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Ball lift in a water pump.

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Dennis Rayner12/02/2015 15:34:34
115 forum posts
7 photos

I'm building a water pump and plan to use 7/32" balls on 3/16" seats. Does anyone know what I should restrict the lift to?

Bob Brown 112/02/2015 15:56:28
1010 forum posts
127 photos

1/4 the diameter of inlet hole size as anything above that gives no gain in flow.

Dennis Rayner12/02/2015 16:01:26
115 forum posts
7 photos

Thanks very much Bob. That's very helpful (I'm trying to recover from miss-machining a casting which should have had 5/32" balls on 1/8" seats)

Derek Drover12/02/2015 19:36:28
85 forum posts

I think most people aim for about 30 tho. Any more and you loose out on the time it takes to re-seat from the lift, especially if running fast.


Dennis Rayner12/02/2015 19:44:34
115 forum posts
7 photos

Thanks for that Derek - from the formula given by Bob I calculated 47 tho. so I'll settle on a value in between. This is for a steam operated water feed pump from a Southworth set of castings. I do not intend to operate it very quickly. With an injector and two axle pumps I'm not short of boiler feed so this will operate mainly for visual interest.

Bob Brown 112/02/2015 20:56:18
1010 forum posts
127 photos

If the seats were supposed to be 1/8" then 0.03" works and anything up to 0.047" would be fine.

As a cover all statement "I think most people aim for about 30 tho" does not work as you increase the size of the valve, a 1" valve with only 0.03" of lift would be a big restriction to flow. Time to re-seat is dependant on how the valve is re-seated, gravity or spring.


Harry Wilkes12/02/2015 21:32:21
893 forum posts
61 photos

I was once told by a wise man of steam the ball seat should 3/4-7/8 of the ball diameter and that the ball lift should never exceed a 1/4 of the seat diameter ! Having put this into practice on both clacks and pump on my engine everything now works fine.


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