Just wondering what everyone has been doing to seal up steam domes. I was reading in one discussion on how the dome flange gets bent from tightening the dome cap too much. How do you keep the gasket from sliding into the dome now that the dome is bent in?

That is one of the reasons you need a dome lid that is thick enough to resist being bent. I remember having that very problem before we made the thicker lids.
On some boilers there is a small groove that is in the area where the gasket is which helps keep things in place.

I have seen copper "trolley wire" used for the gasket with good results. There are lots of great high performance products available today that were unavailable in the days of steam.

And remember to properly anneil the copper gasket.

There's a product out there called, If I remember correctly, "MetalBestos" or something like it.......which is made from a coil of copper filament spun and glued together into a short, flat "slinky". A friend installed one of these, which under steam, unwound and the resulting bird's nest of wire got stuck in the throttle and held it open, resulting in a very interesting trip. Heavy gage wire, formed and annealed with a joint scarfed or otherwise made no harder than the wire itself and correctly annealed before tightening seems the most reliable solution. There might have been some improvement in flat gasket material but I'm unaware of any proven robust in this application.

dave

I don't believe it is wise to be substituting other materials for your gasket than what is used in your dome lid factor of safety calculations, as the compressive force per square inch needed for some of the gasket materials commercially available (flexotallic, etc) can be 8 to 10 times higher than that of a properly sized and annealed copper gasket and can lead to the conditions discussed above about bent studs and misshaped dome lids. This was actually discussed at the ASME Locomotive subgroup meeting, another good reason for attending these meetings if one has the chance.

my 2 cents,
Mike Tillger

Annealing the copper gasket is important. Also, tightening down the dome evenly prevents leakage and slippage of the gasket. It is a good idea to number the holes in the cover to coincide with the dome bolts or have a tic mark on the dome and cover so you can line it up the right way each time. You can then tighten the nuts evenly with a torque wrench. We had several water leaks around the steam dome when doing hydros till we got it right. It still takes the patience of Job every year!

Our experience and extensive research has shown that dome lids deform when the studs are over tightened. In fact too many people have seen the fix for a leaking dome gasket to be tighten the nuts tighter and tighter while sledging on the dome lid.
This was the condition of the Milwaukee 261's dome when we began the restoration. All the studs were bent outward and had to be removed first before the dome could come off. I think the lid was bent down so far as to touch the steam dome at the outer edge of the lid. When the studs get tightened this hard, and then you fire up the boiler and add the boiler pressure to the already overloaded studs - they deform. We have adopted stringent torque values for each size of studs. Tight enough that a good copper ring won't leak - but not so tight that you exceed the yield limit of the stud material when the boiler is pressurized.

The initial cold preload on a newly-placed copper ring should be only sufficient to offset the calculated dome lid lifting force from the maximum boiler pressure acting inside the ring's circle of contact with the lid. The torque applied to each nut at this stage should should be sufficient only to deliver its share of the total calculated preload on the lid.

On initial (hydrotest) pressurization with a new ring, lid nuts should be gradually and uniformly retighted in proper sequence until the copper ring is seated and leaktight. Since boiler pressure pushes up on the lid, the lid preload on the copper ring will diminish as boiler pressure rises, and increase again when boiler pressure diminishes. Since copper thermally expands more than steel does, the ring seating preload during hydrotesting should not need to be readjusted for fireup.

Applying proper dome lid preload and nut tightening torque not only avoids damage to the lid and studs, but also avoids the need to retrofit the dome with an excessively thick replacement lid.

I understand the point of not over tightening the studs, but you still have to satisfy the minimum thickness formulas. It doesn’t matter how tight or loose you make the nuts as that doesn’t change the bolt load requirement for gasket seating. You can certainly get the lid to not leak by being careful with the torque, but what do you hang your hat on concerning the calculations which must be submitted to the FRA?

Rick

In my shop class I teach a whole unit on metal fasteners and I still have to tell my students over and over is not to over tighten. If I had a dollar for each time I told the kids "you don't have to tighten it like you're Mighty Joe Young".

This has me wondering if any of the newest steam locomotives were built with a stationary boiler type manway?

I will be needing a new copper gasket for the J&L 58's steam dome, so I was doing some research and found this old thread. Where does one obtain a large diameter copper gasket? The boiler drawing lists a No. 6 copper gasket 17 1/4" diameter. I am assuming that is 6 gauge or 0.194" thick. Is there a firm that still makes large dia. copper gaskets, or is this something that I'll have to cut out of sheet?

Number 6 copper wire.

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Huh! I had no idea it would have been wire. Well that makes sense. Problem solved.