Application Spotlight Detail

Super Air Knife™

Replacement for Expensive Noisy Blowers

Energy conscious plants might think a blower to be a better choice due to its slightly lower electrical consumption compared to a compressor. In reality, a blower is an expensive capital expenditure that requires frequent downtime and costly maintenance of bearings, belts and filters.

Here are some important facts:

Filters must be replaced every one to three months.
Belts must be replaced every three to six months.
Blower bearings wear out quickly due to the motor that must turn at 17,000-20,000 RPM in order to generate effective airflows.
Poorly designed seals that allow dirt and moisture infiltration along with environments above 52°C (125°F) decrease the one year bearing life.
Typical bearing replacement is at least once a year at a cost over $1,000.00.
Many bearings can’t be replaced in the field, resulting in downtime to send the assembly back to the manufacturer.
Many blowers generate heat, making conditions uncomfortable and difficult to use for cooling applications.

Blowers take up a lot of space and often produce sound levels that exceed OSHA noise level exposure requirements. Air volume and velocity are often difficult to control since mechanical adjustments are required.

Blowoff Comparison

There are a variety of ways to blow the water from the bottles shown in the photo, but which method is best? The following comparison of drilled pipe, flat air nozzles, a blower and the Super Air Knife proves that EXAIR has the best choice for your blowoff, cooling or drying application.

Our goal for each of the blowoff choices was to use the least amount of air possible to get the job done (lowest energy and noise level). Compressed air pressure required for each was 4.1 BAR (60 PSIG) which provided adequate velocity to blow the water off. The blower used had a ten horsepower electric motor and was a centrifugal type blower at 18,000 RPM. The table below summarises the overall performance. Since your actual part may have an odd configuration, holes or sharp edges, we took sound level measurements in free air (no impinging surface).

(2) Model 110012 12″ (305mm) Super Air Knives blow water off bottles prior to labelling.

Compare These Blowoffs

Drilled Pipe

This common blowoff is very inexpensive and easy to make. For this test, we used (2) drilled pipes, each with (25) 1/16″ (1.6mm) diameter holes on 1/2″ (13mm) centers. As shown in the test results below, the drilled pipe performed poorly. The initial cost of the drilled pipe is overshadowed by its high energy use. The holes are easily blocked, and the noise level is excessive – both of which violate OSHA requirements. Velocity across the entire length was very inconsistent with spikes of air and numerous dead spots.

Flat Air Nozzles

As shown below, this inexpensive air nozzle was the worst performer. It is available in plastic, aluminium and stainless steel from several manufacturers. The flat air nozzle provides some entrainment but suffers from many of the same problems as the drilled pipe. Operating cost and noise level are both high. Some manufacturers offer flat air nozzles where the holes can be blocked – an OSHA violation. Velocity was inconsistent with spikes of air.

Blower Air Knife

The blower proved to be an expensive, noisy option. As noted below, the purchase price is high. Operating cost was considerably lower than the drilled pipe and flat air nozzle but was comparable to EXAIR’s Super Air Knife. The large blower with its two 3″ (76mm) diameter hoses requires significant mounting space compared to the others. Noise level was high at 90 dBA. There was no option for cycling it on and off to conserve energy like the other blowoffs. Costly bearing and filter maintenance along with downtime were also negative factors.

EXAIR Super Air Knife

The Super Air Knife did an exceptional job of removing the moisture on one pass due to the uniformity of the laminar airflow. The sound level was extremely low at 69 dBA. For this application, energy use was slightly higher than the blower but can be less than the blower if cycling on and off is possible. Safe operation is not an issue since the Super Air Knife cannot be dead-ended. Maintenance costs are low since there are no moving parts to wear out.

Blowoff Comparison
Type of Blowoff	PSIG	BAR	SCFM	SLPM	Horse Power Required	Sound level dBA	Purchase Price	*Annual Electrical Cost	Approx. Annual Maint. Cost	First Year Cost
Drilled Pipe	60	4.1	174	4,924	35	91	$50	$4,508	$920	$5,478
Flat Air Nozzles	60	4.1	257	7,273	51	102	$168	$6,569	$1,450	$8,187
Blower Air Knife	3	0.2	N/A	N/A	10	90	$5,500	$1,288	$1,500	$8,288
Super Air Knife	60	4.1	55	1,557	11	69	$1,742	$1,417	$300	$3,459