A common expression about the weather here in The Netherlands is “April doet wat ie wil” (April does whatever it wants). Just when we thought Spring had arrived in the Northern Hemisphere we were treated to some arctic cold - oh no! Trust me, dear readers, there is nothing worse than the warm promise of spring being pulled from your reach at the end of April.
But that’s enough of the weather. The topic of low temperatures (and potential dangers) brings me to our current LNG issue, and in particular: cryogenic testing.
As the popularity of LNG continues to increase, more manufacturers are entering the cryogenic valve market. The standards to govern these newcomers—and the most prevalent specifications to which a cryogenic valve design is tested and qualified—are MSS SP-134 and BS 6364. While these standards have been applied for years, and variations have been generated by others, I’m hearing concerns that these standards do not address what actually happens when cryogenic liquid is flowing through the valve.
For example this month we feature a technical article by Neeraj Batra (Piping Materials Engineer) and Hitoshi Suzuki (Technical Leader-Material Technology & Management group) from Chiyoda Corporation. These gentlemen have spent much time interviewing members of the industry to investigate the applicability of cryogenic valve testing standards. An example cited were ball valves purchased for an LNG facility which passed BS6364 factory testing, yet could not reach the required leakage rates once installed. Herein lies the problem: the testing method allows cooling from the “outside in”, whereas real conditions cool the valve from the “inside out”. During the test the body contracts around the trim yet in the field the trim contracts first. As a result, it was eventually necessary to replace the position seated ball valves with torque seated ball valves to reach the required shut-off.
A few weeks ago an industry professional expressed to me the risk of designs being engineered to seal against helium at low temperature without a true indication of how the valve will perform during a thermal transient at high pressure. He observes end-users having a multitude of issues with cracked seats and unexplained leaks—and manufacturers are not able to recreate failures. In fact, one of the biggest struggles for manufacturers and end-users alike in his mind is a lack of a well-defined standard for testing product with cryogen flowing through the valve at pressure. In his own words: “although an expensive proposition, true cryogenic testing is the only method to prove a design can withstand the abuse of real-world service”.
What are your thoughts? For example, if a valve is simply built with an extended bonnet or material compatible for cold service can it be defined as a cryogenic valve? And do standards go far enough?
If you’d like to send your thoughts on the topic (or just chat about the weather), I’d be happy to listen firstname.lastname@example.org