Author Topic: Help with fittings on a Boiler  (Read 3356 times)

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #15 on: September 06, 2017, 09:53:48 PM »
Thomas:

Don't know if you've already covered this or not, but I've got a couple of questions.

1) What are you using for a heating element?
2) How did you determine if that heating element would be large enough to supply the volume of steam you need at the pressure you want?

I've been kicking this idea around in my head for a while, and I've found information that will hopefully allow me to convert Lbs/hour of steam into Watts.  From this I SHOULD be able to determine the heater size needed to run a specified size of engine at a given RPM.  BUT, I don't have a lot of confidence in my calculations.  What can I say, I'm a EE, not an ME - I wrangle angry pixies for a living.

Don

Hi Don,

I have ordered a Camco 1000 watt screw in element ( has 1" thread ) which will provide plenty of continues steam at 20 psi. I have built similar units in the past with much larger volume of water ( over 2 gallons ) and used the same element, so I did not do any calculations for this smaller Boiler.

The Camco is a 120vac unit and I will control it with a 25A SSR via the Digital Controller. The Controller will be connected to the Boiler with a RTD that is inserted in the water at the same level as the element ( see my drawing ). I will be able to set both an "upper" and "lower" limit on the temperature so as to maintain a constant water temperature even as the water level ( volume ) drops. If the temp gets too high (my preset value) the unit will shut down and must be Reset before it can be started again. I will also have audible alarms ( not at the very first ) to give a warning before the temp reaches the preset value.

Thank you,
Thomas

Offline Steamer5

  • Full Member
  • ****
  • Posts: 769
  • The "Naki" New Zealand
Re: Help with fittings on a Boiler
« Reply #16 on: September 07, 2017, 01:03:18 AM »
Hi Thomas,
 Not wanting to put a dampener on your ideas but a cylindrical boiler would be a much better idea, as Jason says the force on a flat plate gets big quick, even at 20 psi!

Steam Guy Willy hopefully will join this discussion as he has a nice rig to do just what you are after.

Cheers Kerrin
Get excited and make something!

Offline bent

  • Full Member
  • ****
  • Posts: 73
Re: Help with fittings on a Boiler
« Reply #17 on: September 07, 2017, 03:15:27 AM »
Man, I hate to pile on, Thomas, but ditto to ditching the flat sides.  I worked for a company that made espresso machines for awhile, and one of their designs was a square boiler much like what you have drawn, similar dimensions too, and also operating at 15 psi or less, using 1/4" thick 316 stainless steel.  The ends of the boiler would flex (oilcan) with each pressure cycle, and eventually fatigue and leak; or in places with hard/brackish water, the fillet welds would corrode and fatigue crack (stress corrosion cracking?) from the inside at the water line, due to salt/chloride buildup (these boilers rarely got purged until we built a purge cycle into the controller).  We mostly fixed both issues by using a rolled and welded tube, with formed (dished) ends, and all welds done full penetration with purge gas on the inside, and by using the afore-mentioned regular purging of the water.

I do approve of the plan to add a few spare ports, you never know what kind of add-ons you might want down the road.  And ditto to a build log, including the controller details.  Sounds like a great project to complement your engines.

Offline MJM460

  • Full Member
  • ****
  • Posts: 305
  • Melbourne, Australia
Re: Help with fittings on a Boiler
« Reply #18 on: September 07, 2017, 03:38:34 AM »
Hey ddmckee54,

I outlined the procedure for your calculations in answer to one of Willy's questions on his electrical boiler in the Talking Thermodynamics thread.  I don't want to hijack this thread, so have a peruse of what's there, and if it is not clear to you, don't hesitate to ask a question there.  There are no silly questions.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #19 on: September 11, 2017, 11:54:17 PM »
Hey everybody,

OK had a few minutes between projects this afternoon so I decided to run several calculations on the Boiler pressure/material thickness. I have attached a pdf document showing the three formulas that I used to verify that I do have a safe working pressure at 20 psi for my design. The numbers in parentheses (i.e. for d = 5.625) are the values that I used in each formula. The end result for all three calculations show a material thickness of .188" (+ -)gives a safe working pressure ( with a built in safety factor) of 65 psi.

Thomas
      

Offline Jasonb

  • Full Member
  • *****
  • Posts: 4664
  • Surrey, UK
Re: Help with fittings on a Boiler
« Reply #20 on: September 12, 2017, 07:42:30 AM »
I assume C is your factor of safety. For our UK calculations 0.16 to 0.12 would be used eg a factor of 6-8 but depends what your state code requirs

What calculations have you done for stay diameter and spacing?

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #21 on: September 12, 2017, 10:37:25 AM »
I assume C is your factor of safety. For our UK calculations 0.16 to 0.12 would be used eg a factor of 6-8 but depends what your state code requirs

What calculations have you done for stay diameter and spacing?

Hi Jason,

What do you mean about "stay diameter spacing"?

Thomas

Online Vixen

  • Full Member
  • ****
  • Posts: 511
  • Hampshire UK
Re: Help with fittings on a Boiler
« Reply #22 on: September 12, 2017, 11:14:14 AM »
Stays are those essential side to side, top to bottom and sometimes end to end supports which stop the flat sides of any boiler bulging out like a balloon. You will need to decide the number, the diameter and the spacing of these stays for your proposed boiler. What does your State boiler code say?

Mike
« Last Edit: September 12, 2017, 11:18:58 AM by Vixen »
It is the journey that matters, not the destination

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #23 on: September 12, 2017, 11:44:46 AM »
Stays are those essential side to side, top to bottom and sometimes end to end supports which stop the flat sides of any boiler bulging out like a balloon. You will need to decide the number, the diameter and the spacing of these stays for your proposed boiler. What does your State boiler code say?

Mike

Hello Mike,

I do not need external stays, my design incorporates an internal baffle which is welded to the sides, top and bottom. This design / construction meets the ASME Boiler and Pressure Vessel Code (BPVC). My pressure relief valve will be pre-set at 15psi which will be close to a 4 to 1 safety factor above the allowable safe working pressure.

Thomas

Online Vixen

  • Full Member
  • ****
  • Posts: 511
  • Hampshire UK
Re: Help with fittings on a Boiler
« Reply #24 on: September 12, 2017, 11:50:09 AM »
Thomas,

It's good to hear you have the design under control.

Take care

Mike
It is the journey that matters, not the destination

Offline Jasonb

  • Full Member
  • *****
  • Posts: 4664
  • Surrey, UK
Re: Help with fittings on a Boiler
« Reply #25 on: September 12, 2017, 04:26:25 PM »
Baffles will do a similar job to stays, I had not seen them on the earlier drawings you posted so assumed there was nothing there.

The stays would be internal if you had them, basically a rod passing right through and welded at the ends externally, either flush or slightly protruding. Probably easier to weld than getting down inside a tube with your welding gear

J

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #26 on: September 12, 2017, 05:14:37 PM »
Baffles will do a similar job to stays, I had not seen them on the earlier drawings you posted so assumed there was nothing there.

The stays would be internal if you had them, basically a rod passing right through and welded at the ends externally, either flush or slightly protruding. Probably easier to weld than getting down inside a tube with your welding gear

J

Hello again Jason,

I did not show the baffles in the concept drawings, I had turned that feature "off" in AutoCAD to keep the drawing as clean and simple.

I am not using rods, but rather using steel plate with a special cutout and bend. This style is what I have always used and it really adds a lot of strength to the vessel.

Thanks again,
Thomas

Offline Tennessee Whiskey

  • Full Member
  • *****
  • Posts: 3132
  • Springfield, Tennessee. USA
Re: Help with fittings on a Boiler
« Reply #27 on: September 12, 2017, 08:44:56 PM »
Thomas, kudos on a "different " boiler design. I was a boiler/ welding inspector on the first Gotatverken designed recovery boiler in the US.  The old timers said it would never work with just one drum, but , we were burning black liquor and generating when I left.

Cletus

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #28 on: September 12, 2017, 10:12:53 PM »
Thomas, kudos on a "different " boiler design. I was a boiler/ welding inspector on the first Gotatverken designed recovery boiler in the US.  The old timers said it would never work with just one drum, but , we were burning black liquor and generating when I left.

Cletus

Howdy and thank you Cletus,

Should be able to start building it sometime next week if the material gets here on time. I am anxious to get some steam to run several of my engines.

Have a great day,
Thomas

Offline Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 420
  • Deep East Texas on Sam Rayburn Lake
    • Ye Ole Steam Dude
Re: Help with fittings on a Boiler
« Reply #29 on: September 14, 2017, 03:27:14 PM »
Hey everyone,

Received the steel tube in late yesterday and started to work on it in the shop this morning. First photo is the cut length of the 6" x 6" x .188 wall square tube and a piece of 1-1/2" square tube for the stack. Second photo is showing all of the holes drilled. I have changed the location of the holes on the stack to just one side and I now plan to weld the stack with the holes facing on the same side as the RTD outlet.

Thomas