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[Dave Gone]

Hello,

It has been SOP at my refinery to run a pressure test using nitrogen (usually between 5-15psi ) on all vacuum distillation towers, columns and vessels, anytime after they have been opened for cleaning or maintenance.

We have always pumped in a small amount of process oil about 10% to 20% on bottoms level, then filled with the nitrogen and held for one hour while checking for leaks.(wet test)

My question is this.

Recently we have hired a new engineer and she says, we should always do this nitrogen test dry, before any oil has been brought in to the vessel / tower / column.

The wet test has always served us well, but I do see her point of the dry test. 

Is there a best practice or industry standard for this?

Thanks in advance.