Piston valve removal

Sometimes valve heads need to be removed for examination or repair. On modern LMS and (I suppose) on BR standard engines, it is relatively easy to remove the front valve chest cover.

It's not easy to split the valve rod from the crosshead, but once that is done the combination lever (when detached at the bottom) can be used as a lever to push the valve assembly towards the front of the engine.

However, it gets difficult when the valve heads are pushed beyond the end of their habitual travel, and the valve rings start to bind on the slightly less worn valve liner. The rings, needless to say, are packed out with carbon so they won't compress back into the grooves.

At this stage the combination lever simply flexes when pushed.

The next step, which seems obvious but painful, is to take down the slidebar assembly, make a cap for the taper end of the valve rod, and get a person of ample muscular proportions to whack the rod out with a large hammer.

Has anyone managed this job without resorting to sledgehammering the things out?

Any pearls of wisdom eagerly anticipated.

James Friel

 

I've never had the joy of removing a piston valve as all our locos have slide valves but I'd have thought that it was a fairly easy task to make up a piece of kit to press them out with a dumpy hydraulic jack. Four bits of hex bar drilled and tapped to screw onto the valve cover studs, four other bits of round bar of suitable length screwed into the other ends and a suitable piece of 1" plate with four holes in attached at the other end for the jack to push against. A 30T jack ought to do a better job than a sledgehammer. I use a similar piece of kit for splitting crossheads from piston rods.

 

The device I have experience of pulls the valve spindle from the front with a long threaded bar. I don't know if it is an LNER design but the I've seen it used on the K1, A2 and A4.

The most important thing we in NELPG have learned is to remove the valves as soon as possible after the loco has come out of traffic, (usually within the hour). The hot valves come out much easier because the carbon deposits are relatively soft.

 

If your P&V exams are done at reasonable intervals, you use decent steam oil suitable for your loco on your line and correct rate of feed. Piston valves are not too difficult to remove. In fact, we find that re-fitting them with new rings and the stupid bits of paper to hold the rings into the grooves is harder than removal.

 

Steve, thankyou for your suggestions, which we tried (combined with a puller as described by Martin to pull the rod from the front end). Unfortunatley nothing was moved once the ridge of carbon was hit! ](*,) So we're going to try Martin's suggestion of yanking them out while hot next, which hopefully when combined with jacking and pulling should produce some results.

twr12, you are of course quite correct in your comments. These valves should be easy to remove.

I will let you know how we get on! Thanks again for the helpful suggestions, it is good to know that this knowledge is out there and that there are people willing to share it.

JJF

 

Some photos taken today of the K1's valves being pulled.

http://martin188.fotoblog.org.uk/c1584334.html

 

Do I have a recollection of the rearmost valve liners, heads and rings being slightly smaller (? 1/16") on the larger Gresley locos in BR days to make removal easier?

 

Caption on my third photo!

 

Chaps, thankyou all for your helpful suggestions, the valves are now out and hopefully before long they can be put back in again!

JJF