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Post by standardsteam on Jul 24, 2007 10:14:53 GMT
My little engine (Tich) has very little dome hight as the regulator pick-up is directly under the safety valve. This isn't the spring balance type as is sometimes fitted to this engine but a ball and spring valve. The safety itself doesn't pick up water (although LBSC did describe an anti-priming adaption to a safety vavle, he used a top feed on his version described some years after the Tich serial), but when you open the regulator you can see hot water spitting from the valve as well as the chimney.
I would guess that I need to make some adaption that reduces the pressure drop when the regulator is open such as a series of smaller holes like a watering can rose or something. Can anyone point me towards some such modification?
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Post by baggo on Jul 24, 2007 13:29:18 GMT
I presume you have the large boiler version with the disc in tube regulator? One suggestion I can think of is to fit a disc type baffle onto the vertical steam collecting pipe where it enters the dome, either leaving a small gap around the edge for the steam to pass or drilling some small holes in the baffle. That may help reduce any water carry over. You would have to be careful not to restrict the area of the holes or slot to less than that of the safety valve seat though.
Is it possible you are running with too high a water level in the boiler? Do you get water out of the chimney all the time or just when the loco starts off?
John
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Post by albertsell on Jul 24, 2007 18:14:22 GMT
Hello standardsteam, My first thought is boiler contamination,I would as a first go fill the boiler ( with known clean water) to the top of the guage glass bring the boiler to full steam pressure remove the heat then blow down as fast as possible (do this process at least twice) and then do a test steam up and run.In my copper boiler days this was a known fault especially with new boilers.
Good steaming Albert.
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Post by lordsimon on Jul 24, 2007 19:06:16 GMT
from my exprience that is not a good move personally
if you blow down at full pressure even on a new boiler you are running a very high chance of damaging the boiler
because i have known 2 boilers in 15 years a one pro boiler snap stays through the boiler going from full high temprature to nothing in a minute or too and the worst thing would be to add any water to the boiler straight after.
if you want to clean it by blowing down you only need about 15psi not 80 but that my feelings and i would never do that personally
simon
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Post by spurley on Jul 25, 2007 6:51:11 GMT
Hi all
I think it could well be contamination either oil or maybe dissolved flux(?) and the way to clear it is by blowing down in steam. Definitely not advisable to empty the boiler with the fire still in though. A good blow down, or two, from full glass to 'just in the bottom nut' ought to solve contamination problems.
However, as John (Baggo) says, a look at where the opening to the main steam pipe and regulator are set relative to water level in the boiler might show up a fault too? With the boiler cold remove the safety valve/dome cover from the dome bush to allow you to see into the boiler and fill with the hand pump and try to see if water could carry over easily into the regulator assembly. The small boiler Tich ought to be immune to this if the Stroudley regulator is used which projects up into the dome and should be clear of the water level in normal operation.
Hope you find the problem?
Cheers
Brian
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Post by Shawki Shlemon on Jul 25, 2007 9:09:09 GMT
To me it looks as if water level is too high .The water must cover the crown by say 1/8" at the bottom of the glass and should not be as high as regulator pick up at full glass. If these are not as should be you can put marks on the glass tube to indicate min and max as above . I also fully agree with Simon on blow down conditions . Best of luck .
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Post by standardsteam on Jul 25, 2007 11:40:46 GMT
It's the large boiler version so the steam intake is lower than the spring balance valve version. I don't have easy access to a 3 1/2" gauge track at the moment and I'll need to get a steam cert at my club before I can go to one with a raised track, but I don't think this priming will preclude passing the test though. As such I'm running the engine on blocks as the only rolling road I had access to doesn't clear because of the small wheels. This generally means the engine races away and water shoots from the chimney like a shower.
I'm pretty sure it's not contamination because water spits from the safety valve too, but only when the regulator is opened indicating pick up with the pressure drop. It may be that this action is not so violent when the engine has the balancing effect of running on a track, but if I can cure it now it should be less of an issue when running.
I can see your point about running with a lower level in the gauge glass. Being the first steamings I ran with a high-ish level, but once the firehose has started it doesn't tend to stop until the glass is nearly empty. The crown is comparatively high on a Tich boiler though, the regulator itself being just above it. I was wondering whether water was getting in via the thread for the steam pipe where it joins the disc-in-tube body.
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Post by baggo on Jul 25, 2007 12:07:22 GMT
"I was wondering whether water was getting in via the thread for the steam pipe where it joins the disc-in-tube body"
That is a possibility. Might be worth checking all the joints on the regulator assembly that may be below or near the water level. The fact that water comes from the safety valve though (presumably only when it's operating) does indicate that water is being lifted into the dome. My Helen Longish has a very similar setup with a very short steam collecting pipe on the top of the regulator body and a very shallow dome and so far I've had no trouble with priming. The only difference is that I used 1/4" dia. pipe rather than 3/16" which gives a larger area for the steam to enter. Not sure if that would have any effect though.
Perhaps the combination of opening the regulator and the safety valve blowing off is not helping matters.
John
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Post by Shawki Shlemon on Jul 26, 2007 10:17:19 GMT
Is the safety valve close to water level ? I had an experience during steam test on my Stirling Single without dome ,once the safety valve lifted it emptied the boiler . Fitting baffle on safety valve and raising it slightly solved the problem completely .I also converted the valve to pop type .The valve should draw steam only and not water , once water is being sucked , it creates venturi action and draws all the water out .
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Post by standardsteam on Jul 26, 2007 11:12:10 GMT
Since it's a Tich boiler the valve is fairly close to water level, but it doesn't prime whilst raising steam, and there is no real scope to raise it. I bought a commercial fitting and it didn't fit under the dome so I went back to the one I made and had another go at the ball seat and fitted a new ball which solved leakage problems that I had.
I think I'll go with the baffle option. I think you're right though, once the lifting action starts it doesn't stop! I did think about a pop valve as my safety isn't very positive in action and in order to evacuate properly at working pressure releases steam very early as the pressure rises. I'll have to work out some dimensions, I saw an article which detailed pop valves in either ME or EIM
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Post by AndrewP on Jul 26, 2007 12:41:18 GMT
Me vol 162, 1989 p497 and 634 and subsequent has an article on safety valves and pop valves including an exhortation from Curly not to hit them with the shovel - that's me told then
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Post by greasemonkey on Jul 26, 2007 13:07:11 GMT
You want to give Gordon Smith a call, his email address is gordonssafetyvalves@gmail.com. He will supply you with a design that has a small hysterisis and will pass the steam accumulation test for a very small fee (about 25p). He can also supply the correct rate spring and stainless stell balls. You wont need to hit the valve with a shovel then.
Andy
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Post by mackintosh on Jul 26, 2007 18:31:21 GMT
I agree with Andy on this one I recently had a drawing and springs for my safety valve for the Tich from Gordon. Nice to find someone genuine and not trying to make a killing. He buys the hardware in bulk which allows him to sell at good value prices. (no connection). Some of the members of our club have fitted valves to his specs. and they perform perfectly. Bob
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Post by Deleted on Jul 26, 2007 19:31:58 GMT
Hi Have to agree with Andy and Bob about Gordon's safety valves, he did me a special design for my 4F, and they certainly seem to pass plenty of steam. As regards the priming, I had exactly the same thing when I tested the 4F in the garden proped up on blocks. I think it was just me having the water level too high, with such a small boiler the minimum and maximum levels really aren't very far apart. Is the water gauge top fitting screwed into the backhead or is it on a fitting on top of the firebox? Mine is the latter and if the water is much over half way up the glass, the boiler barrel is pretty much full up and if i open the regulator, I get a shower! When I steamed it a second time I kept a tighter control over the water level and it seemed to be ok, whether I'll be able to keep the level under that much control whilst on the move remains to be seen. Regards Trevor
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