Hydro Electric Turbines, Steam Turbines, and the EPA Spill Prevention and Control Plans (SPCC)
The US Environmental Protection Agency (EPA) has mandated enforcement of the Federal Oil Pollution Prevention Regulation (Title 40 Code of the Federal Regulations CFR Part 112) concerning planning and preventing oil spills.
SPCC Plans are required for all hydroelectric generation facilities and many fossil and nuclear plants which qualify as adjacent to navigable waterways. All facilities with underground storage capacity of 42,000 gallons of oil or more or above ground storage of 1,320 gallons qualify under the regulation regardless of proximity to navigable waterways.
This law has a major impact on turbine control and lubrication systems, and will require the submission of action plans prior to July 1, 2009 to hold compliance. This paper will present expedient end economical means of turbine compliance through systems modifications and upgrades.
2.0 General Acceptance Plans, Turbine Oil Systems
Turbine components using hydraulic oil as an operating medium for both lubrication and control require the following basic safeguards to conform to SPCC:
2.1. All pressurized lines must be guarded by a fully enclosed gravity drain established conducting any leak at any point in the main tank or pressurized line runs to a leakage holding vessel.
2.2 The leakage holding vessel must have greater capacity then the total oil volume in the system plus twenty percent.
2.3 A transfer system must be provided for removing oil in the leakage vessel, also using guarded lines.
2.4 A low leakage risk filling and oil changing transfer system for the operating tank or reservoir, using guarded lines.
Guarded lines have been established as "pipe in pipe", "pipe in hose", and "hose in hose" depending upon the working oil pressure. Leakage holding vessels are designed and located such as to collect both guarded line leakage and primary reservoir leakage with level measurement instrumentation alerting operators of a primary system leak.
In addition to mechanical modifications the facility must also include in their plan provisions to:
- Document Spill Histories
- Describe Potential Spill Scenarios
- Define Potential Contaminants (e.g., Turbine Oil, Fyrquel, etc.)
- Describe Facility Drainage System
- Provide Elevations Drawing to Nearest Navigable Waterway
- Identify Oil Bulk Storage Methods
- Define Loading and Unloading Areas and Procedures
- Define Security Plan to Prevent Tampering with SPCC Devices
- Outline Personnel Training for SPCC
- Define Spill Response Procedures
These elements are to be included in the facility's overall Facility Response Plan (FRP).
3.0 Governor Control System Specifics
3.1 Hydro Electric Turbine Control Systems using older mechanical-hydraulic governors pose an expensive and risky compliance issue. Unlike steam turbine applications, hydro governors were generally not designed for guarded oil lines since high temperatures and resulting fire potential were not a concern. Compliance requires major modifications to piping and hydraulic actuators to provide gravity drain guard piping and valve actuator containments to preclude leakage upon seal damage. Because the oil used by the valve positioning actuators is pressurized, the guarded line systems must be qualified for potential local pressurization, further complicating the compliance strategy.
A much simpler and straightforward approach to SPCC compliance is the total elimination of the existing control system reservoirs, actuators, and pressurized oil lines.
This can be accomplished through the retrofit of a modern digital electric governor such as the LCC Series 2 controlling a roller screw electric actuator for inlet gate modulation and speed/load control. In addition to SPCC compliance issues the retrofit also benefits the plant in providing simpler maintenance and improved reliability while often replacing obsolete systems with difficult to obtain spare parts and complex tuning and adjustments.
3.2 Steam Turbine Control Systems hydraulic are of two varieties, segregated high pressure (2000 psig typical) synthetic fluid oil systems and lower pressure 100 to 600 psig systems tapping bearing lubrication oil. The high pressure systems represent the greatest challenge, in that little or no leakage control is evident in original designs since the fluid is not flammable. The fluid is considered toxic, however, and leakage prevention plans must be burdened with the additional problem of safe handling. Since high pressure systems usually are designed with stainless steel feed, return, and trip dump headers run to each individual valve actuator, compliance demands guarded enclosed drains. This is difficult considering the elevations many valves are located and the support structure required for the guard pipes, making compliance very complex and expensive. The low pressure systems generally fair better, since the flammable oil was managed in original guarded pipe systems. Off pedestal piping which carries the turbine oil needs guarding and leak basin installation. An option, as in the hydro electric governors, is again the whole scale replacement of the hydraulic operating system with roller screw electric actuators and compatible digital governors to eliminate the oil systems rather than harden them with leak management.
4.0 Lubricating Oil System Specifics
4.1 Hydro Electric Turbine Lube Oil Systems provide low pressure (5 to 20 psig) pressurized feed to journal and support bearings. Since these feeds are at modest pressure and often internal to support castings the primary compliance issues are the main reservoir and potential oil seal leaks. A circumferential drip pan with drain line can be arranged for most vertical shaft seal installations. Reservoir catch basins remain the primary task.
4.2 Steam Turbine Lube Oil Systems by previous fire code conventions generally are guarded designs. As in hydro, oil seal pans and reservoir catch basins are the major tasks.
5.0 Summary of Compliance Strategy for Hydro and Steam Turbines
An efficient and immediate cost benefit strategy to aid compliance with the new oil spill regulations is the retrofit of digital electronic governors, servo drives, and roller screw electric actuators to replace existing mechanical hydraulic control systems. The best spill prevention is control oil elimination which is accomplished in the retrofit. Further efforts to secure lubricating oil are less intensive due to lower pressures and few external lines.
Lovejoy Controls Corporation will assist in all aspects of a customer's EPA SPCC compliance. Contact LCC for site specific direction.
EPA SPCC Page: http://www.epa.gov/oilspill/
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