Thursday, 13 October 2011

Why you need a Pointy Hat

As delivered, this elegant, Penberthy, displacement lubricator will flood the cab-mounted Worthington Simpson Boiler Feed Pump's (WS BFP's) steam chest every time it's topped up. Not good!
Looks good but hides a flaw
Let's see why.
Mounted on top of the WS BFP's Steam chest
The lubricator relies on being mounted vertically with steam oil filled to the top of a centrally located, internal tube.
Main pot removed to show the internal tube
In operation, some steam from the steam chest below is pushed up into the air gap at the top of the main pot where it condenses into water.

Being heavier than oil, the water sinks to the bottom and raises the level of the oil. The oil then spills over into the internal tube and back down into the steam chest below. So this is how the steam oil gets into the steam chest at the same pressure as the steam.

How does the oil get into the main pot? Well, you take off the filler cap and pour it in or so you expect until you actually have a look inside.

The top of the tube is open!
The tube has nothing to prevent oil being poured straight down it into the steam chest. Whilst this probably would not do any great damage, the steam chest would certainly get more oil than required!

I've concluded that there must be a missing part which blocks the hole but still allows the oil to spill over into the tube as intended.

I spent a lot of time figuring out how this part could block yet not block the tube top. Eventually I came up with a sort of castellated pointy hat thing!

Castellated, pointy, hat thing drilled from below to meet six holes and...
...which can sit on top of the tube like this
Now when you look in the top of the pot, it's like this:
Pointy hat top
So pouring oil into the filler will now put it into the pot and not straight into the steam chest!

I wonder if it will still work and what was there originally?


  1. 22nd April 2013. Comment received by email from Steve Roberts at the Middleton Railway, Leeds. Steve is restoring Sentinel 8837 (see

    Your displacement lubricator is no different from any I've ever seen and is not missing any part. It doesn't need your 'castellated pointy hat' thingy.

    When filling your lubricator, the first thing you always do is shut the isolation valve at the bottom. You then open the drain valve and let all the water (and any pressure) out of the lubricator before removing the filler plug. You can then fill the lubricator and, yes, the standpipe will be filled as well as the body.

    It doesn't matter as the valve is closed so oil won't pass into the steam chest. Once it is full and the filler plug replaced, you then partially open the isolation valve, but not fully. How far you open it controls the rate of feed of oil and is found by experience The oil in the tube will start to drip through the valve but can only do so if it is replaced by steam/water.

    I don't think your pointy hat will create any problems but the lubricator will function perfectly well without it.

    And so continues my education! Good to know people are keeping an experienced eye on my activities! Thanks Steve.


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