Author Topic: Stuart Boiler Feed Pump  (Read 62248 times)

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #105 on: December 04, 2013, 09:39:51 PM »
Gentlemen - I guess I owe you the solution to the reason of the pump not running properly:

After thinking about what could cause the problem and listening to the Pump, I found out that the d-Valves were too short. They were just as long as the distance was between the outer edges of the cylinder ports. Theroetically. In fact, the ports were a little wider than they should have been and so there was a position where the d-Valve couldn't cover them completely and in the same time let the steam in to both of them.

This alone wouldn't be a problem but the ports are wider than the d-valve wall. That results in a "short circuit" for the steam which was enough to get the pressure dropping below the required level for moving the shuttle valve.

So I had to make another pair of d-valves. The old ones in front of the raw material:
And that is it. The new ones on the left and the old ones on the right.

That was then also the cure for the problem of the pump getting stuck. The pump still gets kind of stuck but it will restart by itself if I increase the pressure.
I will have to exchange the o-rings aswell because at the moment I am using nbr o-rings but silicone would be better for this (which I don't have in stock that is why I first took some nbr rings)
However, here you can see what I am talking about of "getting stuck":

<a href="https://www.youtube.com/watch?v=OlVJvIKo4lw" target="_blank">http://www.youtube.com/watch?v=OlVJvIKo4lw</a>

Well - I am confident that the steam also will help to get the pump running smoother. We will see.  ;)

« Last Edit: August 12, 2017, 09:56:40 PM by Florian Eberhard »

Offline derekwarner

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Re: Stuart Boiler Feed Pump
« Reply #106 on: December 05, 2013, 02:05:25 AM »
Florian....as George has suggested....Silicone [MQV] rubber O-rings will provide superior service

This MQV material is rated to 220 degrees C and a similar 85 Shore hardness [to NBR]

NBR material is only rated to a nominal 100 degrees C....but at this temperature [or above] swells & becomes sticky & natural  lubricity diminishes greatly

At say 3.5 Bar WP....you are feeding steam @ say 140 degrees C into the pump........which certainly could have contributed to NBR swell & the issues you experienced......Derek

Derek L Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #107 on: December 05, 2013, 09:11:01 AM »
Hi Derek

Yes, I know that nbr is not suitable for that use.  I only used the nbr rings to start and I have to order silicone rings.

Florian

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #108 on: December 06, 2013, 11:12:25 PM »
Now the pump is running, I'll have to make all the rest:

1. making studs, nuts and washers
2. fixing the pump to the cast iron base
3. milling the outside of the cylinder covers (and the cylinder ends aswell) 
4. making the gland packing from teflon for the water side
5. making drain cocks
6. making the plug screw for the pump backside
7. making the check valve plunger (I am not going to use the balls - I will make them from brass and use an o-ring for sealing)
8. making the cylinder cladding (I will not use that aluminum sheet piece delievered with it - I don't like its color - doesn't fit together with gun metal I think...)
9. making main steam valve with oiler aswell as steam exhaust pipe

So you see its quite some work left though some poits will be done within one or two hours.

But lets start with the first task.

I began with the undercut for the threads. Then the chamfer for the thread start was cut, followed by cutting the thread using the tailstock as support.
And the same procedure was repeated on the other side.

The washers were cut off from a bar which I drilled with the required diameter first.
I just noticed I didn't take any pictures when making the nuts  :o
However, on the last picture, you can see the finished nuts.

One point done then  ;) ;D
Thats it for now - 'till soon.
« Last Edit: August 12, 2017, 10:00:45 PM by Florian Eberhard »

Offline derekwarner

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Re: Stuart Boiler Feed Pump
« Reply #109 on: December 07, 2013, 04:00:44 AM »
Florain......I am unsure of your philosophy in using a square undercut for the inboard side if the stud & a radiused undercut for the fastened or outboard side

In a perfect world...would you not have a greater stress riser with the square undercut?........Derek
Derek L Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #110 on: December 07, 2013, 09:33:15 AM »
would you not have a greater stress riser with the square undercut?

If I had a square undercut yes.
But my undercut has a radius which is quite small (too small maybe...?).

However - those studs are not under such big stress that it makes any difference I think. The Undercut is in this case only to have a clean end of the thread and not for optimizing force flow.

Cheers Florian

Offline derekwarner

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Re: Stuart Boiler Feed Pump
« Reply #111 on: December 07, 2013, 10:10:33 AM »
Florian...I am sure that the pressures & stresses being applied to these studs are within the design requirements .....and would have been calculated many years ago by Weir or Stuart etc

It was simply when we see a generous radius undercut being applied to one section of the stud......& then a near visual square edge undercut being applied to the other section of the stud that prompted my question

Mind you....as far as I could see.....there is no nomination of the material grade used........this subject [material grade for studs] was discussed however became shall we say WARM & at one recent stage locked

Without contravening the previous thread assurances.......the selection of different bar stock here for your studs could range from say 500 to 850 MPa which is a tremendous variance....Derek



« Last Edit: December 07, 2013, 10:39:10 AM by derekwarner_decoy »
Derek L Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #112 on: December 07, 2013, 10:18:40 AM »
It is 1.4301 that was used for the studs wich has in about 660 MPa typically (can be between 500 and 700)

And yes you are right - I should make the radius as big as the one on the front. 
However - I've been making the radius with a honing bar and I thought it might get bigger than it actually got.  :embarassed:
« Last Edit: December 07, 2013, 12:29:07 PM by Florian Eberhard »

Offline steamer

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Re: Stuart Boiler Feed Pump
« Reply #113 on: December 07, 2013, 10:24:00 AM »
Let's also keep in mind that these are models, that the stresses from load go down dramatically with scale.....

Please proceed Florian....you're doing fine.

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

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #114 on: December 10, 2013, 09:44:25 PM »
Hello Hello - its me again  ;D


I am now happy with how the pump runs:
<a href="https://www.youtube.com/watch?v=266v_ZgGt6s" target="_blank">http://www.youtube.com/watch?v=266v_ZgGt6s</a>

I guess that is quite good (though still running dry)

« Last Edit: December 10, 2013, 09:56:06 PM by Florian Eberhard »

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #115 on: December 10, 2013, 10:27:13 PM »
And yes - I also continue with the report:
Next, I milled the sides of the cylinder covers and the cylinder as well. I again used the expanding mandrel held in the 3-jaw chuck of my rotary table.
And I made a terrible mistake, I didn't tighten the mandrel tight enough. And this is what happens then:  :hammerbash: :Mad:

So I ordered another cylinder cover casting. Unfortunately, my dealer said it is going to take in about one month as he had to oder it from england. Well - what could I do - I just had to wait.
I then continued with mounting the pump to the cast iron base. For this, I had to drill a hole into the base and also cut a thread.
The Idea is to make a tapered bore into the pump body (which sits in the base with a tight fit) and to fix it with a setscrew that has a taper on its tip as well. To get a tapered bore, I had to make a tool (d-bit again) and as the compound slide was set to the angle I directly continued to machine the set screw. That "pocket" in the pump body you can see on one picture is actually tapered.

I am going to try using a teflon seal for the pump ram. So I had to machine a ring that fits into the gland. That thin part of the seal will go into the gland nut. The Idea is to seal and guide the pump ram with teflon in order to prevent the ram from wearing.
One and half a week after I ordered the spare cylinder cover it arrived. I machined it and it all went well Phew!
Looks like my dealer had a cover laying around somewhere in his shop.  :whoohoo:
The Stub was machined slightly different as I was a little unsatisfied with the look of it. The new version looks more pleasant to me. However, i should not get used too much to get a second chance though  O:-)
I also added screws beneath the shuttle valve bore to support the cover (you can see them on the picture just above)

Thats it for today. See you soon  :cheers:
« Last Edit: August 15, 2017, 08:42:34 PM by Florian Eberhard »

Offline swilliams

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Re: Stuart Boiler Feed Pump
« Reply #116 on: December 11, 2013, 08:54:09 AM »
Looking good Florian, and it's running very smooth in the video too

Cheers
Steve

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #117 on: December 11, 2013, 09:48:10 PM »
Hi all  :happyreader:

Next time in the shop, i machined the cylinder drain cocks.
I have once ground me a straight edge tool for making the tapered plugs. Instead of needing around 30 seconds to get a good finish, I now need somethink like 4 seconds to get the taper done cleanly.
Also for the cock body and the spheric head of the plug. Here the time saving is even more - I now need in about 10 seconds to finish the ball head of the plug - with a ball turning attachment that was something around 2 to 5 minutes!
For giving you an impression how this works, I have made a short video of the ball end being machined. The interrupt cutting is due to me holding the cam in one hand and feeding with the other one (so its going even a little faster if I am not recording):
<a href="https://www.youtube.com/watch?v=xU4j4zzR2xI" target="_blank">http://www.youtube.com/watch?v=xU4j4zzR2xI</a>

The tapered Plug has got a square on the lower end for driving the washer. To make a square hole, I used a square punch which i had made some time ago.
Then the handle bars are pressed into the ball head of the tapered plug.
The handles were made from boxwood wich machines extremely well and also looks good in my opinion.

That is now where the project ACTUALLY is in my shop. Next time I will write as I continue.  ;)
« Last Edit: August 15, 2017, 08:49:27 PM by Florian Eberhard »

Online sco

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Re: Stuart Boiler Feed Pump
« Reply #118 on: December 11, 2013, 09:56:11 PM »
Beautiful work Florian!

Simon.
Ars longa, vita brevis.

Offline Don1966

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Re: Stuart Boiler Feed Pump
« Reply #119 on: December 12, 2013, 01:22:05 AM »
Nice video Florin, beautiful job all around.  :ThumbsUp:

Don

 

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