We have two functional 2-1/2" Crosby safety valves on our locomotive #25. One is set at 160 psi and the other is set at 163 psi, both clearly marked on the body. When these valve were offered for sale they were sold by boiler horse power not lbs/hr relieving capacity. While that was fine back then it doesn't serve today. So my new inspector wants the capacity of the valves. I argued that they are the original and do their job of opening crisply at pressure and snapping shut after a blow down of 4 psi. That is apparently not good enough. I don't want to give up these valves.

So my question is, what is the approximate capacity in lbs/hour, and where did that information come from. It needs to be traceable.

Example of valve below from 1900 catalog.

Thank you for any resolution to this issue.

Chris De Witt
Nevada State railroad Museum

You could figure your boiler HP and compare with the specs on the safeties. Many of the old texts for boilers have a formula based on grate area, fuel, heating surface, etc for that calculation. Not that I have one in front of me right now to quote, unfortunately.

What does the "pounds per hour" mean? Does it mean pounds of (evaporated) water, or pounds of steam reduction at a given pressure?

I guess you have to reverse engineer the valve spec.

Well, this is getting interesting....

the only potentially useful thing I've found so far is in the Butterfield Jennings Luce book STEAM AND GAS ENGINEERING, Van Nostrand 1938 edition. On page 167 they explain that boilers are arbitrarily rated at one BHP per 10 square feet of heating surface. Other sources talk about how long it takes to raise 35 pounds of 100 degree water to 70 PSI steam........ figuring the HP of the locomotive and assuming the boiler was matched to it might be easier, but that's not strictly BHP. On page 145 they spec out 33,472 BTU / Hour as one BHP, and then explain that this is an obsolete consideration since in the modern world boilers are rated by number of square feet of heating surface.

So, try it - it isn't the only text I have that mentions the 10 square feet per BHP estimate. Probably some of yours do too........ and you can put them in from of him.

Someone is going to complain they don't trust Wikipedia...but here goes anyways:

https://en.wikipedia.org/wiki/Horsepower

1 boiler horsepower=34.5 pounds per hour, or 33,475 BTU an hour.

From the entry, it is apparent that the ASME maintains a definition of boiler horsepower. Seeing as how they are 'the keeper of the code' what you/someone needs to do is find where in the code they define the boiler horsepower.

While I appreciate the discussion of boiler capacity I need to somehow validate the safety's. I can take one apart, measure the orifice, determine the lift, allow for loss due to the huddling chamber turbulence, but what I really need is a source that says this valve has a relieving capacity of such and such.

So, Dave, there are no specs on the safety except for manufacturer, date patented, set pressure, and size (which I assume is orifice size). I already know the heating surface, lbs/hr generated, horsepower (another worthless number), and other associated numbers for the boiler. And I know that the valves have sufficient capacity as demonstrated in an accumulation test. I do love the accumulation test.

I know they function as needed because I have been running that locomotive for 36 years and they are the original valves or exact replacements of the OEM valves. What I need to do is satisfy a new inspector not with evidence but with paper work.

Of course I can buy new valves with seals and paper work but I really like the old valves. If it isn't broke don't muck it up.

You did not make clear that you have no idea the capacity of your valves.

Try the people who made them:

http://valves.pentair.com//brands/crosby/

If that does not pan out, try their service centers:

http://valves.pentair.com/en/about_us/locations

With any luck you can find a service center who's been in it a long time and still has their old books.

FRA or State inspector?

Sounds like a state inspector..........

Or here is at least one conversion of BPH to lbs/hr http://www.engineeringtoolbox.com/boile ... _1061.html . You may try google searches for more....PD

Sorry Chris - you indicated they were originally sold by BHP measurement, so I assumed you had that number and needed to prove they were adequate for the boiler. How to find the BHP capacity of the safety.... well, unless you can find manufacturers specs you probably can't. I have a limited amount of Consolidated pop valve information around here somewhere but nothing Crosby. I think you might have to run the accumulation test as Matt has documented if nothing on paper shows up.

Some of this stuff defies sensibility and it's getting worse. I'm supposed to put on a 20 cal suit now just to turn my desk lamp on.

My understanding, perhaps wrong, was that 'BHP' was a legal measure, akin to taxable horsepower in early European automobiles, and has little real correspondence to lb/hr steam mass flow being generated by a particular boiler.

I don't think there is a practical solution - certainly not one I'd consider either adequate or 'safe' - other than actually testing the mass flow of steam through the valve when it is popped. That could be approximated from physical constants, but there is probably no substitute for empirical testing (of the kind prescribed by the National Board).

I think there is a practical issue in testing the 160lb valve directly on your boiler, as it would involve carefully balancing boiler pressure and injection while keeping the 160lb pop open and the 163lb pop closed for a time sufficient to get a measurement. I would not gag the higher-pressure valve to simplify measuring the 160lb mass flow!

It is simpler, of course, just to try the measurement with both safeties lifting, control the boiler pressure with the injector, and do any nit-picking mass flow corrections mathematically after 'dividing the result by two'. You can decide what kind of flowmeter you put in the injector line to measure the mass flow in, and how you keep the level 'determined' -- the gauge-glass reading may not represent actual level with the pops lifted, etc.

If it were mine, I'd do the test 'on the bench' or put the valve on a boiler with a known higher pressure rating with known adequate relief capacity through its own (separate) safeties, run at the appropriate lower pressure. Option 3 from the list Mr. Austin provided might represent the best of the protocols for a practical test in this situation. The National Board synopsis of state regulations is here:

http://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select

And of course, once you do all this, you really want to document it so you don't have to do it again, when the state employee quits and is replaced by another new employee.

Try here:http://www.crosby-steam.com/Crosby_Catalogues/Cat_24x/1_to_5.htm

You may want to contact the owner of the website for a higher resolution copy of the page

Mike Tillger