Hello everyone. Welcome back to Mako Products, Superlok TV.
Today we're going to take brief look at check valves. What they are,
how they work and ah, it should be a fairly short one so, let's get into it.
Alright, let's start with what a check valve does and how it accomplishes it. Um,
so basically what a check valve does is it keeps all of your media, gasses of liquids,
flowing in the same direction. So, it just prevents those gasses or liquids from
back flowing up your system, somewhat like a one-way street. You know, you can only move one
direction. Um, the way that this is accomplished is by having some kind of a sealed ball, or disk,
or some would call it a poppet. and it seals against the inside of the inlet of the valve.
These closures are often spring assisted, but they don't have to be. Um, especially some
of the larger swing valves work solely off of gravity and back pressure. Back
pressure an- actually closes that valve up preventing any back flow or backwards flow.
Alright, so let's look at an example of how you might use a check valve. Say for instance you were
working on a system that generates pressure into some kind of a reservoir, be it tank or cylinder.
Once that tank is up to pressure, more than likely the compressor would shut off to prevent over
pressuring of the system. When that occurs, after some of the pressure in the tank has been used,
that compressor is going to need to restart to gain that pressure back. If that is a high amount
of pressure already in the system, it's going to be a lot of work for that compressor to actually
restart and gain pressure back into that system. Adding a check valve into the system just after
the compressor, would allow the user to bleed the pressure off before the check
valve without having to completely drain the reservoir of pressure that's been built up.
So that the compressor is not under pressure before adding pressure back the system.
so, there are a couple different styles of check valve out there. Um, for larger applications,
more commonly the swing type is used. Um, this is the one that uses gravity on a- you know, heavy
disk that, as media pushes it open, um- it rises with the flow and then as soon as that flow stops,
gravity pushes that heavy disk back into place and the back pressure actually holds it closed.
For smaller applications, for- you know, instrumentation or- you know, smaller
plumbing needs, you'd probably have something like this, which is um, a ball type check. So, these
have just a small ball inside on a spring, and as pressure pushes on the ball, it opens up allowing
flow through. Those come in a variety of sizes. But, once you get up into kinda the medium size,
you're going to start seeing things where they have what is called a poppet. which is, a shaped
machined disk that is on a spring. And so, it'll push out of the way like a ball, but it's got more
of a flat sealing surface. The spring along with the back pressure allows that to slam
closed and keep closed for a bubble tight seal. One of the last things we need to consider when
choosing a check valve for your application is the cracking pressure. what cracking pressure is,
is the pressure at which this valve is going to open to allow media to flow through. Um, this can
range anywhere from a third of a PSI to 600 PSI just depending on the valve that is chosen and
what spring that's inside of it. Some check valves are even adjustable, you know, you can- you can
tighten that spring a little bit to add pressure to your cracking pressure.
It is important to mention that cracking pressure is not the only thing you obviously
have to overcome because back pressure is still used to close these valves. Say you're working
on a system that is already containing 2,000 PSI. You want to add more pressure to the system. Your
check valve has a- you know, 12 lb. spring in it. As you add pressure, you're actually going
to have to overcome 2,012 lbs. before any media will actually begin to flow through that valve.
Because once you hit 2,000 PSI you've actually only reached an equilibrium point. There is a
12 lb. spring still holding the valve closed. One more thing to consider with cracking pressure
is actually gravity. If you have a check valve at the bottom of a 20' piece of tubing. the media in
the line will actually add or reduce pressure from your cracking pressure depending on how
much it weighs and whether the check valve is headed in an upward or downward direction.
alright, now I think that is going to about do it for check valves. If you guys are still with me,
I appreciate you for sticking around till the end of the video. Certainly,
let us know down in the comments if there is a topic or something else that you'd like to see
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us out on Superlokworld.com. There you'll find all kinds of information about our products,
other types of valves and fitting that we carry. And with that, we'll see you in the next video.