Nitrile ball check valve?

[vk7krj]

To (hopefully) cure persistent sealing problems, I mn going to change my 5 inch gauge NSW Z12 boiler water feed check valve from a steel to nitrile ball. After much searching, I can't find anything specific on the angles, diameters, widths etc. for the nitrile ball check valve.
Anyone have any data or thoughts on this- width of the seat, angle of the seat, etc. specifically for a nitrile ball?

Ken.

 

[Bruno Mueller]

For steel balls, the free flow should be approx. 80 % of the ball diameter. With steel, the seat is flat. The ball is hammered into its seat.
Nitrile balls become soft when heated and tend to migrate into the seat with the same dimensions and jam.
Therefore, the seat should be made with a 90° countersink and the diameter of the nitrile ball should be approx. 40% larger than the free passage.

 

[vk7krj]

Thanks Bruno, that's exactly the information I need

 

[Actionman]

Visit your local auto transmission shop, tell them what you are doing and ask if they have an old valve body you can have. There are usually several viton check balls inside. These are good for oil at up to 200c. Usually 6mm or 1/4".

 

[Charles Lamont]

With steel, the seat is flat. The ball is hammered into its seat.

Gently. One smart tap with a soft (eg brass) and preferably guided punch.

 

[vk7krj]

That's a good idea Actionman- I have already ordered the balls from Winters, but a trip round the gearbox reconditioners for more spares won't go amiss.

And Charles- thanks, but we have already been down that route a couple of times- it worked on one check valve, but for reasons unknown it didn't work on this one. So I will try a coned seat & nitrile ball this time.
The loco came from the deceased estate of a friend- basically a sound build, with just a few small problems to sort out.