Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[firedup]

I have a problem built the steam engine ,ran the steam engine on steam, ran the water pump fine so far.
The problem is when I connecting to the boiler the bump is unable to overcome the pressure of the boiler.
Pump has a 1/4" ram the engine is the Borderer twin slide valve which I have posted on this site before.
Any help would be most welcome.
Mark

[HS93 (RIP)]

Put a pressure Gauge on the out put of the pump to see what does come out then look at the pump valves. any pictures

Peter

[firedup]

Try this:
http://www.youtube.com/watch?v=dLMWGrIGjHA

[ooyah/2]

Hi ,
Make sure that the pump is primed before doing as Peter suggests.
I made one to Bertinant's design and it needed priming if laid up for a while.
George,

[firedup]

George looks like the same pump design, as I said pump works when not connected to the boiler however when I connect up I can see that the pump is struggling to pump(as seen by the bubbles in the fuel line tubing).

[firedup]

Just had a thought  I know that the clack valve is not sealing well and intended replacing the steel ball with a bronze one or a nitrile one. Would the back pressure from the leak be causing the problem with the pump?

[derekwarner]

firedup....most of these model pumps work on similar principals to larger scale pumps

a] Ideally the ball should be stainless steel & be seated to the circular knife edge within the pump brass body by a gentle tap with a pin punch
b] A brass ball on the knife edge of a brass seat is not ideal as the tap by the pin punch may mark/deform the ball & it will never seal
c] A nitrile ball on the knife edge of the pump body will cut the ball with the back pressure from the boiler when the piston is on the return stroke & the ball will self destruct in a very short period of time & never seal
d] If your boiler has a steam relief valve setting @ say 150 PSI, your make up pump will need to have a pressure pumping capacity of approx 5% higher that the boiler relief valve ......or say ~~~160 PSI [this is needed to overcome in efficiencies & hysteresis
e] Does your pump set up have a relief valve function?....if not you will simply consume engine power & over pressure the boiler to open/crack the boiler relief valve

As previously suggested by HS93 ....by disconnecting the pump from the boiler & installing a gauge to the pump discharge will prove a few points .....Derek

[south steyne]

Hi firedup I think your pump has an air lock (struggling to pump(as seen by the bubbles in the fuel line tubing). ) it cannot overcome the boiler pressure pumping compressed air so make sure there are no leaks in the delivery side.

[Bunkerbarge]

If you have any air in the line, as demonstrated by the bubbles, the pump will not move water, it will simply compress the air on the pressure stroke.  The line must be completely free of air.

I also notice that you mention "fuel line", does that mean you are using silicone tubing as discharge pipe?  If so again the pump will be simply be expanding the silicone rather than moving the water.  You must fit pipe that is not flexible such as copper tube.

[firedup]

Thanks for the input so far.
The fuel line is on the input side
Thanks for the information regarding the use of Nitrile balls
I had considered replacing the steel balls with bronze as I had been advised that they offer a better seal.
Working pressure is 40lbs

[firedup]

Does your pump set up have a relief valve function?....if not you will simply consume engine power & over pressure the boiler to open/crack the boiler relief valve
Derek could you expand on this or provide photos to explain?
Mark

[ooyah/2]

Mark,
In my opinion your problem lies in that the suction valve isn't seating, it will draw air from the suction pipe and as it isn' sealing the air bubble will just swing back and forward.
This pump has a banjo fitting on the suction side so take out the valve box ream the hole and the with sharp tool face it,
if you are going to give the ball a hit with some thing make sure that the punch is vertical, may have to make a guide, after punching throw the ball away and use a new one.
Make sure there are copper washers on both sides of the banjo and smear a little thread lock on the thread before locking up, I at wone time after about a week traced the leak to air passing up through the thread.
After it's assembled stick a piece of fuel tube on the inlet and suck and before releasing stick your tongue over the hole , you should feel suction, make sure the ball is wet.
If this doesn't work start again.
The suction valve must work

[derekwarner]

firedup....I do not have a boiler make up water pump....but the attachment mud map should explain 

1) as the piston pump retracts....two things happen....firstly the pressure in the boiler closed the non return valve, secondly the piston creates a vacuum in the suction line...lifts the suction valve off its seat & draws water into the pump casing
2) as the piston extends..... the increasing pressure closes the suction valve & pressurises the line to the boiler with free flow over the non return valve

In addition to this.....if the boiler relief valve to atmosphere is ~~~~~40 PSI, ideally a relief valve should be placed between the pump non return valve & the boiler...as mentioned previously....an approx differential of 5% should be maintained to overcome in efficiencies & hysteresis ...so your pump relief valve should be set @ approx 42>44 PSI

The discharge from this relief valve should be ported at atmospheric pressure to the pump makeup water tank

Naturally all of these functions are a balance between steam consumed.. to makeup water pump displacement etc....Derek

[firedup]

Thank you very much Derek I will have a good look at the drawing .First step will be to make the pump suction parts from phosphor bronze I used brass and I think the real problem results from a poor seat.
I have followed all the standard steps to make this including the reaming of the hole, using a guide to ensure that the "tap" is parallel to the hole ,discarded the steel ball replaced with new one.
Looks like the next step is to change the material God I hate making these dam seats

[derekwarner]

firedup...... phosphor bronze .....BS1400 LG2 is certainly harder & tougher than brass...although any of the common garden variety of RED brass listings should suffice .....although technically not necessary....if space permits......orientate the water suction valve in a vertical plane & also minimise the clearance between the diameter of the S/S ball & the gallery

Remember we are only talking low pressures here.....the weight of the ball must also contribute to itself positioning over the knife edge seat that you have just created

Keep us posted as we all learn...........Derek

[ooyah/2]

Mark,
I am really at a loss as to how much advice is flying about on your problem on pumping against boiler pressure.

Dereks exposition I think applies to full size pumps and I fear he has never made a model pump before.

I have made model pumps over the years and have lost count of how many that I have made.
I have made them from pumps working at 60 psi x 120 rpm up to 1000 psi plus x 2600 rpm on my flash steamer and have never made anything as elaborate as has been suggested.
There is no need to use any other material than brass for your valve boxes and seats..
However if you are having trouble getting it to work why not try as you have suggested using Nitril or Viton balls. The leakage on your boiler clack should have no effect on the pump but if you go down the rubber ball road I would change it as well, but make sure that the hole into the boiler won't allow the Viton ball to be sucked into the boiler as it cools down

Take your valve seats and very gently take off the sharp edge with a Slocum centering drill, you only need to touch the edge.
Fit a bypass valve on the delivery side which will allow you to prime the pump and also adjust the boiler feed.
I have used rubber balls in p-umps and found them to be very effective.

On looking at your excellent engine on you-tube and your machining skill you will have no trouble curing the problem.
George.

[firedup]

Thank you very much for the support Georgie extra special when things are going wrong.
I have taken in all the advice, thought about it and tried to make sense of the problem .
Before I did anything drastic I took another look at the pump,took a skim off the suction pump end, reamed the hole then sat the steel ball with a tap.
Pump seems a lot better so I tried again.
Fired up and primed the pump (made sure that the pump was working ) sat back and took a good look at what was happening pump. Working lifting water only a slight leek so as the water was going down in the supply tank it must be going into the tank but not quickly enough.
The pump is geared down to 10:1 so must be too high.
As I had tried to take advantage of gears I had to hand worm and spur I view this problem not as a waste of time but a lesson learnt.
Now I am trying to source spur gears to give me a reduction of 4:1.
Once again thanks for ALL the support and advice offered.
Mark

[flashtwo]

Hi Mark,

When testing my pumps, I always use a piece of clear plastic tube on the suction side and introduced a small bubble of air by lifting the tube out of the feed tank for a brief period while the pump is running. If the bubble of air is seen to move to and thro about the same position then the suction non-return is passing. If the bubble moves up the tube, stops and then moves again then the valves are closing.

I've found stainless steel balls on brass have worked fine right up to 300psi.

Ian.

[gondolier88]

Another option open to you is to use the excellent check valve supplied by steamfittings.co.uk that use a PTFE seat and are super reliable in service.

Greg

[firedup]

I am sure that Steamfitting can supply the answer to my problem (in fact I purchase an excellent pressure gauge from them) however I would like to make as much of the project as I can even if it means lots in the scrap box.
Mark

[ooyah/2]

Mark,
I buy all my gears from http://www.hpcgears.com/
They make a very good product and I think if yo contact them they will post you a catalogue.
In the 32 D.P. range they do a steel worm with a hard bronze spur wheel machined to match the worm having 1--> 4 starts.
I notice that on the you-tube video that you drive the ram via a disc on the cross shaft, can you increase the dia of the disc to allow a longer stroke.
It may not be possible if you have made the pump to the drawing, or is the ram going straight into the pump barrel.
It could be cheaper to make a new pump to a different design which if you wish you can P.M. me and I will scan and send a sketch to you.
Don't know where you live but H.P.C. is in Chesterfield.

Good idea to make your own clack.
George.

[firedup]

Once again thanks for the help and the offer.
I had considered increasing the stroke on the ram and making a new pump body .Think I will chew on it.

[derekwarner]

Guys....I had previously acknowledged that I have not built a MODEL single cylinder makeup water pump...... ....but suggest that full size engineering principals still are relevent 

Could I ask our member Bernhard to offer comment....as he has displayed a number of differing variations on boiler water make up piston pumps......& his photo images will be far more informative than my mud map sketch or various member comments    ,....Derek

[ooyah/2]

Derek,
My apologies as I am fairly new to MBM I didn't know that you had already acknowledge to the forum that you had never built an engine pump and my remarks were not meant for you but just a general comment.
Yes you are quite correct that full size principles do apply and if rubber balls are to be used the sharp edge must be removed.
However I think that FIREDUP has found the cause of his pump problem.
George.