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injectors

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Garry Coles04/11/2019 17:52:27
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56 forum posts

Hi, This might be a stupid question and I might get a stupid answer. But why does the water to the injector not drain the water from the tank when the steam supply is off, or do you need a another shut off valve in the water supply line as well as the steam supply line.

Garry

RMA04/11/2019 18:00:14
231 forum posts
4 photos

Yes, you do need a valve for the water.

Garry Coles04/11/2019 18:38:39
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56 forum posts

Thanks for that. I thought you must, but my plans only mentioned the steam supply valve.

Garry

Paul Lousick05/11/2019 00:44:54
1321 forum posts
526 photos

There are also lifting injectors which suck the water vertically and do not need a valve in the water supply. I have used them on full size engines but have not seen them used on models. Probably because of the higher steam pressures used in full size engines.

Paul.

Brian Oldford05/11/2019 10:53:22
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598 forum posts
4 photos

The water valves on many standard gauge engines are at just the right height on which you can bruise your calf or ankle.

Harry Wilkes05/11/2019 14:30:48
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829 forum posts
60 photos

Garry if you do fit a water shut off valve make sure the bore of the valve doesn't restrict the water flow

H

duncan webster05/11/2019 15:19:31
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2437 forum posts
39 photos

If it's time for silly questions, could you take the overflow from the injector back above the level of the tank so that it didn't drain the tank. I realise you wouldn't then be able to run water through the injector to cool it if it got too hot

John Alexander Stewart05/11/2019 18:52:41
759 forum posts
51 photos

A lifting injector is "the same as" a non-lifting one, with the exceptions:

- a lifting one needs to work as an "ejector" to lift the water up into the injector; (some full size ones lack this ability) - it means that the overflow needs to be quite large to reduce back-pressure;

- any injector needs to not heat the incoming water too much; in our small injectors, there's a large surface area to water volume as compared to the full-size; having water drip through it keeps it cool, so the steam from the steam cone has a better chance of condensing.

Duncan - on one coal-fired steam crane I used to supervise over here in Canada, one of the volunteers had trouble with the Hancock Inspirator, which should have been self-priming, and lots of steam went out the overflow, which was plumbed BACK into the water tank. Water was low in the boiler; I could not get the injector to lift; the water tank was very warm to the touch; got a fire hose to fill the water tank with cold water, and things were back to normal.

Anyway, just my tuppence on this beautiful day.

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