A Guide to Understanding How Check Valves Work

While you might suspect inefficiencies and added expenses for misused industrial items, there is
research to show their real costs.

If your facility is using the wrong kind of valves to modulate or regulate flow in and out of your
system, you’re going to have issues. You need to learn how a check valve works before you try
adding one to your system.

The general definition of a check valve is a valve that only allows flow in a singular direction and
works automatically, will open in positive system pressure but then will close when system
pressure drops to prevent reverse flow.

Here are four of the most common types of check valves and how they function.

1. How Swing Check Valves Work

If you’re installing a swing check valve or a tilting disc valve, you’re going to have a clapper and
disc setup. There is a convex angle on the upstream side. Over on the downstream outlet side, you’ll
find that it’s flat.

If you’re looking for an API 600 valve, you’ll find the disc swings on a hinge. That disc’s hinge is
mounted on the bottom of the valve’s bonnet.

API 5D valves are a little different. They’re usually constructed as a cast pocket with a drop-in pin
and shaft array. The bushing arrangement is carefully set to ensure that the clapper is going to turn
on.

2. How Ball Check Valves Work

If you’re installing a ball check valve, you’re going to be putting together a ball clapper that’s likely
spring-loaded. O-Rings provide sealing at pressures that stay below cracking pressure. They’re built
to be durable while remaining flexible based on whatever conditions arise.

The only downside of the spherical design is that they’ll wear out from prolonged use. They require
lots of frequent maintenance and could wear down over time. If you find that you’re having to do
too much maintenance, this might not be the valve for you to rely on.

3. Consider Diaphragm Check Valves

If you’d prefer something with a rubber diaphragm clapper to flex open when under pressure, a
diaphragm check valve is for you. When pressure increases on the upstream side over the
downstream side, the diaphragm opens up. When pressure is balanced or it lowers, the diaphragm
clapper closes and seals.

This is a good choice for a durable and tight fit. However, you may have to switch out the rubber
diaphragm over time as the valve wears down.

4. Stop-Check Valves Are a Little Different

If you’re looking for something with a secondary control mechanism, consider using a stop-check
valve. A stop-check valve is a hybrid between a shutoff valve and a check valve. When the handle
(or actuator) is in the “closed” position, the valve will always be closed regardless of system
pressure. When the handle is in the “open” position, the valve will operate like a check valve,
opening and allowing flow in only one direction and closing immediately when back pressure or
reverse flow is applied.

Sometimes, the flow increases to a point where you have to intervene. A stop-check valve gives
you the control you need in this case.

Learning How A Check Valve Works Is Half the Battle
When you’re trying to eliminate inefficiencies in a system, you can’t be wondering how does a
check valve work. You need to know how they work within your system, what makes the type you
use best for your system, and when to replace old valves.

When it’s time to pony up for a replacement, check out our guide to make the right decision.