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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Lubrication Supply System Design<br />

Design <strong>of</strong> the lubrication system is usually provided by the original<br />

equipment manufacturer (OEM) as part <strong>of</strong> the scope <strong>of</strong> supply for the main<br />

steam turbine generator unit. The utility as owner and operator must<br />

provide specifications for the system and the numerous interfaces for power<br />

supplies, oil supply, and instrumentation and control. To aid in obtaining<br />

satisfactory performance <strong>of</strong> the lubrication system, the American Society for<br />

Testing and Materials (ASTM) has issued a standard practice titled ‘‘Design<br />

<strong>of</strong> Steam Turbine Generator Oil Systems (D 4248-83)’’ [112]. This standard<br />

provides recommended practices for design <strong>of</strong> the turbine generator<br />

lubrication system including the high-pressure supply, bearing oil, control<br />

oil, generator seal oil, and drain oil return subsystems [114–116].<br />

Operation <strong>of</strong> the lubrication system is relatively simple when the<br />

turbine generator unit is at full operating speed. A main shaft oil pump<br />

(MSOP) connected to the turbine shaft provides high-pressure oil to the<br />

system. The complexity <strong>of</strong> the lubrication system is increased when the<br />

turbine generator unit is below full operating speed because the MSOP is<br />

not capable <strong>of</strong> providing high-pressure oil when the shaft speed is below<br />

approximately 90% <strong>of</strong> full operating speed. Auxiliary motor-driven oil<br />

pumps (AOP) and subsystems are necessary to replace the MSOP during<br />

turbine generator startups and shutdowns. Emergency oil pumps (EOP) and<br />

subsystems are provided as backup to the MSOP and AOP subsystems to<br />

allow safe shutdown <strong>of</strong> the turbine generator unit. Either a dc electric motor<br />

or a steam turbine may drive the EOP. Elaborate instrumentation and<br />

power supply schemes are involved to start up the AOP and/or EOP when<br />

the bearing oil pressure decays below aspecific set point (Fig. 55).<br />

Steam Turbine Lubrication System Pumping Systems<br />

The primary pumping system supplies oil during the full-speed operation<br />

through the main shaft oil pump. The MSOP is driven by the main turbine<br />

generator rotor shaft. The MSOP is usually a centrifugal pump that is not<br />

self-priming, and since it is located above the oil reservoir it must be<br />

supplied with oil from the reservoir by another means. Oil to the MSOP<br />

suction is supplied by a motor-driven suction pump (MSP), an oil turbine<br />

driven booster pump, or oil ejectors. The MSP supplies suction oil when the<br />

turbine generator shaft is rotating below approximately 90% <strong>of</strong> its normal<br />

speed. When the turbine generator shaft is rotating above 90% <strong>of</strong> its normal<br />

speed, oil from the MSOP discharge can be used to supply either an oil<br />

turbine-driven booster pump or oil ejectors located in the main oil reservoir<br />

along with associated flow regulation valves.<br />

Copyright © 2003 Marcel Dekker, Inc.

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