Lotte Petrochemicals has a requirement to upgrade their ageing mechanical-hydraulic governor, the Woodward PG-PL to a sophisticated redundant digital governor, to improve on the hydraulic distribution system to the actuation, and to replace the safety trip protection of the Siemens extraction steam turbine driving a propylene 2-stage compressor.
OLD TRIP BLOCK
The Lotte’s operators found the old hydraulic trip block complicated to operate.
The high pressure (HP) and the low pressure (LP) left and right servovalves are hydraulically operated through complex servo mechanism.
In order to increase the reliability and the availability of the turbine, Lotte Petrochemicals decided to retrofit to the existing mechanical control systems.
A stainless steel cabinet with a pressurized purging system was used to house the Woodward 5009FT digital governor, HMI and Protech GII.
Woodward 5009FT – This is a completely redundant digital controller. This steam turbine controller includes specifically-designed algorithms and logic to start, stop, control, and protect industrial steam turbines or turbo-expanders, driving compressors, generators, or pumps.
A Protech GII was installed as added safety to the turbine as an independent 2-o-o-3 Overspeed Protection Control.
Woodward Quicktrip trip block assembly is designed for use in gas or steam turbine shutdown systems for quick and reliable dumping of the turbine’s trip oil header. It uses low-pressure (5–25 bar / 73–363 psi) hydraulic trip oil headers. The trip block assembly’s 2-out-of-3 voting design provides a very high level of system reliability as well as compliance with industry standard API-670. Quicktrip is designed to allow turbine controls and/or turbine safety systems to quickly dump (bleed off) hydraulic header pressure during emergency trip or normal trip conditions.
When applied in conjunction with Woodward’s ProTech-GII logic solver, the QuickTrip allows operators to independently test each trip leg to verify operation and trip time.