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.