Boiler Design Questions

[Pipescs]

As I approach the design of the boiler for the Rust Bucket I am coming up with questions

I am working on a boiler design based around a ten inch pipe. The length will be 41 inches.

The firebox will be built of HRS 3/8 plate. (Is this OK or is there something better?)

My other question is on the use of stays verses girders to reinforce the crown sheet. (Is one better than the other?)

[Bill Shields]

pipe and hrs plate are NOT the material to build a boiler, unless the pipe is something like oil well casing which has the same specification / inspection requirements as boiler tubing (I worked for an oil company for 10 years and know this from experience)

You need to get certified material that is OK for Pressure Vessel application.

A36 is a grade that comes to mind -> here are others, but my head is in European / DIN grades and for the life of me cannot remember the ANSI equivalents at this time.

Marty K can toss out the alphabet soup of grades quicker than I can breathe. Whatever says, take it to the bank and BE SAFE.

[Marty_Knox]

I prefer to use rod stays. It is easier to calculate the stresses, they don't put a bending stress on the side stays, and they allow better circulation.

[Marty_Knox]

Seamless pipe, SA106B, would be my first choice for the shell. Flat plates should be Pressure Vessel Quality, SA516-Gr70 is the most common. Couplings and half couplings should be 3000# forged steel, ASTM A105. Stays and mudrings can be made from SA36.

[Marty_Knox]

As I approach the design of the boiler for the Rust Bucket I am coming up with questions

I am working on a boiler design based around a ten inch pipe. The length will be 41 inches.

The firebox will be built of HRS 3/8 plate. (Is this OK or is there something better?)

My other question is on the use of stays verses girders to reinforce the crown sheet. (Is one better than the other?)

10" pipe is 10 3/4" OD. In a boiler this size I usually use 5/16" plate.

[srrl5]

As I approach the design of the boiler for the Rust Bucket I am coming up with questions

I am working on a boiler design based around a ten inch pipe. The length will be 41 inches.

The firebox will be built of HRS 3/8 plate. (Is this OK or is there something better?)

My other question is on the use of stays verses girders to reinforce the crown sheet. (Is one better than the other?)

10" pipe is 10 3/4" OD. In a boiler this size I usually use 5/16" plate.

Do you use HRS or firebox grade 285C? I used HRS many years ago and had to replace it with 285C within a couple years.

[redneckalbertan]

My other question is on the use of stays verses girders to reinforce the crown sheet. (Is one better than the other?)

If a person uses girders, does that increase the ability of the crown sheet to transfer heat into the boiler, like the fins on a radiator do?

[Marty_Knox]

Do you use HRS or firebox grade 285C? I used HRS many years ago and had to replace it with 285C within a couple years.

I use only PVQ plate. Sa285 GrC is getting harder to find these days. SA516 Gr70 is much easier to get.
Boiler plate used be sold as firebox quality or flange quality. Those terms fell into disuse in the early 70's, about the time I started building boilers. The current term used is PVQ, for Pressure Vessel Quality.

[boomerralph]

As a former ASME code shop manager, I completely agree with Marty. One other comment, when you order material, request certs. even though it may not be a code boiler, certs. will assure that you are getting quality material.

[Pipescs]

Here are some photos of the pipe I am looking at using for the outer shell.

It is labeled ASTM A53 being seamless, (after this is some marking I do not understand and then) Outside Diameter is 10.3/4, Weight is 40.48 pounds per foot (assumption).

I found this on the internet for ASTM A53

ASTM A53 is a carbon steel alloy, used for structural steel pipe. The alloy specifications are set by ASTM International, in specification ASTM A53/A53M.[1] A53 pipe is suitable for structural or pressure applications.

A53 pipe comes in three types and two grades, A53 Type F, which is longitudinally furnace butt welded or continuous welded (Grade A only), A53 Type E, which is longitudinally electric resistance welded (Grades A and B), and A53 Type S, which is seamless pipe, produced by hot working, and possibly cold finishing, the steel (Grades A and B). ASTM A53, Type S is now currently an outdated specification and has been replaced by ASTM A106 specification for seamless carbon steel pipe.

So the question is: Does ASTM 53 meet the requirement for ASTM A106?

[Bill Shields]

nothing wrong with what you have...just because a specification is old does not mean the material is unsuitable for our applications.

HOWEVER if you get into a situation where a national board inspection is required, that may be a different kettle of fish.

In some states, if the material specification is not met AT THE TIME OF CONSTRUCTION, then approval becomes awkward. I have no idea what is required in Alabama. Not having certification papers is also a similar problem, if required.

[Fred_V]

I have a PDF file of the Alabama code boiler exemptions. I you are interested send me a PM with e-mail and I'll send it along to you.