Drying a Piping System Following a Hydro 1

[KenRad]

I have a tubing network made up of various sizes of stainless steel Swagelok, to be used for a 5000 psig nitrogen (gas) system. The system owner is concerned about removing all water following a hydrostatic test.

There are plenty of vent/drain points for removing most of the water. Beyond that, can anyone tell me which would be quicker for drying this system - (1) putting a vacuum pump on it for some number of hours to flash off the water, as we do in the refrigeration world; (2) Purging the system with very dry N2 for some amount of time?

I know either would work, but I'm interested in which would dry the system faster.

---KenRad

 

[zdas04]

You're right, either would work. I recently designed a dilution purge procedure for a client and was amazed at how ineffective dilution was for that application (it took 21 pipe volumes of natural gas to get the oxygen below 10 ppm).

You are doing much the same thing (with water vapor instead of air) and after that exercise if I had this job and the piping system wasn't huge I'd go with vacuum.

David

 

[btrueblood]

Apply vaccuum, then backfill with dry nitrogen, repeat. The backfill helps to dilute and sweep water vapor to the vacuum pump. With your system you have an advantage in that you may be able to put vacuum pump on one end of piping, and purge from the opposite end. We used to remove residual hydrazine (remarkably similar properties to water, except you can detect it in ppm trace amounts in the effluent stream) from rocket engine test plumbing this way, and found the cycling method was most effective compared to either purging or single cycle (long duration) vacuum.

 

[Jmoore1]

On my site we blow dry with N2, standard practice and works everytime.