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Boiler feed pump design

Andy_C

Joined: 1-01-70

Topics: 2

Replies: 1

Posted: Thu 17th Oct 2013, 3:23pm
Boiler feed pump design

Hi all

I wish to add a means of continuously adding water to the boiler of my engine and have acquired half a scratch built steam powered boiler feed pump for the purpose. My question is how do I decide on the bore of the water pump side, which, unless I'm being stupid which is quite possible, can't be larger than the steam side but should it be the same or smaller? And if smaller by what sort of amount?

I have a couple of hand pumps that cold be donors including one fitted to the loco, so am hoping to use one of them if possible. I also assume that I will need a check valve between the pump and boiler as well?

Thanks

Andy Comley
 

Replies To This Post

Alan Pollock

Joined: 15-12-06

Topics: 6

Replies: 48

Posted: Thu 17th Oct 2013, 6:03pm

Andy

Is it not better that it's the same size to keep thing smooth flowing? Be interested to hear what the people who know more about it tbh as am clearly no expert but wood have though it better if it's kept the same size as explained earlier.

Alan
 

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Thu 17th Oct 2013, 6:42pm

The point is, that you only have boiler pressure to push the water past the clack, which means that you need the water pressure to be higher than the boiler pressure or it just won't go in, so equal sized bores just won't work. The amount of steam that a given amount of water makes is many times, so the water side can be considerably smaller and still supply enough. If the pump still supplies too much then the extra can be bled off by an adjustable by-pass valve (same as an axle pump), enabling finding a setting that should take care of steam usage with very little messing, assuming fairly constant load, and other running conditions.
 

Richard

Joined: 1-01-70

Topics: 10

Replies: 37

Posted: Thu 17th Oct 2013, 7:31pm

Hi Andy. It really depends on how much water you want to pump into your boiler in a given time period.

This might be useful:

http://www.nelsonslocomotive.com/Shay/AirCompPump/AirCompPumpI/AirCompPumpI.htm
 

Richard

Joined: 1-01-70

Topics: 10

Replies: 37

Posted: Thu 17th Oct 2013, 7:32pm

Hi Andy. It really depends on how much water you want to pump into your boiler in a given time period.

This might be useful:

http://www.nelsonslocomotive.com/Shay/AirCompPump/AirCompPumpI/AirCompPumpI.htm
 

Andy_C

Joined: 1-01-70

Topics: 2

Replies: 1

Posted: Fri 18th Oct 2013, 8:07pm

Thanks for the suggestions, I'll remove the piston end plate and check the bore.

On the bypass, I take it I would need to use a manual bypass valve or is there anyway to automate the switch over? The reason for asking is that it's a water tube boiler and therefore water level sensitive and hence the desire for continuous feed.

Thanks

Andy Comley
 

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Fri 18th Oct 2013, 9:06pm

Yes, manual by-pass is easiest to produce, though there are automatic systems, some electronic, sometimes used in the 'boat' world.
 

paul winstone

Joined: 8-12-05

Topics: 1

Replies: 4

Posted: Tue 15th Apr 2014, 10:28pm

I run mine with a manual block valve on the water delivery. This slows the pump down and minimises steam usage. It gives very fine control.
 
 
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