What Is The Difference Between Pressure & Flow In A Compressed Air System?

There is rarely a day that goes by that I don’t receive a call from someone who has a need for a compressed air product and when I state the SCFM requirements of the device they respond back with the psi rating of their air compressor.  Many technicians simply do not understand the difference between the two.  Simply put psi (pounds square inch) is force and CFM (cubic feet per minute) is flow.

A simple illustration would be to contrast a 12 VDC powered air compressor that many people carry in their trunks to inflate car tires.  They will inflate your car tire to 35 psi in a matter of minutes.  While the air compressor at a tire shop can inflate a car tire in a minute or less.  What is the difference?

12 VDC Air Compressor
12 VDC Tire Inflator

 

Simply put, the flow. Both inflate the tire to the desired pressure but the one with largest flow (volume) does it much faster.  In the case of a compressed air product such as an air nozzle, the pressure required to operate is only one part of what is necessary to operate the device effectively, you need to have enough flow or CFM.

Let us now consider an EXAIR 1100 Super Air Nozzle, its rated performance of 13 ounces of force at 12″ distance from the nozzle is derived from supplying 14 SCFM @ 80 psi.  The typical home use air compressor that runs on 110 VAC (Generally 2 HP maximum) will not generate the flow (volume /CFM) at 80 psi to run the nozzle at peak force, just as it would not generate enough flow to fill the tire as quickly as the industrial compressor at a tire shop.

When an open tube, pipe or inefficient nozzle is placed at the end of an air line to provide blow off for cooling or cleaning it demands much greater volume from the compressor. If the compressor cannot keep up the force (pressure) of the system will decline. Replacing an open tube or pipe with an EXAIR engineered nozzle will require less compressed air volume which, in turn, will give the compressor more ability to provide full pressure and force upon your application.

1100group
EXAIR 1100 Super Air Nozzle

If you would like to discuss air consumption of any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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12 VDC Tire Inflator Image courtesy of Moto Service Dinamarca

 

Protect Personnel from Noise with Engineered Products

Sound can be defined as vibrations that typically travel as an audible wave through mediums that can be a gas, liquid or solid. For this blog we will concern ourselves with sound travelling through a gas (atmosphere) in an industrial setting.

Sound is energy that travels in waves and is measured by its frequency (cycles per second) and amplitude (intensity). A common unit of measurement for sound energy is the decibel. The decibel (abbreviated with dBA) is a unit-less number that is based on the logarithm of a known measured quantity to a reference quantity. Without reciting the equation for every increase of 3 dBA is a doubling of sound energy or twice as loud.

Since our focus is on industrial sound one might question why be concerned at all, after all sound emanates from most machines and devices. The reason for concern is that there are OSHA regulations regarding the amount of time workers can be exposed to different levels of sound in their workday as illustrated below. These limits are in place to protect personnel from Noise Induced Hearing Loss or NIHL. When the damage to anyones hearing is caused by their profession, it is also referred to as Occupational Hearing Loss or OHL.

After monitoring for noise, NIOSH and the CDC next recommend administrative controls to minimize or eliminate the noise hazard (click for their helpful PDF). This would include the use of noise reducing EXAIR products like Super Air Nozzles, Air Knives and Air Amplifiers.

dBA Chart.JPG
OSHA Maximum Allowable Noise Exposure

When considering the many items in an industrial setting that produce loud sounds the list would be exhaustive. Many of them simply produce loud sounds that can’t be eliminated or reduced while on the other hand there are some that can. Some of the noisiest offenders that plants have control over are air powered tools and open tube blow-offs.  Eliminating inefficient methods of part blow off & part cleaning with an engineered solution allows a company to significantly reduce the level of sound in their plant, improve worker safety and save money on compressed air consumption.

Employers are required to provide hearing protection to employees whom are exposed to sounds above 90 dBA on a Time Weighted Average (TWA). Without digressing into the formulas TWA calculates a workers daily exposure to occupational sounds by taking into account the average levels (in dBA) and the time exposed to different levels.  This is the how OSHA assesses workers exposure and what steps should be taken to protect the workers.

To conclude, plants need to be mindful of the OSHA regulations for sound levels, time of exposure and that hearing protectors wear out. Earmuff seals can lose their elasticity and reduce their effectiveness and the soft pre-molded earplugs can wear out in a day and need replaced.  Keep a good supply on hand and OSHA suggests letting workers with noisy hobbies take them home for protection off the clock!

If you would like to discuss reducing noise or any EXAIR product, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer

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Do You Need 30 Days for Testing?

Not long ago while checking out of a motel my laptop bag that was attached to the handle on my suitcase fell forward and the impact shattered the screen on the laptop.  Upon turning the computer on I realized that a new screen was in order.

I waited until I arrived at home and found what I thought to be the correct monitor and quickly ordered it.  It arrived two days later and I painstakingly took the laptop apart and exposed the mounting frame.  The removal of the broken screen and the installation of the new was not too difficult but the cable connector was less than robust and was very tight.  Carefully I worked it back and forth and it came free.

Installation and reassembly went quickly and then I powered up the machine.  I was only greeted with a series of very loud and annoying beeps.  At that point I shut it down and called the company I purchased the screen from and described the issue.  They determined that the resolution of the screen was incorrect for my laptop and that I needed a different model.  They said I could return the incorrect one and upon inspection receive a credit less the return shipping.  At that point I ordered the correct screen and packaged up the wrong one and dropped it off at the parcel delivery service.

The new model arrived and it installed easily and worked perfectly.  I waited patiently and never did see a refund so I called the company and they said that it was an oversight on their end and that it would be corrected within 48 hours.  Sure enough they issued the credit and money was credited back to my account with one exception, the 40% restocking fee!

I can tell you that EXAIR is not that way!  If you order the wrong item or are not satisfied for any reason and the item was purchased within the last 30 days we will facilitate the return and ZERO restocking fee. There are a multitude of reasons our customers would want to take advantage of our 30 day guarantee and we make it a simple transaction if you need to take advantage of it too. Testing is one reason a customer would use this 30 days, other customers may have ordered incorrectly or released product inadvertently, they may have wanted a small sample for a meeting or demonstration at a customers location.

30 day money back guarantee
EXAIR Guarantee

If you want to discuss any EXAIR product, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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Measuring and Adding Sounds

Sound

My colleague, Russ Bowman, wrote a blog about “Sound Power Level and Sound Pressure”.  He discussed the logarithmic equations around sound.  I will be discussing what happens when you have more than one sound source, as often heard within manufacturing plants.  Sounds can be added together to determine the overall sound level that your hear.  This is very important when it comes to minimizing hearing loss.

In looking at a single source of sound, sound pressure is created by the loudness of a noise.  The units are measured in Pascals.  The lowest pressure perceived by human hearing is 0.00002 Pa, and we can use this value as a reference point.  From sound pressures, we can arrive to a sound pressure level which is measured in decibel, dB.  This correlation between sound pressures and sound pressure levels are calculated by Equation 1:

 

 

L – Sound Pressure Level, dB

P – Sound pressure, Pa

Pref – reference sound pressure, 0.00002 Pa

As an example, the sound pressure from a passenger car as heard from the roadside is 0.1 Pa.  With Equation 1, we can get the following decibel level:

L = 20 * Log10 (0.1Pa/0.00002Pa) = 74 dB

Because human ears are sensitive to different frequencies, the sound pressure levels can be modified, or weighted, to indicate an effective loudness level for humans.  This adjustment is done in two different ways; A-weighting and C-weighting.  The C-weighting is for very loud noises with high peaks or sharp impacts like gunfire. The A-weighting is the most commonly used value as the sound pressure levels are adjusted by the frequency level.  For higher and lower frequencies, the change in the sound value is much greater than the mid-level frequencies that are within our hearing range.  Sound measurements for safety are measured in the A-weighted scale.  OSHA created a chart in the 29CFR-1910.95(a) standard that shows the noise levels over exposure times for an operator.  To use the OSHA chart accurately, the total noise level in dBA should be calculated.

OSHA Chart

To determine the total sound level, we can add all the sound pressure levels together by Equation 2:

 

 

Where L1, L2… represents the sound pressure level in dBA for each sound source.

As an example, a manufacturing plant had an operator using a machine that had four copper tubes to blow off a cutting operation (reference photo below).

Blow off station

The decibel level for a copper tube was measured at 98 dBA.  The total amount of sound that the operator was exposed to was determined by Equation 2 with four values.

L = 10 * log10 (109.8 + 109.8 + 109.8 + 109.8)

L = 104 dBA

In looking at the OSHA chart, the operator would only be allowed to operate the machine only a little over one hour without hearing protection.  In this same example, we replaced the copper tubes with an EXAIR Super Air Nozzle, model 1110SS.  The noise level for each nozzle is 74 dBA.  By replacing all four copper tubes with Super Air Nozzles, Equation 2 becomes:

L = 10 * log10 (107.4 + 107.4+ 107.4 + 107.4)

L = 80 dBA

The total sound level is now in accordance with OSHA regulations for the operator to work all 8 hours at the machine without hearing protection.

A commonly used acronym in hearing safety is NIHL, or Noise Induced Hearing Loss.  To keep your operators safe and reduce NIHL, it is important to measure the total sound level.  As a protocol in safety, it is a requirement to use engineering standards before purchasing personal protective equipment or PPE.  For the customer above, they followed that protocol with our Super Air Nozzles.  If you need to reduce noise levels in your facility by engineering standards, EXAIR offers a large line of blow-off products that can meet the safety requirements.

 

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

 

Photo of Ear auricle Listen by geraitCC0 Create Commons.

 

EXAIR Heavy Duty Safety Air Gun With Accessories Improves Effectiveness and Safety

1310-12
Model 1310-12 Heavy Duty Safety Air Gun, With 12″ Extension & 1100 Super Air Nozzle

In rugged industrial environments the EXAIR Heavy Duty Safety Air Gun delivers powerful blasts of compressed air right where it is needed.  It features a 3/8 NPT metal inlet to allow for increased air flow to the Super Air Nozzle of your choice and there are many configurations are available from stock.  It is constructed of a durable and robust cast aluminum body with an ergonomic and comfortable composite grip that allows for extended use without fatigue.

The Heavy Duty Safety Air Gun can be configured with extensions that are available in 6” increments up to 24” in length and 12” increments from 24” up to 72”.  Combine the extension with our optional Chip Shield for maximum operator safety and comfort.

 

Extension Tubes For Air Guns
Different Length Extensions For Every Application

 

Chip Shield
Chip Shields Offer Safety & Comfort For Operators

We offer a wide variety of nozzles to allow you to configure the Heavy Duty Safety Air Gun to you specific application.  EXAIR has a large selection of nozzles that are engineered to entrain surrounding air with the compressed air supply creating a synergistic blast that is very powerful.  Most importantly they operate much quieter than the limits of OSHA standard 29 CFR 1910.95(a) and can’t be “dead ended” therefore meeting OSHA standard 29 CFR 1910.242(b).

OSHA Chart
OSHA Maximum Allowable Noise Exposure

 

The EXAIR Heavy Duty Safety Air Gun is available in the configurations shown below or many others.  If you have an application you would like to discuss or to see how the Heavy Duty  Safety Air Guns will improve your process, give us a call, we are happy to help.

Heavy Duty Safety Air Gun Configuration Chart
Heavy Duty Safety Air Gun Sample Configurations

Steve Harrison
Application Engineer
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Blowoff Systems Makes it Easy to Clean Extrusions

A metal cutting facility would cut pieces of aluminum extrusions, bars and cylinders to specific lengths as requested by their customers.  They used a variety of different types of cutting equipment depending on the size and profile, but every cutting machine would use coolant. At the end of the cutting process, they would run the parts through a washing system to remove any coolant and then through an inkjet marking system.  They would print the corresponding tag information on the top of each product.

The surface had to be dry or the ink would run and become illegible.  To try and speed up the drying process, they attached four soft copper tubes to blow compressed air along the top of the parts.  They flattened the ends slightly to give a wider blowing area as well as to direct the air into the T-slots of the extrusions.  The customer liked the flexibility of the copper tubes as they would need to change the position often to fit the appropriate size and profile.

The problem that they had with their setup was that the blowing was too loud and it used a large amount of compressed air.  They found EXAIR which looked to have a better solution to blow off the water from the product.

Blow Off Application

The customer gave some additional details on their process.  They could cut a wide range of diameters from 2 inches (51 mm) to 12 inches (305 mm) within their bar and cylinder stock.  They also would cut square and rectangular extrusions that had a variety of profiles and dimensions.  They requested a flexible product that could conform to the different sizes and types and also be adjusted manually for optimum blowing positions.

1122-9412 Blowoff Kit

EXAIR offers a great product line that would fit their requirements for this application, the Blowoff Systems.  With their requested specifications, the flat blowing pattern and flexibility, it directed me to the model 1122-9412 Blowoff Kit.  This kit comes with a Magnetic Base, Flat Super Air Nozzles, and flexible Stay Set Hoses.  The model 1122-9412 has two 2” Flat Super Air Nozzles which will give a wide blowing area.

The Magnetic Base contains two outlets with shut off valves on each port to allow for an easy way to turn off a nozzle when not needed for the smaller products.  Between the Magnetic Base and the 2” Flat Super Air Nozzle, a 12” (305mm) long Stay Set Hoses connects them together which will allow for precise blowing and maneuverability.

By installing two pieces of the model 1122-9412 to his system, the customer was able to remove the four pieces of the copper tubing which were loud and inefficient.  The noise level dropped to 77 dBA with the 2” Flat Super Air Nozzles which was a relief, and they realized that the air compressor was working less.  By adding the Blowoff Kits to their system, they now had a flexible, efficient and effective way in drying the products prior to printing.

With the customer above, they saw much improvement in blowing off the water which kept the ink jet printing process from running or smearing.  If you need flexibility in your blowing application, EXAIR offers a variety of kits with different types of nozzles to accommodate the best blowing feature for your application.  If you would like to discuss these options, you can contact an EXAIR Application Engineer, and they will be happy to help.

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

Dollar Savings: Open Pipes vs EXAIR Air Nozzle

Early one morning we received a call from a local metal stamping company that had a problem. They had outstripped the volumetric capacity of their (2) 50 HP air compressors.

They were using open copper tubes to facilitate separating the part from the die on the upstroke and then blow the part backwards into the collection chute. The (5) 1/4” copper tubes were all connected to a single manifold with a valve to control each tube.  Compounding their compressed air shortage was that this setup was duplicated on approximately (8) presses.  Per the plant they run the presses for approximately (4) hours per day.  The volume of air required for one press was calculated as:

One 1/4” open copper pipe consumes 33 SCFM @ 80 PSIG, therefore:

EDV Blog.JPG

Due to the award winning design of EXAIR’s engineered air nozzles the plant achieved faster separation of the part from the die and greater efficiency moving the part to the collection chute, while averting the need to purchase a larger air compressor. They are saving air, reducing energy costs and lowering the noise level in their facility.

If you would like to discuss saving air and/or reducing noise, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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