Blowers for Extreme Environments

Blowers for harsh environments: Specifying to withstand high humidity, dirt, particulate, and temperature-differential condensation

Detrimental environmental conditions abound in industrial and even commercial-grade blower environments. The top three environmental challenges to blowers are:

• Pollutants such as dust, dirt, and fumes associated with the process at hand

• Excessive ambient heat and winding-generated heat that accumulates in tight design spaces

• Moisture and condensation associated with temperature differentials

In this white paper, we outline what design-engineer and end-user responsibilities are for protecting blowers from the detrimental effects of these factors. Then we detail the latest blower design features designed to mitigate the effects of environmental conditions … and extend the applicability of certain blower designs.

DFS WP 04 01 Windjammer PRO Blowers for extreme environments.psd CAPTION >>>>

AMETEK DFS Windjammer PRO blowers can run various performance profiles to satisfy disparate application requirements.

Ingress of pollutants such as flour, dust, and fumes

Consider the challenge of particulate ingested into industrial blowers. Here, contaminated air can dramatically reduce blower operating life. But a lot of blower applications — as those for vacuum applications or fume-exhaust equipment on paint booths, for example — are specifically required to interact with environmental contaminants.

So for applicable blower models, AMETEK Dynamic Fluid Solutions (DFS) details in its specification sheets which blowers are supposed to get clean air … especially for cooling the motor and housing containing the controller. Where such directives aren’t followed, the blower installation will be suboptimal … with air returns that ultimately pollute the controller housing and motor with dust.

According to Kris Diehl, engineer at AMETEK DFS, there’s a fine line between acceptable use and misuse of blowers in challenging settings.

“Some end users assert that because a blower is their property, they have the right to use it any way they wish — even in dirty environments without filtering. What’s more, many designs face fairly challenging space constraints that don’t easily accommodate the addition of subsystems to protect the blower from contaminated environments.”

But for some environments, Diehl underscores that the only way to get optimal system performance is to filter air entering the blower. An industry rule of thumb is that an inlet filter should be used wherever working or cooling air for a blower is polluted with particles 2 μm or larger. This filter system should introduce the smallest possible pressure drop to maintain blower efficiency.

Otherwise, through-flow blowers (which make double use of one working airflow by channeling it motor and electronics) may not be the best choice. Instead, a better choice may be a bypass blower — which segregates the airpath for performing the application’s working function from that to cool the motor and electronics during operation.

Another blower-industry rule of thumb is that if an environment’s air is polluted enough to necessitate that personnel wear breathing masks, then any blowers in that environment should also have protection.

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The Windjammer PRO (and its incorporation of a separate inlet for motor cooling) offers design engineers a new option to address issues related to heat and blower ingestion of airborne contaminants. In contrast with traditional blower designs that rely on unchanneled airflow for cooling, the Windjammer PRO includes a molded scroll into its motor-cooling circuit to promote airflow circulation. Better cooling means the motor (and blower) can be run harder to deliver more power density. Plus improved sealing prevents contamination from reaching the bearings, which (after electronics) are the second-most delicate element in the assembly. That sealing ultimately extends the bearing (and blower) life.

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Motor-cooling air in the Windjammer PRO flows over  a small heat-exchanger plate mounted to the underside of the electronic board’s power module that executes the switching for the motor (including PWM current to the motor in setups using such speed control). Active channeling of air in this manner helps keep this critical portion of the blower cooler.

Adding to the importance of considering pollutants during the specification of blowers is that no matter a blower’s duty cycle or hours of actual operation per day, exposure to the environment is a 24-7 proposition.

“Engineers primarily use catalogs to identify suitable blowers based on performance, voltage input, and other core parameters,” said Diehl. “No wonder then than sometimes we see failed blowers after a challenged run in service … because the environmental challenges aren’t often top of mind during the design process.” After all, even a blower that operates cyclically — running for one hour and then sitting off for three hours — still experiences four hours of exposure to the environment — with dirt just raining down onto (and into) the blower, to give an extreme example from a real-world bulk material-handling application.

“Protecting the blower electronics is particularly important, because the motors themselves — particularly brushed motors — are relatively durable,” concluded Diehl. In contrast, electronic-board connections are inherently delicate and susceptible to shoring and failure from the presence of all kinds of substances.

Addressing excessive blower-application heat

Blowers must endure the most extreme temperatures in combustion, chemical processing, printing, and wastewater applications. Here, it is the job of the specifying engineer to heed maximum operating temperatures listed in blower catalogs.

More specifically, designers should ensure that normal blower operation doesn’t cause the motor winding temperature to exceed maximum values — 130° C for Class B motors and 155° C for Class F motors, for example. Otherwise, a blower with a higher motor-winding rating should be chosen. In many cases, the upper limits on these temperature values are also those of the blower’s outlet air.

Where temperatures at a blower’s inlet are predicted to exceed those listed for the required level of performance (as suction or pressure points based on 40° ambient air, for example) the engineer AMETEK for recommended solutions.

In fact, the motors within blowers include an array of features specifically for the mitigation of heat — even beyond higher winding ratings. Case in point: Small brushed dc motors for miniature AMETEK DFS blowers now include longer lengths to boost output toque by 40% for a given diameter in some cases. More importantly in this context, the extra motor length facilitates heat dissipation better than comparable motors that are shorter motors.

DFS WP 04 03 performance of the Windjammer PRO despite contaminants NEED VECTOR VERSION.ai CAPTION >>>>

Windjammer PRO blowers run cooler than comparable blowers, and that extends the life of its brushless motor, bearings, and electronics.

Consider another example of blower-motor design to mitigate the effects of heat — that on universal motors. Sometimes the rate-limiting factor in universal-voltage offerings is the stator, as this part of the motor is what gets hot during operation. One option is to choose a different blower size or speed. “We recently had a customer that couldn’t run a sealed blower at 120 V because the environment was very hot, and the blower would shut down,” said Diehl. “So we reprogrammed the blower to run at a slower speed so it wouldn’t overheat.”

Another option is to choose a blower with more efficient cooling — such as the new AMETEK DFS Windjammer PRO, for example. “Applications as the one Diehl describes could benefit from the new blower as it actually performs better (cooler) when sealed,” Diehl added.

Condensation associated with temperature differentials

As mentioned, onboard blower electronics are the most delicate subsystem in a brushless blower — so protecting the electronics module is vitally important. Silicone encapsulation of onboard blower electronics is a leading solution where condensation on internal subcomponents is an issue.

However, in the case of the AMETEK DFS Windjammer PRO, there’s less likelihood that potential applications would need such electronics encapsulation. That’s because the polymer housing of this blower accumulates less moisture than metal housings of traditional blower designs.

“One exception is in settings where condensation is an issue — where the blower setting cycles between hold and cold … or the blower runs in a freezer or other exceptionally cold environment and then gets hot after it’s run for a period of time,” noted Diehl. “Here, encapsulation with nonconductive silicon keeps the electronics safe from the detrimental effects of unavoidable condensation.”

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Shown here is a small blower motor with encapsulated electronics.

AMETEK DFS provides electronics encapsulation for many of its blower customers. Much of this work is done at the AMETEK manufacturing facility in Rock Creek, N.C. Drawbacks are that it’s a costly process and also takes time to allow curing. However, rubber silicone gel serves other protective functions that go beyond shielding from moisture — preventing corrosion from caustic fumes and even preventing damage from thermal and mechanical shock and vibration.

Visit ametekdfs.com for a follow-up piece on shock and vibration mitigation for blower applications.

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