I have recently purchased 3 PRR all Bronze 1/2" globe valves. My inquiry concerns the unique valve discs these valves posess. The disc is a floating ball which I believe to be Stainless Steel. The disc swivels and rotates so as to not grind into the valve seat as is normal. What is not so normal is the manner that the disc is attached to the stem. It appears that the disc has no means to be applied or removed from the stem and is simply pressed onto a ball(?) on the end of the stem. Also, I would not know how one would make the disc stationary for lapping purposes. Does anyone have any experience with these valves or any thoughts?

I am attaching a photo of the valve stem and valve disc in question.

I currently have 2 of these valves listed on eBay, if interested you may view them at:

http://www.ebay.com/itm/221097573781?ss ... 1555.l2649

http://www.ebay.com/itm/221097537379?ss ... 1555.l2649

Thanks, happy steaming,
Don Fenstermacher

I've seen similar valves for very high pressure compressed air (~3000+ PSIG), but the seats and balls on them were much smaller. IIRC, these valves used stellite balls and stainless seats. The idea was that the very hard stellite ball would deform the softer stainless seat to give a good seal. Since the ball could rotate, there would be little or no sliding on the seat and consequently very little wear.

I don't think you'd want to do a conventional lapping operation on a valve like this and hopefully it won't be necessary since the ball shouldn't wear the seat. If the seat does get worn or otherwise mangled, I think you'd have to make up a tool to lap it; something with a stationary ball shaped end that could be used to lap the seat.

I think the ball might bear on a chamfered surface, rather than a spherical one. That's been the case with other valves I've had to reshape the seats for with spherical discs. They were not PRR, so given the standard RR of the world had their own standards, i could be mistaken here.....

dave

Thanks, Hugh and Dave, I think you both are on target. The ball does bear on a chamfered surface. In fact, I believe it is a removable seat in that it has two lugs in the center of the bore. The seat looks to be a 45 degree bevel. A tool could probably be used to "clean" up the surface in lieu of removing the seat to turn a new face. Lapping seems to be out of the question.

An 'ol timer once told me, "The Pennsylvania Railroad was the Standard Railroad of the World - 'cause all the rest were Deluxe." LOL :)

-Don Fenstermacher