Cryogenic treatment
A cryogenic treatment is the process of treating workpieces to
cryogenic temperatures (i.e. below −190 ¡ãC (−310 ¡ãF)) to remove
residual stresses and improve wear resistance on steels.
Benefits of cryogenic treatment includes longer part life,
less failure dut to cracking, improved thermal properties,
better electrical properties including less electrical resistance,
reduced coefficient of friction, less creep and walk, improved flatness,
and easier machining.
Cryogenic Test(low temperature test)
Standard: BS 6364: 1998 Valves for cryogenic service
Cooling Medium: Liquid Nitrogen
Test Medium: He
Test temperature: -196¡æ
Soak the valve in the cooling medium until the body temperature is fixed.
Operation Test:
Open and close the valve under test temperature and nominal pressure
for 20 times. Make sure the operation is smooth, and no obstructive,
no crawl occurred.
Leakage Test:
Closed the valve under test temperature and nominal pressure.
Filled the valve with He according to the flow direction. Report the leakage rate.
Make sure there is no visible leakage for soft seal valve. For metal seal valve,
the rate should be 0.1DN mL/s.
Sealing Test:
Open the valve. Increase the pressure to nominal pressure and keep it for 900s.
Check the tightness of packing, connecting part between body and bonnet.
Make sure there is no visible leakage.
|
Name |
Test pressure /MPa |
Keeping Time /s |
Results |
|
Sealing test |
Pc |
900 |
No visible leakage |
|
Leakage test |
Pc |
300 |
Leakage Rate
mL/s |
Soft seal |
No visible leakage |
|
Metal Seal |
0.1DN |
|
Operating test |
operation is smooth, and no obstructive, no crawl occurred |
