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Setting Injectors properly.

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mgj22/01/2010 18:24:50
1017 forum posts
14 photos
I need some advice please.
 
How do I start and run an injector?. 
 
I have a water stop valve - OK open that and look for water coming out of the overflow. Then open the steam valve - how far?. I open it and the water stops. So is that it, or do I open the injector some more until steam starts to come out of the overflow?
 
The clacks are sound, and the injector is behind the firebox, behind insulation. It feels cool until you whack steam in there.
wheeltapper23/01/2010 11:35:21
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424 forum posts
98 photos
Hi
I'm no expert but seeing as no one else has answered I' ll try.
as far as I know you seem to be doing it right, turn water on till it come from the overflow , whack the steam valve wide open and the water should stop overflowing, and yes, that is it I think.
 
then you check the water level gauge glass to see if the level is rising.
 
unfortunately there are so many little things that can stop these gadgets working.
 
for example; steam feed pipe to small a diameter, water feed ditto.
 
as I said, I'm no expert but it seems to me if you have water going in and steam going in they have to be going somewhere  and if they aren't coming from the overflow........................
 
hope this has helped somewhat. I'm surprised no one else helped with this. there must be loads of loco drivers out there.
 
cheers
Roy
 
mgj23/01/2010 15:46:54
1017 forum posts
14 photos
Wheeltapper - thank you. I worked with that and it went fine. I think before  I was expecting a more rapid rise in the gauge glasses. - but it does go up.
wheeltapper23/01/2010 15:53:41
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424 forum posts
98 photos
Hi
I'm glad you got it working.
quite frankly I'm amazed, I know next to nothing about injectors except what I've read and I've never used one so I think it's a case of the blind leading the blind
 
at least if I ever get to use one I now know that what I know works.....................I think????????
 
cheers
Roy
mgj23/01/2010 18:17:40
1017 forum posts
14 photos
Roy - I think the idea is that you shouldn't get too much steam out of the overflow.
 
If you put too much steam in there, you should theoretically get a back pressure. I'm fairly sure that one should put enough steam in to cause suction behind the cone. Then the acceleration through the cone, plus the drop in temperature increases pressure which is what allows it to go into the boiler. but one is looking at 2 sets of conditions - one in front of the cone, and one after it.
 
 
(PV/T)^gamma = a constant. or P1V1/T1  = P2V2/T2
 

 
 
wheeltapper23/01/2010 19:00:04
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424 forum posts
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Posted by meyrick griffith-jones on 23/01/2010 18:17:40:
 
snip 
(PV/T)^gamma = a constant. or P1V1/T1  = P2V2/T2
                                                                                          snip
 
what a pity, this thread was quite understandable and then you start speaking some obscure language
 
sorry but me no speekee higher math ( or lower math for that matter)
 
the main thing is , it works
 
cheers
the thick side of Roy

 
 

 
 

 

mgj23/01/2010 20:16:53
1017 forum posts
14 photos
Sorry - but it means that everything on one side = everything on the other, provided you don't get too much in the way of losses.
 
So if you up one, the other goes down to keep it in balance. (Just so there is no free lunch) ........
 
I'll see tomorrow if full steam is as good as just keeping it ticking over, because while i know the theory, the practise can be a little more obscure.
 
Speaking as a man who can get steam out of the suction pipe of a water lifter.
Phil Ashman25/01/2010 14:02:39
33 forum posts
 
Meyrick,
 
Did you make the injector? I'm trying to decide whether to have a go, along the lines of the recent ME articles, or buy one in and save the (possibly wasted) time.
 
Phil
mgj25/01/2010 18:06:12
1017 forum posts
14 photos
Bought it in - I'm not a teeny drills sort of person. Just one of the bog standard jobs from LSM.
 
I don't think, looking at the drawings that they are all that difficult to make, just a bit fiddly, and if one can machine reamer/d-bits accurately they should work.
 
The advice I was given was to ensure that the injector is kept cool - ie not heated by the firebox, and to keep water supplies clean and cold. Doing it again, I would use a model aircraft line filter like the Crap Trap as a pickup in the tank. For what its worth.
 
Designed and built own water lifter, and that works fine!

Edited By meyrick griffith-jones on 25/01/2010 18:06:38

Phil Ashman26/01/2010 13:44:10
33 forum posts
Only one or two reamers are needed for the ones described recently, so I think I'll give it a go.  I asked the question because LBSC's injectors were thought to be a bit hit or miss. I don't know about the DE Lawrence ones described in the 70's. (or  80's).

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