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ARO Air Operated Diaphragm Pumps CRUSH the CompetitionAir Operated Diaphragm Pumps CRUSH the Competition

Several months ago I visited a customer in middle Georgia with the ARO fluid products rep. The customer we visited was using several different size Sandpiper AOD (Air Operated Diaphragm) pumps in their plant. They were having some serious issues with stalling, freezing up, and not getting long life out of the Sandpiper pumps. The main pump was used to unload their trucks and was a 2” non-metallic AOD pump. The ARO rep crossed the pump over to an ARO PD20P-FPS-PTT pump.

The customer purchased the ARO PD20 pump to replace the 2” Sandpiper they used to unload the trucks.

After a couple weeks I went back to check on how the pumps were performing.

The customer was ecstatic with the performance he was getting out of the ARO PD20 pump. They were not stalling or freezing up and the customer was getting better flow than they had been able to get out of the Sandpiper.

Normally when unloading the trucks, they would have to pressurize the tank at 30psi AND use the pumps on the tank to help the Sandpiper pumps get the flow they needed. With the ARO pump they did NOT have to pressurize tanks or use the pumps mounted on the tank and yet they were getting the same flow.

Needless to say, the customer is now looking to replace all their Sandpiper pumps with ARO pumps.

Over the years ARO has refined their AOD pumps and now provides the best “Total Cost of Ownership” pumps in the industry.

This is just one example of what ARO AOD pumps can do. Call us today and let us improve your production capabilities.

The Right Viking Pump for your Job

Some things can be made to work; but just because it works doesn't mean it's the best approach.

I had a customer in Columbus who was metering vegetable oil to spray on baked goods on a conveyor belt. The excess oil would drain to a pan and was then screened before recirculating to the pump.
Some 28 odd years ago, a surplus Viking H32 internal gear pump was installed with a direct drive 1HP 1750RPM motor. A variable speed drive and flow control needle valve were added to control the flow of the oil.

However, the actual flow needed is 1.5-2GPM and the Viking H32 is capable of 16GPM at 1750RPM even though the max speed for the pump is 1150RPM or about 10GPM. Also, the shaft was not being supported by a bearing bracket which is recommended for this pump and the pump had Bronze Bushings which are not suitable for this vegetable oil service.

To further complicate the problem the variable speed drive could not run slow enough to meter the oil without tripping the motor (horsepower is proportional to speed (Hz)) which left the flow control needle valve doing most of the metering work but this would easily clog with crumbs. The needle valve restricted flow causing the pumps 50PSI relief valve to be continuously open and bypassing, and creating backpressure and increasing power requirements limiting the variable speed drives effectiveness.

As a solution we installed a Viking G32 with carbon graphite bushings and a bearing bracket. We used a 3/4HP gear motor with 410RPM out for 2GPM at 60Hz, and utilized their existing variable speed drive.

This completely eliminated the needle valve and now flow control is done solely with the variable speed drive.

Finally we installed an Eaton duplex strainer downstream to better collect the small crumbs.

 

CFM for Air Compressors and Positive Displacement BlowersWhat is a CFM?

CFM stands for cubic feet per minute. It is the rate of flow of air or gas and is the basic unit of measure of performance for air and gas compressors, blowers and vacuum pumps. It indicates how much air a compressor or blower can move at a given discharge pressure.

Confusion usually develops when an additional letter is added before CFM, i.e. SCFM, ICFM, ACFM. Basically the prefix (S, I, A) indicates the conditions under which the capacity is measured.

SCFM is standard cubic feet per minute. This relates the CFM to a fixed set of standard conditions of atmospheric pressure (14.7 PSIA), ambient or inlet temperature (68 deg F.), and relative humidity (36% RH). AOL desktop gold customer support Standards expressed here are Compressed Air and Gas Institute (CAGI) standards.

ICFM is inlet cubic feet per minute. This is the CFM at actual inlet conditions at the point of installation. Again, the conditions are specified in terms of actual atmospheric pressure, temperature, and relative humidity.

ACFM stands for actual cubic feet per minute. This is generally measured at the discharge of the compressor, and is the compressed volume, minus any losses through seals, etc. This expression is erroneously used interchangeably with SCFM and ICFM and can be confusing. Air using equipment manufacturers will usually specify the air requirements as SCFM. Rarely will you see requirements specified as ACFM. When we do see this, we question it and probe for more specifics.

SCFM and ICFM can be used interchangeably if the standard conditions and inlet conditions are the same. With positive displacement compressors (rotary screw and reciprocating) and blowers, they will be very close and manufacturers will specify their advertised performance as SCFM. Only in centrifugal compressors and blowers will there be a significant difference.

Positive displacement compressors are designed for a specific discharge pressure, optimizing the performance to secure the maximum flow for a given horsepower. A compressor designed for 100 PSIG will deliver more CFM at a given horsepower than one designed for 125 PSIG. The speed of the air end (pump) is adjusted via gears or v-belts, or by adjusting the effective compression volume of the air end for this optimization.

Customers frequently ask what the capacity of a 125 PSIG compressor will be if they lower the pressure to 100 PSIG. The answer is “not by any significant amount”. The capacity is essentially the same at either pressure since the compressor is designed for one specific point. The converse is also true. A 100 PSIG compressor cannot be increased to 125 PSIG, as it will overload the motor due to the same effective CFM being compressed.

Pye-Barker Supply Co. sales engineers offer their expertise in evaluating your plant application and developing a compressed air system best suited for your needs.

Considerations for -100 Degrees F Dew Point AirMaybe you need really, really dry air.

Maybe that air is even dryer than -40⁰ F dew point achieved with a typical regenerative desiccant dryer. Maybe you need a -100⁰ F dew point. It’s a rare requirement, but there are applications for it. You would do well to consider Fick’s law before proceeding.

I’ll admit I wasn’t familiar with Adolf Fick, who in 1855 postulated his law of diffusion. I must have missed it in my years of sitting (sleeping) in a classroom. But I was struck by how this law applies to dry air when reading a section of the CAGI Compressed Air and Gas Handbook.

Fick’s Law states that “The rate of diffusion in a given direction is proportional to the negative of the concentration gradient.” Diffusion in this case means the process where two gases intermingle moving from a region of high concentration to a low one. In a compressed air system the law applies to the difference in moisture vapor outside the system to the dry air within the pipe.

When it comes to super dry air, that differential, or gradient, is quite extreme compared to moist ambient air. So any leaks in the piping downstream of a dryer will allow diffusion of atmospheric water vapor to enter the compressed air line. Even if it is at full line pressure.

The clear implication is that proper piping material should be used, and that a vigilant eye be maintained on any leaks in the piping. We have spoken about proper piping material before in our post here: Gardner-Denver Quick-lock Tubing.

But here’s a more startling fact mentioned in the CAGI handbook: To purge residual moisture out of a piping system downstream of a dryer takes an extra ordinary amount of dry air. The book states that tests to obtain a 94 deg. F dew point takes a mind-boggling (and expensive) 1,000,000 cubic feet of air dried to that dew point for every 1 cubic foot of piping volume. For reference a cubic foot of 1 inch schedule 40 pipe has a length of 166.7 feet.

What ever your air needs are, if you need extremely dry air then you need to talk with a specialist to make sure you have all your bases covered. Your system might not be able to handle the demand.

Gardner Denver Certified Technicians

I have run across occasions where the use of our certified Gardner-Denver technicians has saved the customer a lot of money and time.

A case in point was at a customer with five 500 Horsepower Gardner-Denver compressors. We received a call and were asked to look at a leaking main seal on one of the compressors. The customer was told by 'another' compressor repair AOL desktop gold support number company that the main seal would need to be replaced which would cost thousands of dollars for the seal and the labor to replace it.

Our technician evaluated the problem and within a matter of minutes found a faulty check valve that cost less than $10.00. The customer’s mechanics were also with our technician and learned what to look for should this problem arise on one of the other compressors.

This same customer also benefited from some in house training provided by our service manager.

We had a similar thing happen with another customer when they were told that their airend was bad on one of their compressors. Our service manager evaluated the compressor and found that the cushions in the coupling were bad and that the inlet valve needed to be repaired. We supplied the parts and the customer’s mechanic was able to complete their own repairs saving them a lot of money.

If you have a $50K or a $150K compressor it pays to have certified technicians who are trained on these compressors evaluate and resolve the problem. The cost savings can be huge.

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