Hydro Test on Cryo Piping 1

[Siciliano376]

All,

In place of a pneumatic pressure test, my project is opting for a Hydro test be done no cryogenic piping. Can this be done? Are there reasons to stay away from the hydro test?

Thank you.

 

[iainuts]

We don't generally hydro test cryogenic piping because of the potential for leaving water in the lines which will obviously solidify. In addition, water is often a contaminant for these systems.

If a hydro test is required, the piping must be capable of being cleaned out after the test.

 

[Siciliano376]

Subsequent nitrogen drying has been proposed in order to remove the water from the piping? But I am not sure that we will be able to successfully remove the water from the valve crevices, welds, etc... I am not sure if I am right but this is my line of thought: "Since evaporation at ambient temperature is diffusion driven phenomena (limited by surface area) there is a potential for leaving water in the pipe, even after drying".

What do you think?

Thank you again.

 

[iainuts]

I agree getting water from all the 'nooks and cranies' is the worst part about contaminating the system with water. Makes it very tough to clean out.

Can you pull a vacuum? That essentially boils off the water. The lower the vacuum the better. Note that this tends to reduce the temperature of the water locally, so external heating of the pipe will help.

You might also consider running hot nitrogen through the pipe to help remove water. Or just heat it externally. Can you get the temperature of the line above the boiling point?

Performing a combination of heat and vacuum would work best.

 

[Siciliano376]

you have a valid point. I need to look at the piping spec and find out at what temperature we can put the nitrogen in the line.

Thank you.

 

[EdStainless]

This is why these lines are usually tested with nitrogen.
I have seen small lines flushed with alcohol after hydro, not something to do on a large system.

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Plymouth Tube

 

[dcasto]

I had to laugh when the plant manager re-tested a line with methanol, in a N2 rejection plant. The methanol froze up and I got the call. I pumped Hot (130F) N2 for 2 days drying out the plant. it was a costly mistake.