Author Topic: 3 inch boiler build  (Read 8874 times)

Offline gary.a.ayres

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3 inch boiler build
« on: July 10, 2018, 10:03:06 PM »
Hi -

I thought I should start a bespoke thread on this work in progress rather than indefinitely hijack my own 'introduce yourself' thread http://www.modelenginemaker.com/index.php/topic,8234.0.html.

Following my experience with a leaky check valve during the first hydraulic test, I followed advice from some of you and took two remedial steps: replacing the steel ball in the check valve with a nitrile one, and adding a globe valve between the pump and the check valve. This really did the trick, and the result was version 2 of my test rig which has no leaks in the water feed system. When that globe valve is closed, it's closed! Photo below.



And now the bad news: the improved system showed clearly that what I had thought was a repair was an improvement, but not a repair. The offending tube still leaks, albeit more slowly. During the test, the pressure dropped from 90 psi to 78 psi over a 30 minute period - better than it was, but a leak nonetheless. The photo below (top left tube) shows the problem - there is a gap under the fillet which I added, probably due - I think - to insufficient heat during the attempted repair. My plan is to reheat it and try to melt the solder which is already in place so that it will flow around and into the joint more than it has. The boiler is now back in some new pickle for 24 hours to get it as clean as I can prior to reheating it, hopefully tomorrow evening. I will, of course, use plenty of flux and follow the previous advice on giving the whole thing an overall background heat with propane before focusing on the flaw with oxy/mapp.

However, if anyone has any other ideas I'd be happy to hear them.

Photo below:



gary

Offline crueby

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Re: 3 inch boiler build
« Reply #1 on: July 10, 2018, 10:59:36 PM »
I had a spot like that, and wound up having to grind off the solder overhang so that I could clean the metal underneath properly, the pickle was not enough to get rid of soot/etc under there. If you have something like a Dremel rotary tool, and a small bur, that is very wuick to do. Then reflux, heat, and add a little more solder there as if it was a new joint being done - more reliable a method than hoping it will reflow.

Also, if you have more than one grade of silver solder, using one with a lower melt point for the repair can reduce the risk of opening up something else.
So close, keep at it!!
 :popcorn:

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #2 on: July 10, 2018, 11:10:08 PM »
Thank you, crueby    :)

I did think about the grinding idea as I had heard it before, and in fact wondered if I would be given that very advice!

I think I'll give it a whirl tomorrow evening with my cheap and cheerful Dremel copy.

Regarding melting temperatures, I have already figured that in, as I used three different silver solders for the reason you suggest. Most of the soldering around the end caps was done with high or medium temp. I used low for the attempted repair and will do so again.

The encouragement is much appreciated - even knowing that you had a similar problem and fixed it is reassuring!

Cheers,

gary

Offline crueby

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Re: 3 inch boiler build
« Reply #3 on: July 10, 2018, 11:11:39 PM »
Oh yes, I spent weeks getting my first boilers to be leak free! Later ones, just many days instead...   :facepalm2:
Chris

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #4 on: July 10, 2018, 11:13:04 PM »
It can be done!!

 :)

Offline zeeprogrammer

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Re: 3 inch boiler build
« Reply #5 on: July 11, 2018, 12:09:30 AM »
Keep at it! This is a very helpful thread.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #6 on: July 11, 2018, 06:14:41 AM »
Thanks Carl.

As a beginner I'd have been in trouble without the advice I've been given here. I'm hoping that the thread will serve as a good resource for others too.

Keep at it I certainly will! I'll be glad when the boiler is finally steam-tight but too much has gone into this for me to quit now...  :ThumbsUp:

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #7 on: July 11, 2018, 10:17:13 AM »
Hi Gary,

Its go to see you making progress on the boiler. I can't really offer any advice but I'm hoping to make something similar later in the year so it's interesting to follow along :-)

Offline john mills

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Re: 3 inch boiler build
« Reply #8 on: July 11, 2018, 10:34:25 AM »
try to bring the tube plate hotter the silver solder should melt with the propane torch the hole end of the boiler will get close to the temperature needed.

Offline Jasonb

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Re: 3 inch boiler build
« Reply #9 on: July 11, 2018, 10:58:54 AM »
The other good reason to grind away the blob is that it needs more heat to melt the solder second time around so using new will mean you don't have to get things quite as hot.

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #10 on: July 11, 2018, 11:05:14 AM »
I don't want to hijack Garys thread but do you think I'd be able to build something similar using just a small MAPP gas torch ?

Offline Stuart

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Re: 3 inch boiler build
« Reply #11 on: July 11, 2018, 12:35:33 PM »
The hard fact is no

Even for a small boiler the heat required is considerable at least a 25mm /1 inch burner head would get it done , donít forget it has to be hot and even , tube plate and foundation rings are the worst because you cannot easily inspect your work on the inside , so it needs to be heated though the job to get a good penetration of the joint

To the OP

I think your problem with the tubes not sealing was because you expanded the tube into the tube plate thus preventing any solder penetration of the joint have a read of Alex farmers book he recommends a rough rat tail file to give a bit of clearance in the joint , which is vital to get a good seal

Three roller tube expanders are normally used in steel boilers with copper tubes no other sealing was done


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

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #12 on: July 11, 2018, 12:41:02 PM »
@ John and Jason - good advice, thanks. Makes much sense. Will proceed down the route you suggest. Fingers crossed.

@Peter - feel free. Doesn't feel like a hijack to me  :-)

My guess is that the torch you are asking about may provide too localised a heat (albeit at a high temperature), whereas I think a more generalised source - such as a larger propane torch - is required to get the whole boiler up to temperature. But listen to me - the 'expert'  :lolb: .  Let's see what some of these people that actually know their stuff have to say about it.

gary

Edit:
PS - Stuart replied while I was typing the above, hence sequencing issue.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #13 on: July 11, 2018, 12:46:25 PM »

I think your problem with the tubes not sealing was because you expanded the tube into the tube plate thus preventing any solder penetration of the joint have a read of Alex farmers book he recommends a rough rat tail file to give a bit of clearance in the joint , which is vital to get a good seal

Three roller tube expanders are normally used in steel boilers with copper tubes no other sealing was done


Stuart - I'm sure you are correct, and I will not be expanding the tubes on the next boiler I make. However, it's a done deal on this one. I take heart from the fact that there are ten joins in total between tubes and end plates on this boiler, and only one of them leaks. Not ideal, but hopefully fixable. Thanks.

gary

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #14 on: July 12, 2018, 08:22:40 PM »
The hard fact is no

Even for a small boiler the heat required is considerable at least a 25mm /1 inch burner head would get it done , donít forget it has to be hot and even , tube plate and foundation rings are the worst because you cannot easily inspect your work on the inside , so it needs to be heated though the job to get a good penetration of the joint
Stuart

Thanks Stuart, I have wondered if my soldering torch has the guts

I was hoping to build something similar to the one Gary has built but possibly in a horizontal design. I did manage to successfully silver solder a foundation ring / base for my 5" dia boiler by using the ceramic burner that powers the boiler as an extra heat source to supplement my MAPP gas set up.

Fortunately the materials I have for the boiler were items that friends have given me so I don't have a lot to lose in trying. I did even consider buying a second MAPP gas torch and getting someone to lend a hand.

Ideally I need a more substantial torch but I don't have a garage or shed so storing a gas bottle indoors isn't ideal  :(