Video Post: Air Logic’s Umbrella Check Valve Explained

The following text is the transcript of the Air Logic educational video on umbrella check valves.

What we’ve been making a lot lately is umbrella check valves.

How the Umbrella Check Valve Works

If you don’t know how an umbrella check valve works, it’s shaped like an umbrella of course. You apply pressure in some through-holes and then as that pressure increases the umbrella is going to lift up, just like a big umbrella in the wind, and your flow is going to go around it.

Air Logic’s In-house Designs

These are both just a nice design, and they’re also well suited for us. We design and manufacturer both our own tooling and our own plastic parts here at Air Logic. We can control a lot of the aspects of the umbrella check valve design; that includes how thick the center section is inside of an umbrella check valve, the surface condition, how much we let the overall movement happen.

Customizable Flow Control Solutions

We’ve been having a lot of success with those on the low cracking pressures and also dialing in an exact cracking pressure. We have standard cracking pressure, something like 3 inH2O or 0.11 psi, and then people will come to us and say “Hey can you do 0.2, can you do 0.3?” and so we can make those adjustments inside the check valve. And we just get great performance out of it, because again we have a hard seat inside there with a nice soft elastomer. We can adjust a lot of different factors inside the umbrella check valve to make it work how our customers need it to.

If there’s anything there that we can help you with, please reach out to us air-logic.com! Would love to hear about your application and what you’re working on, thanks!

Video Post: Cracking Pressure in Check Valves

The following text is the transcript of the Air Logic educational video on issues with check valves.

Intro

Alright, I want to make a video just about talking about cracking pressures and check valves here. Cracking pressure is the amount of pressure you need to open the check valve essentially. Not fully open it but where it just starts to crack open, where it just barely gets a little bit of flow going through the check valve. That’s the cracking pressure. Another way to think about cracking pressure is the amount of pre-load that’s internal to the check valve and wants to keep it closed. Normally when you have a check valve there’s some amount of spring force, and if there’s no pressure either way, the check valve is closed. That amount of force is the pre-load.

So that pre-loaded force has to overcome in the flow direction in order to get flow through your check valve. You can imagine there’s some relationship then between the amount of pre-load, the cracking pressure, and how well the check valve seals.

Technical Trade Off

The harder you keep that check valve closed, the better seal you’re going to have if everything else is constant. Generally if you need a really tight seal, you’re going to want a higher cracking pressure. But higher cracking pressures come with their own problems because generally as you start applying pressure in the forward direction you want flow to occur. So then there’s this relationship you have to decide on in your check valve of what’s that balance between how good of a seal do I need and how much cracking pressure can I get away with for my application.

In a perfect world a lot of check valves won’t have any cracking pressure. As soon as there was a little bit of forward pressure the valve would be completely wide open. That’s just not possible from a practical standpoint and so we have to make the tradeoffs again between that preloaded force and the cracking pressure and how good of a seal we get.

Cracking Pressure Tolerance

One last thing I wanted to talk about then was the tolerance of the cracking pressure. There are some things that are just inherent to any check valve design. Things like:

• mechanical stack up
• the spring rate tolerance
• the durometer tolerance inside a check valve

Those will all certainly impact the cracking pressure tolerance. But there’s one thing that is really going to impact it from an application standpoint. That is the fluid that’s going through the check valve. When we make a check valve, we test it with air pressure to make sure that cracking pressure is correct. But if you’re putting a different fluid through there (that could be a lubricated air, that could be water, that could be a chemical) it’s gonna get in between all the components inside the check valve. When the check valve goes to close, there’s gonna be a little bit of that fluid left there and that’s gonna impact how much the check valve wants to stick or not stick closed.

This isn’t such a big deal when you’re talking about some higher pressures but when you get to lower pressure, especially let’s say under one psi, those little sticking forces actually do add up to something and will actually impact how much it takes to open the check valve. Something to think about there and I’ll just encourage you to test it in your application with your fluid and just see if you get different results in air versus whatever fluid is going through your system.

So we talked about what cracking pressure is kind of some of the things internal to the check valve that affect that and then also some things that can affect the tolerance in there. We love talking about check valves especially for OEM applications. We provide check valve solutions to a lot of different industries, so reach out to us we would love to talk to you about your application and find something that works for you guys! Visit air-logic.com if you want some samples or some help with your application!

Video Post: Common Issues with Check Valves

The following text is the transcript of the Air Logic educational video on issues with check valves.

Intro

Hey everybody, my name is John Hayden from Air Logic. We’re talking about some common issues with check valves today. This goes for all check valves, not just at Air Logic, and things we’ve seen across the industry.

Decrease in Performance

So, one question I get from time to time is:

Hey I got this check valve it tests right initially, but after it’s been in my application for a while, the performance drops off what’s going on?

I would say a lot of times this comes down to lubrication.

It’s common in the industry for a lot of manufacturers to add a lot of lubrication to their check valve, and it makes the check valves test really nice especially right after they’re produced. Lubrication helps seal, so from a leak rate perspective, lubrication is going to take up any inconsistencies at the check valve seat and give you a really nice seal.

This is especially true for lightweight check valves with lightweight cracking pressures. It’s also going to add some consistency to the cracking pressures as well.

Lubrication Degradation

But what can happen though is depending on the application, what the flow rate is through there, if there’s any liquid, or any way for that lubrication to wash away, after a while the lubrication goes away. And then what you’re left with is a check valve that can stick a little bit or just not operate as consistently as it did when it was first assembled or first put into the equipment. This is something to think about if you’re having any issues with check valve performance that’s maybe degrading over time.

Anyway, we got some more videos like this talking about specific issues with check valves, so check us out on LinkedIn or at Air-Logic.com.

Thanks!

Video Post: Brief Overview of Check Valves

A Brief Overview of Check Valves

The following text is the transcript of the Air Logic educational video on check valves.

Intro

Hey guys, today we’re talking about just the basics of check valves in a system. Air Logic makes inline check valves for miniature applications, but check valves are used all over the place. They’re one of the most basic valves in any hydraulic or pneumatic system. From a really simplistic standpoint, they give you flow in one direction and no flow in the other direction. So, really basic from a functionality standpoint, but when it comes down to it, there’s a whole host of different types of check valves out there. When you get into the finer details of what makes a check valve right for an application, there’s just a lot of different aspects that go into it and so a lot of different designs come out of that to fit the different needs. So, we’re going to talk about some of the things you might want to think about when you’re specifying a check valve for your application.

Nonreturn Valve Cracking Pressure

One of the first things you want to think about when you’re going to specify a check valve for your application is the cracking pressure. The cracking pressure is this term we use to say when does a check valve open. So, again, from a basic standpoint in the flow direction you’re going to get a flow through the check valve, but the cracking pressure is going to determine exactly when that starts. So, you might have a very low cracking pressure check valve that’s almost essentially a zero. Right at the zero point, you’re going to get flow. Or you might have a cracking pressure that’s much higher, 5 or 10 or 20 psi cracking pressure check valve. That means even in the flow direction, as you start applying pressure, you’re not going to get any flow in that direction until you exceed the cracking pressure. So, this is important for your application because it depends where your operating pressures are and when exactly you want that flow to occur.

Pressure Relieving Applications

So, in a pressure relieving application, you’ll have your normal operating pressure that your circuit is running at and then you use a check valve that’s above that somewhere so that if something goes wrong in the system the check valve is going to release excess pressure. It’s a really economical way to do pressure relieving versus using like a back pressure regulator or a more expensive relief valve. A check valve is usually a lot cheaper and so it’s good for high volume applications where you’re going to be using a lot of these things and you want a safety device in the circuit that’s going to protect your device from any excess pressure.

Flow Rate in Both Directions

The other thing you want to consider when you’re specifying a check valve is your flow rate in both directions. The flow rate in the forward direction is going to tell you how much flow you’re going to get in the normal operating circumstances when you’re just trying to flow through the check valve. Also, you want to consider your reverse flow. So, you might say, well I thought the check valve didn’t give you any reverse flow, right, but in practical terms, all check valves are going to make some tradeoff between how well they seal and how much back pressure they can handle and so you’ll get some amount of back flow or people will call that a leak rate in the backwards direction and so you want to consider the type of check valve and it’s specified leak rate or reverse flow for your application as well.

Other Considerations when Specifying One-Way Valves

So, then lastly there’s a couple other things you want to consider. Things like the materials that are used in the check valve, you want to make sure those are compliant for your application whether you’re running a certain type of fluid through there or a certain type of gas, you want to make sure that those materials are compliant to the ones in the check valve. And then also your connection type: what size tubing you’re using and what type of connections you’re going to have for the check valve.

Outro

So those are the basics of what to think about when you’re specifying a check valve. We’re going to have some more videos getting into more in depth topics on this so come check us out either on LinkedIn or at Air-Logic.com.

Thanks!