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Injector testing

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Speedy Builder509/04/2020 15:34:08
2006 forum posts
140 photos

It may be some time before I have access to steam in sufficient quantities and pressure, but at the stage of making an LBSC injector for a 5" SPEEDY loco.

Is there a way of testing the injector without steam ??

Bob

Andrew Tinsley09/04/2020 16:16:47
1109 forum posts

Hello Bob,

In a word, no. You need steam so that it is able to condense and liberate energy which is transferred to the water. So compressed air will not work.

Best to find someone local with a boiler who would be willing to help.

Andrew.

Andrew Tinsley09/04/2020 16:16:48
1109 forum posts

Sorry, double posted!

Edited By Andrew Tinsley on 09/04/2020 16:17:47

Simon Collier10/05/2020 23:15:36
avatar
348 forum posts
56 photos

I just found this thread and urge Bob to read this:

http://modeleng.proboards.com/thread/10988/injector-design-musings

Speedy Builder511/05/2020 07:03:02
2006 forum posts
140 photos

Thanks for that Simon, quite a long read! I do wonder if it is worth making up a simple test boiler and burner, or just risk it all on testing with the finished loco.

AdrianR11/05/2020 07:50:55
475 forum posts
23 photos

A slightly off topic naive question. I just about know what an injector is.

Could you use an injector to feed a flash boiler? i.e. connect a coil of pipe between the inlet and out let of the injector, fill with water and heat the coil?

Adrian

Andrew Binning18/06/2020 20:11:00
avatar
24 forum posts
9 photos

You need a test boiler and an injector test rig. There have been a number of constructional series on small test boilers but they are an essential piece of equipment for the locomotive builder if your are making any small fittings for a steam engine.

The injector test rig comes from an article by Bill Carter in ME Volume 141, Issue 3519, page 818. I made a test rig in line with the article and it has been very useful. A colleague in the Cambridge & District Model Engineering Society complained recently he had a box of injectors and no way of knowing if they worked. We had a testing session and weeded out the one's that did ! One of the advantages of the tester is you can measure the delivery of the injector and test its ability to pick up under varying conditions.20190905_142521r.jpg As you can see ( Summer of last year before Corona Virus) , the injector under test was working and although you can't see the pressures being registered on the gauges, the interesting fact that the delivery pressure is actually higher than the test boiler pressure! If you need any further help with designs for a test boiler or making the test rig I should be pleased to help.

Speedy Builder518/06/2020 21:12:16
2006 forum posts
140 photos

Thanks for the update Andrew - I would be interested in a simple design for a test boiler. I have several of the disposable CO2 gas bottles used for MIG welding and thought they could be the basis of a boiler. Being smaller capacity, probably would not need an official test, but suffice with applying the test conditions for self certification.

Andrew Binning18/06/2020 22:19:00
avatar
24 forum posts
9 photos

I could not recommend one of the CO2 bottles even if it is only for your use.. I think there was a design published for a small boiler in ME not too long ago. Kennions do a kit of parts for a nice vertical boiler in copper very similar to mine with prices starting at £154 + VAT. It is worth spending a bit of time to put something like this together as I suggested already , it will come in handy for testing all the other fittings that Speedy will need.

Best Wishes for the build.

Paul Lousick19/06/2020 02:27:50
1405 forum posts
540 photos

"Could you use an injector to feed a flash boiler? i.e. connect a coil of pipe between the inlet and out let of the injector, fill with water and heat the coil? "

Hi Adrian,

From my little experience with flash steam boilers I think that an injector would not work for a number of reasons.

Injectors will not work if they get too hot and require a supply of cold water. Also very difficult to regulate the volume of water thru the injector as it changes with the supplied steam pressure.

Have a look on Youtube. Lots of explanations of how they work.

Paul.

Paul Lousick19/06/2020 02:40:29
1405 forum posts
540 photos

Attention The ME Administrators.

The injector test rig comes from an article by Bill Carter in ME Volume 141 would be of interest to a lot of readers who have an interest in model steam engines but the ME archives do not go back that far.

Is it possible to re publish this article.

Paul.

Jon Cameron19/06/2020 09:17:17
336 forum posts
90 photos
Posted by Paul Lousick on 19/06/2020 02:40:29:

Attention The ME Administrators.

The injector test rig comes from an article by Bill Carter in ME Volume 141 would be of interest to a lot of readers who have an interest in model steam engines but the ME archives do not go back that far.

Is it possible to re publish this article.

Paul.

+1 to that.

It looks a relatively good test rig, and i assume you can also vary the boiler pressure to see if it will pick up and deliver water at varying test pressures, so as little as 20-80psi to instance. Knowing that the injector will reliably pick up at varying pressures is certainly reasuring especially on the move.

Jon

Baz19/06/2020 09:28:58
374 forum posts

A very similar test rig is described in the excellent book by D.A.G Brown, Miniature injectors inside and out.

Clive Brown 119/06/2020 09:33:48
426 forum posts
12 photos

Bill Carter's test rig is described, in slightly modified form, in D A G Brown's book "Miniature Injectors Inside & Out"

He also describes a test-boiler.

A book worth getting by anyone considering making injectors.

Beaten to it!

Edited By Clive Brown 1 on 19/06/2020 09:34:19

Andrew Binning19/06/2020 12:11:39
avatar
24 forum posts
9 photos

I have copied the Bill Carter article. Hope this is useful .

injector_test_article_me141_818-page-003.jpg

injector_test_article_me141_818-page-004.jpg

Andrew Binning19/06/2020 12:14:53
avatar
24 forum posts
9 photos

Sorry ! I seem to have lost the first part of the article.

injector_test_article_me141_818-page-002.jpg

Howard Lewis19/06/2020 13:53:15
3259 forum posts
2 photos

D A G Brown wrote a book on Injectors, relating to the theory of their operation and their construction.

"Miniature Injectors, Inside and Out", published by TEE publishing..

Howard

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