Natural gas dehydration units required valves for process and regeneration gas
A major LNG project in Australasia incorporates two process trains,
with a production capacity of more than 8 million metric tons per
annum. LNG is produced by cooling natural gas to about –162 degC
[–260 degF]. Any water in the gas can lead to formation of hydrates,
which can damage equipment and have a detrimental impact on the
quality of the final product.
Four molecular sieve dehydration units per train provide an effective
means of drying the gas. The molecular sieves adsorb water and are
subsequently regenerated using a heated stream of treated gas. Each
dehydration unit includes a drying tower and four switching valves—
two each for process gas and regeneration gas—making a total of 32
such valves. The operator split the award, selecting ORBIT ball valves for
the process gas and 16 third-party valves for the regeneration gas lines.
Third-party valves struggled to handle operating conditions
Based on more than 40 years of proven technology, the ORBIT valves
have been functioning flawlessly on the project for years, but issues
emerged with the third-party valves right from commissioning and
startup. The valves were sticking and failing to open or close fully
despite multiple remedial attempts across two years, disrupting
operations and reducing LNG production.
Eventually, the operator decided to replace the malfunctioning
valves with 16 ORBIT valves, which had irrefutably demonstrated
their reliability. The drying tower regeneration process at this plant
runs at temperatures up to 315 degC [600 degF]. The valves are also
potentially exposed to abrasive impurities emerging from the
towers and must withstand three regeneration cycles per day.
