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?