Determining Leakage Rate and Cost of Compressed Air Leaks

The electricity costs associated with the generation of compressed air make it the most expensive utility within an industrial environment. In a   poorly maintained compressor system, up to 30% of the total operational costs can be attributed simply to compressed air leaks. While this wasted energy is much like throwing money into the air, it can also cause your compressed air system to lose pressure. This can reduce the ability of the end use products to function properly, negatively impacting production rates and overall quality. Luckily, it’s quite easy to estimate the leakage rate and is something that you should be including in your regular PM schedule.

According to the Compressed Air Challenge, a well-maintained system should have a leakage rate of less than 5-10% of the average system demand. To estimate what your leakage rate is across the facility, first start by shutting off all of the point of use compressed air products so that there’s no demand on the system. Then, start the compressor and record the average time it takes for the compressor to cycle on/off. The compressor will load and unload as the air leaks cause a pressure drop from air escaping. The percentage of total leakage can be calculated using the following formula:

Leakage % = [(T x 100) / (T + t)]

Where:

T = loaded time (seconds)

T = unloaded time (seconds)

The leakage rate will be given in a percentage of total compressor capacity lost. This value should be less than 10% for a well-maintained system. It is not uncommon within a poorly maintained system to experience losses as high as 20-40% of the total capacity and power.

A leak that is equivalent to the size of a 1/16” diameter hole will consume roughly 3.8 SCFM at a line pressure of 80 PSIG. If you don’t know your company’s air cost, a reasonable average is $0.25 per 1,000 SCF. Let’s calculate what the cost would be for a plant operating 24hrs a day, 7 days a week.

3.8 SCFM x 60 minutes x $0.25/1,000 SCFM =

$0.06/hour

$0.06 x 24 hours =

$1.44/ day

$1.44 x 7 days x 52 weeks =

$524.16 per year

A small leak of just 3.8 SCFM would end up costing $524.16. This is just ONE small leak! Odds are there’s several throughout the facility, quickly escalating your operating costs. If you can hear a leak, it’s a pretty severe one. Most leaks aren’t detectable by the human ear and require a special instrument to convert the ultrasonic sound created into something that we can pick up. For that, EXAIR has our Model 9061 Ultrasonic Leak Detector.

ULD_Pr
Model 9061 ULD w/ parabola attachment checking for compressed air leaks

Implementing a regular procedure to determine your leakage rate in the facility as well as a compressed air audit to locate, tag, and fix any known leaks should be a priority. The savings that you can experience can be quite dramatic, especially if it’s not something that has ever been done before!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

EXAIR Supports your ROI Efforts

EXAIR not only has products that will reduce your air consumption, cost and noise levels but also has the tools to help you calculate the annual savings and Return on Investment (ROI). Sometimes you have the materials in house to make your own pneumatic tools so you get that piece of pipe in the maintenance crib, drill several holes and connect your compressed air. It works, your team is proud of the solution and everyone moves on to the next fire, right?

Several projects later you notice that your compressed air usage seems very high so a team is assembled and challenged with a cost savings program geared towards compressed air savings. EXAIR is the company that can help. We have Intelligent Compressed Air Products, Free Expert Technical Help and savings calculators that can be used to show the savings in your reports and presentations. EXAIR’s cost savings calculator will simplify the savings for each process you study and help your efforts in purchase justifications.

We have several examples of helping our customers save money such as this blog by one of our talented Application Engineers. You will realize more than cost savings as you should also see significant sound reductions and safety improvements as all of our products meet or exceed OSHA standard 29 CFR 1910.95 (a) which outlines allowable noise exposure for personnel and OSHA standard 29 CFR1910.242 (b) Dead End Pressure requirements.

When you begin compressed air cost savings program and have questions as to where to start, how to calculate and how to prepare your justifications please give EXAIR a call and talk with one of our many talented Application Engineers. EXAIR’s Intelligent Compressed Air products and Application Engineers will support all your efforts to decrease compressed air usage, reduce sound levels and increase the safety of your environment.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: Twitter: @EXAIR_EK

Top Ten Preventive Maintenance Items For Compressed Air Systems

Anything that has moving parts is, sooner or later, going to need maintenance.  One popular school of thought is “If it ain’t broke, don’t fix it.”  One major problem with that is, when it DOES break, you HAVE to fix it before you can keep using it.  That’s where preventive maintenance comes in: you get to choose WHEN you work on it.  This allows you to do that work at planned times that are convenient, and that have the least impact on your operations.

Patrick Duff, a production equipment mechanic with the 76th Maintenance Group, takes meter readings of the oil pressure and temperature, cooling water temperature and the output temperature on one of two 1,750 horsepower compressors. Each compressor is capable of producing 4,500 cubic feet of air at 300 psi. The shop also has a 3,000 horsepower compressor that produces 9,000 cubic feet of air at 300 psi. By matching output to the load required, the shop is able to shut down compressors as needed, resulting in energy savings to the base. (Air Force photo by Ron Mullan)

Compressed air systems not only have moving parts, they have parts that air moves through.  Periodic preventive maintenance can not only keep your system running; it’ll keep it running efficiently, meaning it costs less to operate.  Different types of air compressors in different environments will have different specific requirements, but following is a decent general list of ten items it might make sense to stay on top of:

  1. Intake vents. The air your compressor pulls in is going to go through some pretty tight passages.  Particulate can do some damage in there, and some of it will end up in your system where it’ll wreak havoc on your air operated equipment too.  Take care to keep your air compressor’s intake vents clean.  Many manufacturers and service professionals recommend a weekly inspection, and cleaning as needed.
  2. Lubrication.  Don’t be fooled by the term “oil-less” in an air compressor’s description.  This often means that there’s no oil in the air end.  The drive end is going to have bearings & moving parts that are lubricated.  Again, the compressor manufacturer will likely include periodicity and procedure for this in the manual.  This should include period oil (and oil filter) changes or grease renewal.
  3. Motor bearings.  Many air compressors are either direct coupled or belt driven by an electric motor.  Checking the temperature with a contact thermometer, or monitoring for changes in the ultrasonic signature (EXAIR Model 9061 Ultrasonic Leak Detector is a quick & easy way to do this) can give you indication of pending bearing failure.
  4. Belts.  Drive belts have a finite life span.  Vibration can also affect their tension and alignment.  If you have a belt driven compressor, check these out on a regular basis to make proper adjustments to the motor slide base.
  5. Lubrication, part 2. A friend of mine had a car that leaked oil.  He carried a couple of quarts with him…it was so bad that he had to add some every few days.  He called this replenishment system “self-changing oil”.  It isn’t.  Finding and fixing oil leaks is critical from both operational and housekeeping perspectives.
  6. Dryer.  Most industrial air compressors have a system that removes moisture from the compressed air before discharging into the system.  Different types of dryers require different types of maintenance.  Desiccant and deliquescent dryers, for example, will require media changes from time to time.  Refrigerated and membrane dryers will have parts like condensers or cartridges that you have to keep clean.  Keep up with the manufacturer’s recommendations, and you’ll have one less thing to worry about.
  7. Air leaks.  Air is free.  It’s literally everywhere, in great abundance.  COMPRESSED air is expensive, which makes leaks costly.  Good news is, compressed air leaks, like failing motor bearings (see #3, above) generate an ultrasonic signature, so you can get even more use out of an EXAIR Model 9061 Ultrasonic Leak Detector.  Find & fix leaks, and start saving money today.

    In addition to compressed air leaks, there are many industrial maintenance applications for Ultrasonic Leak Detectors. Contact an EXAIR Application Engineer for details.
  8. Filtration. Almost all pneumatically operated products work best with clean, moisture free air.  The compressor’s intake vents (see #1 above) and dryer (see #6 above) are there, primarily, to protect the compressor and the distribution system, respectively.  Good engineering practice dictates the need for point-of-use filtration.  EXAIR Automatic Drain Filter Separators have 5-micron particulate elements, and a centrifugal element to ‘spin’ out moisture.  Our Oil Removal Filters have coalescing elements to catch any trace of oil, and provide additional particulate filtration to 0.03 microns.  As filter elements capture debris, they start to clog, which reduces downstream pressure.  You should change these elements when the pressure drop across a filter reaches 5psi.
  9. Condensate drains.  Even the best dryers allow trace amounts of moisture into the compressed air system…even more so if the humidity in the area is high.  Properly designed compressed air distribution systems will have strategically placed drain traps to collect this moisture and rid the system of it.  They can be automatic, timed, or manual.  Inspect them periodically for proper operation
  10. Compressed air operated products.  Last but not least, make sure you keep up the maintenance on the tools and equipment that your compressed air system is there for in the first place.  Worn or damaged parts can increase consumption…and present very real safety risks.

EXAIR Corporation manufactures quiet, safe, and efficient compressed air products to help you get the most out of your compressed air system.  If you’d like to find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Save Your Compressed Air Today with These Simple Methods

When discussing ROI, return on investment, for an industrial compressed air system it is necessary to  understand what it costs to produce compressed air.  Generally we calculate that it costs .25 cents to produce 1,000 SCF (Standard Cubic Feet) of compressed air here in the Midwest of the United States. For our example let’s consider a typical 250 HP industrial compressor running 24 hours per day/5 days per week for 52 weeks.  This compressor can generate 374,400,000 SCF per year, using the industry standard utility cost for the Midwest of .25 cents per 1,000 SCF it will cost $93,600 to produce that volume of compressed air.

To avoid wasting money on compressed air generation it is extremely important to eliminate unintended or wasteful compressed air use in your plant. The two main offenders are leaks and open tube blow-offs.  While soapy water is a good method for discovering leaks, EXAIR offers the Ultrasonic Leak Detector.  This handy device allows leaks to be detected at distances of up to 20′ away! Also consider how safe and convenient it is to find leaks in overhead pipes while standing on the ground instead of on a ladder. Using a tool like this to do an entire system leak audit can easily result in many small leaks being identified and when fixed result in a large savings.

open tubes
Thirteen Open Tube Blow-Offs

Now let’s look at what an open pipe or tube may consume. A single 1/4″ OD copper tube can use 33 SCFM @ 80 PSIG inlet pressure.  Using the manifold pictured above as our example with 13 open tubes, each tube can consume 33 SCFM @ 80 PSI inlet pressure. With 13 open tubes running 24 hours a day, 5 days a week, 52 weeks per year equates to a total consumption of  160,617,600 SCF annually.  If we installed the EXAIR model 1100 Super Air Nozzle  using a simple compression fitting we would reduce the air consumption dramatically.  The EXAIR 1100 Super Air Nozzle consumes 14 SCFM @ 80 PSIG inlet pressure, running 24 hours a day, 5 days a week, 52 weeks per year equates to a total consumption of 68,140,800 SCF annually.  That change will save you 92,476,800 SCF annually which is equal to $23,119.20 and 24.7% of air compressor capacity!  These calculations are all based on continuous running applications, if intermittent operation is possible consider the EXAIR Electronic Flow Control for even greater savings.  The EXAIR Electronic Flow Control combines a photoelectric sensor with timing control that limits compressed air use by turning it off when no part is present

Open pipe blow offs also violate OSHA standard 29 CFR 1910.242(b) requirement for using compressed air for cleaning when pressurized above 30 PSIG. Not to mention they generally are louder than 90 dBA, which is the maximum allowable noise exposure without hearing protection under OSHA standard 29 CFR – 1910.95 (a). The EXAIR engineered Super Air Nozzle is a great way to avoid a OSHA fine.

A great product that will help you keep your fingers on the pulse of compressed air consumption and demand is by incorporating the EXAIR Digital Flow Meter.  This handy item mounts directly to the pipe.  The digital display shows the amount of compressed air being used in any leg of your distribution system.  The Digital Flow Meter is offered in sizes for 1/2″ – 4″ Schedule 40 Iron Pipe and 3/4″ – 4″ Copper Pipe.  It also is available with the Summing Remote Display that is prewired with a 50′ cable, it is powered by the Digital Flow Meter and with a push of the button will display either the current compressed air consumption, consumption for the previous 24 hours or the total cumulative usage.

The Digital Flowmeters are also available with wireless capability using the ZigBee mesh network protocol, data can be passed from meter to meter to extend the distance over which the wireless system can operate.  Each meter has a range of up to 100′ (30 meters). Or you can opt for the USB Data Logger option.  The USB Data Logger can store approximately 9 hours of readings if set to sample once every second or up to 2 years if sampled every 12 hours.

If you would like to talk about any of the quiet EXAIR Intelligent Compressed Air® products or our line of Optimization Products, feel free to contact me or any EXAIR  Application Engineer.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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