labelled The compulsory labeling of equipment must be checked to ensure that the equipment actually fitted is that specified. Further, the tag numbers must correspond with the tag numbers used in the control room basement,




6*

Enclosures, glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory

IP ratings are sometimes essential. 7, 8

There are no (visible) unauthorized modifications This includes exchanging one type of device with a similar (but not identical) unit, e.g. a new series.

9

Safety barrier units, relays and other energy limiting devices are of the approved type, installed in accordance with the certification requirements and securely earthed, where required

(Shunt-diode safety) barriers require a high-quality earth connection in order to provide protection. 10

Electrical connections are tight Loose connections can cause loss of protection, e.g. earth connection on barrier, earthing of screens and redundant cores.

11*

Visible printed circuit boards are clean and undamaged




2B

INSTALLATION

1*

Cables are installed in accordance with the documentation

The insulation properties and inductance and capacitance values of the specified cable are critical for safety. 2*

Cable screens are earthed in accordance with the documentation Generally, screens are earthed at one point i.e. in the safe area. They must however not be cut off.

3

There is no obvious damage to cables

4

Sealing of trunking, ducts, pipes or conduits (or both) is satisfactory Openings in walls for cables and conduits between different hazardous areas and between hazardous and non-hazardous areas shall be adequately sealed, for example by means of sand seals or mortar sealing to maintain the area classification where relevant. Trunking, ducts or pipes connecting differently zoned areas must be sealed, for example by a sealing compound (e.g. expansion foam) or sealing devices. For trenches, adequate venting or sand filling may be used.

5

Point-to-point connections are all correct

This check only needs to be done during the initial inspection.




Point-to-point generally refers to a connection restricted to two endpoints. In this case, the termination points of conductors. The reliability of a termination is influenced by the termination method. For example, soldered, bolted or screwed connections may have infallibility status. 6*

Earth continuity is satisfactory (for example, connections are tight and conductors are of sufficient cross-sectional area) For an earthed (shunt-diode safety) barrier, earthing conductor must be at least x2 1.5mm2 or x1 4mm2 .

7

Earth connections maintain the integrity of the type of protection Check continuity of essential earth connections, e.g. transformer screen earth, barrier relay frame earth.

8*

The intrinsically safe circuit is isolated from earth or earthed at one point (see the documentation)

This check is only needed on a sampling basis. Insulation from or connection to earth, as required by the loop design, to be verified. Not necessary to test if a fault is self-revealing. If shunt-diode safety barrier (Zener barrier) earths have to be disconnected for such a test, ensure that loops are first de-energized. 9

Separation is maintained between intrinsically safe and non-intrinsically safe circuits in common distribution boxes or relay cubicles Clearance of at least 50mm is required, or insulating or earthed barriers.




10

As applicable, short-circuit protection of the power supply is in accordance with the documentation Output voltage restricted to Um shown on the label of the associated apparatus; normally 250V. The prospective short-circuit current of the supply shall not be greater than 1500A.

11*

Specific conditions of use (if applicable) are complied with Specific conditions of use are determined by the ATL as part of explosion prevention and stipulated in the equipment certificate. They address the user as they comprise essential information for the installation, use, and maintenance of the equipment must be complied with by the user. They can either be shown in full on the equipment lable or if there is a lack of space, be referenced by including an “X” suffix after the certificate number.

12

Cables not in use are correctly terminated All screens, armour and conductors of redundant cables must be earthed inside the hazardous area using an explosion protected junction box. In the safe area, follow standard isolation protocol.

2C

ENVIRONMENT

1

Equipment is adequately protected against corrosion, weather, vibration and other adverse factors

2

There is no undue accumulation of dust and dirt




8. Conclusions 1 . Q : W h a t i s t h e P UR P OS E o f a n E x i n s p e c t i o n ?

A: To preserve the explosion protection features (and certification). 2 . Q : W e k n o w w e n e e d to i n s p e c t i n -s e r v i c e Ex e q u i p m e n t at l ea s t o n c e i n 2 years (periodic ins pection ). - W h a t G r a d e o f i n s p e c t i o n m u s t b e u s e d (V /C /D ).

A: V and C are prescribed. 3 . Q : W h e n m u s t a d d i t io n a l i n s p e c ti o n s b e d o n e ?

A: Firstly, “Initial” inspection before putting replacement equipment or equipment that has been opened for calibration or routine servicing back in operation. Partial or comprehensive, for example only the terminal box of a repaired motor. Secondly, sample inspections must complement periodic inspections to reveal hidden damage due to equipment design weaknesses and environmental conditions. Premature failure can generate ignition sources. 4 . Q : W h o i s c o m p e t e n t t o d o i n s p e c t io n s ?

A: The OHS Act requires inspectors to have appropriate competence. Operatives shall possess, to the extent necessary to perfo rm their tasks, the following competencies according to SANS 60079-17: a) b) c) d) e) f) g) h) i) j)

understanding of the general principles of explosion protection; understanding of the general principles of types of protection and marking; understanding of those aspects of equipment design which affect the protection concept; understanding of certification of Ex equipment and installations; understanding of the additional importance of Permit to Work systems and safe isolation in relation to Explosion Protection; familiarity with the particular techniques to be employed in the inspection and maintenance of Ex equipment; comprehensive understanding of the selection and erection requirements of Ex equipment and installations; general understanding of the repair and reclamation requirements of SANS 10086-3; use and availability of certification documentation; practical skills necessary for the inspection and maintenance of relevant concepts of Ex protection.

THANK YOU

QUESTIONS ?




Annex A

Equipment selection

A.1 Information required In order to select the appropriate electrical equipment for hazardous area caused by gases, vapours or dusts, the following information is required: Classification of the hazardous area including the equipment explosion protection level (EPL) requirements where applicable; Where applicable, gas, vapour or dust classification in r elation to the group or subgroup of the electrical equipment; Temperature class or ignition temperature of the gas or vapour involved; Minimum ignition temperature of the combustible dust cloud, minimum ignition temperature of the combustible dust layer and m inimum ignition energy of the combustible dust cloud; External influences and ambient temperature.

A.2

Selection according to EPL

Statistical approach and Zones In the past, a statistical approach to equipment selection was followed: probability of a fire or explosion occurring can be expressed as:

The

pe = pg x pi

Where - pe is the probability of a fire or explosion occurring; - pg is the probability that an explosive atmosphere will be present in a particular place at a particular time (given by the zone); and - pi is the probability that the above explosive atmosphere can be ignited. pe and consequently the product p g x p i must be acceptably low. (A probability of 10 -5 is considered acceptable, refer to Hickes and Brown). This means that if the probability of an explosive atmosphere being present increases, the probability that it can be ignited must decrease and vice versa. Equipment protection is selected in accordance with the zone in this approach. Risk-based approach The equipment selection standard now also allows for a risk-based approach. In a risk-based approach, the consequence of an explosion is also taken into account, together with the probability of an explosion. This means quite simply that under certain circumstances, the occurrence of an explosion is more t olerable (or less tolerable) than normal. Copyrigh t of this material belongs to



Example: A typical example is of two neighbouring plants of similar design, but due to differences in the materials being handled, the one is Zone 1 and the other Zone 2. Some engineers will decree that Zone 1 equipment is used even in the Zone 2 plant, because the danger exists that the wrong replacement equipment will be selected from stores during a breakdown. Equipment Protection Level (EPL)

To facilitate the risk-based approach, the concept of Equipment Protection Level (EPL) was introduced. The EPL for each explosion protection technique has been determined, based on its likelihood of becoming a source of ignition. The EPL ranges from a “Very High” to b “High” to c “Normal” and distinguishes between explosive gas (G), dust (D) and mine (M) atmospheres. The table below shows the relationship between types of protection and EPLs. Protection afforded

Very High

EPL Group I „Ma‟

Very High

Type of protection Group II

High

Conditions of operation

Group III

„Ga‟

Intrinsically safe Encapsulation

„Da‟

„Mb”

„Gb‟

„Db‟

„ia‟ „ma‟

SANS 60079-11 SANS 60079-18

Two independent type of protection each meeting EPL „Gb‟ Protection of equipment and transmission systems using optical radiation Intrinsically safe

„iD‟

SANS 60079-11

Encapsulation

„mD‟

SANS 60079-18

Protection by enclosure Same as „Gb‟

„tD‟

SANS 60079-31

Flameproof enclosures

„d‟

SANS 60079-1

Increased safety Intrinsically safe

„e‟ „ib‟

SANS 60079-7 SANS 60079-11

Encapsulation

„m‟ „mb‟

SANS 60079-18

Oil immersion

„o‟

SANS 60079-6

Pressurized enclosures

„p‟, „px „or „py‟ „q‟

SANS 60079-2

Powder filling

High

According to standard

Same as „Ga‟

Very High

High

Code

SANS 60079-26

SANS 60079-28

SANS 60079-27

Protection of equipment and transmission systems using optical radiation Intrinsically safe

SANS 60079-28

„iD‟

Equipment remains functioning in Zones 20, 21 and 22

Equipment deenergised when explosive atmosphere present Equipment remains functioning in Zones 1 and 2

SANS 60079-5

Fieldbus intrinsically safe concept (FISCO)


Equipment remains functioning when explosive atmosphere present Equipment remains functioning in Zones 0, 1 and 2

SANS 60079-11

Equipment remains


INSPECTION OF IN-SERVICE EXPLOSION PROTECTED EQUIPMENT Page 28 of 29 Protection afforded

EPL

Type of protection

Group I

Normal

Group II

According to standard

Conditions of operation

functioning in Zones 21 and 22

Group III

„Gc‟

Normal

Code

„Dc‟

Encapsulation Protection by enclosure Pressurized enclosures Intrinsically safe Encapsulation

„mD‟ „tD‟

SANS 60079-18 SANS 60079-31

„pD‟ „ic‟ „mc‟

SANS 61241-4 SANS 60079-11 SANS 60079-18

Non-sparking

SANS 60079-15

Restricted breathing

„n‟ or „nA‟ „nR‟

Energy limitation

„nL‟

SANS 60079-15

Sparking equipment Pressurized enclosures

„nC‟ „pz‟

SANS 60079-15 SANS 60079-2

Fieldbus non-incendive concept (FNICO) Protection of equipment and transmission system using optical radiation Intrinsically safe Encapsulation Protection by enclosures Pressurized enclosures

Equipment remains functioning in Zone 2

SANS 60079-15

SANS 60079-27 SANS 60079-28

„iD‟ „mD‟ „tD‟

SANS 60079-11 SANS 60079-18 SANS 60079-31

„pD‟

SANS 61241-4

Equipment remains functioning in Zone 22

Selection If risk is normal, which is mostly the case, the probability of an explosion is the only controlling factor and a direct relationship between EPL and Zone exists that is used to select equipment: Table A.1 – Equipment protection level (EPLs) where only zones are assigned Zone 0

Minimum Equipment Protection Level (EPL) Ga

1

Gb

2

Gc

20

Da

21

Db

22

Dc

Where in exceptional circumstances, the risk is not normal, a higher or lower EPL than that defined in the table may be required. It is recommended that the required explosion protection levels (EPLs) are recorded on the area classification drawing, even if the risk-based approach has not been followed.




A.3

Selection according to equipment grouping

Relationship between gas/vapour subdivision and equipment subgroup Environment

Gas, vapour or dust (sub)division

Permitted equipment group

I

I

IIA

II, IIA, IIB or IIC

IIB

II, IIB or IIC

IIC

II or IIC

IIIA

IIIA, IIIB or IIIC

IIIB

IIIB or IIIC

IIIC

IIIC

Underground mines Gas and vapour, Surface

Dust, Surface

A.4

Selection according to the ignition temperature of the gas or vapour

The electrical equipment shall be so selected that its maximum surface temperature will not reach the ignition temperature of any gas or vapour which may be present. Relationship between the equipment temperature classes and surface temperatures and ignition temperature Temperature class required by the area classification

Ignition temperature of gas or vapour (°C)

T1

Suitable equipment temperature class

>450

Maximum surface temperature of equipment (°C) 450

T2

>300

300

T2 - T6

T3

>200

200

T3 - T6

T4

>135

135

T4 - T6

T5

>100

100

T5 - T6

T6

>85

85

T6


T1 - T6


ex inspaction

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