Author Topic: Need some help with a leaking Stuart hand pump.  (Read 286 times)

Offline AOG

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Need some help with a leaking Stuart hand pump.
« on: August 11, 2017, 03:11:14 AM »
I just got done building a boiler pressure testing rig consisting of a PMR water tank, Stuart hand pump and a pressure manifold with gauge. This evening I started to pressure test the rig to make sure it was watertight. I found and fixed a couple leaky pipe joints but I am having problems with the pump itself. I was successfully able to pressurize the rig to my max test pressure of 200 psi. The problem is that when I stop pumping the pressure immediately bleeds down to 52 psi through the pump. It seems to hold indefinitely at 52. In an attempt to fix the problem I have lapped the port face, seated the ball and even added a spring. None of that did any good. Am I asking to much from this pump? Should I go to an external check valve? Suggestions would be appreciated.

Thanks

Tony

Offline AOG

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Re: Need some help with a leaking Stuart hand pump.
« Reply #1 on: August 11, 2017, 03:13:05 AM »
I forgot to add a pic of my setup



Tony

Offline crueby

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Re: Need some help with a leaking Stuart hand pump.
« Reply #2 on: August 11, 2017, 03:24:14 AM »
Can you tell where it is leaking from? Are you pumping water through to the exit valve, then sealing it up, to get all the air out? If there is air in the pipes, its a lot harder to spot leaks.

On the one I recently made (not Stuart's, but very similar design), I started out using an o-ring around the ram where it goes into the pump body, held with a retainer. Looks like yours might be same setup? Anyway, mine leaked there, letting water out the back end of the ram, and I fixed it by cutting a groove for an O-ring near the inner end of the ram, and sealing it that way, against the inner bore of the body. That held very well.

If yours is leaking back into the water tank, that would indicate a leak at the check valve on the exit of the pump. If there was any chatter in the drilling, it could have left a leak spot around the ball. After seating the ball into the body, did you keep that ball or change it out? The seating operation could deform the ball.

One other option would be to add another shutoff valve before the gauge, to take the pump out of the equation for holding pressure.

Offline steamer

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Re: Need some help with a leaking Stuart hand pump.
« Reply #3 on: August 11, 2017, 03:27:44 AM »
If I recall ...and I may not!     there is a stacked ball check arrangement on that pump correct?


If so, is there a threaded seat under the delivery valve?

If so, make sure your threads are sealed with pipe dope or similar.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline AOG

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Re: Need some help with a leaking Stuart hand pump.
« Reply #4 on: August 11, 2017, 03:52:33 AM »
Chris, I pumped water through the system until I got water through both valves and then sealed the system. From what I can tell, the water is leaking back into the tank so I have a problem with my outlet side check valve. I didn't change the ball after seating it (the kit only comes with one of each).  Dave you are correct it's a stacked ball arrangement but there is no seat beyond the drilled hole in the casting. In order to get the balls to seat they specify that you drill flat bottom holes which I did using endmills. That's why I'm wondering if a 200 psi test pressure is to much to ask of this design.

Thanks

Tony

Offline Stuart

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Re: Need some help with a leaking Stuart hand pump.
« Reply #5 on: August 11, 2017, 07:43:45 AM »
Tony

When seating ball clacks do not use a stainless steel ball ,use a hard steel ball as used in a bearing ( you can get them use ) one hit with small hammer and a brass drift , then bin that ball , now put in the stainless steel one and assemble the valve

Opps forgot the hard ball needs to be the same size


If you have hit the soft stainless ball it will be deformed and is now useless

Stuart
My aim is for a accurate part with a good finish

Offline Jasonb

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Re: Need some help with a leaking Stuart hand pump.
« Reply #6 on: August 11, 2017, 07:46:11 AM »
  Dave you are correct it's a stacked ball arrangement but there is no seat beyond the drilled hole in the casting.

Holes where balls seat should really be reamed to give  atrue round hole not a 3 lobed one. replace ball if you have hit it to seat it.

Boiler will also have a clack when running.

For hydro testing it is common to fit a shut off valve so the pump is isolated as you are testing the boiler not the pump.

Offline Ian S C

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Re: Need some help with a leaking Stuart hand pump.
« Reply #7 on: August 11, 2017, 10:27:44 AM »
The other method of sealing the valve seat is to seat on an O ring, or to use a Nitrile ball.
Ian S C

Offline steamer

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Re: Need some help with a leaking Stuart hand pump.
« Reply #8 on: August 11, 2017, 11:24:38 AM »
Tony

When seating ball clacks do not use a stainless steel ball ,use a hard steel ball as used in a bearing ( you can get them use ) one hit with small hammer and a brass drift , then bin that ball , now put in the stainless steel one and assemble the valve

Opps forgot the hard ball needs to be the same size


If you have hit the soft stainless ball it will be deformed and is now useless

Stuart

Was there any chatter in the hole?    a rough finish on a flat bottom hole would leave a less than crisp edge to seal against
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline AOG

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Re: Need some help with a leaking Stuart hand pump.
« Reply #9 on: August 11, 2017, 12:39:11 PM »
Thanks everyone, the seats were lapped so that should take care of any burrs. I have decided on a belt and braces approach on fixing this issue. I ordered some new balls and I also ordered a PMR check valve that I'll put on the outside of the pump.

Thanks

Tony

Offline Stuart

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Re: Need some help with a leaking Stuart hand pump.
« Reply #10 on: August 11, 2017, 12:49:17 PM »
Looks like there is as many ways to seal a clack up as there are model engineers  :slap:

To be honest I use the poppet type with a o ring half way up the cone but they are a bit bulky
My aim is for a accurate part with a good finish