A small boiler

[Circlip]

Yep, I thought you'd designed on the fly, and in this application, low duty cycle it's not too important, but if you apply "O" rings for things like piston seals or pressure vessel seals it essential to size the grooves correctly.
Regards Ian.

 

[firebird]

Hi

This is the setup I am going to use to hydraulic test the boiler. I made a stand for the boiler out of MDF. It will only be used once so I'm not to bothered about any water damage. The boiler is held securely to the stand with a couple of cable ties. I have rigged up a couple of dial indicators, one on top of the barrel and one on the end plate, which will show me how much expansion/movement there is. It remains to seal the plugs, make a pipe to go from the pump to the boiler and mount the guage. I'll have to wait till the weekend to find sufficient time to carry out the test when hopefully all will be well. I'll record the results and let you guys know how I got on.

Cheers

Rich

 

[Julian]

Hi Guys,

I've seen this pump in person and its impressive. Also it does what it says on the tin.

To Circlip....regarding the o rings. What do you call correctly sized? What tolerences do you suggest? What would be correct dimensions? A 1/16 wide ring surely needs a 1/16 clearance grove. I understand that very little needs to protrude from the groove to give a good seal. Please aswell as stating "..it's essential to size them correctly" give us some hard advice and give numbers. I am sure there are many who would be interested.

Julian

PS not having a go but interested enough to learn more.

 

[Bernd]

Here you go Julian. All you need to know about "O" ring sizing.

http://www.marcorubber.com/sizingchart.htm

Hope this helps.

Regards,
Bernd

Woops, wrong chart. Try this one. http://www.marcorubber.com/gd-directory.htm
Scroll down to "Industrial Groove Design Charts".

 

[Julian]

Many thanks for reference.
Have printed it out as I am soon going to need to do several

Julian

 

[Bogstandard]

Rich,

Very impressive measuring setup.

I was thinking just wacking a vernier about the boiler when there was pressure in it. Just to get a 'feel' to what the boiler is doing. Yours will do it a lot more accurately.

I must say, that boiler is really now looking the part.

If all goes well that should give you many years of good service.

John

 

[Circlip]

Thanks Bernd, you beat me to it and you've obviously had to use the information before. OK Julian, it may seem like criticism, but any advise is given in the name of safety.(See another post raised by Rake {Rick} on this) You should have noticed that I said in my reply that in THIS instance, low duty cycle, it wasn't too important, but I qualified the exceptions. The problem is, that on the side of the pond that this site resides, boiler building is the exception rather than the rule, for operating small engines, compressed air being the norm. Not many on the forum have built their own compressors, so the integrity of design is catered for by the manufacturers, and the designers have to comply with the rules and regs. so Joe public doesn't damage him/herself, litigation and all that. The information for the correct design for "O" ring grooves for whatever application is "out there", one only has to look OR ask and as inconsequential as it may seem, It's to be hoped that whoever designed the brake calipers on your car made good use of the tables for the piston seals to give correct diameter, depth, clearance AND profile.
Sandy went to a great deal of time and trouble to prove to Rich that the bit of copper tube he had was ok up to a certain pressure, had Rich had a look in one of the readily available ( at OUR side of the pond ) books on model boilermaking,he could have proved it for himself, ( K.N. Harris Model boilers and boilermaking) Another STANDARD work that WE should have on hand is Model engineers handbook by Tubal Cain, and you'll find "O"ring grooves dimensioned in THAT one. Unfortunately, some individual effort is required on own designs to make sure that if copyed no one endangers themselves due to our recalcitrance.
Regards Ian

PS. not having a go but our hobby CAN be dangerous!

 

[Julian]

Ian,
Thanks for your comments but my point was merely to say that it would be more helpful so backup comments with some further info. Not just in this case but in many other replies in many other threads people respond with a short sometimes terse reply that with slightly more info would be less terse and more helpful. A hyperlink to a page with further info or just a location is far more helpful and saves a long hard search when the writer already has the search done.
I appreciate what you are trying to say about safety but you are preaching to a safety expert and someone who deals with far more danger than most everyday at work (working amongst 70+mph traffic on the motorway). I agree we have to do it right so anyone copying gets it right and as the forum is for everyone to share info I asked the question about o rings.

Thanks

Julian.

 

[firebird]

Hi
I'm starting to look into the making of a safety valve for the boiler. I've got a couple of design Ideas in mind. One question, can I use 'O' rings instead of balls in the safety valve? Do 'O' rings stand up to steam OK?

Cheers

Rich

 

[Bogstandard]

Viton or silicone will withstand the sort of temp and pressure you will be using. Viton is a bit more hard wearing, but silicone seals better because it is softer.

I invariably used phos bronze balls in mine. They are easy to obtain if you want to go down that route.

Amost anything you want relating to steam can be obtained from Blackgates.

http://www.blackgates.co.uk/body_index.html

They don't do web ordering, but the young lady on the other end of the phone is very knowledgeable and helpful.

John

 

[firebird]

Thanks John

I have a selection of 'O' rings so I will have a play with what I have in stock. I also have some bronze wire in various guages to make the spring from.

Cheers

Rich

 

[firebird]

Hi

Well I had most of the afternoon in the workshop today so I got the hydraulic test done on the boiler. I made up another pipe to connect the pump to the boiler. I then sealed all the bungs with ptfe tape and filled the boiler with the filtered rain water through the hole were the pipe from the pump goes. after connecting the pipe the pump was operated until water came out of the top of the dome. The guage pipe was then fitted to the dome and the pump operated again to fill the pipe then finally the guage was fitted.

The two dial indicators were set to zero, the time noted, and the pump operated to bring the pressure up to 10psi. No leaks. The dial indicator readings were recorded. Approximately every 3 to 4 minutes the pressure was increased by 10psi, the readings recorded and the boiler checked for leaks. Finally, after about 20 minutes, with the pressure at 60 psi (double the eventual working pressure) I left the boiler for a further 20 minutes. After this time, I'm pleased to say, the boiler held pressure and had no leaks. I released the pressure by undoing the pipe nut on the pump. Very little water comes out and the guage drops back to zero. I carried out the same test twice more and recorded the results. The dial indicators registered small movements on the top of the boiler and the end plate on the first test but very little by the time the third test was complete. Here are the recorded results.

Heres a video, the sounds a bit iffy in places you will ned to turn the volume up.



All in all quite a successful afternoon. Its been an interesting ride. There has been highs and lows along the way, a few heartaches but mostly joy. I think I can safely say that I now have a boiler. I would like to thank all of you for the help and support you have given me these past months, I couldn't have done it without you. Don't go away though, theres plenty to do yet.

Cheers

Rich

 

[Bogstandard]

Rich,

A perfect test, well done.

You have now satisfied not only the authorities (if you were willing to put your name on a test certicate), but you have put your own mind at rest, in the knowledge you now have a perfectly safe boiler.

Plus you now have all the gear to do it any time you want.

There is no need to check for leaks, if you had any, the pressure would have dropped instantly. You most probably saw how little water comes out when you release pressure.

Now onwards and upwards.

John

 

[CrewCab]

Its been an interesting ride.

Sure has .......... and a very enjoyable one, thanks for all your efforts in keeping us updated Rich.

Congratulations on the successful test ............ and the whole project 8) ............... .......... So ........... what's next

CC

 

[firebird]

Hi

Next..........Ive already started on a safety valve then back to the meths burner then build something for the boiler to sit on then a feed pump and injector and then........................

cheers

Rich

 

[firebird]

Hi

I've just finished making and testing a safety valve. Heres a quick video. Its a bit jumpy. I'm afraid operating a camera, pumping and talking all at once is too much for me. I'll do some drawings and post them along with some photos later.



Cheers

Rich

 

[Bogstandard]

Rich,

As Selwyn Froggit used to say, 'Magic' or 'Nice one Cyril'

John

 

[Mcgyver]

Rich, looks great, you are inspiring me to do something with that cooper tube I've had sitting around forever. very nice.

 

[firebird]

Thanks John

Firstly a couple of drawings. These are not to engineering standard but should be understandable.
This one is actual size.

This one is enlarged, easier to see.

Turning the valve spindle between centres in the lathe. Made from stainless steel.

Moved to the mill and rotary table to mill the triangle.

The body, lock nut and spindle laid out on the drawing.

The body on the mill in the rotary table using a laser to centre it. You can see the red dot.

4 holes cross drilled.

Milling a slot in the adjuster.

Winding the spring round a 2.7mm drill in the lathe. The spring is made from 26swg bronze wire.

Cheers

Rich

 

[Bernd]

Very nice detailed description of making that saftey valve Rich. First time ever I've seen the use of an "O"-ring on a saftey valve. Usally they use a stainless steel ball. Very interesting. It'll be interesting to see how it'll work with steam pressure.

Kep up the good work.

Bernd