Hi Everyone - take a look at this photo. The valve spindle that is eroded was in service a few weeks ago. We have not operated a great deal due to COVID, and there was a drought shutdown in 2019. We maybe had 50-70 days operation in the last 2 years.

I have a rough idea of where to start, but I would like your comments.

It appears to me more like mechanical failure. Note the way the broken off part of the plug is deformed as though it was pressed down through the seat opening of the valve. My guess would be that it cracked from stress, either from freeze damage or being tightened, and then was forced down into the valve seat in an attempt to shut it off.

What does the other seat look like? Steam cut I bet.

It looks like the valve in the photo had been lapped into the seat in the body to the point where it became concave, thinning the cross section of the replaceable end. It may be that the seat in the valve needs to be recut to spec and a new end for the stem made to spec lightly lapped onto it rather than simply replacing the broken part.

Dan Ranger told me about the end of steam on the SP, firemen having been issued cheater handles for steam valves so they could torque them way down and free the shop crews from maintaining valves on engines working out their last days before the new diesels came in. I'm sure something similar has been done with this one.

I made valve seat truing tools of steel that ran in a brass bearing made to fit the valve and hold them centered while lapping the internal seats back to spec for similar problems. Making a new "button" for the end of the stem of steam bronze or something similar and only lightly lapping the seat to the newly cut one is probably going to solve the problem, providing the stem itself is true. Good luck.

These spindles are solid.

Is everyone happy with the water treatment?

This valve is normally open and sits below the water level.

All the erosion I have seen in valves and fittings has been relatively smooth. Keep in mind I am talking water, not steam. To me that looks like either a casting failure or electrolysis. Did you have those parts made or were they purchased from a trusted supplier. If made, what material were they cast and/or machined from?

What is the function of the valve? You said it was below the water line but controlling what? Thanks.......mld

These are all-in-one injector and feed valves in one big casting. The clack or non return valve is in the injector body. The injector is bolted to the backhead and this valve is the stop valve to the boiler feed. You need to close it to do any maintenance in the injector. It is normally open and wet.

We have not made any of these. So far they are all scavenged from old stock, but this is the last one.

Thanks Stephen,
I'm a bit unsure from your original post so I'll next ask if you're looking for repair ideas or theory on how/why it failed?
Stumbling forward anyway with failure theory - It is difficult to tell from the pictures but is it possible the plug material was cast onto the stem? Is this valve shut as a normal part of shutting down the engine for the day? I'll agree with others that it looks like the plug has been machined down compared to the other stem and that also someone applied a 3 meter long wrench to shut off a leaky valve more than once.

I'll also request a picture or two of the injector and valve seat if possible. If nothing else it will be educational on seeing a different way of doing things..........mld

Trying to wrap brain around this.... does it control steam or water or both? One seat or back-seated as well? No wonder Hamlet was depressed, dealing with this sort of quandary.

Dave,
If I understand Stephen correctly this valve is the boiler delivery shutoff. It would be the valve between the clack (check) valve and the boiler proper in US parlance. It sounds like the injector, check and boiler shutoff are all one casting. If not, I'm looking forward to learning something new.........mld

I've seen backhead mounted injectors on PRR and N&W (I think) power. Never been inside one. If it is as you think, cavitation and contaminated water would be added to potential problems. I prefer the shutoff be downstream of the check since checks seem to need lapping from time to time.

I should have taken photos at the shop last night. It’ll be a few days before I have a chance again.

Right now, someone is taking the blame for over tightening. He is a big guy and a trainee. The argument is he over tightened a worn valve. This valve does not have a handle. It has a larger square head and you use a hand wrench to close it. We don’t carry a wrench extension in the cab and certainly don’t advise it.

I look at the fracture surface and I don’t think it is good. I once owned a house in Bangor, Maine (a long, long, time ago), and the cold water shutoff spindle valve seat retaining screw turned to dust in my hand.

Our water quality isn’t. We have extremely hard water.

This website has photos and diagrams of the same injektor model, on a different locomotive.

http://www.teknikaliteter.se/2017/11/06/att-kora-anglok-i-bergslagen/

Quick bit of information to help assist the conversation. The injector is a Gresham injector of the same style that the brits and many other Europeans use. The valve is not the steam valve, and is indeed the shut off valve (on the boiler side of the clack valve). The photo is bad but the valve was not turned down much thinner than the other, max 1/8'' smaller or such. Two years ago this valve was crack tested and showed no pre cursors or warnings for what has happened. Being that the past two years has seen relatively little running with the C word and such, this seems highly irregular to have occurred from normal use. The valve began a slow habit of leaking lightly when shut during the christmas runs last year. I suspect unfortunately that this is the result of people trying to use the next size up crescent wrench one too many times. The end result being that heating and cooling cycles + normal and extreme tightening finally caused the valve head to fail and cave in on itself on the final time it was tightened.

Thanks. Looking at figure 4 on the drawing, it shows the valve seating on the ID of the plug, where it is backed by the stem. The broken one looks as if it was seating further out on then plug, perhaps beyond the diameter of the stem in the center, putting unsupported stress on it which could have led to this kind of failure if seated a bit too firmly over time. Don't know what the seat in the casting looks like, but if there's a way to have the plug seat on the part supported by the stem I think it would be much more robust. Good luck and thanks for an opportunity to do some interesting thinking again.

All those people in the linked site look just like my wife's cousins.