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Post by Jim on Apr 5, 2015 8:27:23 GMT
Ed forgot to mention the unforgettable Stag smell....  Jim |
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Post by ejparrott on Apr 5, 2015 17:42:23 GMT
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Post by runner42 on Apr 10, 2015 22:49:01 GMT
My first attempt at pressure testing the boiler is as shown in the photograph, the three jet streams emanating from the regulator bush. Stag was used to seal it. After tightening the eight screws the leak improved to a drip. However, that was at a relatively low pressure. I think that the small bush size and the need to increase the number of screws from 4 to 8 was counter-productive. I used 6BA screws and drilled right through the backhead because the depth of the bush was small to accommodate enough thread. Maybe a bad move.
I need to rethink the regulator bush design to overcome this problem. Any suggestions welcome.
Brian.
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jma1009
Elder Statesman
Posts: 5,917
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Post by jma1009 on Apr 10, 2015 23:36:15 GMT
hi brian,
you dont need to have a re-think, just make up proper fitted stainless bolts without a threaded section through the boss of the regulator backhead fitting. 6BA commercial screws are usually quite a bit undersize. getting these bits ok is annoying but once the 'art' is mastered you will be ok.
take off the regulator glnad boss and check carefully for raised bits on the tapped holes on the bush and remove and check the bush and use micrometers blue with the boss. make up the stainless bolts to be a close fit in the clearance holes. you can NEVER get as good a tight seal with cheese head screws and a screw driver when compared to fitted bolts using a box spanner with a tommy bar!
take careful note of sealant times. most moderm sealants require quite a long time before tightening up. 24 hours being usual.
the safety valves ought to be replaced with blanking plugs.
dont get disheartened please by a small leak on 'fittings'!
(i would have to say that turning up fitted bolts out of stainless hex is one of my least favourite jobs! if you turn a slight recess on the outboard face of the hex head they then look like studded nuts as per fullsize. and of course fullsize locos never had cheese head screws!)
cheers,
julian
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Post by runner42 on Apr 11, 2015 4:01:36 GMT
hi brian, take careful note of sealant times. most moderm sealants require quite a long time before tightening up. 24 hours being usual. cheers, julian Hi Julian,
your point about sealant requiring 24 hours to seal is spot on. Stag is thinned with methylated spirit and when applied is quite runny so applying pressure soon after was not the best thing to do. Today I tried the pressure test and the result were OK on the regulator bush, Stag going off overnight changed matters considerably. It however put stress on other areas and I have two small leaks around the foundation ring and three stays on the outer wrapper, so we are not there yet.
The plastic tube connection to the water pump is a pressed fit and blows off when reaching about 50 PSI, so I will have to get some small jubilee clips to hold the tube in place.
Brian
PS Yes I am going to produce a couple of plugs to replace the safety valves, because in the event I can reach twice working pressure the safety valves aren't going to allow me to achieve it.
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Post by ejparrott on Apr 11, 2015 7:26:35 GMT
One of my pet hates is people unscrewing safety valve all the time. Mine never are. I fill the boiler through the blowdown or the pump clack, and the valves are clamped in position, undisturbed, for the hydraulic. Eventually threads get worn, and boilers get scrapped. Very bad practice in my book.
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Post by Cro on Apr 11, 2015 8:40:21 GMT
Not overly sure what "stag" is as a sealer but for any mating faces like that I used loctite flange sealer and it works a treat every time, cleans off easily enough after if you have to disrupt the faces.
Good luck with it, almost there.
Adam
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Post by Shawki Shlemon on Apr 12, 2015 9:30:15 GMT
The size and number of screws required for any pcd is in the code , but that is behind you now , its done , don't worry about little leak from fittings , that is not serious , depending on the boiler inspector attitude any leak from longitudinal is more important than plugs for bushes . It seems you have done a good job and I can't see why it wouldn't pass the test .
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jma1009
Elder Statesman
Posts: 5,917
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Post by jma1009 on Apr 12, 2015 20:44:54 GMT
hi brian,
next step is i think to present the boiler to your club inspector and decide a course of action re the foundation ring and outer stay leaks. he can pump up the boiler and advise you what may be required. without seeing at first hand or knowing exactly what the leaks are it's best not to speculate and rely instead on your club boiler inspector and his advice.
cheers,
julian
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Post by runner42 on Apr 12, 2015 23:36:34 GMT
I have used a caulking medium to seal the leaks (more like weeps) in the foundation ring and stays, I used www.bunnings.com.au/cigweld-15g-acid-core-soft-silver-solder_p5914026. I am told that this is miscible (mixes with silver solder) and being lead, zinc and cadmium free an ideal soft solder that can enable silver soldering to be undertaken elsewhere on the boiler without destroying the copper.
I hope this is others understanding also.
Brian |
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Post by runner42 on Apr 13, 2015 7:54:33 GMT
The size and number of screws required for any pcd is in the code The code specifies a minimum PCD of 25mm using 6 M3 screws, this is another example that the code is more directed to 5" gauge and above, than the 3 1/2" gauge or smaller. LBSC specified for the regulator bush having an OD of 13/16" with 4 8BA screws at an unspecified PCD. I used 6BA screws being the nearest to M3 size and 8 in number specified by the BI. The increase in screw size was not optimum for the bush OD because of the smaller bush size.
There are other examples where the code specifies minimum requirements that makes smaller gauge boiler construction somewhat tenuous and not in accordance with the code. However if the basis of the requirements of the code are understood then by extension these can be demonstrated to meet the spirit if not the letter of the code requirements.
Brian
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Post by Shawki Shlemon on Apr 14, 2015 10:54:26 GMT
Brian , I agree that the objective of the code is safety and sometimes the code can't be met to the letter and that is why the boiler inspectors have some discretionary powers and as I said it is done and not an issue .
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Post by runner42 on Apr 18, 2015 6:56:44 GMT
Being unhappy with the regulator bush I decided to modify it to increase the OD from 13/16" to 15/16", increase the flange depth by 3/32" and reduce the number of fixing screws from 8 to 6. I did this by plugging all the existing screw holes with gunmetal 6BA thread forms and soldering them in, soldering an 15/16" OD x 3/8" ID x 3/32" gunmetal annulus to the existing bush with six 6BA screws at a 21/32" PCD. This design change gives me more clearance from the screw holes to the edge of the bush for better gasket forming. I use Loctite 587 Blue Maxx gasket forming RTV silicone and the reduced screw number provides the ability to use nuts or hexagonal screws for increase tightness. 8 6BA screws on a 13/16" dia bush did not give good gasket forming capability. Now to see if I can obtain stainless steel 6 BA hex screws or nuts.
The photograph is poor quality my camera having a macro capability but not on normal picture taking.
Brian |
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Post by GWR 101 on Apr 18, 2015 12:20:04 GMT
Brian glad to see that you are happier with the progress you are making, as I stated recently I cannot believe how much trouble  the regulator caused me when is basically just a tap. Not much use to you but we have reasonable suppliers of stainless BA bolts in the UK, unless you are not in a hurry and we could post some, let me know if you can't source them nearer to home. Regards Paul |
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Post by runner42 on Apr 18, 2015 22:39:29 GMT
Hi Paul,
thanks very much for the offer, however I have found a supplier that can provide 6 BA stainless steel hexagon, from which I can produce my own screws or nuts. Producing your own thread forms gives you some leeway in how tight the thread is by adjusting the die closure device.
Brian |
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Post by GWR 101 on Apr 19, 2015 9:36:48 GMT
Brian very true, but I am sure you will take more care than I did when I recently "snapped" a 5BA die trying to open it to its maximum (hangs head in shame) . Can only assume that the die stocks were perhaps a bit oversize !!!. as there was no one else to blame. Regards Paul |
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Post by runner42 on Jun 4, 2015 0:01:44 GMT
An update,
I hoped that I could after all this time I could claim a complete success in sealing the boiler, unfortunately it is still the main focus of my waking hours in trying to get it correct. If you had viewed my threads on pin hole leaks and thread repair you will understand that to be able to detect pin holes leaks that the threaded parts need to be sealed. I had the assistance of a SASMEE colleague with oxy-acetylene to correct the pin hole leaks, but with the problem of leaks in the threaded parts the pressure could not be raised to 2 X WP, so there where latent pin holes that were not detected at a lower pressure. So after correcting the threaded parts I was able to raise the pressure to 2 X WP and low and behold further leaks.
The link to the video shows the boiler and 2 stays on the outside wrapper weeping and not so obvious drips at the foundation ring coming from inside the firebox and/or foundation ring. I have not attempted to clean the boiler after the rework, I shall do that when I am certain that it will pass the pressure test of 2 x WP for 20 minutes,
the link www.youtube.com/watch?v=ea72D_de15M
Brian. |
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Post by runner42 on Jun 4, 2015 7:45:05 GMT
This is my final update, I can't claim a roaring success and it still has to pass the BI's pressure test. On advice from a SASMEE colleague I add something to the water and left it overnight. The testing today showed that it worked. I understand that the pressure test is to test the shell and that the code doesn't require that the 2 X WP is maintained throughout the test period without re-pumping, apparently re-pumping is allowed. Shell integrity is the requirement not a leak free boiler. The present status is that the pressure dropped from 200 psi to 150 psi in an hour. 160 psi is the 2 x WP.
Brian
PS Let me add that should anyone contest my words not a leak free boiler, during the test no visible signs of water leaking was apparent. My assumption is that the pressure drop was back through the pump, since I borrowed the pressure test rig from a SASMEE colleague and wasn't aware that the closing valve is like a tap and has to be screwed right up. I thought it was a gate valve that had to be turned 90 degrees to close it. |
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Post by ejparrott on Jun 4, 2015 8:44:18 GMT
Sounds to me like the pump was leaking back. Looks like you've cracked it now  |
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Post by Shawki Shlemon on Jun 4, 2015 9:24:15 GMT
Brian , well done and you are absolutely correct , the objective is a sound and safe boiler construction and that is why the code allows soft solder to stop NON structural leaks . The tiny weeping leaks from stays or screwed fittings like longitudinal stays are more of nuance than a risk . I personally rather pass a boiler with a NON structural tiny weeping leak from a stay than sealing it with soft solder .
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the regulator caused me when is basically just a tap.