HELP! H2S certification? 1

[jraef]

I am being asked to provide the following information, quoted from a CE specification review on our 5kV class Metal Enclosed switchgear: ..."certification of H2S withstand with respect to being suitable for use in H2S concentrations per OSHA regulations for continuous worker exposure".

Aside from getting the OSHA concentration limits, does anyone have experience in obtaining said "certification"? As in who does it, an Electrical PE or a Chemical Engineer, or an Environmental company? This project is for the Sate of New York.

"Venditori de oleum-vipera non vigere excordis populi"

 

[dpc]

I don't see what relationship there would be between OSHA standards based on worker safety and equipment protection. I'm not aware of any "certification" on protection agains hydrogen sulfide for equipment protection.

I have dealt with high concentrations of H2S in wastewater treatment plants. It does attack copper and other unprotected metals.

We found the best approach was to get all bus and conductors tin-plated (not silver-plate).

Sounds like a reviewer trying to justify his hourly rate by making comments.

 

[jraef]

No doubt about that. My interpretation of the OSHA issue is just to establish a concentration level without their having to actually research it to find out what is potentially damaging and defend it if challenged.

The only other time I came across this was in a Geothermal Power Plant, and they were very specific about concentration levels, as well as exactly what they wanted for coatings and plating (gold was their preference!). This engineer seems to be hedging by off-loading his requirements onto a standard established by someone else, then asking for "certification" without referencing any acceptable testing agency. The application is a WWTP. Did you do anything else besides tin plating? We are doing that, plus conformal coating of the PC boards on any electronics, plus using vacuum contactors woth epoxy encapsulated coils wherever necessary. What about switchgear contacts, i.e. Fused Load Interrupt Switches? They have silver contact points in open air.

"Venditori de oleum-vipera non vigere excordis populi"

 

[jraef]

By the way, thanks for the quick response dpc.

 

[dpc]

Silver-plating should be avoided, if at all possible. We did generally specify conformal coating of PCBs. We also specified insulating boots on all bus joints.

We used PVC-coated rigid steel conduit. Sealing of conduit openings through rooms or floors is advisable.

Best solution is to establish a separate electrical equipment room and keep it under positive pressure. NEMA 12 enclosures may offer some improvement over NEMA 1. You can specify encapsulated dry-type transformers up to about 30 kVA.

I don't remember dealing with interrupter switches, but we saw a lot of problems in motor control centers if exposed to a lot of H2S.

I don't think there is a way to completely protect electrical equipment if it is exposed to H2S. I would focus on ways to prevent the H2S from getting into the room, if possible.

 

[buzzp]

Not sure about where your switchgear will be used so this suggestion may not be applicable. In the oil fields, the H2S migrates up the submersible cable right into the switchgear cabinet. Hence, they use J-boxes for all their terminations before it enters the switchgear. The thought is this will vent the H2S in the J-box and not the switchgear. I don't know if your application will benefit from such a design. Also, in my oil field experience, I do not recall any H2S certifications (I was a newbie then so there may have been).

 

[jsummerfield]

Check the ISA control room environment standard in the S60 series that categorizes corrosion levels. You may be able to state that the gear is rated for a specific level and require the commentor to assure compliance with that clean level.

John