Does presence of H2S> 50 ppm in Pumped fluid require use of Double Mechanical Seals 1

[Raj_2958]

I am doing a preliminary seal plan selection for various API 610 pump services. In the Client Specification for mechanical seal, i find a note for Foul Water service i.e. "H2S concentrations greater than 10,000 ppm requires dual seals". I have got foul water services with H2S concentration in the range of 400 to 2600 ppm.

I found another article by EagleBurgmann, where i find Single Seal w/Plan 65 for leakage detection if H2S concentration in pumped fluid <50 ppm and double seals i.e. Plan 52 up to 1000ppm (w/buffer liquid being changed on monthly basis) & Plan 53 above 1000 ppm is recommended.

So, how do we come to the conclusion if a double mechanical seal is required?

 

[CHoff07]

While this is typically customer/site specific, H2S has an IDLH (immediately dangerous to life and health) exposure limit of 100 ppm. Therefore, many people have historically set this as the basis for specifying dual seals. With that said, the short term exposure limit is 15 ppm and since a seal leak may be present for more than 15 minutes and expose operators to higher concentrations of H2S I have seen services with as little as 10 ppm H2S get specified with unpressurized dual seals as a minimum.

 

[Raj_2958]

CHoff07 Thanks for the response. The Client informed to use single seals for H2S concentration up to 10,000 ppm.