Hydro
Electric Turbines, Steam Turbines, and the EPA Spill Prevention and Control
Plans (SPCC)
1.0 Background
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.