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The pumps can be either centrifugal or positive displacement types. The centrifugal pumps should have a head curve continuously rising toward the shut-off point. The standby pump should be piped into the system in a manner that permits checking of the pump while the main pump is inoperation. To achievethis， a restriction orifice is required with a test bleeder valve piped to the return oil line or the reservoir.
Twin oil coolers (Figure 15-3) should be provided and piped in parallel using a single multiport transflow valve to direct the oil flow to the coolers. The water should be on the tube side and the oil on the shell side. The oil-side pressure should be greater than the water-side pressure. This ratio is noassurance that water will not enter the system in the event of a tubeleak， but it does reduce the risk. The oil system should be equipped with twin full-flow oil filters located downstream from the oil coolers. Since the filters arelocated downstream from the oilcoolers， only one multiport transflow valve is required to direct the oil flow to the cooler-filter combinations. Do not pipe the filters and coolers with separate inlet and outlet block valves.

Figure 15-.. Cooler-filter arrangement.
Separate block valves can cause loss of oil flow from the possible human error of flow blockage during a filter switching operation.
Filtration should be 10 microns nominal. For hydrocarbon and syntheticoils， the pressure drop for clean filters should not exceed five psi at 100 .F operating temperature at normal flow. Cartridges will have a minimum collapsing differential pressure of 50 psi (3.44737. Bars).
The system should have an accumulator to maintain sufficient oil pressure while the standby pump accelerates from an idle condition. An accumulator becomes a must if a steam turbine drives the standby pump. Overhead tanks are specified by many users to assure flow to critical machinery components. The sizing of the tanks varies depending on the application. In some gasturbine applications， the bearings reach maximum temperature as long as 20 minutes after shutdown.
The oil coolers and filters are controlled by a local temperature control loop with remote control room indication and high/low alarm. The coolers and filters also have an indicating differential pressure alarm. These usually feed into a common high alarm to pre-warn a need for switching and filter element replacement.
To ensure the required constantpressure， a local pressure control loop isprovided on each system.turbine lubeoil， compressor lubeoil， and control oil. .ach oil pressure system should be recorded in the control room to provide troubleshooting information. The success of the oil system dependsupon not only the instrumentation， but upon proper instrument location.
The minimum alarms and trips recommended for each ma.or driver anddriven machine should be a low oil pressure alarm， a low oil pressure trip (atsome point lower than the alarmpoint)， a low oil level alarm (reservoir)， ahigh oil filter differential pressure alarm， a high bearing metal temperaturealarm， and a metal chip detector. See Table 15-1.
.ach pressure-and temperature-sensing switch should be in separatehousings. The switch type should be single-pole， double-throw， furnished
.able 15-1 .larms and .rips
.larm .rip
Low oil pressure  x  x 
Low oil level  x 
High oil filter  x 
High thrust bearing metal temperature  x 
High thrust bearing oil temperature  x 
Metal chip detector  x 

　
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本文鏈接地址：燃氣渦輪工程手冊 Gas Turbine Engineering Handbook 2(107)