This might be a silly question. I was doing some reading about staybolts and as I understand it, a flexible staybolt is not mechanically connected to the outside sheet. It's simply a ball end floating in socket. That would lead me to believe that under pressure the staybolt cap would fill with water. If I'm thinking correctly here, is there a method to purge the caps of water during winterization? If not, wouldn't the caps be extremely susceptable to freeze damage?

Yes in rare cases water can be trapped in the cap. I can remember finding a couple many moons ago on CP 2317 in Vermont while prepping the locomotive for service in Scranton, for the most part they will self drain when the locomotive is under reduced or no pressure. and it is not something you want to be taking off every time you lay up the engine.

Al P.

Water can sometimes remain between the ball end and the cap. Not sure about freeze damage, but it is advisable to be very careful if you resort to heat to remove a stubborn flexible staybolt cap. There is a chance that if the ball end is seated well enough to hold pressure, the trapped water turning to steam could cause the cap to shoot out. I've seen it happen.

-Sam

If you winterize the engine, most of any water that would be in the caps will disappear from the heat.
When you fire the engine up, blow everything out and shut it down it cools gradually and helps get rid of any water.
We would fire up, slowly blow down while operating all the appliances, then cap the stack and let it cool naturally.
Next weekend, we would charge the boiler with air, move the engine back and forth to make sure the superheater units would get well blown out, operate the appliances again. We would pull a couple of washout plugs and put screen plugs in their place for air circulation, make sure no water is in anything and go away until spring.

Thanks for the replies! I guess in my mind the the inner sheet would expand more than the outer sheet under steam which would tend to lift the ball enough to fill it with water. Then when cooling down the ball would re-seal trapping the cap full of water. Sounds the absence of pressure but the presence of heat usually lets the water escape before any re-sealing occurs.