Dry Running Secondary Mechanical Seal

[CobraS]

When is dual unpressurized seal with dry running the secondary used?

My situation:
I have a pump for sour water service where a dual unpressurized cartridge with dry running secondary is used. I'm trying to prevent h2s from being released in case of a seal leak. I'm not sure whether dry runnign the secondary is enough containment or whether i should just switch to a plan 53.

 

[JJPellin]

I would not consider a dry-running secondary containment seal as a good choice for sour water with significant H2S. First, the dry running secondary needs to remain dry. Any leakage of water from the primary seal will need to be diverted away from the seal gland with a drain from the low-point connection on the gland. We only use dry running secondary seals of this type in streams that vaporize at flare pressure.

For a new pump in this service, we would default to a Plan 53, pressurized double seal to reduce the risk of H2S exposure for our personnel.

Johnny Pellin