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STOP Cooling Your AODD Pump Air Hose to Eliminate Recurring Symptoms

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Hello, RCIA Family!

Over the 30 years of experience with these Air Operated Dual Diaphragm Pumps, we, at Pressure Washer Products noticed that some pumps seem to have recurring issues.  These symptoms present as frozen mufflers (with ice), air motors that seem to fail too frequently, foamy output  and a few others.  These symptoms don't hit just one AODD Pump manufacturer.  It seems to occur across the brands.  It always seems to occur in the most humid of climates, to a select few users and often in the bigger pumps .  

We pride ourselves on carrying the best products available for the best prices as well as providing free technical support to you.  These symptoms were baffling until we discovered a blog entry by All-Flo.  Contrary to a lot of information out there, the air from the compressor should not be cooled.  This means that you shouldn't submerge the air hose supplying the AODD pump in water.

I apologize in advance.  We do not wish to create anything other than adding to the vast resource we have all created here on RCIA.

I copied and pasted the whole entry below.

Air operated diaphragm pumps have earned a reputation in the industry as the low maintenance, easy-to-operate pump option–and rightfully so. However, seasoned diaphragm pump operators know the importance of getting clean, dry air to their pumps in order to avoid a common challenge: freezing. Built-up ice can block your pump’s exhaust system, resulting in slowing or stopping of production. This post will briefly explain how freezing happens as well as several steps All-Flo has taken prevent freezing in our air operated diaphragm pumps.

How Freezing Occurs

Compressed air expands as it runs through the air operated diaphragm pump and becomes very cold very quickly, sometimes dropping down to -10°F. These low temperatures typically are a result of using the pump at high-discharge pressures. Cold air can’t hold as much water vapor as warm air, so this creates a condition known as “super-saturated air,” when the air contains more moisture than it can hold in a stable condition.

Ice forms when that super-saturated air impacts a cold surface, such as a bend in an exhaust pipe or some place that acts as a seed surface for vapor to condense on. Points of impact build up ice for two reasons:

  1. They provide a place for tiny ice particles in the air to stick. Any points of impact—anything that sticks out into the air flow—becomes a place where ice build-up can occur.
  2. The surfaces are colder, so they accumulate ice through deposition faster. Deposition is where vapor in the air turns directly into solid ice on a surface. Ice buildup is highly dependent on the surface temperature. In the same way that wind-chill is the worst when you are facing directly into the wind, surfaces that are impacted by cold air will be colder.elbow-185x300.png

One step you can take to reduce the freezing problem is to install a dryer on your compressor and only run clean, dry air through your pumps. Removing the muffler—including the muffler plate and rubber seal—is one solution that usually eliminates icing completely, as ice typically only forms on those components. However, the increased exhaust noise usually makes this option impractical for most users. Adding a dryer should be the first step to minimizing the freezing issue.

Fluids Being Pumped Can Contribute to Freezing
Fluids with a higher viscosity will cause the pump to work harder and could contribute to more ice build-up.

For example, consider a 2” All-Flo pump running at 60 psi inlet air pressure. If this pump is running at 10 psi discharge pressure, the temperature at the exhaust will be around 42°F. However, if this same pump is running at 55 psi discharge pressure (closer to its maximum capacity) the temperature at the exhaust will be about 2°F.

As the pump approaches its maximum capacity, the temperature at the exhaust significantly decreases, which can result in freezing.

hole1.jpg

Normal Single Muffler

Preventing the Problem Through Research

We are constantly examining and testing our pump designs to minimize the risk of freezing. So, even if you don’t have a dryer installed on your air compressor, All-Flo pumps have built-in mechanisms to keep the risk of ice build-up at bay. Some of these design features include:

 

hole21.jpg

Muffler Plate with Heat Sink. All-Flo research showed that ice buildup could be dramatically reduced by adding a large heat sink to the muffler plate

 

  • Straight exhaust path. The fewer turns the air has to take, the fewer opportunities there are for ice to form and accumulate. But when surfaces obstruct or redirect air flow, ice can form (see Figure 1).
  • Single exhaust. At All-Flo, we have engineered all our pumps to have a common, single exit port for the main exhaust, allowing cold air to exit directly into the muffler with minimal contact with impinging surfaces.
  • Thermally engineered muffler plate

In an effort to continue offering the finest engineered diaphragm pumps available, we are continually researching and testing new pump designs and configurations using real-world tests along with the latest mechanical and thermal Finite Element Analysis software. One of the newest pump designs All-Flo will soon release features an exhaust system designed to function as a heat-sink, drawing heat to the inside surfaces from the surrounding environment and the rest of the pump, effectively preventing those surfaces from becoming cold enough for excessive ice buildup.

http://all-flo.com/blog/how-all-flo-is-breaking-the-ice-in-the-aod-pump-industry/

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I disagree. The problems people are having are not due to air line hose length or cooling...they are caused by excess water in the airline. Even if a pump does not ice up, removing excess air line water is best practice. And removing excess air line water by implementing passive airline cooling by running long lengths of hose or by running the hose through water IS, within CFM limits,  the most cost effective way to reduce moisture problems in the context of a properly designed AODD pump system. Let me explain my reasoning: 

All Flo states very clearly in the article that the best possible solution (all other AODD Pump manufacturers will tell you the same thing) to air end icing is to remove the water from the air stream. It states right in the article... "Adding a dryer should be the first step to minimizing the freezing issue."  Let me explain the reason for running an air line through water to cool the air charge. Once you understand this, you will understand the entire reason for this recommendation.

1) In an Air Diaphragm pump system, water line moisture removal is best practice when engineering a system. No professional compressed air operated system is ever engineered without airline water management and it is recommended by every air diaphragm pump manufacturer as best practice, regardless of whether they engineer icing resistance into the air valve.  

2) Of the three most commonly utilized methods of removing entrained excess airline moisture, a passive water separator is the only practical and cost effective method to remove airline moisture in a mobile cleaning system. Properly sized Desiccant systems are too large and too expensive for mobile AODD use and 120 or 240 Volt Refrigerated air driers are not an option for most mobile cleaning systems due to power usage. Thus, passive air line drying via a Passive Water Separator is the solution that is practical and likely to be implemented. 

3) Passive water separators work most efficiently with cool air. 

WHY do you need to cool the air charge when you are running a passive water separator? Because passive water separators work by creating a vortex to disturb the air and drop the pressure with the goal of releasing excess moisture from the air stream. It is here that the air line temperature becomes an important factor. Compressed air coming from an air compressor is hot. Compress a gas and it gets hot, expand it and it gets cold. Anybody who studies basic gas physics knows that the hotter a gas is, the more water or other liquid it can hold. The hotter the gas is, the further away from the dew point it will be. The further from the dew point, the harder it is for entrained liquids to be separated from the gas. 

Anybody who lives in a southern or eastern US state will have experienced this. When the air is hot, it holds a lot of moisture and it becomes very humid. As soon as a cold front moves through, it displaces the hot air mass vertically and additionally disturbs said hot humid air mass. That humid air mass cools as it rises. As it cools and is disturbed, the moisture is released and you get rain as the moisture is squeezed from the air. While simply disturbing the air *will* remove some of the moisture, it is nowhere near as efficient as both disturbing AND cooling the air. Cooler air simply cannot hold the same amount of moisture as hot air because the molecules are closer together leaving less space for water molecules. This is why cold winter air is so dry and why refrigerated air driers work. It is also why icing in pumps occurs in the first place...as the air decompresses it cools rapidly and the cold air can no longer hold the moisture which is then released. THIS is the entire point of air line cooling.  

Location Location Location.

Where you place the water separator is important. Too many times I've seen designs which show the water separator placed right next to the output of the air compressor. This is completely incorrect from an efficiency standpoint. The water separator must be as far from the compressor and as close to the pump as possible so the air charge can be cooled. The way to properly implement a water cooled airline system is by running a long length of air line out of the compressor, through a tank and only then into the water separator. 

Cooling the air charge makes it much easier and more efficient for a properly engineered, efficient water separator to effectively remove the entrained moisture from the air stream by getting the airline temperature down closer to the dew point. This is why it makes total sense in the context of an AODD system with a passive water separator to cool the compressed air BEFORE it runs into the water separator. It is the entire purpose of running either long lengths of airline, or running the airline through water. IF you cool the air AFTER the water separator, it will not work. And if you do NOT remove the moisture, then you will get excessive icing. A pump running dry air will not have moisture problems. 

The REASON I recommend running the air line through a water tank prior to the separator for a contractor who runs a fresh water rinse or buffer tank on their rig is because it highly cost effective and it is fairly effective on AODD pump systems up to about 20 CFM. Above this CFM rate, an after cooler with fan should be considered as an add on as it is more efficient than long line or water cooling. It goes without saying that you need water in the tank for this to work. 

Why Remove the Water at All? 

So, why is it so important you reduce the air moisture from the air on any properly engineered air diaphragm pump system? If the systems are designed to handle airline moisture, why bother?

1) Because it is best practice, recommended by all AODD pump engineers, and in field experience has proven its worth. I've rebuilt, run, sold and tested nearly every pump known...ARO, Wilden, Price, Crane Deming, Yamada, Marathon, Versa-Matic, Dayton, Sandpiper...and yes All Flo. Matter of fact, the entire REASON I started running and recommending proper water separation systems is due to severe icing and stalling issues I had with a pump. That pump was a 3/4" All Flo Kynar/Teflon. They will ALL stall out if there is too much airline moisture. Of them, the least prone is the ARO Expert series, Price, and Sandpiper S1 series. The worst is the Yamada. The All Flo is in the middle...as long as that expanded plastic muffler is taken off.  

2) Because you WILL lose pump efficiency. Cooler, drier compressed air is more dense and thus efficient than hot wet compressed air. Compressed air is expensive to produce, so getting the maximum amount of efficiency from the system is  simply good design and operational practice. Yes, it CAN make a difference in the distance you shoot. 

3) Excess airstream moisture creates premature wear on the air end components. I've seen blown O-rings from water slugs in the spool. It can also create corrosion and scale deposits in the interior metal pump components such as spool/sleeve and pilot valves. I've cleaned and replaced plenty of rusty and corroded spool valves from pumps I've rebuilt over the past few years. Below is one from a Yamada NDP-25 1" Kynar/Teflon pump which is currently in my shop on my bench with a severe air end corrosion problem. This pump will not operate and requires an entirely new spool valve and sleeve assembly. I've also replaced a number of air end valves on 3/8" All Flo pumps with rusted air valve springs. Point is...it is best practice to design a system to limit the amount of air line water going through your pump.  

IMG_0658_zpst2tjaqsh.jpg

Now, yes it is absolutely true that if you do NOT run a water separator, then keeping the air charge hot will help minimize icing as it keeps the air temperatures high, but it will NOT necessarily eliminate it. Your pump will not operate efficiently, will be prone to stalling and it can be subject to premature wear. Field experience and plenty of rebuilds has shown this wear issue to be true. Running a system without a water separator should not be an option. Air charge cooling and water separation/drying is the de facto standard throughout the entire compressed air industry and is best practice for any professional air diaphragm pump or any other compressed air operated system.  

"But water separators don't work". I've had this comment made to me plenty of times. Typically if somebody is having an issue with a water separator, it can nearly always be traced to one of three problems. 

First, because the water separator design sucks and doesn't work properly.

Second, the water separator is incorrectly installed near the compressor output and thus is running far too hot and not working efficiently...if at all.  

Third, the water separator is too small and is being overwhelmed. 

The heat we deal with by cooling the air stream and placing it far down line from the compressor...see above.

Poor design is easy...buy a Tsunami. Fixed.

But the sizing is something that is rarely talked about and the fact is a lot of people running air diaphragm pumps are using undersized water separators that are WAY TOO SMALL for the constant high CFM air usage. Passive water separators are typically not designed for constant high CFM air flow and the CFM ratings on them assume small burst usage such as air tool use and not constant high CFM throughput rates as is the case with an AODD system. Add to this the fact that the separators are often run right next to the compressor output and thus are far too hot to be very effective plus the fact that many of the separators out there are of poor quality and questionable design (cough...Harbor Freight...cough) and it explains why so many people don't believe water separators do much.

Sizing wise as a general guideline, what I have found to be most effective (and consultation with the engineers at Tsunami has borne this out) is to run a significantly oversized water separator. A larger separator has the capacity to handle the constant high CFM throughput. It gives you enough surface area to be effective and aids in the cooling. A 10 CFM compressor running constantly in a humid environment can overwhelm a 3/8" 20 CFM water separator. This happened to one of my clients and it was solved by upgrading to a larger separator after consultation with engineers. 

Thus, the recommendation is to run an air system up to 6 CFM with a 20 CFM 3/8" separator. An air system up to 25 CFM with a 1/2" 50 CFM separator, and a 26-75 CFM system should be run with a 3/4" 120 CFM separator. I run a 120 CFM 3/4" separator on my air screw rig and 1/2" 50 CFM on our 20 CFM piston compressor rig and we never EVER get icing or stalling. My experience trying just about everything passive has shown that the Tsunami passive separators are the best. I use and recommend them to all my clients and do not sell them so I have no skin in that game.  

So...in conclusion...I believe a cooled airline in the context of running a properly engineered AODD system with water management utilizing a properly sized, correctly engineered passive water separator IS absolutely appropriate and is indeed the best way to go. 

Edited by PeakOfPerfection

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I understand and appreciate your explanation as we all try to work together to provide only the best to our customer base.  

We recommend that the regulator/filter and separator are not right up on the air valve of the pump to avoid physical stress on the air valve.  I've personally crimped many sets of hoses to put it somewhere in the middle.  I upside the hoses as I think I remember doing for you!

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No personal attack implied or taken. We disagree on the premise and that is why I laid out my counter argument and the technical reasons as to why I believe that running Air Line Water management and cooling systems is, in my belief, necessary in a mobile AODD based cleaning system. Personal experience running hundreds of different kinds of pumps in varying moisture conditions up through pouring rain at 40 degrees F has proven this out. The issue is that most clients are new to AODD pump systems and they don't realize what it takes to properly run a compressed air system driven effectively using high volumes of air.  Reliability is one of the key advantages of running an AODD based pump system, but those systems can be made to be unreliable if you don't know the nature of the way a compressed air driven system functions.

It is why I explained that dropping the temperature of the compressed air is ONLY effective when a properly engineered and correctly sized water separator is placed inline and fed with air that is as close to the dew point as possible and that you are correct that without proper water separation, that you can get more icing through line cooling ONLY. What I am saying is that line cooling in and of itself is not enough. Good water separation in combination with air line cooling is the key. The entire reason for cooling the air charge is to significantly increase the efficiency of the water separator which is all too often undersized. Cooled air run in through a well engineered, properly sized water separator is the absolute best way to feed the driest air to the AODD air end  in a mobile cleaning system. That setup assures the most reliable AODD pump operation under varying environmental conditions and helps to increase the life of the air end components, meaning extended service life.

The setup I recommend has solved a lot of stalling problems for guys on pumps from numerous different manufacturers, including All Flo. It is also increasingly necessary as you go up in pump size as the volume of compressed air running through the system increases exponentially as does the moisture management issues. 

Edited by PeakOfPerfection

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Atlas1   

@PeakOfPerfection    Kevin, do you think that a 50' or 75' coil of 1/2" air line, cooled by ambient air only, would be sufficient to condense the air line moisture, or should I plan on running the line through a water tank? (In my area our hottest summer days are in the low 90's with pretty high humidity)

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just my 2 cents but don't run it through a water tank haha we run 4 1in air setups each with a 10 -15ft lead. Having a 75 ft coil just means it takes longer to hit the pump. I am sure someone will chime in and say how wrong this is but I am just telling you how it is. Our pumps have never frozen we have high humidity. We do run a water separator which takes out water but coiling 75 feet of air hose is just a waste IMO. Hell if your going to coil 75 feet why not coil 200 :) now there is an idea!

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Atlas1   

Thanks for your input. I am definitely going to have a Tsunami and regulator right before the pump. To clarify my earlier question, I should mention that I do believe that running the hose through my water tank is a good idea, but my roof cleaning equipment is on a trailer and my buffer tank is on my truck, so letting a "longish" coil of hose act as a condenser would be a bit easier than running it through the buffer tank, IF it will work.

The fact that "it takes longer to hit the pump" is the entire goal of the longer hose....giving the moisture time to condense before reaching the Tsunami. My only concern is whether or not it will be effective enough as a condenser (compared to running it through the buffer tank)

Of course, 50 or 75 feet was mentioned just for the sake of the question....if 10, 15, 20 feet, etc will work, then that's what I'll go with.

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I suggest you keep everything as simple as possible, especially in the beginning. If and only IF you learn over time that you need to go with something more complicated do it then. I seriously doubt that going to the trouble of running your air line through the buffer tank is even worth considering at this point. 

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Atlas1   

I suggest you keep everything as simple as possible, especially in the beginning. If and only IF you learn over time that you need to go with something more complicated do it then. I seriously doubt that going to the trouble of running your air line through the buffer tank is even worth considering at this point. 

I agree with you. That's why I'm asking if Kevin thinks a coil would work well enough as a condenser. A coil of hose is about as simple as it gets, in my opinion. 

I just want to make sure my pump won't have problems freezing up. As I said earlier, if I can run a 10' air hose and not have trouble, then that's what I want to do. But, if I NEED to run a longer hose to ensure the moisture will condense enough to get removed, then that's what I want to do. What you said in your post makes sense....I just hate having to go back and change things. I'd rather do a bit of overkill to begin with than have to keep making changes. 

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I agree with you. That's why I'm asking if Kevin thinks a coil would work well enough as a condenser. A coil of hose is about as simple as it gets, in my opinion. 

I just want to make sure my pump won't have problems freezing up. As I said earlier, if I can run a 10' air hose and not have trouble, then that's what I want to do. But, if I NEED to run a longer hose to ensure the moisture will condense enough to get removed, then that's what I want to do. 

Your going to get mixed answered man don't over think it like Shingle Brite said. We have 2 rigs both with no more than a 15 ft lead and we have never got close to ice in the pump. If you feel better at night making a 100 FT coil then do it. What Lori posted is from the MANUFACTURE so it should hold some weight. Right now its 32 outside yesterday it was like 70 and we have had 0 issues. Having a long coil may trap water but 1. water sep catches most of the water and 2. your pump is not going to freeze lol so keep it simple man your not going to lose much by having a coil nor are you going to  gain a lot having a 10 ft lead.. Do whats easy for your rig.and make changes as you learn and grow. You will never know until you do it yourself because everyone is going to have different thoughts.

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I agree with you. That's why I'm asking if Kevin thinks a coil would work well enough as a condenser. A coil of hose is about as simple as it gets, in my opinion. 

I just want to make sure my pump won't have problems freezing up. As I said earlier, if I can run a 10' air hose and not have trouble, then that's what I want to do. But, if I NEED to run a longer hose to ensure the moisture will condense enough to get removed, then that's what I want to do. What you said in your post makes sense....I just hate having to go back and change things. I'd rather do a bit of overkill to begin with than have to keep making changes. 

More than likely if you do have issues it will be very sporadic. You might go weeks without anything going wrong then one day you have to unhook your quick disconnect on your airline to the pump once or twice which fixes any stalling issues every time then you might go weeks again with no issues. Like CAP said above, don't over think it. It will drive you nuts and usually won't happen anyway. 

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A longer hose doesn't work to condense the moisture, it works to cool the air so it can be condensed by a water separator. The more CFM your compressor had and the higher throughout through your system, the mote important airline moisture management is. I've had dozens and dozens of calls over the years for stalling issues with all different pumps.  Even a cheap water separator and a coil of hose is better than nothing. 

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Lots of good information on this thread.... FWIW we run a water seperator and removed the muffler after the first "ice-up" and haven't had an issue with it since...we run a 1/2 All-Flo and any moisture blows right out out instead of being trapped inside behind the muffler.

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A longer hose doesn't work to condense the moisture, it works to cool the air so it can be condensed by a water separator. The more CFM your compressor had and the higher throughout through your system, the mote important airline moisture management is. I've had dozens and dozens of calls over the years for stalling issues with all different pumps.  Even a cheap water separator and a coil of hose is better than nothing. 

I agree with you Kevin and I think that is what he should do to get started-a cheap water separator and a coil of hose and If he has lots of issues then he needs to get more serious about it.

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