Why Pairing a Paxton Blower to a Paxton Air Knife is Important

In order to maximize system performance and efficiency, Paxton's Application Engineers utilize both blower performance curves and air delivery device resistance curves to properly size a Paxton blower system. Often, an ineffective drying system will have been pieced together without consulting these curves - resulting in an inefficient system with non-optimal airflow. 

Figure 1: Paxton Blower vs. Regenerative Blower
	Blower sizing is more limited and complicated for regenative blowers, because they have a much steeper blower performance curve than a Paxton centrifugal blower, as shown in Figure 1.
Figure 1: Since the regenerative blower curve is very steep, the efficiency of the blower drops very quickly compared to the PX-series blower curve.

Figure 2: Paxton Blower and Paxton Engineered Air Knife Curve
	It is necessary to engineer the air knives so that their resistance curve crosses the blower performance curve a the desired flow and pressure and ideally, at the highest blower efficiency (See Figure 2).
Figure 2: The peak efficiency for this PX-series blower and the Paxton 60'' Air Knife, 0.055'' Gap, is about 70%, at 750 cfm and 75'' H2O.

In fact, as shown in Figure 3, if not properly engineered the blower performance curve and the air knife resistance curve may not intersect, requiring extrapolation to a high pressure-low flow operating point. This would result in poor performance for drying and blow off. This usually occurs when blowers are puchased from one company and the air knife is paired with the blower is purchased from a low-priced alternative or vise versa. This means, to be efficient and effective, you must size the air knife/knives to match up properly with the blower, preferably at its highest efficiency point. If you do not properly size the air knives with the blower, you can end up with blower surge, i.e. a region on the blower performance curve at maximum pressure that results in unstable air flow and can cause the blower to generate excessive heat, aerodynamic vibration and ultimately premature blower failure. Or you could size the system with too much air flow for the motor power size and over-current and fail the motor. 
 

Figure 3: Paxton Blower Curve and Compressed Air Knife Curve
Figure 3: A surge will cause unstable air flow and the blower can overheat.

Figure 4: Paxton Blower with Non-Paxton Air Knife
	Further, the blower's operating range (see RED box in Figures 4 and 5) is 550 CFM to 1400 CFM at 80'' H2O to 40'' H2O respectively. Figure 4 shows a non-engineered air knife that is 60'' long with a 3/16'' gap, with its resistance curve in yellow. If this knife is paired with the Paxton blower, it results in an operating point of 1475 CFM at 25'' H2O (see GREEN circle). This point falls outside of the operating range of the blower. Operating at this point will result in low back pressure and an underperforming system, with the blower only about 32% efficient.
Figure 4: The Paxton blower paired with the Homemade air knife curve is outside of the suggested operating range.

Figure 5: Paxton Blower with Paxton Air Knife
	Figure 5 shows (in green) an engineered Paxton Products air knife, that is also 60'' long, but has a standard gap of 0.055 inches. The resistance curve for this air knife crosses the blower curve within the operating range and provides a blower efficiency of nearly 70%. This example demonstrates how blower efficiency can drop preciptously when the wrong air knife is paired with the blower.
Figure 5: The Paxton blower and the Paxton air knife fit inside the suggested operating range.

Paxton's Application Engineers, having a combined 75+ years of air system design experience, will work with the given information of airflow rate and pressure in order to provide the most efficient solution which will greatly exceed the drying and blow off performance of an ad hoc system. Once the Paxton team arrives at the necessary solution for a particular application, they will proeperly size an air knife/knives with a blower that will operate at peak efficiency (about 70% as shown in Figure 5.