Author Topic: Help with fittings on a Boiler  (Read 13245 times)

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #45 on: October 16, 2017, 01:45:03 PM »
Hey everyone,

Now have all the half-couplings and both end plates welded on in place. I will grind and sand the welds and remove the splatter today and get it ready for the pressure test. Hopefully there will not be any leaks and I can get a coat of primer on today.

Have a great day,
Thomas

« Last Edit: October 25, 2017, 12:33:15 PM by Ye-Ole Steam Dude »

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #46 on: October 16, 2017, 07:35:43 PM »
Hey everyone,

OK we have the “good news and the bad news” situation. Bad news first, my welds have more leaks than the Titanic after she hit the iceberg. I fix 2 little leaks and re-test and find 3 news one $%*&^$(*. :hammerbash:

The good news is that even with a couple small leaks I had a successful pressure test up to 80psi with no effort. :cartwheel:

I will take a break before I get too frustrated and give it a go again in the morning.

Have a great day,
Thomas

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #47 on: October 20, 2017, 09:14:01 PM »
Hey everyone,

Finally got time to work on the Boiler today and fixed the last pin hole leaks. Ran another pressure test with the tank about 80% full of water and raised the pressure up to 90psi and let it rest for about 5 minutes. Eureka no more leaks other than around several temporary plugs.  :whoohoo:

Used a wire wheel and a 80-grit flapper disc to clean up some of the welds, then applied some JB Weld Stillstick epoxy putty for appearance. Did not have enough to do all the outlets so ordered more this afternoon. Should be able to complete this portion by mid-week and get a coat of primer sprayed on.

I bought a quart of Rust-Oleum High Heat paint and cannot decide to paint the inside of the tank or not. Anybody have any suggestions?

Have a great day,

Thomas

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #48 on: October 21, 2017, 10:48:48 AM »
Update on what to do for the interior of the Boiler.

I have received real good information from a number of folks about treating the water to prevent rust and scale and have decided to use this method. I will use the High Heat paint for the exterior.

Have a great day,
Thomas

Offline bent

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Re: Help with fittings on a Boiler
« Reply #49 on: October 23, 2017, 05:51:38 PM »
Using distilled water and regular flushing should keep it pretty rust-free Thomas.  It's 316 stainless, right?  Since it only gets pressure once in a while (not continuously) it should last a long while.

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #50 on: October 23, 2017, 07:47:15 PM »
Using distilled water and regular flushing should keep it pretty rust-free Thomas.  It's 316 stainless, right?  Since it only gets pressure once in a while (not continuously) it should last a long while.
[/quote



Hi Bent,

No the material is ASTM A500b steel so it will need some kind of protection. I have ordered some chemicals that the model steam locomotive folks use in their boilers and will actually "coat" the interior. I do plan to completely drain it when not in use for any long period of time.

Have a great day,
Thomas
« Last Edit: October 23, 2017, 07:51:12 PM by Ye-Ole Steam Dude »

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #51 on: October 24, 2017, 11:08:17 AM »
Hello everyone,

Finally received the last part that I had on order for the Controller and was able to run the first test today. All test went OK and confirmed that all the wiring is correct. I went ahead and connected the RTD sensor to read the ambient air temperature so that I could set all the parameters for mode “M”. The top number in red (74) is the RTD reading, which will be the water temperature when installed in the Boiler. The lower number in green (185) represents the “target value” that I choose for the first test. If the Boiler had water in it, the Controller would turn on the electric heating element and bring the water temp up to 185 and hold that exact temp until the Controller is turned off.

After I get the Boiler painted and the insides coated with the protective chemical, water will be added and I can run more test using various “target values”. I will make changes until I find the “perfect” temperature that gives me the best operating pressure to operate a steam engine. I have a pretty good feeling that I will need to replace the current Safety Valve that has a set pressure of 15-psi with one of 30 to 40-psi or maybe higher.

Have a great day,
Thomas

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Re: Help with fittings on a Boiler
« Reply #52 on: October 24, 2017, 11:34:33 AM »
4 to 1 factor of safety is appropriate.   That said the working pressure should be 15 psig.   Per your calculations.

That is a parameter that is set when the boiler is built, and then verified with a hydrostatic check to no more than 2x working pressure after completion.

Now is not the time to raise the working pressure.   

Dave


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Damned ijjit!

Offline Jasonb

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Re: Help with fittings on a Boiler
« Reply #53 on: October 24, 2017, 11:48:50 AM »
If it is the type of water treatment we use over here then you don't actually apply a coating to the inside of the boiler. You add it to the water and it will leave a deposit on the inside surfaces as the boiler is used, they are usually tanin based and exclude oxygen

Dave beat me to the other bit, I'd also add that the three calculations you showed all had diameter as part of the calculation which you used the ID of your pipe as the figure used. A round pipe will have a lot more inbuilt strength than a flat sided (square) pipe. You should really be using the calcs for fireboxes or tubeplateswhich are flat.
« Last Edit: October 24, 2017, 11:55:49 AM by Jasonb »

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #54 on: October 24, 2017, 12:23:28 PM »
4 to 1 factor of safety is appropriate.   That said the working pressure should be 15 psig.   Per your calculations.

That is a parameter that is set when the boiler is built, and then verified with a hydrostatic check to no more than 2x working pressure after completion.

Now is not the time to raise the working pressure.   

Dave


Good morning Dave,

I have tested the tank at 90psi on the last pressure test so I can increase the working pressure a bit more. I also have an additional safety factor built in my calculations. I used 29,000 for my modulus of elasticity which is A36 steel, the tube is actually ASTM A500b which has a higher psi yield value.

Maintaining a 4 to 1 using the 90psi, I can easily increase to 22.5 psi for a working pressure. If I choose to go higher than that, I would do another pressure test to an appropriate value.

I am hoping that I do not have to change the current Safety Valve and just stay with the set 15psi.

Thanks and have a great day,
Thomas

Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #55 on: October 24, 2017, 12:45:54 PM »
If it is the type of water treatment we use over here then you don't actually apply a coating to the inside of the boiler. You add it to the water and it will leave a deposit on the inside surfaces as the boiler is used, they are usually tanin based and exclude oxygen

Dave beat me to the other bit, I'd also add that the three calculations you showed all had diameter as part of the calculation which you used the ID of your pipe as the figure used. A round pipe will have a lot more inbuilt strength than a flat sided (square) pipe. You should really be using the calcs for fireboxes or tubeplateswhich are flat.

Hi Jason,

I am pretty sure the chemical that I have ordered is the same that you are using. The product description does state that it cleans and leaves a protective coat. I will add the chemical to the water every time that I use the Boiler, so it should work OK for me.

The formulas that I used are for non-cylindrical vessels, ie. flat side, not pipe or tube.

Have a great day,
Thomas

Offline Jasonb

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Re: Help with fittings on a Boiler
« Reply #56 on: October 24, 2017, 01:15:43 PM »


The formulas that I used are for non-cylindrical vessels, ie. flat side, not pipe or tube.

Thomas

The three formulas you posted all have "D" in them for ID of tube so don't know how you can say they are for flat surfaces and not tube?

I just ran some sizes through a spreadsheet that is used by a commercial model boiler maker here in the UK

With 3/16" wall a round seamless pipe would be good for 783psi

Ignoring wall thickness the bottom of your boiler on the large side of the Z shaped baffle will be 6" x 9" that just about squeezes in at 15psi MAX WORKING PRESSURE see 6x61 below

Now if you were to run one stay from side to side and end to end of each of the 9 opposed faces you could get the boiler so it would work to the pressures you are now talking about see 6x62 below


Offline Ye-Ole Steam Dude

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Re: Help with fittings on a Boiler
« Reply #57 on: October 24, 2017, 02:10:52 PM »


The formulas that I used are for non-cylindrical vessels, ie. flat side, not pipe or tube.

Thomas

The three formulas you posted all have "D" in them for ID of tube so don't know how you can say they are for flat surfaces and not tube?

I just ran some sizes through a spreadsheet that is used by a commercial model boiler maker here in the UK

With 3/16" wall a round seamless pipe would be good for 783psi

Ignoring wall thickness the bottom of your boiler on the large side of the Z shaped baffle will be 6" x 9" that just about squeezes in at 15psi MAX WORKING PRESSURE see 6x61 below

Now if you were to run one stay from side to side and end to end of each of the 9 opposed faces you could get the boiler so it would work to the pressures you are now talking about see 6x62 below

Hey again Jason,

Thank you for showing your math. I did notice that you are using only 12,500 psi for "E". That is much lower than the "E" value of the material that I am using.

Thanks again,
Thomas

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Re: Help with fittings on a Boiler
« Reply #58 on: October 25, 2017, 12:31:47 AM »
I'm a bit confused.   

E is generally the material Modulus of Elasticity.

In Imperial units, generally structural steel ranges from 28,000,000 to 30,000,000 psi.    that is a unit of stress, not pressure.

Yield strength of most structural steels Is in the 30,000 psi range generally, also a unit of stress, with about 20% elongation.

If I can get some time, I'll take a look at the calculations, but maximum working pressure is not determined by hydrostatic test, but by calculation.

Increasing the hydrostatic test pressure can actually damage the boiler.    Additionally, no mention has been made as to calculations regarding the welded joint, the type of rod used, geometry, approved methods of joint prep, and inspection.

Weld joints on a boiler are never to be ground, or covered with putty....they need to be visible so as to be readily inspected.

Nuf said.

Dave



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Damned ijjit!

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Re: Help with fittings on a Boiler
« Reply #59 on: October 25, 2017, 12:41:28 AM »
Well   I read this, and say    Wow Dave, you sound like a grumpy old curmudgeon!   

Well....Not quite old yet....though I'm getting there by most standards,

Grumpy?  well maybe.   but not mean......hear me out

I want everyone to have fun.    If you haven't gaged by my handle, I'm a steam guy   have been for some time.

I love it when people run steam, and have fun doing it, and showing others how much fun it is.       That said.

I want everyone to go home with as many eyes, teeth and other various body parts as the came with.   Poor practice gets my attention.

I especially don't want to see the wondrous eyes of a child hurt by a bad joint, or a broken bit even on a small boiler.  That's my own personal nightmare scenario.

So lets be safe, and get the facts.    There are a good deal of small boilers on this site that run and make steam a plenty.   Some have been designed by pro's who really do know how to design and build a hobby boiler.     

ok......now   nuf said.

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