When catapults would hurl stones and projectiles at castles there weren’t thinking of how the stones flew or what could make them fly better, often they went with the “Tim Taylor method” of MORE POWER. It wasn’t until thousands of years later that mathematicians started to talk about gases and liquids and how they react to different scenarios. Things like how does air react to a stone being launched through it. Johann Bernoulli played a significant role and calculated a lot of this out throughout his life and discovered what is now called the Bernoulli Principle.
Bernoulli discovered that when there is an increase in the speed of a fluid, a simultaneous decrease in fluid pressure occurs at the same time. This is what explains how a plane’s wing shape matters. It also can showcase how a curveball coming into the strike zone can fall out and cause an outlandish “STTTeeerriike Three” from the umpire. It is also sometimes confused with the Coandă effect. While both effects have a tremendous impact on our modern lives, the best way I have learned these effects is through videos such as the one below.
As mentioned within the video, there are numerous effects that can closely relate to the Bernoulli effect, the best example I see is the curveball which when implemented correctly can cause a very upset batter, while the pitcher has the game of his or her career.
If you would like to talk about some scientific discoveries that have you puzzled, or if you want to figure out how we can use one of these effects to help your application, contact us.
Compressed air regulators are a pressure reducing valve that are used to maintain a proper downstream pressure for pneumatic systems. There are a variety of styles but the concept is very similar; “maintain a downstream pressure regardless of the variations in flow”. Regulators are very important in protecting downstream pneumatic systems as well as a useful tool in saving compressed air in blow-off applications.
The basic design of a regulator includes a diaphragm, a stem, a poppet valve, an orifice, compression springs and an adjusting screw. I will break down the function of each item as follows:
Diaphragm – it separates the internal air pressure from the ambient pressure. They are typically made of a rubber material so that it can stretch and deflect. They come in two different styles, relieving and non-relieving. Relieving style has a small hole in the diaphragm to allow the downstream pressure to escape to atmosphere when you need to decrease the output pressure. The non-relieving style does not allow this, and they are mainly used for gases that are expensive or dangerous.
Stem – It connects the poppet valve to the diaphragm. This is the “linkage” to move the poppet valve to allow compressed air to pass. As the diaphragm flexes up and down, the stem will close and open the poppet valve.
Poppet valve – it is used to block the orifice inside the regulator. It has a sealing surface to stop the flowing of compressed air during zero-flow conditions. The poppet valve is assisted by a spring to help “squeeze” the seal against the orifice face.
Orifice – it is an opening that determines the maximum amount of air flow that can be supplied by the regulator. The bigger the orifice, the more air that can pass and be supplied to downstream equipment.
Compression springs – they create the forces to balance between zero pressure to maximum downstream pressure. One spring is below the poppet valve to keep it closed and sealed. The other spring sits on top of the diaphragm and is called the adjusting spring. This spring is much larger than the poppet valve spring, and it is the main component to determine the downstream pressure ranges. The higher the spring force, the higher the downstream pressure.
Adjusting screw – it is the mechanism that “squeezes” the adjusting spring. To increase downstream pressure, the adjusting screw decreases the overall length of the adjusting spring. The compression force increases, allowing for the poppet valve to stay open for a higher pressure. It works in the opposite direction to decrease the downstream pressure.
With the above items working together, the regulator is designed to keep the downstream pressure at a constant rate. This constant rate is maintained during zero flow to max flow demands. But, it does have some inefficiencies. One of those issues is called “droop”. Droop is the amount of loss in downstream pressure when air starts flowing through a regulator. At steady state (the downstream system is not requiring any air flow), the regulator will produce the adjusted pressure (If you have a gage on the regulator, it will show you the downstream pressure). Once the regulator starts flowing, the downstream pressure will fall. The amount that it falls is dependent on the size of the orifice inside the regulator and the stem diameter. Charts are created to show the amount of droop at different set pressures and flow ranges (reference chart below). This is very important in sizing the correct regulator. If the regulator is too small, it will affect the performance of the pneumatic system.
The basic ideology on how a regulator works can be explained by the forces created by the springs and the downstream air pressures. The downstream air pressure is acting against the surface area of the diaphragm creating a force. (Force is pressure times area). The adjusting spring force is working against the diaphragm and the spring force under the poppet valve. A simple balanced force equation can be written as:
Fa ≡ Fp + (P2 * SA)
Fa – Adjusting Spring Force
Fp – Poppet Valve Spring Force
P2 – Downstream pressure
SA – Surface Area of diaphragm
If we look at the forces as a vector, the left side of the Equation 1 will indicate a positive force vector. This indicates that the poppet valve is open and compressed air is allowed to pass through the regulator. The right side of Equation 1 will show a negative vector. With a negative force vector, the poppet valve is closed, and the compressed air is unable to pass through the regulator (zero flow).
Let’s start at an initial condition where the force of the adjusting spring is at zero (the adjusting screw is not compressing the spring), the downstream pressure will be zero. Then the equation above will show a value of only Fp. This is a negative force vector and the poppet valve is closed. To increase the downstream pressure, the adjusting screw is turned to compress the adjusting spring. The additional spring force pushes down on the diaphragm. The diaphragm will deflect to push the stem and open the poppet valve. This will allow the compressed air to flow through the regulator. The equation will show a positive force vector: Fa > Fp + (P2 * SA). As the pressure downstream builds, the force under the diaphragm will build, counteracting the force of the adjusting spring. The diaphragm will start to close the poppet valve. When a pneumatic system calls for compressed air, the downstream pressure will begin to drop. The adjusting spring force will become dominant, and it will push the diaphragm again into a positive force vector. The poppet valve will open, allowing the air to flow to the pneumatic device. If we want to decrease the downstream air pressure, the adjusting screw is turned to reduce the adjusting spring force. This now becomes a negative force vector; Fa < Fp + (P2 * SA). The diaphragm will deflect in the opposite direction. This is important for relieving style diaphragms. This deflection will open a small hole in the diaphragm to allow the downstream air pressure to escape until it reaches an equal force vector, Fa = Fp + (P2 * SA). As the pneumatic system operates, the components of the regulator work together to open and close the poppet valve to supply pressurized air downstream.
Compressed air is expensive to make; and for a system that is unregulated, the inefficiencies are much greater, wasting money in your company. For blow-off applications, you can over-use the amount of compressed air required to “do the job”. EXAIR offers a line of regulators to control the amount of compressed air to our products. EXAIR is a leader in manufacturing very efficient products for compressed air use, but in conjunction with a regulator, you will be able to save even more money. Also, to make it easy for you to purchase, EXAIR offer kits with our products which will include a regulator. The regulators are already properly sized to provide the correct amount of compressed air with very little droop. If you need help in finding the correct kit for your blow-off application, an Application Engineer at EXAIR will be able to help you.
Recently, I worked with a customer that was looking for a way to make a difficult job easier, reducing stress and strain on the body and preventing injury. The customer was in the Environmental Services & Hazardous Waste Management area and regularly was called out to service acid neutralization tanks. These are commonly found in hospitals, laboratories, and schools, to neutralize lab wastewater before it is discharged to the sanitary sewer. The systems typically utilize limestone chips to aid the in process.
Periodic maintenance includes the removal and disposal of the spent limestone chips, tank cleaning and replenishment with new limestone chips. Some of the tanks are tall and narrow, making access to the limestone chips difficult, especially near the tank bottom. Current procedures involved small shovels and unnatural body positions to try to reach the bottom-most material. A better way had to be found.
The customer came across the EXAIR website and found the Line Vac product line. After watching the demonstration video, he knew he had found his solution! The Line Vac is a compressed air operated device that turns any hose or tube into a powerful in-line conveyor. Based on the height of the tanks and the size and weight of the limestone, we agreed the 2″ Heavy Duty Line Vac would provide the power and durability to empty the tanks in a timely manner, and safely and efficiently. The customer would use a tow behind compressor so that a reliable source of compressed air would always be available.
The Heavy Duty Line Vacs are available in sizes from 3/4″ up to 3″ in both smooth end and threaded connections for use with hose or pipe for conveyance.
To discuss your application and how an EXAIR Line Vac can make your transfer process easier and safer, feel free to contact EXAIR and myself or one of our other Application Engineers can help you determine the best solution.
Over the past year I received a contact from a professor and student combination from Madison Area Technical College inquiring about the sizes available for our Line Vac products. They were using a 2″ Line Vac in one of their automation class labs and wanted to try something a little bigger for a new project. The 2″ Line Vac was one they had used in the past on different projects and had always worked well. The new project however increased the bag size and made the conveyance difficult for the 2″ Line Vac.
With the picture below of their current setup and a good understanding that they will be placing three items into a heat sealed bag that is roughly 3″ long and 2″ wide we settled on using the 3″ Aluminum Line Vac at a low pressure to convey the baggies to their secondary function. As you can see in the video below, the Line Vac is activated by a sensor and operates for just seconds in order to convey the bag of parts successfully to the other side of the machine cell where the bag is then picked and placed by a robotic arm.
After the project was completed we received a mention through social media, as well as a brief video showcasing the Line Vac in use. The video showcases how easy it is to install an EXAIR Line Vac into a tight space where adding other conventional mechanical conveying systems would be considerably more elaborate. The Line Vac is being controlled via a PLC that energizes a solenoid valve on a timer to convey the package in a matter of seconds.
We are very pleased to see the projects these kids turned out, and the leadership shown by Peter, their instructor. Manufacturing programs such as this one at Madison Area Technical College are important for our economy and for the future of these kids. We’d like to congratulate them all on their accomplishment.
If you have a project you are trying to move products from one point to another, contact us. If you are a professor, student, or even a mentor to an educational program that would benefit from EXAIR products, please contact me directly.