An oxygen concentrator is a wonderful machine … when it works. Attempts to diagnose and repair a your concentrator when it fails can be very frustrating. But understanding just a few principles of operation may turn frustration to success.
Principle #1 Remember your sand box.
If you have ever played with a sieve in a sandbox, you already understand the science behind an oxygen concentrator. The air we breathe contains about 78% Nitrogen and 21% Oxygen. The other 1% is composed of a few other gasses. An oxygen concentrator is a sieve that lets Oxygen molecules through and holds back the Nitrogen molecules.
So you need to picture some poor quality sand with about 80% pea gravel mixed in. It’s nice and dry, so when you scoop some up in your sieve and shake it a bit over a bucket, you end up with some nice, beach quality sand and a sieve that’s still got a lot of pea gravel in it. Dump out the gravel into another bucket and do the same thing over again. Slowly but surely you fill your sand bucket with some nice sand. This is like the tank of oxygen you accumulate with an oxygen concentrator. The pea gravel dump pile is the Nitrogen that hisses out of the concentrator muffler. Take the muffler off, and you can get a better feel of the process.
Principle #2 – Respect the destructive power of moisture
Now, you might recall that when you get some wet sand in your sieve, the process doesn’t work so well anymore. You might need to shake it more and everything starts to clog up. Moisture causes lots of problems for an oxygen concentrator as well. Once it starts to condense in the sieve material, the sieve begins to break down. It would be like your sandbox sieve falling apart or getting rusty so that either everything just goes straight through or it gets completely plugged and nothing goes through. The sieve material in an oxygen concentrator is in the form of little clay pellets that are treated with zeolite. This material does a great job sorting out the Nitrogen from the Oxygen, but is very vulnerable to moisture.
If the sieve material has been exposed to moisture and has begun to break down, you will begin to see signs of this process with dust that starts blowing out of the exhaust mufflers. It is best to take care of the problem as soon as possible, because the dusting will only lead to more problems. It will begin to disrupt the valve operation and may even totally clog up the mufflers to the point where the Nitrogen can’t exhaust anymore. Chances are, by this time the sieve material is ruined and is not filtering out the Nitrogen anymore.
What to do. Unfortunately, if your sieve material is breaking down, your concentrator sieve beds will need to be rebuilt. The sieve bed needs to be opened up, old material dumped, and new sieve material put in. Sieve beds are typically in the form of two aluminum tubes with some screens and a spring to hold the sieve material in place. These need to be carefully cleaned, inspected for damage, and carefully put back together so that it is sealed up tight. If you’re not up for the challenge of rebuilding the sieve bed, you can send the beds in to us for a re-build.
Principle #3 Valves need to operate flawlessly.
Rebuilt sieve beds may not be the whole solution. There is a good chance that the dust from degraded sieve material has found its way to the valve set. The valves are your arms working the sieve in the sandbox: dig up some sand, hold it over the sand bucket, dump out the gravel into the gravel pile, do it all over again and again and again. If you’re sloppy, you’re going to get gravel in your sand.
In an oxygen concentrator, two sieves are at work together. When one is sifting, it is also at the same time helping to clean out all the Nitrogen being exhausted by the other sieve bed. The valves direct a certain quantity of air for a certain time into the sieve. Too much air, and it is like the sieve overflows and Nitrogen spills into your oxygen, diluting it. If the Nitrogen isn’t dumped properly, the next cycle is ineffective and disrupts the rhythm.
The valves need to open to let compressed air into the sieve for a certain time. Oxygen flows out the other side through an orifice and a check valve. As the air valve closes, it opens a second port to release the Nitrogen trapped in the sieve back into the surrounding air. A second valve lets compressed air into the second sieve. As it fills, some of the oxygen leaving the other end helps force the remaining Nitrogen out of the first sieve.
The valves are typically a spindle that slides back and forth to direct the gas flow. A solenoid pushes the spindle back and forth. When electricity flows through the coil of wire in the solenoid, the magnetic field generated pushes a plunger to move the spindle. The spindle needs to move freely. Dust or contaminants can interfere with its movement so that the air is not precisely measured or timed properly. A careful cleaning of the valve often will fix a sticky valve, but sometimes even when it seems to be operating smoothly, only a new set brings the precision needed for proper operation.
Principle #4 Check valves and orifices may seem insignificant, but they’re not.
What looks like little connectors for oxygen tubing are actually precision parts that work together with the air valves to direct the Oxygen and Nitrogen flow. Orifices are precisely sized holes that limit the flow of Oxygen. In a concentrator, they are often used to allow a limited amount of Oxygen to push out any remaining Nitrogen left after exhausting from the de-pressurized sieve. If it gets plugged, Nitrogen stays in the sieve and ends up contaminating your oxygen supply. The check valves prevent any excess oxygen from flowing back into the sieve. Make sure the oxygen hoses are clear of debris, you can blow air through the orifices, and the check valves work. You should be able to blow through one way, but not the other. They need to be oriented so that the oxygen flows to the oxygen tank and not back.
Principle #5 More O2 flow is not better
A simple thing to overlook when trying to figure out when the O2 purity isn’t what it should be is excessive oxygen flow. Bring back to mind the sieve in the sandbox. The sieve is only so big. It will only hold so much sand and pea gravel. If you exceed the capacity, extra material is going to fall over the sides and not go through the sieve. Try operating your concentrator at a flow rate that is lower than the maximum rating. If you get good oxygen purity at a low flow rate, but it starts to fall off as you approach its rating, you might have some oxygen leaks. An oxygen leak won’t be measured by your flowmeter. Use some soaping water to look for leaks and fix them.
We sell and service most brands of industrial oxygen concentrators, stock parts, and do all we can to keep oxygen concentrators healthy. We also sell and rent oxygen meters to determine the oxygen purity of a system. A diet of clean, dry air is proven to greatly extend their life. They are designed to handle a limited amount of moisture, but it is risky. Continuous use, just like regular exercise, will also extend life. Startup on a humid day will be hard on them. Hot humid air from the compressor is liable to condense in a cooler sieve and begin the cycle of damage. If the suggested remedies do not solve your concentrator problems, feel free to give us a call.