Starting a Leak Prevention Program

Since all compressed air systems will have some amount of leakage, it is a good idea to set up a Leak Prevention Program.  Keeping the leakage losses to a minimum will save on compressed air generation costs,and reduce compressor operation time which can extend its life and lower maintenance costs.

SBMart_pipe_800x

There are generally two types of leak prevention programs:

  • Leak Tag type programs
  • Seek-and-Repair type programs

Of the two types, the easiest would be the Seek-and-Repair method.  It involves finding leaks and then repairing them immediately. For the Leak Tag method, a leak is identified, tagged, and then logged for repair at the next opportune time.  Instead of a log system, the tag may be a two part tag.  The leak is tagged and one part of the tag stays with the leak, and the other is removed and brought to the maintenance department. This part of the tag has space for information such as the location, size, and description of the leak.

The best approach will depend on factors such as company size and resources, type of business, and the culture and best practices already in place. It is common to utilize both types where each is most appropriate.

A successful Leak Prevention Program consists of several important components:

  • Baseline compressed air usage – knowing the initial compressed air usage will allow for comparison after the program has been followed for measured improvement.
  • Establishment of initial leak loss – See this blog for more details.
  • Determine the cost of air leaks – One of the most important components of the program. The cost of leaks can be used to track the savings as well as promote the importance of the program. Also a tool to obtain the needed resources to perform the program.
  • Identify the leaks – Leaks can be found using many methods.  Most common is the use of an Ultrasonic Leak Detector, like the EXAIR Model 9061.  See this blog for more details. An inexpensive handheld meter will locate a leak and indicate the size of the leak.

    ULD_Pr
    Using the Model 9061 Ultrasonic Leak Detector to search for leaks in a piping system
  • Document the leaks – Note the location and type, its size, and estimated cost. Leak tags can be used, but a master leak list is best.  Under Seek-and-Repair type, leaks should still be noted in order to track the number and effectiveness of the program.
  • Prioritize and plan the repairs – Typically fix the biggest leaks first, unless operations prevent access to these leaks until a suitable time.
  • Document the repairs – By putting a cost with each leak and keeping track of the total savings, it is possible to provide proof of the program effectiveness and garner additional support for keeping the program going. Also, it is possible to find trends and recurring problems that will need a more permanent solution.
  • Compare and publish results – Comparing the original baseline to the current system results will provide a measure of the effectiveness of the program and the calculate a cost savings. The results are to be shared with management to validate the program and ensure the program will continue.
  • Repeat As Needed – If the results are not satisfactory, perform the process again. Also, new leaks can develop, so a periodic review should be performed to achieve and maintain maximum system efficiency.

In summary – an effective compressed air system leak prevention and repair program is critical in sustaining the efficiency, reliability, and cost effectiveness of an compressed air system.

If you have questions about a Leak Prevention Program or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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Intelligent Compressed Air: Estimating Your Leakage Rate

waste

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

Ultrasonic Leak Detector: Because Leaks Won’t Find (Or Fix) Themselves

I once worked in an equipment repair shop with a small and simple compressed air system…just a 5HP single acting piston compressor that sat atop a 50 gallon tank, in the corner by “The Big Truck”. The majority of our work was field service, and management was big on maintaining our service trucks, so we checked tire pressures every Monday morning as we rolled out, and kept a tire chuck handy to ensure proper inflation. It was also used to supply a couple of air guns that were used at our drill press and soldering/assembly station. One morning, I noticed the air compressor was running when I arrived…I thought it was odd, because I knew for a fact it hadn’t been used in at least 16 hours, but that compressed air went someplace, right? We had a leak. Well, at least one.

This was mid-December, and the week between Christmas and New Year’s Day was characteristically slow, and typically devoted to a thorough shop cleaning. We also took the opportunity to get some bottles of soapy water and check for leaks at the handful of pipe fittings that comprised the system…for the uninitiated, if you have a leaky fitting, the escaping air blows bubbles in the soapy water (a cheap, messy way in other words). We found some bubbling, undid those fittings, cleaned them, and applied fresh pipe thread sealant (I don’t want to start any arguments, but I was taught that tape is more of a thread protectant than an effective sealing agent) and, in addition to replacing a couple of well-worn hoses, we were up and running.  And we never heard the compressor running first thing in the morning again.

Not all compressed air systems are as simple as that, though.  Many go from a room with several large & sophisticated air compressors, to corners of every building on the grounds.  Through valves & manifolds, to cylinders, machinery and blow offs, with more connections than you could soap-and-water check in a month.

In those cases, the EXAIR Model 9061 Ultrasonic Leak Detector makes short(er) work of finding the leaks.  With both visual (LED’s on the face) and audible (headphones) indications, even very small leaks are easy to detect with the parabola installed.  The precise location can then be found with the tubular extension.

EXAIR Ultrasonic Leak Detector “hones in” on the exact location of a leak in a compressed air line.

You’ll still have to fix the leaks yourself, but finding them is oftentimes more than half the battle.  And, once fixed, it can be worth a million (cubic feet of compressed air, that is.)

EXAIR’s Ultrasonic Leak Detectors are not only useful for finding compressed air leaks; they’re popular in a variety of other areas:

Additionally, they can be used to identify faulty bearings, brake systems, tire & tube leaks, engine seals, radiators, electrical relay arcing…anything that generates an ultrasonic sound wave.  If you’d like to find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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An Ultrasonic Leak Detector Helps with a Pressure Decay Leak Detector

Ultrasonic Leak Detector

A manufacturing company had a pressure decay leak system to check for leaks in compressed air housings.  Their detector was able to find leaks as small as 0.02 cc/min.  The leak program was designed for recording each housing with a batch/lot number and the corresponding leak data.  If the housing reached or surpassed the leak limit, the part would be marked and quarantined.  The pressure decay leak detector was a sensitive instrument, but it could not tell the operator where the leak was occurring.

How the pressure decay leak detector worked was by pressurizing the housing to a target pressure.  The flow valves would shut, isolating the housing.  After the pressure stabilized, the sensitive pressure sensors would pick up any loss in pressure over time.  If the leak limit wasn’t reached, a green light would indicate a good leak test.  If the limit was reached, a red light would indicate a failed leak test, and the housing would have to be segregated.

Reference Filter Housing

The housing design used a head, a bowl, a drain, and a differential pressure gauge.  The leak paths were numerous.  It could be at the drain, between the drain and the bowl, between the head and bowl, at the differential pressure gauge, and even in the casting of the head.  The heads were made from a die-casted aluminum.  If the process was not done properly, porosity could occur in the head.  The leak detector was sensitive enough to find any voids that would allow air to pass through the head casting.  With these many areas of potential leaks, it could be problematic if the reject rate was high.

For the application above, it is important to find where the leaks are occurring in order to create a corrective action.  In order to find the leaks, they purchased a model 9061 Ultrasonic Leak Detector from EXAIR.  Instead of pressure decay, the Ultrasonic Leak Detector uses sound.  Whenever a leak occurs, it will generate an ultrasonic noise.  These noises have a range of frequencies from audible to inaudible.  The frequencies in the range of 20 Khz to 100 Khz are above human hearing, and the Ultrasonic Leak Detector can pick up these high frequencies, making the inaudible leaks, audible.  The model 9061 has three sensitivity ranges and a LED display; so, you can find very small leaks.  This unit comes with two attachments.  The parabola attachment can locate leaks up to 20 feet (6.1 meters) away.  And the tube attachment can define the exact location.  With this application, they used the tube attachment to locate the leaks.  After retesting the failed housings, they found that 80% of the rejects were from a sealing surface.  They were able to replace or repair the o-rings.  10% of the leaks were coming from the drain.  3% of the rejects were leaking at the differential pressure gage.  Both the drains and the pressure gages could be replaced with new units.  7% of the housings had a porosity problem in the head of the housing.  For these, they were shipped back for evaluation to create a modification for a better casting.  The production manager shared with me that an extra vent hole was required to reduce the void.  This was a huge savings for the die-caster and manufacturing plant.

EXAIR Ultrasonic Leak Detector is a great tool.  It can be used in a variety of applications including compressed air systems, bearing wear, circuit breakers, refrigerant leaks, and gas burners to name few.  For the company above, it was a great tool to improve their assembly and testing process for their housings.  If you have an application where you need to find an ultrasonic noise, you can speak with an Application Engineer to see if the model 9061 Ultrasonic Leak Detector could help.

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

Discharge of Air Through an Orifice

My Application Engineer colleagues and I frequently use a handy table, called Discharge of Air Through an Orifice. It is a useful tool to estimate the air flow through an orifice, a leak in a compressed air system, or through a drilled pipe (a series of orifices.) Various tables and online calculators are available. As an engineer, I always want to know the ‘science’ behind such tables, so I can best utilize the data in the manner it was intended.

DischargeThroughAnOrifice

The table is frequently found with values for pressures less than 20 PSI gauge pressure, and those values follow the standard adiabatic formula and will not be reviewed here.  The higher air pressures typically found in compressed air operations are of interest to us.

For air pressures above 15 PSI gauge the discharge is calculated using by the approximate formula as proposed by S.A. Moss. The earliest reference to the work of S.A. Moss goes back to a paper from 1906.  The equation for use in this table is-EquationWhere:
Equation Variables

For the numbers published in the table above, the values were set as follows-

                  C = 1.0,      p1 = gauge pressure + 14.7 lbs/sq. in,    and T1 = 530 °R (same as 70 °F)

The equation calculates the weight of air in lbs per second, and if we divide the result by 0.07494 lbs / cu ft (the density of dry air at 70°F and 14.7 lbs / sq. in. absolute atmospheric pressure) and then multiply by 60 seconds, we get the useful rate of Cubic Feet per Minute.

The table is based on 100% coefficient of flow (C = 1.0)  For well rounded orifices, the use of C = 0.97 is recommended, and for very sharp edges, a value of C = 0.61 can be used.

The table is a handy tool, and an example of how we use it would be to compare the compressed air consumption of a customer configured drilled pipe in comparison to that of the EXAIR Super Air Knife.  Please check out the blog written recently covering an example of this process.

If you would like to talk about the discharge of air through an orifice or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Finding Leaks and Saving Money with the Ultrasonic Leak Detector

Locate costly leaks in your compressed air system!  Sounds like the right thing to do.

The EXAIR Ultrasonic Leak Detector is a hand-held, high quality instrument that is used to locate costly leaks in a compressed air system.

Ultrasonic sound is the term applied to sound that is above the frequencies of normal human hearing capacity.  This typically begins at sounds over 20,000 Hz in frequency.  The Ultrasonic Leak Detector can detect sounds in this upper range and convert them to a range that is audible to people.

When a leak is present, the compressed air moves from the high pressure condition through the opening to the low pressure environment.  As the air passes through the opening, it speeds up and becomes turbulent in flow, and generates ultrasonic sound components. Because the audible sound of a small leak is very low and quiet, it typically gets drowned out by by surrounding plant noises, making leak detection by the human ear difficult if not impossible.

ULD_Pr
Detecting a Leak with the Ultrasonic Leak Detector

By using the Ultrasonic Leak Detector, the background noise can be filtered out and the ultrasonic noises can be detected, thus locating a leakage in the compressed air system. There are (3) sensitivity settings, x1, x10, and x100 along with an on/off thumb-wheel for fine sensitivity.  The unit comes with a parabola and tubular extension for added flexibility.

ULD_Kit
Model 9061 – Ultrasonic Leak Detector and Included Accessories

Finding just one small leak can pay for the unit-

A small leak equivalent to a 1/16″ diameter hole will leak approx 3.8 SCFM at 80 PSIG of line pressure.  Using a reasonable average cost of $0.25 per 1000 SCF of compressed air generation, we can calculate the cost of the leak as follows-

Capture

It is easy to see that utilizing the Ultrasonic Leak Detector, and identifying and fixing leaks is the right thing to do.  It is possible to find and fix enough leaks that a new compressor purchase can be avoided or an auxiliary back-up is not needed any more.

If you have questions regarding the Ultrasonic Leak Detector, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Estimating the Cost of Compressed Air Systems Leaks

Leaks in a compressed air system can waste thousands of dollars of electricity per year. In fact, in many plants, the leakage can account for up to 30% of the total operational cost of the compressor. Some of the most common areas where you might find a leak would be at connection joints like valves, unions, couplings, fittings, etc. This not only wastes energy but it can also cause the compressed air system to lose pressure which reduces the end use product’s performance, like an air operated actuator being unable to close a valve, for instance.

One way to estimate how much leakage a system has is to turn off all of the point-of-use devices / pneumatic tools, then start the compressor and record the average time it takes for the compressor to cycle on and off. The total percentage of leakage can be calculated as follows:

Percentage = [(T x 100) / (T + t)]

T = on time in minutes
t = off time in minutes

The percentage of compressor capacity that is lost should be under 10% for a system that is properly maintained.

Another method to calculate the amount of leakage in a system is by using a downstream pressure gauge from a receiver tank. You would need to know the total volume in the system at this point though to accurately estimate the leakage. As the compressor starts to cycle on,  you want to allow the system to reach the nominal operating pressure for the process and record the length of time it takes for the pressure to drop to a lower level. As stated above, any leakage more than 10% shows that improvements could be made in the system.

Formula:

(V x (P1 – P2) / T x 14.7) x 1.25

V= Volumetric Flow (CFM)
P1 = Operating Pressure (PSIG)
P2 =  Lower Pressure (PSIG)
T = Time (minutes)
14.7 = Atmospheric Pressure
1.25 = correction factor to figure the amount of leakage as the pressure drops in the system

Now that we’ve covered how to estimate the amount of leakage there might be in a system, we can now look at the cost of a leak. For this example, we will consider a leak point to be the equivalent to a 1/16″ diameter hole.

A 1/16″ diameter hole is going to flow close to 3.8 SCFM @ 80 PSIG supply pressure. An industrial sized air compressor uses about 1 horsepower of energy to make roughly 4 SCFM of compressed air. Many plants know their actual energy costs but if not, a reasonable average to use is $0.25/1,000 SCF generated.

Calculation :

3.8 SCFM (consumed) x 60 minutes x $ 0.25 divided by 1,000 SCF

= $ 0.06 per hour
= $ 0.48 per 8 hour work shift
= $ 2.40 per 5-day work week
= $ 124.80 per year (based on 52 weeks)

As you can see, that’s a lot of money and energy being lost to just one small leak. More than likely, this wouldn’t be the only leak in the system so it wouldn’t take long for the cost to quickly add up for several leaks of this size.

If you’d like to discuss how EXAIR products can help identify and locate costly leaks in your compressed air system, please contact one of our application engineers at 800-903-9247.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN