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.