Pop Valves

[nimbus]

I have a max size copper boiler (to the Australian code) of 200mm dia. and 17.5L (water capacity) So my safety valves need to be reaonably large to avoid accumulation under steaming test.
My frustration is this, I just cannot get the pop action to be consistent without chatter at 100psi. Smaller sizes sem to be relaible. I have tried the design ideas reccomended by a Finnish guy whose ideas do work well. However the valves sometimes refuse to close properly, resulting in the quick application of the coal shovel!!! Is there a positive solution to this problem in the larger sizes??

[pault]

Hi Nimbus
You could try increasing the size of the vent holes in the top of the valve. It could be that the holes are on the small side which causes the chattering. As the valves lift you may be getting an increase in pressure in the upper part of the body which is enough to close the valve momentarily. Increasing the vent holes sizes very slightly should prevent this. Using a very slightly higher spring rate may have the same effect. Hope this helps
Regards
Paul

[nimbus]

Thanks pault,
I will try that. At the moment I have two holes blocked up as I discovered that this seemed to make the pop action more positive, but maybe I have gone to far.
These valves are certainly not as easy to get right as people think.

[suctionhose]

No, open the vent holes to stop chatter as the gentleman says...

Ideally the vent holes should total 150% of area of seat.

Have done much experimentation with Pop Valves. Can make 'em do exactly what I want now! Usually takes a 1/2 day of tuning upon first steaming.

Is that you Mike? Might see you at the club in October...

Ross