Hi all,
The oil reservoir in our locomotive's hydrostatic lubricator holds enough oil that it usually lasts for a full operating day. However, I recently had a discussion about the proper way to refill a hydrostatic lubricator that has been hot and under pressure immediately prior to refilling. The danger to be avoided, which some have heard about and others have experienced, is that if you remove the oil reservoir fill plug with the reservoir under pressure, hot oil/water/steam will burst out into the cab and injure somebody or at least make a mess.

Our locomotive has a five-feed Nathan hydrostatic lubricator with feeds to the cylinders, valve chests, and air compressor.

After consulting the ICS book on hydrostatic lubricators and searching old RYPN posts, I have come up with the following procedure.

I would invite comment from others who have dealt with this problem about whether the following procedure is correct or needs changes:

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0.) Wear safety glasses and gloves. Ensure that nobody is present where they might be hit by hot oil if this procedure is done incorrectly. The engineer should not be sitting in the engineer's seat if this procedure is being done by another crew member.

1.) Shut off steam supply to air compressor. Ensure that the throttle valve is well seated.

2.) Close the steam and water valves on the hydrostatic lubricator. Close the oil control valve (which shuts off the flow of oil to the cylinders but not the air compressor) (a.k.a. the "T-handle"). The lubricator's steam shutoff valve on the backhead can remain open.

3.) Close the oil-feed regulating valve for the air compressor feed on the lubricator

4.) Open the oil reservoir drain valve and drain until water flow changes to oil flow.

5.) By the time that the discharge from the drain pipe has changed from water flow to oil flow, the pressure in the oil reservoir on the lubricator should have reduced to atmospheric pressure. This will be indicated by a reduction in the flow rate of the oil/water discharging from the drain pipe. The flow rate should now be slow. If the flow rate has reached a slow trickle and water is no longer being discharged, reduce the opening of the drain valve but do not close it to completely. Leave the drain valve open to vent any new steam that might enter the oil reservoir past leaking valves.

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The following is the original text of step 5, now updated as above:
5.) Reduce the opening of the drain valve, but do not close it completely. Leave it open to vent pressure.
]

6.) Standing out of the path of any oil that might blow out, slowly open the filling plug(s) on the oil reservoir. Be attentive to signs that the plug is still under pressure.

6.a) If pressure is encountered, cease loosening of the filling plug, and open the drain valve further until any pressure is released. If the plug cannot be made free of pressure behind it, do not loosen it any more.

[On our locomotive, we remove both filling plugs so that air can escape from the oil reservoir as oil is poured in. It makes it easier to fill.]

7.) Once the only or first filling plug is fully removed, close the drain valve completely. Fill the reservoir to capacity, then reinstall the plug(s).

8.) Open lubricator steam and water valves.

9.) Open the oil feed valve for the air compressor feed and regulate it to the desired oil feed rate.

10.) Open steam supply valve to air compressor.

11.) Open oil shutoff valve (a.k.a. the "T-handle") and verify that oil is feeding through all sightglasses at the desired rate.

12.) If the locomotive will not move soon, close the oil shutoff valve (T-handle) in order to not waste oil.

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Let me know what you think.

Thanks!
Dan

Ah, memories of doing this at 2 AM in the middle of the winter in Colorado.

I remember once on an eastbound train coming home the hydrostatic ran empty and the only way to refill it without it blowing back steam was to completely shut off the main turret which required tying the train down for a few minutes.

I would add 2 things:

1. Let the lubricator cool for a few minutes before adding fresh oil, this will reduce the possibility of the oil "burping" back out the filler.

2. Add the oil a bit at a time. Quite often you get a bit of water in the valve oil tallow pot. When the water mixed in with the oil hits that hot brass lubricator it will flash to steam, causing another burp out the filler.

Take your time. That's better than cleaning valve oil off the cab ceiling and the engineer's seat cushion.

You may want to secure the locomotive incase you have an air leak and it takes longer than planned.

Robby Peartree

I would make one modification to step #5. Leave the drain valve open until all the pressure is relieved before attempting to remove the fill plug.

With a hot lubricator, this invariably requires completely draining the reservoir of not only water but all the remaining oil as well. Trying to rush refilling before the reservoir is completely drained and de-pressurized is where most of the trouble is found when refilling a hot hydrostatic lubricator.

You have the process in the correct order but I would also stress that the order of closing and opening the valves is very important. When shutting the lubricator down close the valves in this order: 1. oil regulating, 2. water, 3. steam supply 4. oil delivery (if equipped). When starting, reverse the order. When starting the lubricator, varying from this order will cause problems.

Hi Russ,
Thanks for your comments. I think that my wording with step no. 5 in my previous post was ambiguous. I said:

5.) Reduce the opening of the drain valve, but do not close it completely. Leave it open to vent pressure.

By "Leave it open to vent pressure," what my mind intended to mean was, "By the point where the water has drained out, the reservoir should have reached atmospheric pressure. Reduce the opening of the drain valve but leave it open to vent any new steam pressure that might leak past closed valves and enter the oil reservoir."

But, what my wording could alternatively mean is, "Reduce the drain valve but do not close it completely so it can continue the already-occurring process of reducing the pressure in the oil reservoir to atmospheric pressure."

I meant the former. I will update my original post to correct the ambiguity.

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Here is a more detailed listing of my thinking about the process occurring around step 5. I would welcome your feedback about it:

1.) With other valves closed appropriately as described in my original procedure, the reservoir drain valve is opened.

2.) The oil reservoir is at near-boiler pressure, and as a result discharges oil and water under pressure out through the drain valve. Initially water drains out. Eventually all water has drained out and oil drains out instead.

3.) As water/oil are expelled from the oil reservoir, the pressure drops in the reservoir. With the steam valve, water valve, T-handle, and compressor oil regulating valve all closed, there is no way for boiler pressure to reach the oil reservoir and repressurize it. Eventually the pressure in the reservoir drops enough that it reaches atmospheric pressure.

4.) When the reservoir reaches atmospheric pressure, the nature of the flow out the drain pipe changes. Before, the whole pipe had carried fluid out that was being expelled by the pressure in the reservoir. Now, air must flow up the drain pipe as fluid is draining out of it. Because part of the drain pipe must now carry air, the rate of draining is much slower than it had been when the reservoir was under pressure.

5.) When it is seen that the draining of fluid has slowed to this slower flow rate, the crew member can safely infer that that the pressure in the reservoir has equalized with atmospheric pressure. It is now safe to remove the filler plug on the reservoir. But, as a precaution, the drain valve is left open until the filler plug is removed, in order to prevent boiler pressure from passing through a leaky valve and repressurizing the oil reservoir.

6.) Once the filling plug is removed, any steam that might leak into the reservoir can now pass to the atmosphere through the filling port. It is now safe to close the drain valve.

In this scenario, it appears that it isn't necessary to wait for all the oil to drain out of the reservoir. But, of course, the saying goes, "In theory, theory is the same as practice. In practice, theory is not the same as practice." I'm curious--has the sequence that I list here not been your experience in the real world? Did I overlook something?

Thanks!
Dan

Dan, what you need to remember is that the oil reservoir of a hot lubricator is full of water that is at the same temperature as the water in the boiler. At 200 psi. that is approximately 380 degrees. When you open the drain, it is not going to simply run our as water under pressure. As the pressure in the oil chamber is relieved, the water in it will boil off into steam. What will come out of the drain is a mixture of water, steam, and oil at high pressure. Generally, after all the liquid is expelled steam will continue to blow out for a time before the pressure is completely relieved. Only after all pressure stops blowing out of the drain is it safe to loosen and carefully remove the fill plug. Pay close attention to the warning port in the threads of the plug. If any steam blows from that, stop and wait for it to completely vent before removing the plug.

Even after the pressure is gone, there may still be droplets of water in the chamber that will boil off and cause the oil to splatter back as you fill the reservoir or, as Earl mentioned, there could be water in the oil you are filling it with that will boil off causing the oil to blow back out the fill opening. It is best, if possible, to let the lubricator cool a few minutes with the drain and fill plug open before trying to refill it.

If you are filling a cold lubricator with no pressure on it, it will behave more like what you have described. In that case, you can open the drain, and once you are certain there is no pressure in the reservoir, crack open the fill plug until the warning port opens and vents the reservoir, and allow the water to completely drain. Once you start getting oil, close the drain and top off the reservoir.

here is a drawing for a hydrostatic I swiped from an 1920 ICS book. This drawing shows how the water and oil intermix.

Robby Peartree

Russ,
Thanks a lot for the explanation. It seems that the critical part is that I was expecting the pressure to reach atmospheric pressure before the water and oil flow stopped (at which point it the fluids would be slowly dribbling out), when in reality, the pressure will still be falling at that point. Thanks also to John, Earl, and Robby!

Huh. I guess that is why hydrostatic lubricators are not so popular?

I have a hunch that they fell from favor when superheating became common place.

I have to ask based on what you you make this statement?

Robby Peartree

Both the Northerns I've worked on (built 1940 and 1942, some of the last steam power the railroad purchased) had them. One of them even has a huge oil splotch on the roof of the cab where it looks like oil did in fact shoot out of the lubricator.

They used it to lubricate the Water Pump, Air Compressor and Stoker Engine, with a mechanical lubricator for the cylinders, crosshead, etc.