Tag: pressure differential

Pressure Drop vs Differential Pressure

Published on by John BallLeave a comment

I find myself interchanging these terms; pressure drop and differential pressure.  This is very common as both are determined by the change in pressure between two points.  In this blog, I will cover the difference between these two terms in my view.

Pressure drop only occurs when the air is flowing.  The higher the velocity, the higher the pressure drop.  Velocity is created when the pressure changes.  So, the higher pressure will go toward the lower pressure.  But we wish that pressure difference to be as low as possible.  Pressure drops are always a loss, and you cannot regain that energy.  Forms of pressure drop that can be found are small diameter pipes or tubing; restrictive fittings like quick disconnects, and undersized conditioning equipment like after coolers and air dryers.  If a pressure drop is too large, the pneumatic equipment will not have enough power to operate effectively and efficiently.  I have another blog with a video that helps demonstrate this, “Pressure Drop and its Relationship to Compressed Air”. 

Differential pressure can be static or flowing.  It is very similar to pressure drop except that the energy is stored.  The most common device that does this is the pressure regulator.  You can reduce the pressure downstream to the point-of-use.  This type of pressure reduction will save you money, instead of wasting money.  For every 10 PSI reduction in pressure, it will save you 5% in energy.  With blow-off devices, you want to use the least amount of pressure to “do the job”.  Over-driving compressed air pressure is a common and wasteful condition found in facilities.

Here is a graph of a typical compressed air system.  As you can see, the typical pressure drop from the air compressor to the point-of-use.  So, if you can reduce the pressure drop through the system and optimize the differential pressure from the regulator to your point-of-use, you can enhance your compressed air system.

Pressure Drop Chart

In a simple statement, pressure drop loses energy while differential pressure stores energy for later use.  EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side and which can help to reduce pressure drops within a system.  This will include the EXAIR Super Air Knives, Super Air Nozzles, and Safety Air Guns.  If you wish to go further in optimizing your system, an Application Engineer at EXAIR will be happy to help you.

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

Basics of the Compressed Air System

Published on by John BallLeave a comment

Compressed air is used to operate pneumatic systems within a facility, and it can be separated into three categories; the supply side, the demand side, and the distribution system.  In this blog, I will cover each area. 

The supply side is the air compressor, after-cooler, dryer, and receiver tank that produce and treat the compressed air.  They are generally located in a compressor room somewhere in the corner of the plant.  There are two main types of air compressors: positive displacement and dynamic.  The core component of most air compressors is an electric motor that spins a shaft.  Positive displacement uses the energy from the motor and the shaft to change volume in an area, like a piston in a reciprocating air compressor or like rotors in a rotary air compressor.  The dynamic types use the energy from the motor and the shaft to create a velocity with an impeller like centrifugal air compressors.  This velocity converts to a rise in pressure.

How do they work?  Most air compressors are driven by an electric or gas motor.  The motor spins a shaft to push a piston, turn a rotor, or spin a vane.  At the beginning of the air compressor, we have the intake where a low pressure is generated from the displacement to bring in the surrounding ambient air.  Once trapped, Boyle’s law states that when the volume decreases, the pressure increases.  For the dynamic type, the velocity and design will increase the air pressure.  The higher pressure will then move to a tank to be stored for pneumatic energy.  The amount of power required is dependent on the pressure and the amount of air that needs to be compressed. 

The demand side is the collection of devices that will use that compressed air to do “work”.  These pneumatic components are generally scattered throughout the facility.  This would include valves, cylinders, blow-offs, pneumatic clamps, etc.   To condition the demand side, regulators and filters are used.  The Pressure Regulators help to limit the amount of pressure.  For blow-off devices, the lower the air pressure to “do the job”, the less compressed air is used.  To help with the fluctuations in demand, a secondary Receiver Tank can be used.  The demand side can also be a system to do specific jobs. In using pneumatic systems, the “power” must come from the supply side. 

To connect the supply side to the demand side, a compressed air distribution system is required.  Distribution systems are pipes which carry the compressed air from the compressor to the pneumatic devices.  For a sound compressed air system, the three sections have to work together to make an effective and efficient system. An analogy that I like to use is to compare the compressed air system to an electrical system.  The air compressor would be considered the voltage source, and the pneumatic devices would be considered as light bulbs.  To connect the light bulbs to the voltage source, electrical wires are needed which will represent the distribution system.  If the gauge of the wire is too small to supply the light bulbs, the wire will heat up and a voltage drop will occur.  This heat is given off as wasted energy, and the light bulbs will be dim.  The same thing happens within a compressed air system.  If the piping size is too small, a pressure drop will occur.  This is also wasted energy.  In both types of systems, wasted energy is wasted money.  One of the largest systematic problems with compressed air systems is pressure drop.  With a properly designed distribution system, energy can be saved, and, in reference to my analogy above, it will keep the lights on.  To have a properly designed distribution system, the pressure drop should be less than 10% from the reservoir tank to the point-of-use.

Processes lead to continuous improvement.

EXAIR created the “Six Steps to Optimizing Your Compressed Air System”.  By following these tips, you can have the supply side, demand side, and distribution system working at peak efficiency.  If you would like to reduce waste even more, EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side.  This will include the EXAIR Super Air Knives, Super Air Nozzles, and Safety Air Guns.  This would be the electrical equivalent of changing those incandescent light bulbs into LED light bulbs.  If you wish to go further in enhancing your system, an Application Engineer at EXAIR will be happy to help you. 

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

Photo:  Lightbulb by qimono.  Pixabay Licence

Pressure Drop vs Differential Pressure

Published on by John BallLeave a comment

I find myself interchanging these terms; pressure drop and differential pressure.  This is very common as both are determined by the change in pressure between two points.  In this blog, I will cover the difference between these two terms in my view.

Pressure drop only occurs when the air is flowing.  The higher the velocity, the more extreme the pressure drop will be.  Velocity is created when the pressure changes.  So, the higher pressure will go toward the lower pressure.  But we wish for that pressure difference to be as low as possible.  Pressure drop is always a loss, and you cannot regain that energy.  Forms of pressure drop that can be found are like small diameter pipes or tubing; restrictive fittings like quick disconnects, and conditioning equipment like after coolers and air dryers.  If too large of a pressure drop occurs, the pneumatic equipment will not have enough power to operate effectively and efficiently.  I have another blog with a video that helps demonstrate this, “Pressure Drop and its Relationship to Compressed Air”. 

Pressure Regulators “dial in” performance to get the job done without using more air than necessary.

Differential pressure can be static or flowing.  It is very similar to pressure drop except that the energy is stored.  The most common device that does this is the pressure regulator.  You are able to reduce the pressure downstream to the point-of-use.  This type of pressure reduction stores energy, and it will save you money, instead of wasting money.  For every 10 PSI reduction in pressure, it will save you 5% in energy.  With blow-off devices, you want to use the least amount of pressure to “do the job”.  Over-using your compressed air is wasteful.

Here is a graph of a typical compressed air system.  As you can see, the typical pressure drop from the air compressor to the point-of-use.  So, if you can reduce the pressure drop through the system and optimize the differential pressure from the regulator to your point-of-use, you can optimize your system.

Pressure Drop Chart

In a simple statement, a pressure drop loses energy while differential pressure stores energy for later use.  EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side.  This will include the EXAIR Super Air Knives, Super Air Nozzles, and Safety Air Guns.  If you wish to go further in optimizing your system, an Application Engineer at EXAIR will be happy to help you.

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

Pressure Drop Chart by Compressed Air Challenge Organization.

Compressed Air Distribution System, Keeping Pressure Drop to a Minimum

Published on by John BallLeave a comment

Compressed air is used to operate pneumatic systems within a facility, and it can be separated into three categories; the supply side, the demand side, and the distribution system.  The supply side is the air compressor, after-cooler, dryer, and receiver tank that produce and treat the compressed air.  They are generally located in a compressor room somewhere in the corner of the plant.  The demand side is the collection of devices that will use that compressed air to do “work”.  These pneumatic components are generally scattered throughout the facility.  To connect the supply side to the demand side, a compressed air distribution system is required.  Distribution systems are pipes which carry the compressed air from the compressor to the pneumatic devices.  For a sound compressed air system, the three sections have to work together to make an effective and efficient system.

An analogy that I like to use is to compare the compressed air system to an electrical system.  The air compressor would be considered the voltage source, and the pneumatic devices would be marked as light bulbs.  To connect the light bulbs to the voltage source, electrical wires are needed which will represent the distribution system.  If the gauge of the wire is too small to supply the light bulbs, the wire will heat up and a voltage drop will occur.  This heat is given off as wasted energy, and the light bulbs will be dim.  The same thing happens within a compressed air system.  If the piping size is too small, a pressure drop will occur.  This is also wasted energy.  In both types of systems, wasted energy is wasted money.  One of the largest systematic problems with compressed air systems is pressure drop.  If too large of a pressure loss occurs, the pneumatic equipment will not have enough power to operate effectively and efficiently.  As shown in the illustration below, you can see how the pressure decreases from the supply side to the demand side.  With a properly designed distribution system, energy can be saved; and, in referencing my analogy above, it will keep the lights on.

Pressure Drop Chart

To optimize the compressed air system, we need to reduce the amount of wasted energy.  This can be caused from leaks or pressure drop.   Leaks can be hidden and are typically located at connections within the distribution system.  In a poorly maintained system, a study found that 30% of the compressor capacity is lost through air leaks on average.  Even though leaks are the “silent killer” to a compressed air system, they can be found with the Ultrasonic Leak Detector. 

Pressure drop is more of a wide range issue.  It is based on restrictions, obstructions, and piping surface.  Out of these, restrictions are the most common types of pressure drops. The air flow is forced into small areas, causing high velocities.  The high velocity creates turbulent flow which increases the losses in air pressure.  Flow within the pipe is directly related to the velocity times the square of the diameter.  So, if you cut the I.D. of the pipe by one-half, the flow rating will be reduced by 25% of the original rating.  Restriction type of pressure drop can be found in different forms like small diameter pipes or tubing; restrictive fittings like quick disconnects and needle valves, and undersized filters, regulators and valves.

As a rule, air velocities will determine the correct pipe size for the distribution system.  It is beneficial to oversize the pipe to accommodate for any expansions in the future.  For header pipes, the velocities should not be more than 20 feet/sec (6 meter/sec).  For the distribution lines, the velocities should not exceed 30 feet/sec (9 meter/sec).  In following these simple rules, the distribution system can effectively supply the necessary compressed air from the supply side to the demand side.

To have a properly designed distribution system, the pressure drop should be less than 10% from the reservoir tank to the point-of-use.  By following the tips above, you can have the supply side, demand side, and distribution system working at peak efficiency.  If you would like to reduce waste even more, EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side.  This will include the EXAIR Super Air Knives, Super Air Nozzles, and Safety Air Guns.  This would be the pneumatic equivalent of changing those incandescent light bulbs into LED light bulbs.  If you wish to go further in optimizing your system, an Application Engineer at EXAIR will be happy to help you. 

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

Photo:  Lightbulb by qimono.  Pixabay Licence

Pressure Drop Chart by Compressed Air Challenge Organization.