Water Pumps

[Fred Graham 1Participant @fredgraham1]

Hi Folks,

 

I have noticed that on some commercial engines (E.G. Hemmens & Monahan) they have a water pump which is directly driven off the crank shaft and have the ram operating vertically and the valve boxes disposed horizontally.

 

In all the model plant descriptions I have seen over the years, pumps are normally geared down by 4 or 5 to 1 and the valve chambers are arranged in a vertical attitude.

 

I have always thought that pumps were run at a lower speed to improve their perfomance and that valve boxes were arranged in the vertical plane to ‘gravity assist ‘ seating.

 

If anyone has experience with such a plant having a water pump arranged as described, Is it reliable and does it work efficiently.

 

All the best,  Fred Graham

[Fred Graham 1Participant @fredgraham1]

[Phil ButtonParticipant @philbutton47234]

I have tried a ram pump with valve boxes arranged at approximately 45degrees to the horizontal on one of my engines and had great difficulty in getting the ball valves to seal properly. Changing the pump such that the valve boxes were vertical (hence using the ‘gravity effect’) made a huge improvement in valve performance.

 

To date, I have tried feed pumps gear driven from the crankshaft and also direct drive and in my opinion there is no real benefit to either drive method as long as the pump ram diameter and stroke is sized appropriately for the boiler feed rate at the likely engine rpm and the engine has the power to drive it. In general, I have used gear drive with double acting oscillating engines that have limited torque at high rpm and direct drive with slower running slide valve units. 

[Fred Graham 1Participant @fredgraham1]

Hi Phil,

 

Thanks for your comments and It is interesting that you have run at engine speed and geared. I presume that the volume of the pump for an ungeared set up would be smaller.

Did you keep the valves and ram the same size and shorten the stroke. Making the ram smaller would probably have meant reducing the ball valve diameter all of which makes for more fiddly seats etc.

 

As you will have gathered I asked the question because I see that Monahan in particular have apump with the valves arranged horizontally across the top of a vertical ram. There is a U_tube video showing the plant running and water being delivered into a collecting vessel. I wonder how it performs against boiler pressure.

 

Thanks again for your interest, Best regards, Fred Graham

[Brian MorrisParticipant @brianmorris30448]

,Can an electric pump such has a washer pump[, be used to transfer water into bottom of boiler opertated by servo from an onboard water tank ?

[Gerald Gardiner 1Participant @geraldgardiner1]

Hi Brian,

 You would have to measure the pressure output of the pump to see if it is higher than your boiler pressure. Most windshield washer pumps for cars are impeller type, which provides high flow and low pressure. You need to use a positive displacement pump.

Regards,

Gerald.

[Brian MorrisParticipant @brianmorris30448]

Thanks Gerald iwill look at it again regards Brian

[TelstarParticipant @telstar]

Hi Brian  

To give positive displacement for an electric pump you need something like a ‘spur gear’ pump, these give a constant flow, and can reach very high pressure.   A single spur gear pump is often used on car engins as the oil pump, mechanically driven from the camshaft

 

Cheers Tom

 

[Brian MorrisParticipant @brianmorris30448]

Could one of those stuart manual water feed pumps be coupled to a servo and then operted back and forth by a transmitter channel ? regards Brian

[HS93Participant @hs9317166]

Hear  is one that is avalable by Regner not cheap though also Ministeam do one in the uk

[HS93Participant @hs9317166]

also this one

Peter

[Brian MorrisParticipant @brianmorris30448]

thanks for the info looking at it ,it looks like  i could adapt the pump and a servo to make one regtrds Brian

[Gerald Gardiner 1Participant @geraldgardiner1]

Posted by Telstar on 29/07/2010 22:33:56:

Hi Brian  

To give positive displacement for an electric pump you need something like a ‘spur gear’ pump, these give a constant flow, and can reach very high pressure.   A single spur gear pump is often used on car engins as the oil pump, mechanically driven from the camshaft 

Cheers Tom

 

Hi Tom,

Do you know if any one has used a small Gear Pump for a boiler feed pump?

Years back I worked with Hydraulic ones, but never thought of using one as a feed pump. I wonder if you could run the housing close enough to the gears or if you would have to make pressure plates?

Regards,

Gerald.

[Tim Greenwood 1Participant @timgreenwood1]

I have experimented with a Kavan fuel pump marketed by Ripmax, part number              L-FK190. It has brass gears and will pump water into my test boiler at 3bar.

Disadvantages so far, I suspect it is about on the limit at 3bar, its delivery at atmospheric pressure is given as 1.8 litre/min although could be throttled back and how to engineer a safe interface between the plastic output and a hot boiler. Experiments presently on hold. Price around £23.

Tim 

[Gerald Gardiner 1Participant @geraldgardiner1]

Hi Tom,

I never thought about a model fuel pump, most of the ones I had used were impeller types. I will have to check and see what the local shop has.

Regards,

Gerald.

[TelstarParticipant @telstar]

Hi Brian Sorry for the delay in answering.    Yes in full size I maintained a LP (about 3bar) steam generator, that had a spur pump supply water.   It was S/steel  and had plastic gasket/side plates between the side plates and the main body/gears. These were water lubricated plastic.  If run dry(without water) they were easily damaged, but used correctly they were reliable .

Cheers Tom

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