Multi-stage Centrifugal Pump Draining

[wsmith22]

We have found that a horizontal Gould's eHM multistage pump will not totally drain through the diffusers into the pump casing. Our application requires full drainage due to possible freezing conditions. Has anyone had any experience or ideas on a solution? Would it be possible to drill a small hole in the bottom of each diffuser without greatly reducing the pump output pressure or flow rate?

Thank you.

 

[Rputvin]

When we drain a system for shipment we'll fill the pump cases with 100% glycol and drain them again so anything residual has a high glycol concentration for freeze protection. Not sure if you have any fluid restrictions that would prevent this. We'll also lift one end of the base structure to facilitate draining.

The other option is to force warm air through the system to purge as much as possible and dry out the rest.

I would not add holes in the case, you're creating ports open to atmosphere in the item that's trying to develop pressure. Bad plan.

 

[EdStainless]

I have seen horizontal multistage pumps with a drain line running from each bowl back to the inlet side.
These connections had a very small flow restriction device in them.
And they have to all be rated for full shut-in pressure.
You could in theory apply suction to these lines to empty the pump.
I don't like them. The lower efficiency, increase risk of leaks, and are easily plugged by debris.

We used to use Methanol fill and drain to keep water from freezing in pumps in shipment.

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P.E. Metallurgy