Threaded Bowl Pressure Limits

[wellman]

How do I calculate pressure a threaded bowl will hold? The bowl is an intermediate bowl of a submersible multistage centrifugal pump or a multistage vertical lineshaft bowl assembly.

 

[PUMPDESIGNER]

The pump manufacturer must participate somewhat because they know the type of metal i.e. ductile, gray iron, stainless, steel, etc.

Also, just a comment or question really.
We have seen the better companies switching over the past years to "O" ring bowls with bolts from threaded bowls. Threaded bowls have always been a problem and most pump manufacturers have wanted to switch over but some lacked funds to do it.

What do you think?

PUMPDESIGNER

 

[wellman]

Most bigger bowls are bolt together. Say from 7 or 8 inch bowls and on up. There are a lot of 4, 5, and 6 inch bowls that screw together and I am not sure you could convert these to a bolted bowl without compromising the water passage way and in turn the performance. The problem I was trying to figure out was how to calculate the pressure these screw together bowls would hold. In ductile iron I don't think it would be much of a problem. But in cast iron the threaded portion will be in tension and I don't think the will hold a lot of pressure.

 

[PUMPDESIGNER]

This is interesting.
I know what you are talking about with the smaller bowls, it is important to avoid increasing diameter.

Sorry I cannot help more.
We established a company policy forbidding the use of threaded bowls. Everything 6" and larger we use bolted bowls only. Small stuff makes us cringe because we cannot obtain good pumps. You have any sources for good 4" submersible turbines with trimmable impellers?

PUMPDESIGNER

 

[wellman]

Sorry it has taken me so long to respond. I work for a pump manufacturer that produces a 4" cast iron/ bronze pump.
Although we have rarely if ever trimmed that 4" impeller I see no reason why you couldn't. I have not ever tested it with a trimmed impeller. At 3450 rpm and BEP we are looking at 70gpm and 21ft per stage. The effeciency is only
about 66%. I don't know of anybody that does much better on small pumps. These are just to small to get very good efficiency. Hope we might could help you.

Thanks