A drilled pipe has been used for many years to blow compressed air across a span for cleaning, cooling, and drying. They are a simple tool that was created from spare parts and many holes. The cost to make this type of product is not expensive, but to use this product in your application is very expensive. Similarly, an incandescent lightbulb is inexpensive to purchase, but it will cost you much more in electricity than a LED light bulb. Since 1983, EXAIR has been innovating safe and efficient products to be used in compressed air systems. In this blog, I will compare the drilled pipe with the Super Air Knife.
Even though you can find the components relatively easily to design your own drilled pipe, this blow-off design is very costly and stressful to your compressed air system. Typically, the holes along the pipe are in a row next to each other. As the airstream leaves from each hole, it will hit the airstream from the one next to it. This will cause turbulent air flows which has inconsistent forces and loud noises. Also, with turbulent air flows, the ability to entrain the surrounding ambient air is very small. We call this the amplification ratio. The higher the amplification ratio, the more efficient the blow-off device is. For a drilled pipe, the amplification ratio is near 3:1 (3 parts ambient air to 1 part compressed air).
A colleague, Brian Bergmann, wrote a blog about the amplification ratio of the EXAIR Super Air Knife. (Read it HERE.) This blog demonstrates how EXAIR was able to engineer an efficient way to blow air across a span. The unique design of the Super Air Knife creates an amplification ratio of 40:1 which is the highest in the market. Unlike the drilled pipe, the gap opening runs along the entire knife for precise blowing. This engineered gap allows for laminar air flow which has a low noise level, a consistent blowing force, and maximum amplification ratio. With these benefits, the Super Air Knife can reduce the amount of compressed air required, which will save you money and save your compressed air system.
In comparing the drilled pipe to the Super Air Knife, I will relate both products in a simple cooling application. Thermodynamics expresses the basics of cooling with an air temperature and an air mass. Since both products are represented in the same application, the air temperature will be the same. Thus, the comparison will be with the amount of air mass. In this example, the customer did some calculations, and they needed 450 Lbs. of air to cool the product to the desired temperature. At standard conditions, air has a density of 0.0749 lbs/ft3. To convert to a volume of air, we will divide the weight by the density:
450 lbs. / (0.0749 lbs./ft3) = 6,008 ft3 of air
To meet this requirement, reference Table 1 below. It shows the volume of air required by your compressed air system to meet this demand. As you can see, your compressor has to work 13X harder to cool the same product when using a drilled pipe. Just like the LED light bulbs, the Super Air Knife has more efficiency, more innovation, and uses less compressed air. In turn, the Super Air Knife will save you a lot of money in electrical costs. If you would like to see how much the Super Air Knife can save compared to the drilled pipe, we have that information in this blog. (Read it HERE.) For my reference, it will reduce the stress of your compressed air system.
if you would like to compare any of your current blow-off devices with an innovative EXAIR product, you can contact an Application Engineer. We can do an Efficiency Lab to shine an LED light on saving energy and money with your compressed air.
John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb
Drilled pipe is a common blowoff because it is very inexpensive and easy to make. But drilled pipe performs poorly. The low cost to make the drilled pipe is quickly outpaced by the inefficiency and high compressed air costs. The holes are easily blocked and the noise level is excessive, both of which violate OSHA requirements. Also, the air pattern across the length can be very inconsistent, with areas of low flow and areas of turbulent flow.
Flat air nozzles installed along a length of pipe is another inexpensive option, but it can be a poor performer. The flat nozzles are available in many materials, from many manufacturers. The flat nozzles do offer some efficiencies, but similar to drilled pipe, the operating costs and noise levels are high. Air pattern across the length can be inconsistent with areas of high and low flows, leading to incomplete drying or cooling. Also, many of these nozzles are made from plastic material which breaks or cracks when it it hit which causes additional expense and maintenance to replace broken nozzles.
A blower air knife can prove to be an expensive and noisy option. Typically, the initial purchase price is high. Operating costs are lower than the drilled pipe and flat nozzles and in line with the Super Air Knives. The blowers can be very large and space for two 3″ diameter hoses requires extra mounting space compared to low profile other options. Noise levels are high, at 90 dBA. Annual costs for bearing and filter maintenance can be significant.
EXAIR Super Air Knives performed exceptionally well in removing the water in one pass due to the strong, laminar flow of air. Sound level was low at just 69 dBA, well within OSHA requirements for an hour 8 hour exposure time. Safe operation is assured, as the Super Air Knife design cannot be dead-ended. Maintenance costs are low, as the Super Air Knife has no moving parts to breakdown or wear out.
