Occupational Health and Safety Act, 1993 (Act No. 85 of 1993)Code of PracticeNational Code of Practice for Electrical Machinery in Hazardous LocationsRegulatory requirements for explosion-protected apparatusAnnexesAnnex E (informative) : Frequently asked questions regarding certification requirements for equipment forming part of intrinsically safe loops |
Annex E
(informative)
Frequently asked questions regarding certification requirements for equipment forming part of intrinsically safe loops
NOTE 1 Information covering typical scenarios is given in a FAQ format. Consider this information to be a guideline and subject to change.
| E.1 | The definition of "new'' equipment is unclear. Does "new'' refer to the purchase date, the import date, the manufacture date, the date of installation, or the date on which the item type is first released in South Africa? |
"New" refers to the selling date to the user, keeping in mind that the validity period is now extended to three years.
| E.2 | What certification is needed for package units versus individual components, for example an imported skid with several pieces of equipment. What about replacement units fitted to the package at a later stage due to wear and tear? |
Individual equipment for imported skids has to be certified, but individual certificates need not be issued. The individual certificates will be listed in the package certificate.
The replacement unit needs to be identical to the devices being replaced, unless the package is re-certified by an ATL.
| E.3 | Exact marking requirements of equipment with the ATL logo and IA certificate number are not clear. The logo of the test houses will prove difficult to add to smaller equipment such as instrumentation. The manner of fixing such markings to the transmitters is problematic, since no physical modification of a housing is allowed after certification, and adhesive markings may not be durable. Alternatives such as metal or plastic tabs attached by means of wire may not meet the requirement for permanent marking. |
SANS 60079-0 gives instructions for the marking of small and very small EPA.
| E.4 | The certification status of existing ATL approved intrinsically safe loops has to be clarified. These ATL approved loops reference specific models of equipment and specific certificates. For new installations based on the same typical loops, should the typical loops be re-certified? Do they need to be re-certified every time an IA certificate is renewed? |
No re-certification of a loop is required.
| E.5 | The requirement for emergency maintenance replacements needs to be clarified. In a running plant, breakdown of certain equipment may occur and require replacement by identical equipment. Is this equipment considered new? In the case of IS equipment, should the typical loop be re-certified if the original was not based on an IA certificate? This could severely impact on industry. |
It is recommended that the maintenance replacement component should be subject to the requirement for an IA certificate. Should it not be possible to obtain an IA certificate due to changes in the safety requirements from the original certification, then an ATL should be consulted to determine if the installation is safe using that component.
No re-certification of replacement equipment is required.
| E.6 | What is the effect on spares already held in stock? Industry keeps a significant quantity of spare equipment. Some is owned by the plant and some is consignment stock owned by the vendor.Is this stock considered new? Some of it has been in stores for many years. It is also mostly used for identical replacements as discussed in I.5.What are the requirements for IA certification of these items? |
It is recommended that items already in maintenance stock before October 2007 should not be considered new.
"New" refers to the selling date to the user, keeping in mind that the validity period is now extended to three years.
| E.7 | Do IA certificates allow the transfer of "composite" certification? For example, a single transmitter may be supplied with a number of certificates, for example an Ex i certificate and an Ex d certificate. |
Composite certification is allowed. Issues such as warranties may make it attractive to obtain certification from the local agent (if one exists), but this is a separate, strictly commercial issue.
| E.8 | Will the adoption of the IECEx scheme eliminate the need for IA certificates? |
No, an IECEx certificate can be used for conversion into a local IA certificate
| E.9 | Q Scenario 1: You have an existing IS Loop that is in operation for e.g. 15 years and the barrier/isolator must be replaced with a different (new) model for some or other reason. Is it necessary to re-evaluate the loop by an ATL (Approved Test Laboratory)? |
A YES, the new barrier/isolator must be evaluated for compatibility with the existing IS loop (see A10).
NOTE 1 If the existing Loop is changed without getting the changes re-evaluated by an ATL (Approved Test Laboratory), the loop may no longer be safe and will no longer be legal.
The following is required for this evaluation:
| (1) | IA certificate of the new barrier/isolator |
| (2) | Previously acceptable certificate of the field device |
| (3) | Cable specifications (parameters) |
| (4) | New loop drawing |
NOTE 2 In the case where previously acceptable certificate can no longer be obtained but the marking on the device is still intact and clearly legible, a photograph of the label may be submitted as proof of certification and of the entity parameters.
Where the new barrier/isolator with all the same voltage (Uo),current (lo) and power (Po) parameters but the capacitance (Co) and inductance (Lo) have changed (lower than the original barrier/isolator), the following will apply:
If the capacitance or inductance values of the cable / field device combination is more than the barrier/isolator allows, the loop no longer complies to the standards. A safety assessment may be conducted and concession granted by ATL if appropriate (see A.10).
NOTE 3 If the system was evaluated with maximum lengths of cable it is possible that the loop can still pass if the system was not fitted with the maximum length of cable. A simple measure of cable length can be done and the parameter can be re-calculated to determine if the loop will comply with a reduced cable length. In addition, the cable parameters may be physically measured as these values may be less than those originally used.
| E.10 | Q Scenario 2: You have an existing IS Loop that is in operation for e.g. 15 years and the field device must be replaced with a different model for some or other reason. Is it necessary to re-evaluate the loop by an ATL (Approved Test Laboratory)? |
A Yes, the new field device must be evaluated for compatibility with the existing IS loop (see A10).
NOTE 1 If the existing Loop is changed without getting the changes re-evaluated by an ATL (Approved Test Laboratory), the loop may no longer be safe and will no longer be legal.
The followingis required for this evaluation:
| (1) | Previously acceptable certificate of the barrier/isolator |
| (2) | IA certificate of the new field device |
| (3) | Cable specifications (parameters) |
| (4) | New Loop drawing |
NOTE 2 In the case where the previously acceptable certificate can no longer be obtained but the marking on the device is still intact and clearly legible,a photograph of the label may be submitted as proof of certification and of the entity parameters.
| E.11 | Q Scenario 3: You have an existing IS Loop that is in operation for e.g. 15 years and the cable must be replaced with a different model for some or other reason. Is it necessary to re-evaluate the loop by an ATL (Approved Test Laboratory)? |
A Yes the new cable must be evaluated for compatibility with the existing IS loop. (see A10)
NOTE 1 If the existing Loop is changed without getting the changes re-evaluated by an ATL (Approved Test Laboratory), the loop may no longer be safe and will no longer be legal.
What is required for this evaluation:
| (1) | Previously acceptable certificate of the barrier/isolator |
| (2) | Previously acceptable certificate of the field device |
| (3) | New Cable specifications (parameters) |
| (4) | New Loop drawing |
NOTE 2 In the case where the previously acceptable certificate can no longer be obtained but the marking on the device is still intact and clearly legible,a photograph of the label may be submitted as proof of certification and of the entity parameters.
| E.12 | Scenario 4: You have an existing IS loop that has been in operation for 15 years and the barrier is replaced by a later model barrier with all the same parameters (U, I and P) except the capacitance and inductance have changed, i.e. they are now lower than the original barrier. Is it necessary to have the loop re-evaluated by an ATL? |
Yes, it is necessary.
The reason for the re-evaluation is to confirm that the later barrier will be compatible with the existing cable and field device combination. If the capacitance or inductance of the cable/field device combination is more than the barrier allows, the loop no longer complies. A different barrier, cable or even field device can be used to get the loop re-approved.
If the system was evaluated with maximum lengths of cable it is possible that the loop can still pass if the system was not fitted with the maximum length of cable. A simple measure of cable length can be done and the parameter can be re-calculated to determine if the loop will comply with a reduced cable length. In addition, the cable parameters may be physically measured as these values may be less than those originally used.