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

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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Six Steps to Compressed Air Optimization: Step 2 – Find and Fix Leaks.

Since air compressors use a lot of electricity to make compressed air, it is important to use the compressed air as efficiently as possible.  The compressed air system is considered to be the “forth” utility behind gas, water, and electricity.  It is necessary for pneumatic systems, but it is the least efficient of the utilities.  For every $1.00 that is put into making compressed air, you only get roughly 5¢ of work from it.  EXAIR has six simple steps to optimize your compressed air system.  Following these steps will help you to cut electrical costs, reduce overhead, and improve your bottom line.  In this blog, I will cover the second step – find and fix leaks.

One of the largest problems affecting compressed air systems is leaks.  That quiet little hissing sound from the pipe lines is costing your company much money.  A study was conducted by a university to determine the percentage of air leaks in a typical manufacturing plant.  In a poorly maintained system, they found on average that 30% of the compressor capacity is lost through air leaks.  For a 100 hp compressor, you are losing 30 hp into the ambient air.  To put a dollar value on it, a leak that you cannot physically hear can cost you as much as $130/year.  That is just for one inaudible leak in hundreds of feet of compressed air lines.  For the leaks that you can hear, you can tell by the chart below (**Note 1) the amount of money that can be wasted by the size of the hole.  Unlike a hydraulic system, compressed air is clean; so, leaks will not appear at the source.  You have to locate them by some other means.

Most leaks occur where you have threaded fittings, connections, hoses, and pneumatic components like valves, regulators, and drains.  The Optimization product line from EXAIR are designed to help improve your compressed air system, and the most effective way is to eliminate leaks.  The Ultrasonic Leak Detectors can find the air leaks, and the Digital Flowmeters can monitor your system for air leaks.  With both of these products included in your leak preventative program, you will be able to keep your compressed air system running optimally and reduce the “hidden” cost of leaks.

Ultrasonic Leak Detector

EXAIR Ultrasonic Leak Detector:

When a leak occurs, it emits an ultrasonic noise caused by turbulence from the gas escaping.  This ultrasonic noise can be at a frequency above the audible level for human hearing.  The EXAIR Ultrasonic Leak Detector can pick up these frequencies and make the leaks audible.  With three sensitivity ranges and LED display, you can find very minute leaks.  It comes with two attachments; the parabola to locate leaks up to 20 feet away, and the tube attachment to define the exact location in the pipe line.  Once you find a leak, it can be marked for fixing.

EXAIR’s Digital Flowmeter w/ USB Data Logger

EXAIR Digital Flowmeter:

With the Digital Flowmeters, you can continuously monitor for waste.  Air leaks can occur at any time within any section of your pneumatic area.  You can do systematic checks by isolating sections with the Digital Flowmeter and watch for a flow reading.  Another way to monitor your system would be to compare the results over time.  With the Digital Flowmeters, we have a couple of options for recording the air flow data.  We have the USB Datalogger for setting certain time increments to record the air flows.  Once the information is recorded, you can connect the USB to your computer, and with the downloadable software, you can view the information and export it into an Excel spread sheet.  We also offer a wireless capability option with the Digital Flowmeters.  You can have multiple flow meters that can communicate with your computer to continuously log and record the flow information.  Once the flow information starts trending upward for the same process, then you can use the Ultrasonic Leak Detector to find the leak.  It can also give you a preventative measure if a pneumatic system is starting to fail.

Compressed air leaks will rob you in performance, compressor life, and electrical cost.  It is important to have a leak preventative program to check for leaks periodically as they can happen at any time.  The EXAIR Ultrasonic Leak Detector and the Digital Flowmeters will help you accomplish this and optimize your compressed air system.  Once you find and fix all your leaks, you can then focus on improving the efficiency of your blow-off devices with EXAIR products and save yourself even more money.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

**Note 1: Chart was published by Compressed Air Challenge in April 1998 – Rev. 0

Intermediate Storage Tanks & How To Size Them

When evaluating processes that utilize compressed air and adhering to the Six Steps to Compressed Air Optimization, intermediate storage proves to be a critical role coming in at step number five. Intermediate storage tanks may already be in place within your facility and often times can be implemented as modifications to aid existing lines that are struggling to maintain proper availability of compressed air to keep the line at peak performance.

EXAIR Receiver Tank in 60 Gallon Capacity

When determining whether or not a production line or point of use compressed air operation would benefit from a receiver tank/intermediate storage we would want to evaluate whether the demand for compressed air is intermittent.  Think of a receiver tank as a capacitor in an electrical circuit or a surge tank in a water piping system.  These both store up energy or water respectively to deliver to during a short high demand period then slowly charge back up from the main system and prepare for the next high demand.   If you look from the supply point it will see a very flattened demand curve, if you look from the application side it still shows a wave of peak use to no use.

Intermittent Applications are prime for rapid on/off of compressed air.

One of the key factors in intermediate storage of compressed air is to appropriately size the tank for the supply side of the system as well as the demand of the application.  The good news is there are equations for this.  To determine the capacity, use the equation shown below which is slightly different from sizing your main compressed air storage tank.  The formulate shown below is an example.

Where:

V – Volume of receiver tank (ft3 / cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Header Pressure (PSIG)

P2 – Regulated Pressure (PSIG)

One of the main factors when sizing point of use intermediate storage is, they are being supplied air by smaller branch lines which cannot carry large capacities of air.  That limits your Cap value. The only way to decrease the V solution is to increase your Cap. The other key point is to ensure that all restrictions feeding into the tank and from the tank to your point of use are minimized in order to maintain peak performance.

If there are intermittent applications that are struggling to keep up with the production demands within your system, please reach out and speak with an Application Engineer.  We are always here to help and we may even be able to help you lower the demand needed by utilizing an engineered point of use compressed air solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF