Function of the return pipeline from the cold pump outlet to the middle part of the pump body in the low-temperature area
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From the outlet of the cold pump in the low-temperature section of the methanol washing unit to the middle part of the pump, there is a very thin return pipeline (not an exhaust valve or a cooling valve); this pipeline remains open at all times without any valves. It’s not clear whether it serves as a minimum flow return line or is used to ensure even operation of the cold pump. I would appreciate guidance from those with experience in this field! Thank you!
The name of this pipeline is the flushing pipeline. Function, as the name implies, haha.
This pipeline runs from the pump’s outlet to the mechanical seal of the pump body. If you’re referring to this pipeline, I think it is used for the secondary sealing of the pump’s mechanical seal – it utilizes the high-pressure liquid at the pump outlet to seal the mechanical seal, and this is what is known as secondary sealing! !
This pipeline should be used to cool the mechanical seal
After communicating with the personnel in charge of the equipment, I learned that heat in the pump body of the cold zone can easily generate gas! They said that backflow occurs because, during design, there was a concern that gas might accumulate in the center; therefore, high-pressure liquid from the outlet is used to expel the gas generated inside. It can also serve the purpose of cleaning the pump, as mentioned on the second floor. The two-stage sealing is located at the front and rear of the pump, rather than in the middle of the pump body
I think it’s for sealing purposes – a section of medium-pressure methanol is taken from the middle of the pump and used at the high-pressure end for sealing. One pump I saw (a methanol-poor pump, but it’s a heat pump) works in this way: a stream of methanol is drawn out from the middle and divided into two sealed paths, one for the inlet and one for the outlet!
Thank you to all the forum members for their active participation in the discussion. I can assure everyone that that pipeline is definitely not a mechanical seal. In general, for pumps used in cold areas, the mechanical seal is connected to the outlet or a siphon tank is used; what I’m talking about here is a connection from the pump outlet to the center of the pump body, possibly even directly into the impeller. I think what was said by the user on floor 5 makes some sense – could they please elaborate further so that we can all benefit from it?