Valve Actuation by high-pressure hydraulics generally employs mineral oil as the operating fluid, but not always. Santos recently ordered a hydraulically actuated mainline trunnion ball valve, 300 mm Class 1500 RTJ (LF2 body, AED HNBR 985 o-rings, resistant to explosive decompression and compatible with methanol) from Onesteel for their Casino Gas Development Project in Western Victoria.
Because Casino is essentially an offshore development and the hydraulic system supplying the valve is integrated into the offshore hydraulic control system, ecologically sensitive hydraulic fluid was required for actuating pressures up to 20,500 kPa (2940 psi).
MacDermid’s Oceanic HW525 hydraulic fluid was specified, this being the fluid used by Santos in the Casino sub-sea control system.
This critical valve manufactured by SRI was fitted with a Bettis Model G5004.5 SR3 spring-close hydraulic
actuator, which has Bettis-standard
QPQ internal surface hardening and coating on the steel cylinder and rods. This actuator also included optional internal cleaning to American Standard NAS 1638, level 6.
To meet this standard, internal components are flushed several times and a sample of fluid is sent to an independent laboratory where it is examined microscopically and particle size and quantity is recorded and certified.
Although high-pressure water based actuation is an unusual request in Australia, Bettis USA supply it on a regular basis for offshore and subsea actuated valve remote installations.
Cleanliness to American Standard NAS 1638 or International Standard ISO 4406 is an essential safeguard for trouble-free operation.
The completed assembly was retested at Onesteel’s contractor’s works, using a cleaned water-compatible power-pack, and the actuator and mountings were painted with Jade Green paint to Santos spec SPCS 2 (total thickness 370-445 dft) to match the pre-painted ball valve.