Info on Hydrotesting?

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Anne from Little Britan
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Info on Hydrotesting?

Post by csonics » Wed Nov 18, 2009 4:13 pm

Posted on behalf of DetroiTug:

DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Tue Jul 21, 2009 8:46 pm Post subject: Info on Hydrotesting?
Wanting to hydrotest my boiler and looking for some info.

The boiler is 24" in diameter, waterleg type VFT. The tubes are 1-1/2" and I'm assuming they are 1/8 wall. The shell is seamless and 3/8" thick and the tubesheets I was told are 1/2" thick.

I first plan to get a video camera and go inside the bosses and have a look around. It's a snake camera USB type and I can watch it on a laptop. I'll be looking for corrosion on the tubes, see if the diameters look to change on them anywhere. This boiler doesn't have an inspection hole. The outer appearance of the boiler looks really good, it isn't very old. 8 or 9 years I was told and it was only fired a few times. When I look in the bosses, I can see some rust on the tubes, it appears to be just surface rust, no big scales or anything like that. The tubes are welded in.

What should I be looking for?
What would be a safe working pressure? It had a safety valve set at 125.
How many PSI should I take the hydrotest to?
How long should I leave it at that pressure?
Can a boiler without an inspection hole be certified by the state?

From what I understand my state does not require it, but I may get it done anyway. (In the event anything should happen, my relatives will have someone else to blame besides me

If there is anything I should be asking and haven't, fire away. When it comes to this boiler, I'm all ears.

Here are some pics of it, I've cleaned the surface rust and applied a high heat paint to it.

http://www.rogersmachine.net/steamboat2.html

Thanks, Ron
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farmerden
Warming the Engine


Joined: 19 Apr 2008
Posts: 70
Location: Shawnigan Lake,B.C.
Posted: Tue Jul 21, 2009 10:47 pm Post subject:
I take my boiler to 200psi every spring . Make sure you plug the safteys and shut off sight glass and all other valves as you are only concerned with the boiler. Fill the boiler right full of water -no air- and pump the pressure up with your hand pump-it won't take many pumps as water willnot compress. Then check for leaks. The northwest steam society has a dandy hand book for firing your boiler and checking it and putting it to bed in the winter. Buy it -copy and laminate a check list to have on the boat. Make it a habit to run the check list whenever you steam up and you will never have problems [I hope!!] Den
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87gn@tahoe
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Joined: 23 Feb 2009
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Location: South Lake Tahoe, CA
Posted: Tue Jul 21, 2009 10:54 pm Post subject:
also the big locomotive guys here in the US hydro their boilers with he water at about 95-100 degrees F.

Don't ask me why, but the FRA dictates it.
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farmerden
Warming the Engine


Joined: 19 Apr 2008
Posts: 70
Location: Shawnigan Lake,B.C.
Posted: Tue Jul 21, 2009 10:54 pm Post subject:
Oh yeh Ron Just because the safety is set at 125 doesn't mean it will blow off at 125! check it .lift the lever to make sure its free and make sure it reseats ok Den
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farmerden
Warming the Engine


Joined: 19 Apr 2008
Posts: 70
Location: Shawnigan Lake,B.C.
Posted: Tue Jul 21, 2009 11:02 pm Post subject:
Probably they want the boiler warm so the metal is somewhat flexable over a stone cold boiler. Just a guess tho Den
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Thu Jul 23, 2009 8:08 am Post subject:
Warming the boiler would make sense. Getting the material as close to operating temp as possible to simulate the operating conditions. A person could fill the boiler and fire it a little with all valves open just to warm it, then douse the fire and continue filling it, run the test as normal. I'm going to take it to 250. That will be double the operating pressure. And will run two safety valves on it, instead of just one like it had. Take the plunge and get two new ones. Will keep in mind the set pressure is not to be relied upon.

Read something by Bill Durham in the new Steamboats and Steam launches preface, that improperly cared for steel boilers could be rendered unserviceable in as little as five years, that made me go hmm. Maybe he means someone using saltwater, I just can't see steel exposed to an occasional wetting by fresh water, rotting out that quickly. He also wrote that a tube failure (leak) usually only resulted in a doused fire, and that a water tube failure tended to be more violent, throwing sparks etc around the cockpit. Not sure if he was basing that on actual experience or what.

Thanks, Ron
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Maltelec
Site Admin


Joined: 23 Sep 2007
Posts: 156
Location: Cumbria, UK
Posted: Thu Jul 23, 2009 11:16 am Post subject:
Steamboat Jack is the man for boiler testing info.

My understanding is that it should be done cold (thus not to burn you if it should give) and the sight glass should be left open. Nothing worse than the sight glass giving way and dumping 1/2 the contense of the boiler straight towards you.

The standard test over in the UK is twice the working pressure (working pressure being what the safety valve is set to).

The boiler should hold its pressure for a reasonable time (5 minutes) without leaking water out of anywhere. Of course this does mean your check valves have to be spot on.

Most important, make sure you get as much air out as reasonably possible.
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Thu Jul 23, 2009 12:22 pm Post subject:
Wow, lot's of good info, thanks guys.

Regarding the sight glass, I was thinking I would just crack these valves enough to register the water level during normal operation. And never rely on it fully, rather using that in conjunction with the trycocks. In the event the glass were to fail, the discharge would be minimal with valves barely open. Am I incorrect in that assumption? Also may give a more stable reading?

I've also read to close it during a hydro test. Just different methods and philosophy I presume.

Thanks, Ron
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mcandrew1894
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Joined: 11 Oct 2007
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Posted: Thu Jul 23, 2009 7:01 pm Post subject:
--------------------------------------------------------------------------------

also the big locomotive guys here in the US hydro their boilers with he water at about 95-100 degrees F.

Don't ask me why, but the FRA dictates it.
....


Just a educated guess, cold water can have a good deal of air in solution. Now water is not compressable, but air is. If the boiler your hydro'ing happens to have a couple thousand gallons of water in it. like a locomotive...there's going to be a significant amount of air and that can be unsafe during a hydro. Raising the temperature of the water is the best way to get the air out of solution, we do it all the time in our hotwells. If you have 2 gallons of water....it's probably less of a problem I would think......common sense should be your guide, but I see no real problem using warm to hot water to start your hydro.

When I first hydro'd my boiler, at 320psig ( 2X MAWP), I did it outside on the tailgate of my pickup. I had just got everything ready and filled the boiler with the garden hose, when the weather started to turn bad and rain was threatening. I pumped her up to 320 and it had a few minor fitting leaks. Fixed these and ran it up again to 320. I could not find a leak but I was loosing about 2 psi per minute.....puzzled after about 10 minutes I pumped it up again to 320 as the weather was getting colder and the rain closer. Again I got the same results....This went on for 45 minutes and finaly it began to rain.

OK,says I , no problem! I can man handle this beasty onto the bench in the shop, close the door run the pressure back up and go eat lunch. By the time I get back the leak will be apparent on the bench and I won't be hungry...says I.

An hour goes by and I go back into the shop.....to my suprise the boiler pressure is over 400 and there isn't a drop of water anywhere!



OK a thorough check I found no harm done ( she's way over built) but what happened?

When you heat water it grows in volume ( volumetric expansion) and vice versa, if you cool it, it contracts in volume....not a lot, but a enough to be noticeable during a hydro.
When I was outside and the weather was getting worse, the ambient temperature was dropping.......at about 2 psig /minute in my case...if I can use those pressure rate units as a measure of temperature change
When I went in and closed the shop door, the heat went on. The 10F rise in temperature was enough to increase the volume of water slightly and ran the pressure up. My boiler was acting like ...well a Boiler!

Keep your wits about you if you hydro!

I think a very thorough visual inspection internally and externally is a great first step......but be prepared to say NO. If it looks bad, it's probably not good and good is what you want. You need to act on that and have it checked or repaired. Don't rationalize away anything. If you don't know FIND OUT! Remember ...it is a wise man who knows when they don't know........you'll find that right after the 11th commandment of "Thy shall not kid thyself".......... you need to be very objective. I would recommend getting a second opinion from some knowledgable individual in your area.....to be sure

Good luck and be careful,

Dave
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Thu Jul 23, 2009 7:39 pm Post subject:
Great advice and no, I'm not going to take any chances. If something looks suspect, it will be professionally repaired and if it can't be, I'll discard the whole thing and start over, with another boiler. I wish I had just bought a new one. If one weighs the costs against the consequences, they are rather cheap.

My guess if anything is bad, it would be the tubes. I can cut them out with a big chamfer tool, and get new ones welded in if need be.

That makes sense about the cold water retaining air bubbles.

Thanks, Ron
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Maltelec
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Joined: 23 Sep 2007
Posts: 156
Location: Cumbria, UK
Posted: Fri Jul 24, 2009 12:34 am Post subject:
If you are worried about the sight glass breaking, use one with two ball bearings in, which will snap shut should the glass suddenly fail to prevent the steam and water from escaping all over you.

Personally I don't think its a good idea to run with a sight glass's valves only just cracked open. You'll end up with the water doing funny things and quite possibly telling you there is water in the boiler when its empty - which is the worst thing you can do.
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Fri Jul 24, 2009 7:42 am Post subject:
Yeah, like an excess flow check used for liquid propane. I had thought about that too. Seems they would be good for any pipe that comes out of the boiler, if a pipe gets broken off clean they automatically shut it off. Has anyone ever used such a valve with steam?

Thanks, Ron
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farmerden
Warming the Engine


Joined: 19 Apr 2008
Posts: 70
Location: Shawnigan Lake,B.C.
Posted: Fri Jul 24, 2009 2:30 pm Post subject:
I think it would only work in an application like a sight glass-where there is equal pressure on both sides. In most other applications the flow of steam is one way and that horrid little ball bearing would always be stopping the steam flow!! Den
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Fri Jul 24, 2009 5:52 pm Post subject:
They have a disc that is spring loaded. They will allow a certain flow rate, above that, they snap shut. In the event a pipe break etc. All propane motor fuel cylinders have them. If the valve is opened too quickly it will "check", closing it again and opening it more slowly will reset it.

Ron
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mcandrew1894
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Joined: 11 Oct 2007
Posts: 149

Posted: Fri Jul 24, 2009 6:56 pm Post subject:
The ball check gauge glass is code here in the US... Meaning to be to code you must use one. 1/2NPT MINIMUM is code. When/if you buy one....get a GOOD one from a reputable distributor..

Dave


PS I don't use one as my boiler is so small, it just wouldn't fit. Instead I use a 1 1/2" scale locomotive gauge glass.......with no checks.

steamboatjack
Urchin


Joined: 01 Oct 2007
Posts: 39

Posted: Mon Jul 27, 2009 3:11 pm Post subject:
I have been watching the above item without comment but feel that some points do need clarification due to the safety issues.
Boiler examination must be carried out by a competent person; it’s not something you can “just have a go at”. In other words if you don’t know you should not be doing it. This does not mean that you cannot assess your own equipment, but an official test should follow. The hydraulic test for an existing boiler (i.e. not the builder’s original test) should be 1.5 times the safe working pressure which should have been marked on the boiler when it was made. It is dangerous to just pluck a number from out of the air, should the boiler not have the S.W.P. stamped on it, a design assessment should be carried out to ascertain the safe working pressure. A hydraulic test is to test the integrity of the boiler steelwork and not particularly the fittings, the safety valve should either be removed and the hole blanked or a “gag” fitted in place of the spring, the spring should not be compressed down to 1.5 times its normal setting.
The gauge glass fitting can be removed also and blanked as this will have a sufficient test in part B of an examination, a steaming test and safety valve test.
Should the gauge glass be in place for the hydraulic test this should not present a problem as any breakage would result is an immediate reduction to zero which is why all air should be expelled from the water space prior to pressing up.
During service: The gauge glass cocks MUST be fully open and the glass blown through in standard navy practice at each operation. As mentioned by Mcandrew a ball check is a normal fitting to prevent a large quantity of water/steam escaping if the glass breaks, during normal changes in level this ball (sometimes only in the lower cock) will lay dormant in its fitting and not interfere with the level.
Regards Jack
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DetroiTug
Warming the Engine


Joined: 19 Jul 2009
Posts: 73
Location: Outside Detroit
Posted: Mon Jul 27, 2009 9:34 pm Post subject:
Jack,

Thanks for the advice and suggestions. And Yes, you're right about the "competent person". I think I'll do that. Who would I call, just an HVAC outfit to get a boiler inspection? I don't know of any actual boilermakers here in the Detroit area. I'd like to see it certified and stamped etc. It has a tag on it, but there is nothing on it? Maybe there was something written on it at one time.

Where would one find a ballcheck fitting for the gage glass?

-Ron
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