Both pumps use flushing scheme No. 32, and both experience the issue of the flushing oil pump becoming empty as soon as it is started? ?
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There are two slurry pumps (one in operation and one as a backup; the high-temperature pumps operate at around 170 degrees). Flush schemes No. 32 and No. 53 are used for these pumps. Recently, these pumps kept experiencing vacuum conditions; various causes were investigated, and ultimately turning off the flushing system for Pump No. 32 resolved the issue. Now, when the pumps are started without using the flushing oil, they operate normally; but once Pump No. 32’s flushing oil pump is activated, vacuum conditions occur again. There are also two smaller pumps, which are high-temperature pumps operating at around 200 degrees; they too operate in a one-in-operation-one-backup configuration, with Flush Scheme No. 32 being used, and vacuum conditions arise whenever the flushing oil pump for these pumps is turned on. The flushing oil is VGO, with a temperature of around 100. Could some expert please analyze this? Thank you
Preheating method? We first apply sealant, and it needs to be done slowly; however, operators are usually quite lazy, so they may not follow this procedure. Wait until the pump temperature reaches the sealing oil temperature before activating the slurry pre-heater; this process must be done slowly to prevent the slurry from overheating and vaporizing the sealing oil.
The slurry pump has a steam jacket, and it is normally in a heated standby state. Before starting the pump, flush oil No. 32 should be introduced first (flush oil No. 53 is also introduced first; there is a interlock mechanism that activates when the main pump starts). After starting the pump, slightly opening the outlet valve will cause vacuum to occur; by stopping the flushing with flush oil No. 32, the pump will start more easily.
Is VGO containing water? When the temperature rises, the water vaporizes, and flushing should result in a vacuum condition.
It has not been tested yet to determine whether it contains water, but other pumps also use this type of flushing oil; in such pumps, the flushing oil enters the mechanical seal and then exits along with the medium.
Plan 32 is used for single-machine sealing, while Plan 52 is used for dual-machine sealing; it’s not clear which method should be used for machine sealing. The boiling point range of VGO is approximately 370–535°C; given the temperature of the medium transported by the pump you mentioned, vaporization is not a possibility. It is recommended to check from these two aspects: 1. Whether the flushing solution being used is contaminated ； 2. Check whether the mechanical seal is leaking. If the resistance in the inlet pipeline is high, a negative pressure is likely to develop at the pump inlet; as a result, even if there is a seal leak, air may enter the pump chamber, making it difficult to detect such a seal leak. I hope the suggestions will be helpful to you.
It is because the flushing oil exits along with the medium. If VGO contains gases (water vapor), cavitation will occur. Other pumps, which use only VGO for sealing without allowing the medium to enter, will only accelerate the wear of the seals, but no vacuum condition will arise. It is recommended that the poster have the VGO flushing oil tested.
The 32 oil you supplied vaporizes once it enters the mechanical seal; it is recommended to use oil with a higher temperature of supply, as such oil is less likely to vaporize