Displacement lubricator questions

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Chris Hollands
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Displacement lubricator questions

Post by Chris Hollands »

I think i understand how a displacement lubricator works and i will probably answer my own question .

It works by the water displacing the oil ( the water becomes a piston ) and forcing the oil out of the lubricator by surface area pressure over coming the exterior working pressures of of what it is attached to .

My question is -

1. can a displacement lubricator over come a spring check valve ( low spring pressure )

2. can it push oil up hill
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Harold_V
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Re: Displacement lubricator questions

Post by Harold_V »

I'm no expert on displacement lubricators, but it is my opinion that it can do neither, as it relies on gravity to function. That said, if it can introduce a drop of oil to a steam line, the steam itself will propel the oil where it is needed, with no regard to gravity. If the steam can penetrate a spring check, there's no reason why the oil contained within wouldn't accompany the steam. So then, if your idea is to introduce a check valve between the steam line and the lubricator, I strongly suspect it wouldn't work.

H
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Short Line Tom
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Re: Displacement lubricator questions

Post by Short Line Tom »

Hi Chris,

to my knowledge is an oil check valve not permitted on a displacement lubricator system.
Please find some more informations of my own experience on the topic HERE.

Cheers
Tom
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Bill Shields
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Re: Displacement lubricator questions

Post by Bill Shields »

a typical displacement lubricator of that type, depends on a pressure differential to push the oil.

higher pressure from the turret area to lower pressure between throttle and cylinder(s)..and yes they will push uphill

check valves are typically not used (or needed since there should always be higher pressure on the steam side than the oil side)

However needle valves are frequently used to control flow on the outbound (oil) side.

SOMETIMES a small diameter ORIFICE is substituted for the needle valve if the builder has sufficient experience to know what size orifice to install.

I would look for the needle valve on the discharge and / or orifice and start there.
Too many things going on to bother listing them.
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Chris Hollands
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Re: Displacement lubricator questions

Post by Chris Hollands »

Thanks for the replies - i'm using your design Bill so thanks for that
No c/v makes things easier .
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gwrdriver
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Re: Displacement lubricator questions

Post by gwrdriver »

In world "garden" gauge live steam (45mm gauge), where I am also an active builder, 99% of locomotives use hydrostatic lubricators, also called displacement lubricators. Most of the commercially produced locomotives (arguably the majority currently on the rails) rely upon a drilled hole in the feed tube to meter oil delivery. Almost invariably they get it right, but every once in a while they don't. Needle valves are the best control method but are rarely used in small scales because it adds product production costs, and a drilled hole works.

Displacement lubricators work because within that tiny orifice a molecular miracle happens . . . steam goes in (to the lubricator reservoir), and oil comes out, at the same time. The steam which makes it into the reservoir condenses and the accumulation of water under the oil in the reservoir "Displaces" (hence displacement lubrication) the oil, pushing it out into the steam supply line where it emulsifies as it travels to the cylinders. The process is helped along by tiny pulses in steam line pressure as the engine runs. As for Gravity, it has very little effect on the process, except that it pulls the water to the bottom of the reservoir, and in 45mm gauge a guideline is to mount the lubricator as near to the cylinders and as far from the fire as possible. For the lubricator to work the body must be cooler than the steam.

The hydraulic forces are tiny so no check valves are used but the oil entry point (to the steam line), which may be a "Tee" directly connected to the steam supply line, or a short dedicated lubricator line, must be beyond (downstream) of the throttle to prevent oil being drawn back into the boiler by a vacuum when the loco is cooled down.

A necessary construction detail is that there must be a starting air space in the reservoir, otherwise in a completely filled reservoir the condensation phase won't start and self-sustain. Typically the air space is provided by counter-drilling or machining a recess the lubricator cap. A very handy detail to include is a water drain in the bottom of the reservoir.

That's the way it works and has since the invention of displacement lubrication.
GWRdriver
Nashville TN
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Harold_V
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Re: Displacement lubricator questions

Post by Harold_V »

gwrdriver wrote: Thu May 14, 2020 7:32 am As for Gravity, it has very little effect on the process, except that it pulls the water to the bottom of the reservoir,
Harold_V wrote:as it relies on gravity to function.
That was my point. Without gravity, it wouldn't function.

H
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Bill Shields
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Re: Displacement lubricator questions

Post by Bill Shields »

depending on the 'displacement lubricator' type...gravity does not matter.

Bill van Brocklin championed a variation where there is a steam in / water out on either end of a cylinder.

inside of the cylinder there is a free floating piston (sealed - naturally - with an O-Ring!) that serves as a separation barrier between steam (water) and oil.

put steam in one end...pushes oil out the other.

works right side up / upside down / no gravity at all...matters not.

some called it a 'hydrostatic lubricator' as opposed to a 'displacement lubricator' (nit picking....)
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Chris Hollands
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Re: Displacement lubricator questions

Post by Chris Hollands »

Just to let you know the lubricators are for working Westinghouse cross compound air compressors from super power detail ( Mr fraud him self but thats another story )
FKreider
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Re: Displacement lubricator questions

Post by FKreider »

Bill Shields wrote: Thu May 14, 2020 4:13 pm depending on the 'displacement lubricator' type...gravity does not matter.

Bill van Brocklin championed a variation where there is a steam in / water out on either end of a cylinder.

inside of the cylinder there is a free floating piston (sealed - naturally - with an O-Ring!) that serves as a separation barrier between steam (water) and oil.

put steam in one end...pushes oil out the other.

works right side up / upside down / no gravity at all...matters not.

some called it a 'hydrostatic lubricator' as opposed to a 'displacement lubricator' (nit picking....)
Hi Bill,

Is this the style that he wrote about in the 1978 Live Steam article? I've been wanting to see a copy of said article for a while now.

"Get Positive Oil Feed with a Hydro-Force Lubricator", William S. Van Brocklin, Jr, Live Steam Magazine, November 1978
-Frank K.
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Bill Shields
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Re: Displacement lubricator questions

Post by Bill Shields »

Yes
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JBodenmann
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Re: Displacement lubricator questions

Post by JBodenmann »

Hello My Friends
One very important aspect that hasn't been mentioned is the type of oil used. Much steam cylinder oil is of the detergent type. This detergent helps the oil to atomize and also helps it's wetting characteristics. This oil is for a mechanical piston type lubricator and will not work in a displacement lubricator as it will foam up preventing the condensed water from lifting it out of the lubricator. For a displacement lubricator, non detergent oil is needed. Most of you probably already knew this but I thought it should be mentioned.
Happy Model Building
Jack
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