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I've had a couple of guys with 1" pumps running into issues with too much moisture. Particularly back east where you guys can drink the air. Compressed air water management is super important if you run larger pump systems (1"). However...even smaller pumps can benefit from proper water management. Understanding the management of water in your pump system will lead to longer pump life, fewer stalls and less downtime. 

Here are some of the factors and elements that go into a proper Air Diaphragm Pump water management system. 

Understanding Compressed Air Moisture. 

When you compress a certain volume of air, you also compress the moisture contained within that air. Taking the air at surface pressure and squeezing it down into a much smaller space will also take all the moisture in the air and concentrate it. Said water will accumulate in the compressed air tank (if you have one) and will find its way into the air stream which goes to your Air Diaphragm Pump. 

Water is less compressible than air and thus the larger percentage of water you have in the compressed air stream, the less efficient your tool or air pump engine will be. In addition, excess water accelerates the wear on the air end components in the pump. In worst cases. pumps can actually lock up when a giant slug of water gets into the air end. Here is how to deal with that excess moisture. 

How To Make Ice With Hot Air.

When you compress a gas, it gets hot. The hotter air is, the more moisture it can hold and the more difficult it is to remove that moisture from the air. This means that the air getting to your pump will have a potentially significant quantity of water in it. And this is where physics will bite you. You see, when you compress a gas, it gets hot...but when you DECOMPRESS a gas, it gets cold. Feel the air coming out of your air pump exhaust if you don't believe it.  So, here you have a large amount of water trapped in a compressed hot gas...now decompress it and freeze it. The result is ice. Said ice will block up the air end of your compressor, leading to pump stalling. The best way to overcome the excess water/hot air problem is to cool the air.

Drain Your Tank(s)!

Before anything...DRAIN YOUR TANK(S). If your compressor uses an air tank or tanks to store the compressed air, you MUST drain them religiously. They need to be drained with compressed air in them. Your tank has a drain on it, typically a petcock or screw valve. Drain them after every roof. Drain them when you are walking by the truck. Drain them when you take lunch. Keeping your tanks dry is crucial not only for more effective water removal, but also to the safety and longevity of your compressor. Yes, this gets loud but the drain outputs are nearly always threaded (or easy enough to change the valve to MAKE it threaded) and there is no rule that says you can't run a hose from the drain into a muffler, under the truck/trailer/etc. They even make automatic drains that are timed if you or your employees just flat out can't remember. 

Cool The Air

Now that your tanks are drained (you DID drain them...right?), we can move on to cooling the air. 

First: Run a long length of air hose. The longer the hose is, the more time the air coming from the compressor has to cool down. While this is not particularly efficient, it may often be just enough for the next stages to work enough to keep your pump free. 

Second: Water tank. If you run a fresh water rinse tank and you use a long length of hose...simply run the hose through the fresh water tank. The water in the tank acts as a large heat sink and draws heat out. Even better than this is to use a coil or loop of either copper or aluminum tubing in the tank as metal transmits heat far better than air hose. I don't recommend steel or black iron pipe as it will rust. PVC is absolutely a no no for compressed air as it tends to turn into a bomb. 

Third: Use an After-cooler. An after-cooler is a radiator for compressed air. Often combined with a 12V fan, this is one of THE most effective ways to cool the air coming from the compressor. Typically a well matched aftercooler will drop the air down to within 30 degrees of ambient which is more than enough for a mechanical water separation device to work effectively. Aftercoolers are surprisingly inexpensive, with a matched cooler and fan running under $200 for a 20 CFM setup. If you plan to use your compressor to also run a soda or other media blasting pot, this is a must. 

Fourth. Refrigerated cooler. This is the extreme and mostly not applicable to mobile compressed air roof cleaning pump uses. A refrigerated cooler takes the air down to a dew point of about -40F. That is cold enough that nearly every drop of water will be forced out. Harbor Freight sells a 115V Refrigerated cooler for about $400. You would need to install either an inverter or plug it into a customer's home in order for this to work. This is recommended ONLY if you plan to utilize your compressor to also either paint or do Soda Blasting (well, you DO own a compressor...it can be used for other things!) 

Removing the Water. 

Unless you use a refrigerated cooler (in which case you are DONE)...then removing the water from the now cooled air stream in a mobile air system is typically done mechanically.  

The most basic form of water removal is the water trap which is built into many filter/regulator systems. These work but are inefficient at best. That being said, if you have a very effective air cooling system, it may be enough. Remember, you do need to drain the water from your water trap. If you don't then you are right back to square 1. 

Dedicated water separators like the Tsunami are a better option, particularly when you are running larger truck mount or air screw compressors. However, there is a significant problem which limits even the most effective mechanical separator system...heat. 

 

 

Edited by PeakOfPerfection

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