Using nitrile balls in clack valves

Recently been bothered with unreliable injector operation which I eventually traced to the clack valve on the injector feed to the boiler (GWR 5" Pansy). Despite replacing this with a a self made and purchased unit, using both SS and Bronze balls I failed to get a perfect seal. My eventual cure was to use two clacks, one at the boiler and one fitted close to the injector.

The injector now operates to my satisfaction.

Looking further at this issue,I wondered if there was any mileage in using nitrile balls in these clacks.

No one in my club has any enthusiasm for nitrile but cant say definitively why.

Can anyone give me an opion on the use of nitrile ?

They have always worked well for me with a perfect seal every time. I have seen it written that they might extrude into the hole that they are supposed to seal but it has not happened to me and if it did I should just replace it, possibly with a bigger ball.

Mick

Further to the above, when using a nitrile ball, I have found a note to myself to use the next size up. I think that I was advised this by the supplier.

Mick

I seem to recall that Nitrile balls should be used with a conical seat as the normal sharp edge seat used for metal balls can damage the soft rubber?

John

That seems like a very good idea John, and one that I shall use in the future.

Mick

I have not used nitrile, but I have used the stainless steel ball. I always give the ball a tap with a punch and hammer to seat it in the base of the valve. I put a nut on the thread and stand it on the surface plate. This works very reliably.

In the BIG world of steam boilers I have neve known rubber be used anywhere?

Brian

John thanks for the hint on using a conical seat.

I'll try one with a seat edge cut to as close as I can get to the angle of the ball circumference at point of contact with the clack seat.

I note that there are also different hardnesses of rubber avaiable from the pro suppliers. I can only find any comment on the rubber parameters on the Reeves site but still looking

Ian

Re the big world of steam boilers.................Latex rubber was used extensively for the flap valves in air/steam pumps and also rhinoceros hide etc etc etc Willy Bailey

Ball valves are used in hydraulic systems and if they didn't seat properly we used use a brass punch and give the ball a hefty whack! This usually sealed the valve.

Tip.

Whack the ball to form the seat. Then replace the ball with on that hasn't been deformed by being whacked.

I may be wrong, but I think I read somewhere (prob ME) of someone using SS, or bronze balls, and an O-ring as the seat.

Ian S C

One of LBSC's tips from (I think) Shop, Shed and Road. It may also be in the Tich book too.

I've used O ring seats for clack valves with success after seeing an article by Jim Ewins on his Loadstar locomotive. Just make sure that the O ring is retained so that it can't lift with the ball. They make good check valves for lubricator oil supplies.

A commercial design of clack valve uses a poppet fitted with an O ring that seals on a flat seat.

A possible alternative to stainless balls is silicon nitride (ceramic) balls. These are said to be harder than and have a better surface finish than steel. Not my idea but Roger Froud on the MECH forum is using them in his Speedy build. It will be interesting to see how they work out.

John

I used to use them till one got irretrievably pushed into the water pipe. I only use metal now!

Come on folks, not a very good tip is it - and it mostly does not work well enough for me.

O rings are the answer I think. Either O ring on a top hat with fluted shank or ball sitting on an O ring works best for me.

Can anyone recommend a Uk supplier of Viton rubber balls suitable for clack valves please?

Thanks

John

Nitrile balls have a habit of floating, problem becomes obvious with vertical clacks below the boiler water level when the boiler is not under pressure they will leak. Normally once pressure starts to build ( 3-4 psi ) they seal effectively. A solution to this is have a small screw in the top of the clack valve to force the ball down when not under pressure and stopping any leaks. Challenge here is to remember to unscrew it before running or you quickly start wondering why your injectors will not work.

Sorry too quick on the post button

Maccs Models normally have a good supply at reasonable prices

Polly Models stock 1/8, 5/32, 3/16 and 1/4 viton

7/32 is difficult to find in UK - try US.

Edited By Clive India on 15/04/2017 11:30:03

Thanks both.

Polly models has viton balls.

Macc models looks like Nitrile only.

Advice much appreciated.

Nitrile balls are a bit cheaper. I will use them in the tender pump and axle pump.

Viton have a higher temperature rating so I will use these for clacks, snifter valve and whistle valve and hope I can keep them separate from the Nitrile ones.

John