Table of Contents
Inspection #
When inspecting Ex I installations, pay particular attention to the following points:-
- The components of the installation must be certified I.S., unless identified as ‘Simple’ in the documentation/specifications
- All equipment must be as specified and included in the documentation, and be suitable for the location area classification and environment
- Connection facilities (including junction boxes) must be clearly identified or labelled to shoe that the circuits are intrinsically safe.
- I.S. cables must be identified by colour (light blue) or labelling (unless they are armoured or have metallic sheath)
- I.S. and non-I.S. cables must be adequately separated (unless either are armoured or have metallic sheath
- Cable glands must be correct for the enclosure they enter.
- Check the earthing of cable screens – they must be earthed at one point only as shown in the documentation (usually at the I.S earth bar)
- Check that I.S. earth is separate from, and not connected to, protective earth, enclosure metal work etc.
- Unused cable cores must be insulated from earth and one another using separate terminals at both ends (or one end may be connected to the same earth point as the IS circuits)
- I.S. and non-I.S. circuits must be separated inside enclosures.
I.S. and non-I.S. terminals must have 50mm minimum clearance. Separation also applies to I.S. and non-I.S. wiring and cores from I.S. and non-I.S. cables.
Note:
- Safety barrier earth connection shall not be removed before disconnecting the hazardous area circuits except where duplicate earth connections are provided.
- If an I.S. circuit has both Ex ‘ia’ & Ex ‘ib’ equipment installed in the same loop, the overall level of protection of the loop will be Ex ‘ib’.
- On handover of a newly installed IS system, no faults are permissible.
- Point-to-point connections check is only required at the initial inspection.
IEC 60079-17: 2013 #
Table 2: Inspection Schedule for Ex ‘I’ Installations (D=detailed, C=Close, V=Visual)
| Check that: | X = required | Grade | of | Inspection |
| D | C | V | ||
| A | Equipment | |||
| 1 | Circuit and/or equipment documentation is appropriate to area classification | X | X | X |
| 2 | Equipment installed is that specified in the documentation | X | X | |
| 3 | Circuit and/or equipment category and group correct | X | X | |
| 4 | IP rating of equipment is appropriate to the group III material present | X | X | |
| 5 | Equipment temperature class is correct | X | X | |
| 6 | Ambient temperature range of the apparatus is correct for the installation | X | X | |
| 7 | Service temperature range of the apparatus is correct for the installation | X | X | |
| 8 | Installation is clearly labelled | X | X | |
| 9 | Enclosure, glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory | X | X | |
| 10 | Cable glands and blanking elements are the correct type, complete and tight – physical and visual check | X | X | X |
| 11 | There are no unauthorised modifications | X | ||
| 12 | There is no evidence of unauthorised modifications | X | X | |
| 13 | Diode safety barriers, galvanic isolators, relays and other energy limiting devices are of the approved type, installed in accordance with the certification requirements and securely earthed where required | X | X | X |
| 14 | Conditions of enclosure gaskets is satisfactory | X | ||
| 15 | Electrical connections are tight | X | ||
| 16 | Printed circuit boards are clean and undamaged | X | ||
| 17 | The maximum voltage Um of the associated apparatus is not exceeded | X | X | |
| B | Installation | |||
| 1 | Cables are installed in accordance with the documentation | X | ||
| 2 | Cables 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 and/or conduits is satisfactory | X | X | X |
| 5 | Point-to-point connections are all correct (initial inspection only) | X | ||
| 6 | Earth continuity is satisfactory (e.g. connections are tight and conductors are of sufficient cross-section) for non-galvanically isolated circuits | X | ||
| 7 | Earth connections maintain the integrity of the type of protection | X | X | X |
| 8 | The intrinsically safe circuit earthing is satisfactory | X | ||
| 9 | Insulation resistance is satisfactory | X | ||
| 10 | Separation is maintained between intrinsically safe and non-intrinsically safe circuits in common distribution boxes or relay cubicles | X | ||
| 11 | Short-circuit protection of the power supply is in accordance with the documentation | X | ||
| 12 | Special conditions of use (if applicable) are complied with | X | ||
| 13 | Cables not in use correctly terminated | X | ||
| C | Environment | |||
| 1 | Equipment is adequately protected against corrosion, weather, vibration and other adverse factors | X | X | X |
| 2 | No undue accumulation of dust and dirt | X | X | X |
IEC 60079-17 Table 2 (Explained) #
Part A : Equipment #
| IEC No. | Grades | Check That: | Explanatory Note |
| A.1 | D,C,V | Circuit and/or equipment documentation is appropriate to the EPL/zone requirements of the location. | Using the Area Classification of the plant and the hook-up drawings, check that the equipment is suitable for the EPL/zone where installed. |
| A.2 | D,C | Equipment installed is that specified in documentation | Using the material specification check for the type, make and certification details |
| A.3 | D,C | Circuit and/or equipment level of protection and group correct | Group II equipment installations should be checked to ensure that the classification is correct for the gas subdivision in the area of use |
| A.4 | D,C | IP rating of equipment is appropriate to the group III material present (DUSTS) | IP rating shall be appropriate for the Group IIIA, IIIB or IIIC with level of protection “ta”, “tb”, or “tc” |
| A.5 | D,C | Equipment temperature class is correct | Check that the equipment temperature classification as given on rating plate is appropriate to the applicable gases. |
| A.6 | D,C | Ambient temperature range of the apparatus is correct for the installation | Temperature |
| A.7 | D,C | Service temperature range of the apparatus is correct for the installation | |
| A.8 | D,C | Installation is clearly labelled | All required labels, markings and rating plates are to be legible and comply with the requirements laid down in the document. |
| A.9 | D,C | Enclosure, glass-to-metal sealing gaskets and/or compounds are satisfactory | Unlikely that this would need checking except for equipment for use in combustible dust. |
| A.10 | D,C,V | Cable glands and blanking elements are the correct type, complete and tight — physical and visual check | Cable glands, adapters and blanking plugs shall maintain the degree of protection of the enclosure and shall be selected appropriate to maintain the enclosure protection integrity. They must be tight and can only be removed by tool. |
| A.11 | D | There are no unauthorised alternations | The equipment and electrical circuits are to be checked to ensure that there have been no unauthorised alternations. |
| A.12 | C,V | There is no evidence of unauthorised modifications. | As A.11, as far as practical in these inspection grades. |
| A.13 | D,C,V | Diode Safety barrier, galvanic isolators, relays and other energy limiting devices are of the approved type, installed in accordance with the certification requirements and securely earthed | Verify all installed components match the certification requirement and screens are earthed as shown in the circuit diagram. |
| A.14 | D | Conditions of enclosure gaskets is satisfactory | Check for any visible damages to the gaskets |
| A.15 | D | Electrical connections are tight | Connections at the terminals of the are secured tight with appropriate ferrules |
| A.16 | D | Printed circuit boards are clean and undamaged | Detecting modifications to printed circuit boards may present difficulties. Any discolouration or variation in the soldering quality or appearance should be noted and where possible compared with any reported changes or repairs. |
| A.17 | C,V | The maximum voltage Um of the associated apparatus is not exceeded |
Part B : Installation (IEC 60079-17 Table 2 cont.) #
| IEC No. | Grades | Check That: | Explanatory Note |
| B.1 | D | Cables are installed in accordance with the documentation | Check that the correct cables installed. Check that the cores of multi-core cables are used as indicated in the documentation and cores shown as unused are in fact unused, and have not been used for unscheduled purposes. |
| B.2 | D | Cables screens are earthed in accordance with the documentation | Verify cable screens are insulated and earthed as shown in the circuit diagram. |
| B.3 | D,C,V | There is no obvious damage to cables | Check the cable outer sheath, and individual core as it comes out of the gland (D). |
| B.4 | D,C,V | Sealing of trunking, ducts, pipes and/or conduits is satisfactory | Check to ensure conduit entry is sealed and no fitting is installed between sealing and enclosure |
| B.5 | D | Point-to-point connections are all correct (initial inspection only) | Required test every loop prior to further testing or commissioning of the system |
| B.6 | D | Earth continuity is satisfactory (connections, sufficient csa) for non-galvanically isolated circuits | Connections are tight, conductors are of sufficient cross section. |
| B.7 | D | Earth connections maintain the integrity of the type of protection | No corrosion at the Earth connection and cable is tightened adequately |
| B.8 | D | Intrinsically safe circuit earthing is satisfactory | Earthing is present and as detailed in the documentation. The IS circuit is earthed at one point only or isolated from earth. The IS earth loop impedance and any earth rod impedances etc., are satisfactory |
| B.9 | D | Insulation resistance is satisfactory | Insulation resistance for I.S apparatus and associated cabling shall be at least 1.0 MΩ unless specified otherwise in the documentation. |
| B.10 | D | Separation is maintained between intrinsically safe and non-intrinsically safe circuits in common distribution boxes or relay cubicles. | It is important during initial inspections to check that the creepage and clearance distances between live parts of adjacent terminals are to specification. Segregation distances between I.S terminals and other terminals need to be met. |
| B.11 | D | Short-circuit protection of the power supply is in accordance with the documentation | Verify manufacturer or system documentation |
| B.12 | D | Specific conditions of use (if applicable) are complied with | Check ‘X’ certificates for conditions of use |
| B.13 | D | Cables not in use are correctly terminated. | Unused cores are insulated from each other or terminated to unused insulated terminals |
The insulation resistance of cables is only measured during initial inspections, unless circumstances suggest loss of cable integrity. When any cable insulation tests are made, it Is essential to disconnect the cable from the intrinsically safe apparatus. Failure to do so may damage the electronic circuits. Unnecessary measurement of insulation resistance is liable to lead to failure of connected electronic components.
Part C : Environment (IEC 60079-17 Table 2 cont.) #
| IEC No. | Grades | Check That: | |
| C.1 | D,C,V | Equipment to be adequately protected against corrosion, weather, vibration and any other adverse factors. | |
| C.2 | D,V,C | No undue accumulations of dust or dirt. Sources of any release in the vicinity should be noted. |
