Piston Ring Failures - becoming more frequent?

I've getting the impression that piston ring failures on main line tours are becoming rather too frequent of late. A couple of recent ones IIRC are Cromwell at Cleethorpes and a Black 5 down south last week, and I think there have been others this year.

Seems to be more than just coincidence? Could there be have been a change in oil or ring materials now in use? Any tribologists out there?

All thoughts and further examples welcomed ............

 

Good one Sheff, Pistons/ rings on the larger standards had a reputation for being none too clever and perhaps this is still the case

 

It could be down to a change in oil spec. or a variation in material used for the rings. However it could just be down to the current design and method of lubrication. It may well be time well spent redesigning the valve heads etc. to give improved reliability and service life in conjunction with attention to the lube system.

 

Or it could just be that the internet means that everyone, knows everything, immediately it happens?

 

Unless a valve head actually broke, broken valve rings don't ususally do much damage - they just get smashed up and end up in the drain cocks!

 

I thought the failures were actually Piston rings as opposed to Piston Valve rings?

 

I'd be interested to know if people make their own or buy them in, these days? I generally make them because of cost and I know of a couple of other railways that do.

 

I the past i've bought them from Precision Products in Chesterfield and never had any trouble with them. The lads at Ribble have just made a set for Bagnall 2680. Incidently the last set of piston rings i bought were about £150 per ring. The cost of the ring pattern plus material for 4 rings worked out at £200 in total so if you have the time and ability to make your own then a significant saving can be made.

 

I've not had any problem with rings that I've bought, except the price. Just made some for a steam brake @ £28 for the billet which compared favourably with the £105/ring quoted elsewhere. Enough material left for another couple of rings if we need them.

 

Hope to be talking toa British Aerospace tribolohist soon. Would be pleased to hear of specific issues people are concerned about re lubrication systems and their design.