What is the design of the opening in the valve disc of the check valve at the outlet of the auxiliary oil pump?
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The auxiliary oil pump of the hydraulic turbine for the catalytic cracking feed pump in my unit keeps reversing slowly while in the stopped state. Today, when checking the outlet check valve, I found a circular hole of about 1–1.5 mm in the center of the valve disc, similar to an orifice plate; I’m not sure why such a hole was created. When the outlet valve was activated, it was clearly visible that the oil pressure at the pump outlet began to rise; this hole is the cause of the reverse rotation. The unit is from Ebara in Japan.
Is it equivalent to turning the shaft? Don’t let the lubricant stay still?
The auxiliary oil pump remains online and can be started at any time
Keep oil in the outlet line of the auxiliary oil pump at all times, to prevent air from accumulating from the pump outlet to the check valve in the event of prolonged shutdown. When the oil pressure drops and the auxiliary oil pump starts automatically, the oil pressure fluctuates
So, is there any impact on the slow reverse rotation of the auxiliary oil pump caused by this? Could it cause excessive current during startup?
It is not allowed to reverse the pump, whether it is a large pump or a small one; I think the oil hole size of 1-1.5 mm is a bit large
Is the reversal abnormal? Has the flow control hole become larger?
A slight reversal is acceptable; the reasons for making holes have been clearly explained above. Another reason is to ensure that oil keeps flowing in the auxiliary pump while the main pump is operating, thereby maintaining the appropriate temperature. Otherwise, in case of an emergency, it will be necessary to start the auxiliary oil pump, but if the pump temperature is too low, this could cause the pump to seize and get damaged
Will prolonged erosion cause this hole to get larger over time? It is said that at the beginning of construction in 2013, there was no reversal, and it’s not clear when the reversal started
It can be disassembled for measurement; the diameter should be available in the drawings, which can be used for comparison. There’s no problem with the opening size – many units are designed this way