The Shipyard ( Dry Dock ): Builds & Questions > Steam

Boiler Feed Pump Questions

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derekwarner:
 In preparation for the need of boiler feed water [and the new boiler certification rules] I have sourced two identical 6 bore x 5 stroke piston pumps with 4.0 diameter shaft eccentric drives

The initial plan was to have the auxiliary pump electrically driven @ 70 RPM & the primary pump driven from the main engine 4.0 diameter shaft conveniently located between two plummer blocks on the stdb side with  the pump under the engine
A new pump drive eccentric strap & the lubrication hole @ 90 degrees will be required but shouldn’t be a problem
The planned main engine speed is in the order of 130 RPM, so this will create the need for a bypass valve & this is where I am baulked

So a question for ooyah/2 or JerryC…………in the setup of the bypass needle valve
·         Do you simply bench test the engine watching the boiler water level  whilst steaming & adjust the bypass needle valve occasionally to obtain some sort of balance?
·         Or is the same test & adjustment made with the engine underload in water?
·         I have read in the Wear thread on how pleased Jerry was with the makeup water balance, although no real explanation was made in achieving & maintaining the balance
·         I have spoken with our local model steam train guys, but naturally understand they use they bypass valve in a totally different manner

Because of sailing in salty/brackish water, I will need an onboard water supply, however will need to discharge clear makeup water overboard as I cannot pressurise the makeup water tank
Naturally any comment greatly appreciated


Derek

mrsgoggins:
You will not pressurize the feed water tank, simply fit it with a breather.
Have you considered electronic control of boiler level? It's fairly cheap and simple and in my experience very reliable. Using a bypass valve means that your pump is absorbing power all the time rather than just when it is needed.
I like your workmanship.


Keith

Jerry C:
Hi Derek, ref bypass valve and level control. I only open my bypass valve at the start of a run in order to prove it's pumping. I then close it. If I see the level rise above the middle of the glass I allow pressure to rise towards maximum. This reduces the efficiency of the pump (I think) and the level falls. If I see the level fall I run the engine over speed and the pressure falls so the pump works better and the level rises. If I forget about it and just run it as I wish the level in general looks after itself. It just seems to be a perfect match for the engine. I once went for seven weekends without having to intervene. As I'm drawing water from the lake and the lake is perfectly clean I don't have a problem with dirty valves. Last week I did 7 miles on a dirty canal and did get trouble. I'm planning to include some form of filtration this winter. I don't understand about you pressurising your feed tank though. If you can't get it in you won't get it out. It must be vented somehow. If your bypass is open there is virtually no load on the pump.
It looks really nice, I love the lagging but I would also lag the flanges ( a bit like a poodle cut) so you can access them if needed.
Jerry.

hammer:
Derek. Will the hand pump used for the initial fill be one of the 2 methods required ? the engine driven pump the other??? :embarrassed:  Geoff

derekwarner:
Thanks for the responses
Geoff....no, the initial fill will be manually via the boiler top port, subsequent filling or topping up is planned via the steam drive [main] or auxiliary [electric] driven pump
JerryC....I think I had misunderstood the concept you use....... :embarrassed: ...from your latest posting it is similar to the model steam train engine boiler feed/ bypass system....may I ask the bore & stroke of the ooyah/2 [George] ...designed & built pump?
Keith.... I have  a fellow member Southstyne2 a few kilometres from me.........he has designed & built a fully functioning boiler level water control level system & I have witnessed that it works perfectly  :-))
In fairness, I must learn to walk before I can run...so will wait until the primary & auxiliary pumps are running under manual control.........Derek
 
 

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