A chemical company in Poland decided to modernize a governor control system on a 16 MW Brak Zezwolenia (BZKG) steam turbine used for internal power generation.  The plant was having trouble maintaining consistent RPM due to sticking servo valves on the hydraulic pilot assembly, which ultimately lead to turbine trips.  Contaminated oil turned out to be the reason this kept happening.  Spare parts for the 1950’s vintage turbine were non-existent.  A REXA channel partner, Valmet successfully upgraded the mechanical-hydraulic controls with an electronic governor, and replaced the pilot valve/power piston assembly with an X3L10,000-4-2D-E.

The linear cylinder connected directly to the rack assembly, which eliminated lost motion and mechanical hysteresis.  The customer noticed an immediate improvement in control, with the REXA maintaining speed on a 3000 RPM turbine to +/- 1 RPM.  We were able to use a mechanical spring assembly thanks to a short stroke requirement, for a trip time of <1 sec, and a normal stroke time of <4 secs.

The customer was very pleased with the upgrade and plans to duplicate the install on another turbine during the next outage.  REXA’s Representative, ARNAP supports the upgrades and account.