Page 383 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 7 .5 Lube, Seal and Control Oil System Best Practices

Fig 7.5.2 Screw pump performance (Courtesy of IMO Ind.)

breakage during removal or during extreme temperature changes
(as during a fire). Flexible elements should be stainless steel.
The coupling shaft fit configuration and amount of shrink fit
should be checked to confirm correct values.
Driver sizing
Driver sizing must be confirmed to ensure adequate delivered
horsepower during all operating conditions. Utility conditions to
the drivers should be re-checked at this point to ensure that
values are as stated on data sheets. As an example, steam turbine
data (inlet pressure and temperature, and exhaust temperature)
should be checked so that all conditions will exist on site as
stated. Similarly, the minimum starting voltage for motor
drivers should be confirmed. Lower minimum starting voltage
values than stated on data sheets will cause stand-by pump start
Fig 7.5.3 The effect of oil viscosity on centrifugal pump performance
time to be less than anticipated, shorten motor life, and could
result in serious transient auxiliary pump start problems that
could cause critical equipment shutdown.
provide ease of maintenance, and minimize the necessity to Driver sizing must be confirmed with specification re-
remove a pump or driver while the critical equipment unit is quirements, such that driver horsepower equals pump horse-
operating. The type of coupling selected should be of high power times a specified service factor. Selection charts for
quality and reliability, and provide a minimum of three years expansion turbines should be checked, and it should be con-
continuous operation. While either batch lube gear type cou- firmed that proper, standard size, electrical drivers have been
plings or dry flexible element types can be used, the latter are selected. In applications where viscous fluids are used, pump
preferred for their low maintenance requirements. Coupling calculations for horsepower corrections at maximum fluid vis-
material should be steel, as opposed to cast iron, to prevent cosity must be checked. Attention is drawn to realistic sizing of

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