Help with water pump - no pressure

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Bill Shields
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Re: Help with water pump - no pressure

Post by Bill Shields »

I like the return on the tender, since I sit behind the tender (generally). This means you need a high pressure return hose to connect tender to loco.

If you have packing on the pump ram OD, then you do not want an o-ring on the ram itself. If the packing is leaking...fix it.
Too many things going on to bother listing them.
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NP317
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Re: Help with water pump - no pressure

Post by NP317 »

Glenn:
Both my locos have reciprocating axle water pumps. They receive unrestricted water from the tender, and output it to the boiler check valve AND a return line to the tender. The metering valve in the cab (via a long extension handle up through the cab deck) controls water flow back to the tender. This way the pump always fully pumps (no starvation), but you can control how much gets into boiler.
And having the return valve under the cab means the return line to the tender is low pressure, which eliminates a pair of potential leak joints.

'Has worked flawlessly for years.
RussN
Glenn Brooks
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Re: Help with water pump - no pressure

Post by Glenn Brooks »

Bill and Russ, Thanks.

So to clarify - you both recommend the needle valve can be installed on the return line - e.g. indirectly controling water injected into the boiler, by varying the discharge pressure back into the tender?

If so, does the return line need to feed separately back into the tender tank itself, or can it simply loop back to a manifold or Tee at the backhead (between the filter and the pump)?

Thanks much,
Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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NP317
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Re: Help with water pump - no pressure

Post by NP317 »

Glenn:
Correct. And the return valve can be a globe valve. That's what I use. (Pic attached - the 2nd rubber hose and valve under the cab.)

The choice is yours as to where the return flow valve resides:
On the locomotive (low pressure plumbing to the tender),
Or on the tender (high pressure plumbing to the tender).
RussN
Plumbing LSide small.jpg
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Bill Shields
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Re: Help with water pump - no pressure

Post by Bill Shields »

yes...the return line should be separate - and in a place where you can SEE the water being returned into the tender.

this tells you that the pump is working....if you open the valve and see NO WATER coming out when the loco is moving - you know you have a problem.

I like using a needle so that I have better control..
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NP317
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Re: Help with water pump - no pressure

Post by NP317 »

Bill Shields wrote: Tue May 16, 2023 11:59 am [snip]
I like using a needle so that I have better control..
Smaller gauge locos might need a needle for water control due to the size relationship between the pump output and the boiler capacity.
My 1/8 scale locos have large capacity boilers compared to the pump and plumbing. The globe valves provide excellent control in these setups.
Interesting stuff to consider.
RussN
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Bill Shields
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Re: Help with water pump - no pressure

Post by Bill Shields »

Guess that I am missing something...would not be the first time...🤪

The pump output on all of my locos (from the 2.5" gauge to the 7.25" gauge) is proportional to the steaming capacity of the boiler. Why would a pump not be?

But then you have been saying globe valve and my spaghetti brain has been thinking ball valve.

Yeah .a globe valve is very appropriate. 🤪

The needle valves I use are actually radiator drain valves from the NAPA store...and not all that different from the globe valves supplied by our model vendors...they just have larger heavy duty stems that are more resistant to being twisted off...do not ask me how I know this...
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NP317
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Re: Help with water pump - no pressure

Post by NP317 »

👍🏼
RussN
Mike Walsh
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Re: Help with water pump - no pressure

Post by Mike Walsh »

I attached a photo of the appropriate setup, generally speaking.

When your needle valve is open, your pump can pump back into the water reservoir against atmospheric pressure. The reason it doesn't inject into the boiler is because the pressure within the boiler is greater than atmospheric pressure, and water will take the path of least resistance - back to atmosphere (your water tank).

If you close the needle valve, you are closing off one of two exit routes for the pumped water, thus now requiring the pump/water to work against the boiler pressure. As you pump, it will inject into the boiler with every compressive stroke.

Note the additional two check valves. Remember I mentioned two escape routes for the pumped water? I lied. there are three, maybe four.

If you don't have these check valves in place, you are allowing the water to route to atmosphere... So if you were to close your needle valve, and didn't have a check valve before the pump, you'd be pumping water back through the supply line... Essentially just moving water back and forth in your piping. The check valve after the pump is to allow the suction stroke to pull water from your supply, not the piping after the pump.

In small scale steamers, the output into your reservoir is typically visible if you open a hatch. Sometimes helpful for a quick visual if it is easily visible.

I have made the mistake of dragging an engine to the bays with the bypass valve closed. Whoops. At least the engine passed it's hydro test up to the set point of the safety valves. BTW I did not know until the kid who was pulling it with his battery engine emerged from the ROW saying "uh, there's a problem there's water coming out of the safety valves".. "oops... Let's open that bypass shall we?"

I hope this helps. If I had more time today I would draw up a nice CAD version of this diagram... But I am trying to wrap up loose ends before I leave at noon today for a train-filled weekend in the Northeast. Can't wait!

Mike
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makinsmoke
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Re: Help with water pump - no pressure

Post by makinsmoke »

There is also the option of piping your hand pump ( if you have one) in the same circuit. Allowing you to prime the axle pump if needed.
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Charles T. McCullough
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Re: Help with water pump - no pressure

Post by Charles T. McCullough »

Like this:
LocoTenderPlumbing.jpg
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Mike Walsh
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Re: Help with water pump - no pressure

Post by Mike Walsh »

Charles T. McCullough wrote: Wed May 17, 2023 8:59 am Like this:

LocoTenderPlumbing.jpg
Showoff. :)
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