I recently worked with a customer who was using our 36″ aluminum Super Air Knife to remove dust and light debris from a conveyor but wasn’t seeing good performance. They initially called because they read in their catalog that increasing the shim gap would increase their force and flow and wanted to know what kind of increase in performance they would see.
The Super Air Knives are shipped from EXAIR with a .002″ shim installed and the performance data shown in the catalog reflects this gap setting. The shim sets, for aluminum knives, include a .001″, .003″ and .004″ shim and by changing to the .003″ shim, the force and flow would be 1.5 times as great and using the .004″ shim would double these amounts. While some applications do require the additional force and flow, trying to blow off dust or light materials typically wouldn’t fall into this category.
Switching our focus to the supply side of things, it turns out they were using 1/4″ hose and only plumbing one end of the unit. This poses 2 concerns that relate directly to the mentioned poor performance. The first would be the 1/4″ hose is severely undersized for a 36″ Super Air Knife. We recommend 3/4″ Schedule 40 pipe if the length of supply from a main header is 10′ or less and a 1″ pipe up to 50′ of supply run. It is possible to use hose but that hose needs to be at least 1″ ID to be able to carry enough volume to support a 36″ unit. Secondly, for knives that are 24″ in length or longer, you need to plumb air to both ends to maintain an even, laminar flow across the length of the knife.
With the proper supply, the Super Air Knife is going to produce an exhaust air velocity of 11,800 feet per minute when operated at 80 PSIG, which is more than enough to eject lightweight material from a flat surface (in fact you could most likely clean dust and light debris at a lower pressure). If the customer did increase the shim gap dimension, the increase in air demand would only worsen the problem of undersized supply lines.
This is just one example of how proper supply line size and installation is key to achieving optimal performance. If you are experiencing similar issues or need any assistance with a product or application, give me a call, I am glad to help.