Cryogenic valve testing standard and Cryogenic Testing Procedure
Cryogenic valve design standards and performance standards for valves in cryogenic services. Some of the applications where valves are required to operate in cryogenic service include U6 (Liquefied flatural has) processing, intake, storage and satellite facilities, gas to liquids, ethylene plants, LPG terminals and industrial- use cryogenic gases.
Cryogenic Valve Standards:
Applicability and Scope
Cryogenic valve standards that are used in the valve industry include:
- BS 6364: 1984: Valves for Cryogenic service
- MSS SP-134: 2012: Valves for Cryogenic Service, including Requirements for Body/Bon net Extensions.
- ISO 28921-1: 2013: Part 1 – Design material selection and providing testing.
- ISO 28921-2: 2015: Part 2 -Type testing of low temperature valves
- EN 12567: 2000: Isolating valves for LNG.
- ISO 21011:2008: Cryogenic vessels Valves for cryogenic service with 6 active cryogenic valve standards in the industry, it is important to understand the requirements spelt out in each of these standards.
Cryogenic Testing Procedure
While MSS SP-134 and ISO 28921-1
specify production test procedure for qualifying a cryogenic valve, BS 6364, EN 12567 and ISO 28921-2 specify type test requirements for a cryogenic valve . A typical test sequence for a cryogenic test is – pressure testing
prior to cryogenic test, system proving test, valve cavity purging, cooling of the valve, tests at cryogenic/low
temperature, warm-up procedure and post-test examination.
EN 12567 specifies a thermal shock test (Annex A) to simulate the thermal stresses in transient state that are greater than stresses due to static pres- sure. The thermal shock test consists of the following steps:
- Valve shall be filled with cryogenic test fluid
- Valve shall be in partially open position during filling
- Outer surface exposed to atmosphere
- Filling of the valve in 5 minutes
- Valve shall remain filled for 1 hour
- Valve disassembly and crack detection test
This standard also has an endurance test procedure that calls for 500 or 2000 operating cycles with Liquid Nitrogen inside the valve, periodic seat and shell leakage measurements at incremental pressure values. The parameters that can be assessed during the endurance test are the effectiveness of the cryogenic neck extension, stem and body sealing system, seat leak tightness, wear and tear of drive train components after cycling and check in g whether the operating effort doesn’t exceed 360 N. An ambient
To summarize the current trends in cryogenic valve standards,
•ISO 28921-2 is the new type test standard for cryogenic valves
•MSSSP-134 and ISO 28921-1 are popular production test standards for valves.
•BS6364, last update din 1998,is increasingly being replaced by ISO 28921-1 & 2 in end user specifications.
Lastly, EN12567 offers the industry atest procedure for testing valves to thermal shock and endurance test with Liquid Nitrogen inside the valves simulating real life conditions.
Author :- Jaisingh Jadhav, Mareesan Bose & Ram Viswanathan- L&T VaLves