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Displacement lubricator - with or without valve ?

Displacement lubricator - with or without valve ?

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3404605/02/2019 10:25:47
594 forum posts
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For a Stuart beam engine

I can find one without a valve on it, and one with a valve on it and I think also there is a type with a valve to control the steam flow to the engine.

Would like advice on which option to buy.

Thanks

Bill

AJW05/02/2019 13:18:59
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I fitted one with a valve to my Stuart no 4 so the amount of oil could be controlled, without, I can visualise the steam condensing uncontrolled and displacing all the oil rather quickly!

Alan
3404605/02/2019 13:52:07
594 forum posts
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Posted by AJW on 05/02/2019 13:18:59:
I fitted one with a valve to my Stuart no 4 so the amount of oil could be controlled, without, I can visualise the steam condensing uncontrolled and displacing all the oil rather quickly!

Alan
Thanks Alan - point taken and I will do likewise.
Bill
norm norton05/02/2019 14:37:35
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The steam enters the oil chamber and condenses only when there has been a change in pressure, i.e. you start the engine. Then when the pressure drops some oil will be expelled into the steam line. If running at constant speed there will be no additional oil introduced. The volume of oil displaced each cycle also depends on the amount of (compressible) air in the reservoir at the start.

It just needs a reasonable one inch or more of small bore tube to tee off the steam line and possibly a jet of 0.010" or 0.020" in the line if it does empty the oil too quickly.

duncan webster05/02/2019 15:57:30
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Posted by norm norton on 05/02/2019 14:37:35:

The steam enters the oil chamber and condenses only when there has been a change in pressure, i.e. you start the engine. Then when the pressure drops some oil will be expelled into the steam line. If running at constant speed there will be no additional oil introduced. The volume of oil displaced each cycle also depends on the amount of (compressible) air in the reservoir at the start.

It just needs a reasonable one inch or more of small bore tube to tee off the steam line and possibly a jet of 0.010" or 0.020" in the line if it does empty the oil too quickly.

That's not how it works, steam enters all the time whilst there is steam in the feedpipe. It condenses and sinks to the bottom displacing oil back into the steampipe. I think you need to make sure there is no trapped air.

norm norton05/02/2019 19:38:41
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Posted by duncan webster on 05/02/2019 15:57:30:
Posted by norm norton on 05/02/2019 14:37:35:

The steam enters the oil chamber and condenses only when there has been a change in pressure,

That's not how it works, steam enters all the time whilst there is steam in the feedpipe. It condenses and sinks to the bottom displacing oil back into the steampipe. I think you need to make sure there is no trapped air.

Every respect Duncan, but your version makes less sense. You suggest that steam keeps flowing through the pipe, and any small jet or valve, at the same time as oil flows the other way? Which end of the pipe has the higher pressure? A cyclic system however will follow the inevitable pressure changes in the steam supply. A small bubble of air is necessary to allow that cycle to execute and balance the pressure in the reservoir to that in the steam line.

AJW05/02/2019 20:24:17
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The secret is in the name 'displacement'!
Steam will condense in the lubricator which is cooler than the engine turning to water, this will sink and in doing so will displace an equal amount of oil - which flows to the engine
The lubricator will have (as well as a control valve) a drain valve at the bottom, this is to allow the condensed steam (water) to be drained out so the lubricator can be refilled with oil.

Alan
norm norton06/02/2019 09:41:53
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Yes we all agree that the steam condenses in the lubricator vessel and it is this that displaces the oil. My apologies if I misled by not saying that I agreed with this basic principle at the start.

Our discussion is whether this Simple Displacement Lubricator might be a continuous system or a cyclic one. This lubricator uses the same entrance and exit to the steam line, or steam chest as fitted by Stuart. I suggest that the flow direction must cycle. An experiment would be simple to do - just connect a steam line to it and leave it under pressure, and see if it gradually fills with water and all the oil transfers to the steam line.

There is another configuration sometimes called the Hydrostatic or Ramsbottom style that has a steam inlet, typically from the regulator supply, to the displacement vessel and a separate oil outlet to the cylinders. These do not need to cycle and are effectively continuous. They were developed for use on full size steam locomotives and even included sight glasses to observe the dripping oil flow. If configured to take some steam directly from the boiler they would then operate continuously. They are still used on some model locomotives, especially GWR variants.

JasonB06/02/2019 11:15:55
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The small trickle of oil can flow along the bottom of the pipe linking the lubricator to the engine while the steam passes through the rest of the bore so flow is continuous, it does not have to be a full bore flow of oil.

All the time the lubricator is colder than the engine there will be a flow of steam as the cooling effect will make some condense which creates a slight vacuum and draws in more steam and so it goes on. Think of a condenser drawing the remaining spent steam out of a condensing engine

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