While governor valve hydraulic actuators on API-612 Special Purpose Steam Turbines may be economically replaced by electric actuators, the stop/trip valve actuators need to retain the hydraulic actuators to meet trip closing speeds and force requirements. What they need not retain is the use of the turbine lubricating oil as a hydraulic medium with the inherent particulate debris and water content promoting cylinder corrosion and operating friction.

Instead, a self-contained hydraulic system in a small easy to install package is recommended which isolates the stop valve/s from the contaminations and adds redundancy of supply pumps under continuous monitoring. The LCC Series-800 Stop Valve Segregated Hydraulic System further adds features of:

• The reservoir is typically a 17-gallon ridged cast aluminum for passive cooling.
• Each pump suction is protected by a 40-mesh suction strainer.
• All hydraulic components are installed with isolation valves which permit in-service replacements.
• The 2-inch drain pipes first enter a Baffle Tank which breaks the flow velocity and prevents oil foaming in the reservoir
  
• The reservoir is fitted with a level sight glass.
• The Baffle Tank and the Reservoir have separate vent pipes to accommodate the high trip flow rates air bleed.
• The Monitor provides tactile and confirmation back-lighted pushbuttons for manual Duty/Standby selection and pump motor shutdowns. A display screen presents alarm and status data.
• The Monitor includes a serial data link which may be wired to a DCS gateway for system alarm and status displays.
• The synthetic oil hydraulic fluid is ISO-VG-68.
• The final feed oil output is fed through a 5-micron duplex filter.

If the plant process line depends upon the steam turbine then forced outages due to turbine control problems are an very expensive. Investments now to upgrade the obsolete 1960's control technology with state-of-art redundant digital electronics provide major payback at the first “save” and continue to yield benefits for decades.