Hangqi’s steam turbine generator sets
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For Hangqi’s turbine generator sets, the main oil pump is a turbine shaft pump with a speed of 3000 revolutions per minute. In the past, the outlet pressure of this main oil pump was low and subject to significant fluctuations; after the main oil pump was put into use, the auxiliary oil pump would start automatically all the time. Could someone please offer some advice?
For this issue, it is necessary to distinguish between normal conditions during the initial testing and problems that arose later on. The \"shaft-mounted pump\" you mentioned is likely an oil pump driven by the main shaft, which serves as the primary oil pump. During startup, the pressure output by this oil pump increases gradually as its speed rises to the designed value; that’s why an auxiliary pump is installed. It is what provides lubrication during the initial startup phase and the idle stage when the machine is shut down. The interlock design of this auxiliary oil pump is such that it starts when the pressure is below the lower set value and shuts off when it is above the upper set value. As for whether the situation you mentioned is caused by a clogged filter or the need to readjust the pressure using the pressure-regulating bolt on the main oil pump body, this needs to be confirmed. Also, check whether the oil filter, return valve, and pressure relief valve in the oil system are all in normal condition. (For reference)
This situation only occurred after a few years of operation; the switch to shut down the auxiliary oil pump simply won’t stop it.
Operator’s response: During the unit’s standby period, the auxiliary oil pump was started weekly to rotate the unit’s shaft for about 2 hours. However, after the auxiliary oil pump was turned off and shaft rotation stopped, the pressure indicated by the pressure gauge at the main oil pump’s outlet did not return to zero; it remained above the low-pressure alarm threshold. After several dozen hours, when this value dropped to around the level below the low-pressure alarm threshold, the DCS indicated a low pressure at the main oil pump’s outlet. The operator had to restart the auxiliary oil pump in order to raise the pressure indicated by the gauge above the low-pressure alarm threshold and thus eliminate the alarm. This situation occurred almost every day during the unit’s standby period.
The check valve at the outlet of the high-pressure oil pump is likely not functioning properly; once oil pressure is established, the outlet valve (of the high-pressure oil pump) closes
Which oil pump do you mean by this high-pressure oil pump? There is no problem with the check valve at the outlet of the auxiliary oil pump; it has been checked