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Volnei
21-04-2002, 02:54 AM
I would like to know what is the procedure that you use to do pressure test piping after welding conclusion in a big plant with ammonia.

Do you also do vacuum test?

Best Regards.

Volnei

C. Noseworthy
22-04-2002, 03:10 PM
On Large systems, I generally pressurize with perferably dry plant compressed air to the available pressure ( 9 - 10 bar) I then inspect all joints using soapy water to detect leaks (soap bubbles). The pressure should not change more than a few % for 18 -24 hours (overnight) unless there is a large change in ambient temperature.
Any found leaks are repaired and the system is again pressurized to 9 - 10 bar. Test the repairs. If no leaks are now found, use nitrogen to increase pressure to design working pressure. Repeat the soap test.
When no leaks are found, purge the air/nitrogen and evacuate the system. This can take more than 24-36 hours. A vacuum test is useful but due to the typically large size & potential for moisture presence, in the ammonia system, it may prove difficult to attain a deep vacuum. Watch your vacuum pump for signs of moisture in the oil.

Volnei
22-04-2002, 10:55 PM
Thanks C. Noseworthy.

Best Regards.

muddassarusa
14-06-2010, 08:56 PM
On Large systems, I generally pressurize with perferably dry plant compressed air to the available pressure ( 9 - 10 bar) I then inspect all joints using soapy water to detect leaks (soap bubbles). The pressure should not change more than a few % for 18 -24 hours (overnight) unless there is a large change in ambient temperature.
Any found leaks are repaired and the system is again pressurized to 9 - 10 bar. Test the repairs. If no leaks are now found, use nitrogen to increase pressure to design working pressure. Repeat the soap test.
When no leaks are found, purge the air/nitrogen and evacuate the system. This can take more than 24-36 hours. A vacuum test is useful but due to the typically large size & potential for moisture presence, in the ammonia system, it may prove difficult to attain a deep vacuum. Watch your vacuum pump for signs of moisture in the oil.


Very good easy and simple explanation.

gregd1401
15-06-2010, 08:35 AM
If you are doing additions to existing plant, ensure that when testing with dry nitrogen that you do not exceed system pressure or you may inadvertently add nitrogen into the system through leaking stop valves.

aawood1
17-06-2010, 05:54 PM
This side of the pond we pressure test after blanking off ther safety valves at 32 Bar with Nitrogen for 12 Hrs. when using air / water cooled condensers.

Arthur.

gwapa
23-06-2010, 05:53 PM
Volnei
For a big system I make a RX inspection of at least 10 % of the pipe welds. All the 10% weld should be good (see Local Code for Pressured System) If there are at least one weld bad I check at least 20 % more

After I have checked the weld I will perform a neumatic test acording C. Noseworthy have mentioned

I make vacuon till -700 mmHg a break it with ammonia to close atmosferic pressure and then make a secund vacuom

Superfridge
03-07-2010, 10:30 PM
Use calibrated & certified pumps and gauges
X Ray welds as per gwapa post
Pressure test HP to 65degC refrigerant vapour pressure, LP to 45degC refrigerant vapour pressure.
Soap solution on welds, flanges ect.
Stand for min 48 hours = no pressure drop.
Evacuate to 130 microns or lower, rise no greater than 160 microns in 24 hours.