Hydro Testing

This forum is dedicated to the Live Steam Hobbyist Community.

Moderators: Harold_V, cbrew

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Fri Aug 18, 2017 7:44 am

I came to the conclusion that I'm probably not going to live long enough to complete all (or any) of my projects, so I acquired a very nice 1" scale LE Atlantic. This engine hasn't been fired in 10 years, but has been run regularly on air at 110 psi and has been very well maintained. With all of the previously posted information and advice, what's my next step in properly getting this engine under steam? Thanks, John

User avatar
Bill Shields
Posts: 4787
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Re: Hydro Testing

Postby Bill Shields » Fri Aug 18, 2017 8:23 am

HYDROTEST IT at 150% of the safety valve settings

then fire it lightly and give it a run on blocks

some of those older LE engines had cast sections in the boiler that tended to be porous and while it may run on air, may also be leaking in the process.

It isn't soldered with SIL-PHOS solder is it?

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Fri Aug 18, 2017 5:25 pm

Bill, I don't know anything about the boiler's construction except that it's copper and was built by Little Engines. Can I use the gauge and the tender pump to do the hydro test? The pressure gauge reads 0 to 180 psi, the relief valve is set at 110 psi; would a test pressure of 165 psi be too close to the gauge capacity and ruin the gauge? John

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Fri Aug 18, 2017 7:20 pm

Bill, I checked out the boiler, to the extent that I could, and parts of it are castings. John

User avatar
SteveM
Posts: 6182
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Re: Hydro Testing

Postby SteveM » Fri Aug 18, 2017 7:36 pm

jscarmozza wrote:The pressure gauge reads 0 to 180 psi...


I believe that it is typical practice to use a gauge where the needle pointing up is the working pressure, so you might see a 0-180 gauge used when the working pressure was 90 (if 90 was the straight up position).

That would make sure that you could tell if you were at full pressure easily because you didn't have to READ it, you only had to see if the needle was pointing up.

Steve

User avatar
Bill Shields
Posts: 4787
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Re: Hydro Testing

Postby Bill Shields » Sat Aug 19, 2017 8:39 am

Pump away with whatever you have = water pressure is water pressure, you don't need (want) a lot of flow.

I would put 50 psi in it and look around inside the firebox for leaks - which is where those castings habitually caused problems.

If you are good at 50, then work your way up slowly to working pressure - and look again for leaks.

the idea of a straight up gauge is really spot on - do it whenever possible. When not, a red stripe on the glass is another way to go.

FWIW:

I WOULD NOT TRUST and old gauge. TYPICALLY as a gauge gets old, it tends to read LOW (think about it)..

If you can get (borrow) something new, to at least use as a quick comparison it is a good idea. Give or take 5 psi is not really a worry but an error of 30 PSI at full test pressure can be a real problem. This is why clubs have 'standard / tested' gauges.

The 20 year old gauge on my big loco runs about 3 psi LOW at running pressure, 5 psi low at 150 PSI = which is a little bit more than the width of the needle.

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Sat Aug 19, 2017 4:34 pm

It looks like I need a few more items before proceeding with the test. I'll check the engine gauge with the new test gauge to see how far it's off. Just to set the record straight, the engine gauge is 0-200 psi not 0-180 psi as I previously stated and it's sitting straight up, so I'm guessing the operating pressure is 100 psi. I'll let you know how it goes. Thanks, John

User avatar
Bill Shields
Posts: 4787
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Re: Hydro Testing

Postby Bill Shields » Sat Aug 19, 2017 5:40 pm

don't guess at an operating pressure as a function of a gauge pressure range.

unless the boiler is stamped / marked something, perhaps a quick calculation of staybolt load would be in order.

100 psi is a reasonable first guess, and something generally used, but unless you know the loads, best to actually calculate before you pump.

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Sat Aug 19, 2017 7:20 pm

How is that calculation done Bill? I think I can count the bolts inside the firebox. Looking at the fire box, there is a series of three little triangles made of punch marks on the left side behind the water glass, does this mean anything?

The previous owner said the relief valve lifted at 110 psi, that's what I was basing my statement on.

James Powell
Posts: 262
Joined: Fri Oct 28, 2011 10:42 pm

Re: Hydro Testing

Postby James Powell » Sat Aug 19, 2017 9:21 pm

Look at a set of drawings (assuming there are drawings...) for the engine design. Count the # of rows & columns of staybolts- if they match the drawing then the chances are good that the MAWP as per the drawing is the boiler MAWP. If in doubt, then find someone more experienced to do the math for you, to figure out what the MAWP would be for the boiler. Your club boiler inspector should be able to help with all of this.

Good guesses are 60, 80, 100, 125 psi. The way to calculate it is generally the largest flat unstayed area, or the stay pitch is another good tool to use. If the boiler has cast sections, then the absolute MAWP would be whatever the manufacturer designed the castings for- regardless as if the boiler has extra stays or not.

jscarmozza
Posts: 200
Joined: Mon Mar 03, 2014 5:09 pm

Re: Hydro Testing

Postby jscarmozza » Sun Aug 20, 2017 7:58 am

Jim, I don't have drawings or specs for this boiler and I don't belong to a club. The boiler was built by Little Engines and includes castings in its construction...so that being said, fabricated boiler calcs would not appear apply to this boiler. Does anyone out there know what Little Engines would put in a 1" scale Atlantic? These were pretty common engines and LE must have had a standard boiler that they supplied.

I'd still like to know how to calculate boiler components and capacity, a quick look on the Internet didn't produce much worthwhile information, any leads (like a book) would be appreciated. I remember reading an article in Live Steam Magazine a while ago, and (I may be mistaken) Australia was the only country that had standard model boiler design specs. Are they something that I should try to get hold of? John

Ps. I have no plans of trying to build a boiler, I just want to understand them.

James Powell
Posts: 262
Joined: Fri Oct 28, 2011 10:42 pm

Re: Hydro Testing

Postby James Powell » Sun Aug 20, 2017 9:21 am

The book I would use is "Model Boilers and Boilermaking", KN Harris.
http://www.fastonline.org/CD3WD_40/JF/424/19-422.pdf

If the boiler is a commercially made boiler, then the MAWP (which is Maximum Allowable Working Pressure) should be available from the manufacturer. The design pressure is probably in the older LE catalogs too...

100 PSI.

(http://ibls.org/files/Catalogs/Little_E ... atalog.pdf )

The weakest area determines a boiler's allowable working pressure- generally, this is the firebox sides, because a tube (boiler barrel) has a strength calculated by hoop stress, and even fairly thin material can take fairly large working pressures. For example, using a 6" piece of tube with .125" walls, made of pure copper, it will have a burst pressure of ~1000 PSI, and a working pressure of 1/10th that (or 100 PSI...). This uses 25 000 lb as the strength, and http://www.engineersedge.com/calculator ... t_calc.htm (which is just the hoop stress formula in a computer...) to calculate it.

So, if the barrel is 1/8th, and the plates are 1/8th, then you can calculate out stayed surfaces. The cast pieces in a Little Engines boiler are more difficult to calculate strengths for, because they are cast not formed. However, assuming they are all > 0.125 thickness, then they are unlikely to be the limiting factor of strength. The likely limiting factor is the stay pitch & size on the sides of the firebox.

Again, assuming you can get a set of the drawings, and the boiler matches the drawings, then they are usually acceptable to club boiler inspectors for operation. Because of the healthy safety factor (x10) used on model boilers, it is unlikely, (but not impossible !) for a boiler to fail. It is my understanding that the last fatal accident involving a boiler in model use was in about 1925. That is not to say to take boilers as being a joke- they are not, calculate the energy involved and understand that like always, that energy is trying to get out...but be realistic about threats. I am quite certain that more Live Steamers have been killed getting to and from their local track than by boiler explosions.

If you are asking these questions, you are probably underwater as regards safety- at least you know you are under water !. I highly recommend visiting someone with more experience. I find it kind of hard to imagine that any point in North America is more than 6 hours travel from a club- there are a lot of clubs out there. I'd recommend joining a club, with relevant experience, to benefit from said experience. They may not have a 4.75" track, but even a 7.x gauge club is likely to have experience with smaller models.

James


Return to “Live Steam”

Who is online

Users browsing this forum: Art Burkhart, binnaway, Pipescs, Yahoo [Bot] and 13 guests