Not all contaminated seal oil traps are the same. But you provided some clues to how yours are configured. Seal oil that leaked through the seal has contacted process and cannot, normally be returned to the reservoir. This contaminated oil flows down to the contaminated pots. This flow of oil can be encouraged to keep moving by a slight flow of gas. The gas flow is caused by a vent on the top of the pots that is directed to some lower pressure destination. Most of our pots are vented to flare through a very small orifice.

In some of our pots there are float mechanisms that open automatically on high level to drain the pot to some suitable system. The contaminated seal pots could be said to allow residence time with reduced velocity to allow the oil and gas to separate. Depending on where the oil is discharged, this could be important. This separation occurs at low velocity by virtue of gravity. I don’t know what you are referring to as a blowdown valve. Is it a manual drain for draining the pot to a different destination?

Johnny Pellin

Thank Johnny Pellin...The info you provided helped me understand the principle.

Johnny Pellin's description was spot on. I've seen a couple of these things taken apart and the internals remind me of the steam traps you see on utility steam systems.

Also, notice that Johnny's description talks about "contaminated seal oil traps", not "Sour Oil Traps". I've often seen them called "sour oil traps" in plants that process sour gas, I think that is to pound home that opening them in that service is dangerous. Both terms refer to the same device (except maybe materials of construction).

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist