|
|
|
|
|
|
- Check valves are unidirectional flow control
devices used to eliminate potential damage caused by backflow.
- Flow in the desired direction will cause
a mechanism such as a piston, disc, or ball to open the valve, while backflow causes the valve to close.
- Check valves with a soft seat (such as
Buna-N, Viton, and PTFE) provide a bubble-tight shutoff.
- CRACKING PRESSURE is the minimum psi required
to open a valve.
- TEST DEVICE TO DEFINE CRACKING PRESSURE
- SPRING LOADED CHECK VALVES (also
known as silent check valves) have a spring-assist mechanism (controlled by the flow) to open and close the valve. For horizontal
and vertical use.
- BALL CHECK VALVES use a free-floating
ball, which "unseats" to permit flow in the desired direction and "seals" against the seat to prevent backflow. While fluid
is flowing, the ball rotates constantly, equalizing wear on the ball and valve seat. They can be installed horizontally and
vertically in upflow applications, and in downflow applications if spring loaded.
- SWING CHECK VALVES direct flow through
the use of a swinging disc, which requires only minimal back pressure to close the valve. Swing check valves with a spring
seat faster.
- They can be installed horizontally and vertically
(when installed vertically, flow must be upward)
- Vertical-lift (gravity) check valves
have a disc floating in the seat that opens by upward flow pressure.
- For vertical piping runs only.
__________________________________________________________________ |
|
|
- Cv FACTOR (coefficient of volume) is the amount
of water (in gpm) that will pass through a fully open valve at 1 psi with 1 specific gravity (60° F). For pressure
drop other than 1 psi, use this formula:
_________________________________________________ |
|
|
|
|
