Lube oil pressure

An interlock is provided through a centrifugal type of pressure switch (PS) to trip the engine in the case of low lube (lubricating) oil pressure during a run. Since during a. start oil pre.s.sure has not built up, a timer, 7 j is introduced to bypass the trip interlock and avoid a false trip. A relay (contactor), d], is used to provide lube oil pressure interlock. 

Thrust loads on die bearings Seal gas pressure and flow Lube oil pressure... 

A bladder or diaphragm-type aeeumulator should be supplied to provide proper lube oil supply to the bearings during expander-eompressor eoast-down in the event lube oil pressure is lost. The aeeumulator must be fitted with a preload filling system and neeessary bleed and bloek valves. 

Lube oil pressure is generally eontrolled by a self-eontained pressureregulating valve that automatieally maintains a eonstant lube oil pressure aeross the bearings. The valve is normally adjustable, but is usually preset at the faetory. The valve flow eapaeity must be suffieient to bypass exeessive flow if both main and standby pumps are operating simultaneously. 

Before mining on tlie seal gas and lube oil pumps, initiate power to the eontrol panel to eonfirm tlie indieator lights are funetioning. At tliis time, there is no seal gas or lube oil pressure so tlie low lube oil alarm, low lube oil pressure shutdown, and seal gas alarm light should be on. 

After the lube oil pumps have been running for approximaely 15 min, elose the pump and filter bypass and slowly pressurize the system to establish normal lube oil pressure. The alarm and shutdown lights should turn off by pushing the reset button on the annuneiator panel. 

LOW LUBE OIL 1. Faulty lube oil pressure gauge or switch. Note 2. Loose or broken bolting. 

Consider a function designed to detect if lube oil pressure is low on a gas compressor. The architecture of this function given in Figure 3 and it consists of four components and one logic unit. The logic unit also... 

Components 1 and 2 are in a parallel structure, while components 3 and 4 are connected in parallel to the inner system. The logic unit shuts down the system if it receives 2 warnings of low lube oil pressure. Component 1 is a pressure detector, while components 2, 3 and 4 are pressure switches. The logic imit is assumed to work perfectly. The components are non-identical with failure rates... 

Figure 3. The function which detects low lube oil pressure in the gas compressor.

Table 3. The different states of the lube oil pressure system when including the aforementioned simplifications.

Steam turbines are designed to trip off due to overspeed, excessive vibration, low suction pressure, loss of lube-oil pressure, etc. Turbines are... 

The lube-oil pressure to the mechanism activating the trip-throttle valve was intentionally bled down. 

Frequently, a major unit shuts down when a compressor trips off. The cause may be low lube- or seal-oil pressure. The pumps providing the lube- and seal-oil pressure are typically spared (backed up). A steam turbine-driven pump is normally backed up by a motor-driven spare. The motor-driven pump should come on when the lube-oil pressure drops below a preset point. 

But the backup lube oil pump, which was supposed to start automatically on low lube oil pressure to the bearings, failed to start up on auto. 

With a loss of lube oil pressure to the bearings, the bearings were rapidly damaged, and the resulting vibrations destroyed the gas compressor. 

The plant supervisor claimed that the destruction was due to surge. This was not true. The destruction was due to the supervisor failing to verify that his backup lube oil pump would start up on auto, on low lube oil pressure to the bearings. (See Troubleshooting Process Plant Control, Wiley, 2009 for details as to how this is done.)... 

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