Evening All,
for your Lamont boiler circulation pump- how about the drive shaft passing through a really long pipe, - a long stuffing box arrangement filled with all the correct fibres and goops. By the time you get to the gland nut it could be very wet, very slippery, and low pressure - maybe - and not stolen too much power.

Now, your own practical steamcar project might not welcome a long pipe like I contemplate, but mine is a campervan (a dream as yet). A long pipe won't be getting in the way

I was thinking about a helical lobe mono pump sort of thing

another halfbaked idea??
regards All, and good night
JohnnyF

I think a labyrinth seal would be a great Idea. I thought of testing one.
I don’t know how tight the tolerance needs to be or how many rings would be needed to hold a pressure of 1000PSI.

A true labyrinth seal is more then a long packing gland.

I thought of a shaft cylindrical grinding a 3/8 shaft down to .1875 with six 1/16 rings 1/16 apart, the outer housing machined, split in two half’s with a cross key. The whole thing pressed into a pump housing. The labyrinth tolerance of .0005.

The shaft is pretty straight forward, it’s the outer housing that’s the tough part.


The problem is I don’t posses the skills or have the machinery to build it. There must be information and pervious data on this.
Needs more research.

[en.wikipedia.org]

Rolly



Edited 1 time(s). Last edit at 03/20/2008 01:12PM by Rolly.

Hi Rolly:

I had experience with some layrinth seals in the navy. They don't all necessarily have raised projections on both the shaft and the bore, many have smooth bores with the shaft projections in near contact with the bore. This is MUCH easier to build. Another advantage, I would imagine, is that you can easily make the sealing grooves very narrow and pack a large number of them into a smaller length. The seal works by creating a series of pressure drops, so the larger the number of drops the better it works. To my knowledge, no labyrinth seal is truly a seal, there is always leakage. It's just that the leakage is far smaller than without the seal. On steam turbines the LP stages ran subatmospheric and very low pressure steam was injected into the labyrinth near the outer extremity, this steam sealed the shaft against air intrusion. If you think about it, the labyrinth NEEDS leakage to function. If we had a labyrinth seal and put a very good mechanical seal on the end, then next to nothing would ever leak out. The pressure would start to build up between the gaps in the labyrinth until it blew out the mechanical seal. If the mechanical seal was designed to take the pressure, then the labyrinth was redundant anyhow.

Regards,

Ken

Hi Ken
Yes I know not all labyrinth seal are double sides or as I described it, there are a lot on the market as one sided. I have seen them used on jet turbines as well as on steam turbines most built in sections, large shaft diameter.
Where talking about a small pump with a small shaft. The bigger the shaft and longer the seal the more power it requires to pump fluid.
I gave Rod the small permanent magnet motor he used on his Lamont pump. It only used six to eight amps / 12VDC I’m not sure he is still using it.
Small leakage is OK, I like to see it on a packing gland, I know the packing is staying moist and not drying out. Less ware on the shaft.

I just don’t know how to calculate a design, and you need precision grinding equipment to build one that won’t ware out. You also have to worry about end movement and expansion of the shaft and housing up to saturated steam temperature.

Rolly