Check valves vs priority valves?
 

Does anyone know the answer to the question in this forum?

http://www.hostmybb.com/phpbb/viewto...mforum=founder

AFAIK
Check valve Is one way valve Allowing flow in one direction
Priority valve Shuts off at a predetermined level to lower priority services maintaining pressure to the higher

A check valve as stated prevents fluid flowing in the wrong direction (also known as a one way valve)
A priority valve cuts off fluid to a heavy user in the system in the event of low quant. or press. thus keeping the avail. fluid press. for essential systems(ie. gives priority to essential systems)
:)

Brgds

SB03

Thanx for the answers but I think the question is more regarding the difference in construction of the valves rather than how they work... =)

Well I'll have a go......
The simple check valve or a non return valve (NRV). Imagine a pipe with a flange which goes around the inside, only a thin one mind, we don't want to restrict the flow too much. A a thin rod is located accross the diameter of the pipe with a hole in its middle. Through this hole is a further rod, quite a long one, and attached to that is a round plate that sits on the flange and at the other end is a nut that won't pass through the hole. Lets say the pipe is horizontal and the plate sits to the left of the flange, then fluid or a gas or what ever can flow from the right to the left with just a little restriction because the medium in the pipe would push it open. But...... if the medium flowed from left to right it would push the plate on to the flange thereby closing off the pipe. As effective as a stop cock;) now for the priority valve.......

Now for a simple priority valve.......

Same valve as the NRV but this time a spring is on the rod thats attached to the plate keeping this this plate pushed against the flange. Your medium is flowing from right to left. You have an important system to the right of the plate and all pressures are normal so the plate is designed to be pushed open by system pressure and feed a not so important system to the left of the plate. So if pressure is lost to the right of the plate the spring will over come system pressure and close the plate (valve) to ensure the important system has the priority. ah ha

That all make sense chaps. Sorry if it sounds too simplistic but I dont know how technical you are:O

Priority Valve.............Check Valve
http://img77.imageshack.us/img77/715...alve0gd.th.jpg http://img88.imageshack.us/img88/550...alve5ny.th.jpg
HIH