Removing water after hydrotest
Removing water after hydrotest
(OP)
I'm looking for experience, suggetions, advice on dehydrating a tubing system after a hydrostatic pressure test (I did search this forum. Found some quite spirited discussions on testing - but not what I'm looking for).
Here are the particulars:
Code in effect = ASME B31.3
Process Fluid = Proprietary liquid. Adversely reacts with water.
Fluid Category = Normal Fluid Service
Max operating pressure = 3500 psig
Max operating temperature = 140F
System capacity = About 30 lineal feet of 1/4" OD tubing; several valves.
Joints = twin ferrule compression
Testing with the process fluid has been ruled out (for now).
A pneumatic test would eliminate the concern of residual water reacting with the process fluid. I've been involved with a number of pneumatic tests, so I'm aware of the safety concerns. The problem is that the max pressure readily available is 2200 psig nitrogen.
The next option is hydrostatic testing. As stated above, the process fluid reacts with water, so I'm checking on a possible test fluid that's compatible with the process fluid. If that doesn't pan out, I'm left with testing with water......
Which brings me back to the reason for my post: How to dehydrate the system after the hydro? Here are my initial thoughts:
1. Design the system to be as free draining as possible.
2. Determine how dry is dry enough.
3. Determine method(s) to dehydrate. Vacuum? Nitrogen or Argon sweep? Other?
4. How to verify system sufficiently dry?
5. ??
Thanks in advance for your time.
donf
Here are the particulars:
Code in effect = ASME B31.3
Process Fluid = Proprietary liquid. Adversely reacts with water.
Fluid Category = Normal Fluid Service
Max operating pressure = 3500 psig
Max operating temperature = 140F
System capacity = About 30 lineal feet of 1/4" OD tubing; several valves.
Joints = twin ferrule compression
Testing with the process fluid has been ruled out (for now).
A pneumatic test would eliminate the concern of residual water reacting with the process fluid. I've been involved with a number of pneumatic tests, so I'm aware of the safety concerns. The problem is that the max pressure readily available is 2200 psig nitrogen.
The next option is hydrostatic testing. As stated above, the process fluid reacts with water, so I'm checking on a possible test fluid that's compatible with the process fluid. If that doesn't pan out, I'm left with testing with water......
Which brings me back to the reason for my post: How to dehydrate the system after the hydro? Here are my initial thoughts:
1. Design the system to be as free draining as possible.
2. Determine how dry is dry enough.
3. Determine method(s) to dehydrate. Vacuum? Nitrogen or Argon sweep? Other?
4. How to verify system sufficiently dry?
5. ??
Thanks in advance for your time.
donf





RE: Removing water after hydrotest
In terms of drying, does your proprietary fluid react with water vapor or just liquid water. If liquid is the problem, then you can probably get where you need to be with a LP nitrogen purge. If you have to get it to a 32 F dew point at 3500 psig then you have to get it down to around 4 lbm/MMCF. The only way I know to get there is really hot nitrogen purge, then seal it with the hot nitrogen inside. The substance you use is less important than the temperature at start.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Removing water after hydrotest
RE: Removing water after hydrotest
Pneumatically test it to 1.1x the relief pressure and skip the water!
It would be crazy to hydrotest such a small system in my opinion unless people cannot be removed from the area during the test.
RE: Removing water after hydrotest
RE: Removing water after hydrotest
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Removing water after hydrotest
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Removing water after hydrotest
General - The section of high pressure tubing is connected to a larger piping network, so drying in an oven is impractical. (dicksewerrat - thanks for the paint shop oven suggestion. I may use that in another application).
zdas04, TomDOT - I found a gas booster that I can hook to a standard bottle of Nitrogen (~2400 psig) and boost the pressure to what I need. Process fluid does react with vapor as well.
chicopee - Looking at using alcohol as a possible test liquid.
moltenmetal - We're in agreement on the RV set pressure being the number to use.
Again, thanks to all for your help. I'll let you know which option we use.
donf
RE: Removing water after hydrotest
Best regards - Al
RE: Removing water after hydrotest
You can rent a 6000 psig cylinder of nitrogen and test it right off the bottle. No need for a bottle booster pump.
RE: Removing water after hydrotest
donf
RE: Removing water after hydrotest
Keep people out of the area. Make sure that pressure can't get anywhere beyond the test and do damage (i.e. by leaking through a valve etc.). Ensure the tubing is properly supported. Put the cylinder at a safe distance from the line to be tested, install an excess flow check at the discharge of the cylinder regulator to limit flow during a failure, and stand by the block valve during the test to shut it off if there's a failure etc. Above all, make sure that nobody manipulates the fittings under test to try to stop leaks- that's what is going to get someone hurt. Bring pressure up in stages with a hold in between, and snoop (external soapy water test) joints for leaks. Leave the system at pressure for a time at each stage before "snooping". Depressurize prior to ANY attempts at repair.