Check Valve Operation

For the past several SmartTalks, we have highlighted Check Valve Operation - an in-depth look at how our valves operate. This SmartTalk concludes the final stages of this process.  To view an animated graphic of Check Valve Operation and the entire process, click here or on the picture below.



Stage 5: The Descent & Stage 6: Touch Down
Pressure decreases, internal components begin to move back

Stage 5: The Descent is when pressure in an application decreases, and the spring begins to pull the poppet back towards the shut or re-seal position. Watching the process closely, the valve’s poppet begins to shut following a different path. Note – the valve does not instantly return to the shut stage – a slight delay, hysteresis, occurs due to internal friction or a change in forces acting upon the valve. This lag does affect an application’s performance, but for most users it is so subtle that it is not even detectable. The journey back to re-seal is not instantaneous. These factors make a valve have a difference in their opening pressure and reseal pressure. In fact, the reseal pressure is around 20 percent below the opening pressure.

The poppet plays a key role during these stages because it is the connection between the spring and O-ring seal. The poppet sets the spacing between these two components – thus, it directly contributes to the actual pressure the valve operates at during all stages.

When the internal components (poppet, spring, & O-ring) continue to travel, they eventually make contact with the O-ring seat, also known as Stage 6: Touch Down. The valve will not seal well at this stage because there is no force pressing the O-ring back into the seat. As mentioned in Stage 2: Opening, O-rings and other components appear perfectly smooth, but when examining them under a microscope they have tiny imperfections – it is through these ridges and gaps that flow escapes. Therefore, the valve will not fully close until Stage 7: Resealing.

Stage 7: Resealing & Stage 8: Reset
Internal components are back in place & valve is ready to repeat all stages of Check Valve Operation 

In Stage 7: Resealing, the O-ring continues its journey back to the seat. Previously, the O-ring was only touching the seat, but now the spring force (via the poppet) has compressed the O-ring enough to hold it into place and create a seal against every gap.

This stage is particularly noteworthy for customers with applications that cannot drop below a certain pressure because reseal pressure will always be lower than the open PSI. For example, if your device requires a reseal pressure of 10 PSI, then you will want a valve with an opening pressure around 12 PSI. In addition, reseal pressures under 1 PSI may not be repeatable due to the low seat pressure. Thus, the more we know about your specific pressure requirements, the more precise your check valve’s performance will be.

To ensure accurate and reliable flow control, all of our spring-loaded valves have been extensively tested to determine their open, regulated, and reseal pressures.

Once the valve reseals, it is in Stage 8: Reset. The valve has returned to its original position and is ready to go through all eight stages of operation again.

#J02 Union
3/8" x 3/8" Tubing

#J04 Female Connector
3/8" Tubing x 1/2" NPT 

#J05 Male Elbow
3/8" Tubing x 1/4" NPT

#J06 Female Elbow
3/8" Tubing x 1/4" NPT

 

#J07 Union Elbow
3/8" Tubing



#J08 Branch Tee
3/8" Tubing x 1/4" NPT




#J10 Union Tee
3" x 3/8" Tubing



#J11 Run Tee
3/8" x 3/8" x 1/4" NPT