Check Valves: Questions Answered

In summary, a check valve opens when the pressure on the poppet or closing device equals the pressure on the other side.
  • #1
78
1
http://en.wikipedia.org/wiki/Check_valve
from the above wiki link I have understood basic concepts on Check Valves


Suppose I Heat a gas ( air ) in a closed vessel.
It's temp and pressure increase. As soon as the pressure reaches ( or exceeds??) the cracking pressure , the valve opens and I transfer the heated gas to another vessel ( at a lower pressure and temp)
For How long will the Valve remain open
1: Till the pressure in the heated vessel drops below the Cracking pressure
or
2:Till the pressure in both the vessels is evened out ( ie the valve closes to prevent back flow)

Also are valves available that can be adjusted to work on different ( a small range of say 30-35 psi) pressures
 
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  • #2
A check valve will close when the forces acting on the poppet or closing device (swing checks) equilabrate. Forces on the poppet forcing it open include the pressure times a differential area and possibly gravity. Forces closing include the spring load and possibly gravity. You can do a free body diagram on the valving element to determine what pressure it opens or closes at. Generally, the opening and closing value is the same.

Check valves don't always seal up well on closing though. Like any valve, as the contact stress on the seat drops off, leakage occurs. The sealing surfaces might be in contact over most of the area, but leakage through the seat will occur if there's insufficient contact.

There are valves that can be adjusted over the range you need. Swagelok for example has http://www.swagelok.com/search/find...-1&item=c80b8fbe-343c-49a5-8ef1-2a086c6523b7", but I'm sure there are many others. Might want to do a search on adjustable checks.
 
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  • #3
thnx...
 

1. What is a check valve?

A check valve is a type of valve that allows fluid or gas to flow in one direction only. It is designed to prevent backflow or reverse flow in a piping system.

2. How does a check valve work?

A check valve works by using a disc or ball mechanism to block flow in the opposite direction. When fluid or gas flows in the desired direction, the disc or ball opens and allows the flow to pass through. When there is backflow, the disc or ball is forced shut, preventing the flow from reversing.

3. What are the different types of check valves?

There are several types of check valves, including swing check valves, lift check valves, ball check valves, and diaphragm check valves. Each type has its own unique design and functions differently, but they all serve the same purpose of preventing backflow.

4. Where are check valves commonly used?

Check valves are commonly used in various industries, including oil and gas, water treatment, HVAC, and manufacturing. They are also used in household plumbing systems, such as in sump pumps and water heaters.

5. How do I choose the right check valve for my application?

The right check valve for your application will depend on several factors, such as the type of fluid or gas being transported, the flow rate, and the pressure and temperature of the system. It is important to consult with a valve expert to determine the best type of check valve for your specific needs.

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