LCC Quick Notes, EPA Spill Prevention and Control Plans (SPCC)
New EPA regulations needed to prevent contamination of waterways have redefined design requirements of both hydro and steam turbine control systems. Previous practices of specifying high pressure hydraulic valve operators from central oil skid systems are now obsolete in light of increased costs to secure systems against hydraulic leaks.
New Criteria Mean New Approaches
When the EPA instituted Spill Prevention and Control Plans requirements it was not at first apparent that point source control was included in systems subject to fluid release. When clarified, new focus in SPCC emphasizes prevention of not only release of oils and synthetic fluids into waterways, but adds engineering control of point sources. This can be visualized as a two-level defense plan. The last resort defense is a waterway discharge monitoring and diversion system which allows treatment processes to be applied prior to public release when plant contaminants have entered plant drain systems. The first level defense is preventing the various system discharges in the first place into the plant drain systems.
BIG Problems for Fyrquel-type Fluid High Pressure EHC Systems
While older pre-1970s turbine hydraulic controls designed by turbine OEMs observed the practice of Guarded Oil Piping, in which all externally run pressurized lines are surrounded by drain return lines with gravitational paths to reservoirs, newer and retrofit hydraulics did NOT. The reason for not following guarded oil piping practices with Fyrquel hydraulic delivery systems was justified at the time because Fyrquel is not flammable and therefore potential leaks would not produce fire hazards as they would with the flammable turbine lube oil based systems. With the need for SPCC this excuse has vanished and served Fyrquel-based systems users with a major problem... how to retrofit guarded piping, hundreds of feet of it, suspended about the turbine floor.
Since each high pressure synthetic fluid operated valve will have a minimum of three stainless steel lines run from the central hydraulics skid to the valve (high pressure, return, and trip header), some measure of leak control will be needed. If there is any question as to whether these high pressure systems ever leak and whether they qualify as sources requiring point source control, a stroll down a steam turbine floor will evidence the paint damage to turbine lagging below each EHC operated valve. While the assertion can be made that leaks are rare, this in itself is no excuse for not complying to point source control.
The task and expense of implementing point source engineering controls is considerable. Each three-pipe run to each valve will require a guarded protection pipe with leakage monitoring and managed return to qualified vessels.
A MUCH Simpler and Economical Solution
A simpler solution than attempting to guard high pressure EHC piping is to abandon the piping and related valve operators in entirety. With no oil lines there is nothing to guard. Replacement operators in the form of electric actuators for governor and interceptor valves and self-contained hydraulic operators with internal leakage monitoring for stop, throttle, and reheat stop, and bypass valves will not only solve the SPCC problem but also improve turbine control with a state-of-the-art valve control system.
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