How Much PSI

[Schizems]

Im in the process of building a boiler almost exactly like this one.
http://www.youtube.com/comment_servlet?all_comments=1&v=WQ_mBwyTaiM

All my copper tube for steam lines is the same size, Couple Different Brass connections

My Fire Tube will be a 1/2 copper tube going straight into the boiler to a 1/2x1/2x3/4" Copper tee, with another 1/2" copper tube running up for the Smoke stack.

All copper parts will be silver soldered, and all threads will have that white sealant tap, and soldered if its necessary.

Main body is 2"x6" Galvanized Steel Pipe from Home Depot with the Proper Threaded caps

I have a 100 PSI gauge with Siphon, My only problem is my Relief Valve opens at 75 psi it's this one
http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

Will this setup Handle 75 PSI

 

[Jasonb]

Hopefully you will be testing it to double working pressure, this will give you an idea of what it will handle.

As pat says soldering or welding galv is not a good idea, also I would not use PTFE tape as small bits can find its way into the little openings in our size valves etc. If using pipe nipples I would silver solder (silver braze) them to the pipe.

Jason

 

[Schizems]

K im confused, What do you mean by testing it to double working pressure and how would i know what that pressure would be.

K i will braze all my nipples

But how do i seal up the holes in the main body and the 2 caps?

 

[tel]

im confused, What do you mean by testing it to double working pressure and how would i know what that pressure would be.

No offense Schizems, but you really need to read up on model boilers and the making of them before you start. The 'thing' in that clip is a truly frightening device - nothing more than a pipe bomb on a stand.

Galv pipe/caps are simply not acceptable as boiler materials.

 

[Jasonb]

I suggest you read a few of the comments that go with the you tube video such as

"hydralic test to 3 times working pressure"

"I have only run it to 20psi"

"I used pipe sealant on the caps"

As tel says this is a potential bomb as well as an inefficient boiler.

Jason

 

[Schizems]

None taken, But technically from the Topic of Boiler Safety ALL boilers are just big pipe bombs.

theres not alot of info on Scaled Steam Boilers. Specially on materials and such thats why Im here asking questions.

So links or help is appreciated more then what wont work

 

[Jasonb]

You would do well to read this extensive thread on building a small boiler that is similar to the size you have been looking at. If there are any questions at the end then ask away.

http://www.homemodelenginemachinist.com/index.php?topic=2092.0

It would also help if you added an idea of where in the world you are into your profile or signature as some of the soldering terms and materials are refered to differently around the globe.

Jason

 

[Schizems]

So I need a all copper setup, Braze all my connections

I still dont understand the Psi, Only thing i can figure is 25 is max...?

Is there somewhere that sells smaller psi relief valves?

 

[tel]

Well, you need a pressure gauge as well as the relief valve, also a water gauge. Usually a relief valve is adjustable to some extent, or there are plenty of plans and info around for making them.

 

[Jasonb]

So I need a all copper setup, Braze all my connections

A copper boiler in these small sizes is far more efficient as copper is a much better conductor of heat, you can also use thinner material as you do not have to allow for wasting (rusting) as you do with steel.

Braze pipe connections only if you are using pipe nipples, if you use olives then they don't need soldering as they compress down onto the pipe. Nipples slide onto the pipe and need soldering, if you just use soft plumbers solder there is a risk of the joint failing so they need silver brazing. All the boiler joints will need silver brazing

I still dont understand the Psi, Only thing i can figure is 25 is max...?

Its quite possibly the max for that pipe fitting boiler. Its best to decide on the max working pressure you will need for your chosen engine as well as the steam volume. You can then work back from this to arrive at a suitable length and dia for your boiler and do the calculations to find what thickness material is needed and if any of the flat surfaces require stays to stop them bulging under pressure.

Yes you can get lower safety valves but I would suggest you design and build a boiler that can deliver 75psi even if you don't need that at the moment, it will do a bigger engine in the future.

Jason

 

[Schizems]

I have a Pressure Gauge that runs up to 100 psi, And i've read on the siphon for the gauge

http://www.watts.com/pages/_products_details.asp?pid=788
Would this work for a Relief, It runs from 5 PSI to 15 PSI

And the water guage is the clear tube on the back?

 

[Schizems]

So Braze all parts that just slip together, but not the threaded pieces ?

 

[Jasonb]

Yes braze the slip fittings, the threads may want a bit of dope on them thats all.

You don't really want plumbing type safety valves like the watt one. Get a model one something like this

http://www.pmresearchinc.com/store/product.php?productid=3128&cat=118&page=1

Loggin off now

J

 

[Schizems]

Awsome, Thnx for the help when i gather all the supplies left i'll post and go from there

 

[shred]

FWIW, Copper is relatively stretchy for a metal and so when overpressured tends to bulge, then spring a leak. Iron pipe tends to shatter in a much more harmful manner.

 

[steamboatmodel]

Hi Schizems,
If you look in the download section for boilers by Sandy C, and follow that design it will give you a excellent boiler.
Regards,
Gerald.

 

[Ken I]

Re the "Pipe Bomb" boiler design.

I agree with most of the above and you should heed the advice.

Those fittings in 2" are used in industrial airlines at anything up to 200psi and I have personally tested various pipes to destruction I would bet my last cent that those fitting would not fail at anything below 1000psi. (The screw fittings might leak like a sieve.)

That said its cheap, nasty and grossly inefficient. But what the hell - with a 75psi safety valve on it I'd certify it.

Ken

I'll start dodging the Flak now.

 

[tel]

There are a lot more issues than just the straight out ability to contain pressure though. I read an account somewhere of an attempt to test a glass Coke bottle to destruction - at 700 psi they ran out of available pressure, with no effect on the bottle. Now this tells us that a Coke bottle is more than capable of holding the sorts of pressure we use, but I'm damned if I'm gonna make a boiler out of one!

 

[sunworksco]

Here is a very good test sheet on model boilers.
Regards,
Giovanni

View attachment curwat.pdf

View attachment boiler-tests.pdf

View attachment ModelBoilers.pdf

 

[IronHorse]

OK.....I'm going to fess up........That is my boiler in the video. I built it a couple of years ago to run some of my engines on steam. I would not recommend this particular boiler design. It works OK, but requires a lot of heat to build up to 20Psi. I set the safety valve to blow at 25 Psi and did a Hydraulic test to 80Psi on the boiler, so I feel it is safe, but still scary. As a mater of fact, I have not fired it up since I did that video. I think I will build a PMR boiler kit in the future, they have a couple of nice kits and they are reasonably priced.

Here is the original post:
http://www.homemodelenginemachinist.com/index.php?topic=2667.0


IronHorse