How do you seal engine joints?

I have just finished the water pump for my Merryweather Fire King. This the first working engine I have made, so I have no experience in sealing the joints. There are flat surfaces, screwed parts and some glands.

What’s the best way to do this? What should you pack the glands with? I have some fibre paper, Hylomar Blue and ptfe tape.

Bob

Hi Bob, I use a few methods to seal parts depending on application. Depending if its oil, water, steam, etc.

For the pump flanges I would use a paper or neoprene type gasket. Gasket sealant is also available in tubes which is good for machined surfaces. (available from car and hardware parts stores) Check the temperature rating if you are sealing a steam connection. The traditional sealant for steam engines is a graphite paste which is good for flanges and screwed parts.

For the gland packing use graphite or teflon. Available as square or round section to suit the width of your gland and cut to length. For the pump piston rod, I cut rings of packing that go around the rod. Then a second (or more) rings of packing, installed with the gap at 180 degrees to the first (ptfe tape, could be used but not as good as proper gland packing)

Paul.

Edited By Paul Lousick on 09/10/2020 02:44:41

Bob, I prefer to make gaskets from copy paper then oil them with light oil before fitting.

A point about using Hylomar which is an excellent sealant - any surplus that oozes out is extremely difficult to remove without a solvent. Acetone works brilliantly but of course also works just as well on surrounding paint work!! White spirit, WD40, paraffin, methylated spirit nor petrol would not remove it completely either. Having experienced that I shy away from it now if it's near any paintwork. I have just had need to replace a paper gasket on a governor with Loctite pipe sealant - with exactly the same effect. Paint was car aerosol from Halfords and will have to be re-done.

+1 for the graphite packing on glands I prefer PTFE filled packing for pistons

Hope that's of use

Regards - Ramon

On flat surfaces, a soft joint will always eventually lead to torque relaxation of the fixings, (Due to joint settlement ) which may result in leakage.

A sealant on a soft joint can also act as a lubricant, allowing the joint to be extruded in the vicinity of the fixings!

If you are confident of the flatness of the faces, a metal to metal joint, with a sealant to fill any gaps, such as machining marks, will remove the risk of settlement. Suitable sealants could include Hylomar (As already said, difficult to remove any excess without solvent such as Methyl Chloride, or scraping ) Silicon Rubber, but paint will not adhere to it, so again, scrape off any excess.

A non setting sealant will make any subsequent dis assembly easier.

It can be very difficult to break a joint sealed with a hard setting sealants such as Hermetite. So difficult that parts are damaged before they separate.

The old builders of Cornish Beam Engines, admittedly working at not much more than 40 psi, used metal to metal joints with things like putty or lead strip as gap fillers, between cylinders and their covers..

Howard

The problem I find with Hylomar blue on models is that unless you apply it incredibly sparingly, it has a tendency to ooze out and block / obstruct things it shouldn't. (I have used on full sized stuff without any problems.)

Rightly or wrongly, I used Loctite 542 thread sealant on the fuel and exhaust connections of my hit and miss engine. It was very easy to use and clean up, and it seems to resist petrol and oil. The fun may come if/when I need to take it apart!

Thanks for all your useful suggestions. I think I know what to do now. Let’s hope for the best.

Bob