I was recently contacted by a customer who was using (2) of our 18″ Standard Air Knives to keep a sealing surface clean on their leak test fixture during a welding operation. The customer didn’t have a blow off in place before using our Air Knives and saw considerable improvement but were still seeing some residual contaminate on the sealing surface area. Their first thought was to turn up the pressure on the supply in an effort to create more flow, and while this did provide a slight improvement, the end result was similar. Next they were considering ordering a shim kit which includes a .001″, .003″ and .004″ shim, with the thought that opening the gap in the air knife, they would achieve more flow. (The Standard Air Knife is shipped with a .002″ shim installed). While changing to a thicker shim will provide additional force and velocity, we generally don’t need such large shims to blow away dust and light liquids from a surface. I turned our focus to the compressed air supply lines feeding the knives.
The customer was able to send a few pictures which quickly explained the lack of performance:
In the above photo you will notice the undersized 10mm tubing the customer was using to feed the knives. For an 18″ Standard Air Knife we recommend 1/2″ Schedule 40 Iron Pipe for a run up to 10′. Using undersized lines and/or restrictive fittings starves the knife of air volume and will result in a pressure drop which reduces the performance of the Air Knife. They were also using a standard pipe nipple coming off of the other end inlet of the first Air Knife to supply compressed air to the second Air Knife. This type of setup would actually starve the second knife even more as there wouldn’t be enough volume or pressure being delivered for the unit to perform. With the 10mm tubing effectively trying to feed (2) knives, this only compounded the inadequate supply for the air demand of (2) 18″ Standard Air Knives.
Referencing Photo 2 above, the customer was using our 3/4″ Pressure Regulator, Oil Removal Filter and Filter Separator and also supplying them with the 0mm tubing. To maintain their pressure and volumetric flow (SCFM), they would need to increase the supply size to at least 3/4″ pipe or larger. The other concern is the installation itself, with the airflow running from left to right in the image above – the filters should be mounted in line before the pressure regulator to provide clean filtered air to the regulator and accounting for any pressure drops passing through the filters.
The customer advised they have submitted a work order to have the filters placed in front of the regulators and to replace the supply line with 3/4″ pipe. Once the installation is correct, they will quickly learn that EXAIR air knives are the best in the industry and will have a successful application.