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Understanding today’s dryers

Managing Editor Phillip Lawless sits down with Cheryl Dobie of Aerodry Systems LLC.

May 23, 2013
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Phillip Lawless: How important are dryers in the modern carwash market?

Cheryl Dobie: Carwashes are considered a service industry and are therefore, labor intensive. The availability and high cost of a dependable labor force has operators looking for ways to reduce that expense while still providing service to their customer base. Efficient drying systems can replace some or all of the employees at the carwash exit.

PL: What materials are dryer housings typically made out of today?

CD: For longevity and ease of maintenance, materials used in the construction of carwash equipment must be non-absorbent and resistant to water and chemical corrosion. Stainless steel, aluminium, fiberglass, rotationally-molded plastic and coated cloth are among the materials used in drying systems. The choice of materials is generally manufacturer preference based on the design of their specific system.

PL: How have dryers become more efficient over the past few years?

CD: In short, the use of variable frequency drives (VFD) — also known as variable speed drives (VSD) — as motor control devices is one of the best ways for more effective use of energy to power motors in the carwash operation.

“Variable frequency drives, or variable speed drives (VSDs), can greatly increase motor efficiency in a variety of applications. VFDs are electrical devices which adjust the rotational speed of fan and pump motors in response to varying heating and cooling loads, and thus are much more energy-efficient than constant volume systems. VFDs offer direct control over the motor’s electricity input rather than restricting the load itself by using valves and dampers. ...VFDs provide significant energy savings because horsepower in motors varies as the cube of the torque speed. For example, if fan speed is reduced by 20%, then motor horsepower is reduced by 50 percent. The best motor candidates for VFDs are large motors with long operating hours. VFD technology has been available for years and has a proven track record of energy savings and reliability.”

The above quote is taken directly from the website that contains details of the steps taken by Harvard University to reduce energy costs and further advance their green agenda.

PL: How do you see carwash dryers improving in the future?

CD: Drying systems will continue to evolve as new, improved materials become feasibly available. It will be more important for manufacturers to substantiate their claims in relation to sound abatement and energy efficiency.

PL: Have dryers become more common at in-bay automatic carwashes?

CD: Competition with area carwashes as well as the ability to increase revenue generated by the wash facility has added to the number of drying systems at in-bay automatics. Operators have also discovered a free-standing dryer (as opposed to a drying system on-board with the wash) reduces total wash time and markedly improves the number of cars able to frequent the facility ― further increasing revenue.

PL: What types of regular maintenance tasks are important for carwash dryer systems?

CD: Drying equipment, as well as all the wash equipment, needs vigilant routine maintenance to ensure efficient operation and prevent costly downtime and repairs. First and foremost, know and understand the components in your system. This will allow you to establish the proper service schedule and keep a written record of when each service or maintenance check was performed. Failure to maintain the drying system in good condition can result in reduced efficiency and quality of dry, and an increased cost per unit of air moved.

PL: What are some tips owners should remember to keep their dryers operating at an optimal level?

CD: Carwashes are harsh, corrosive environments. Wiring must be protected from this environment by being corrosion resistant, dustproof and waterproof. Periodically, examine wiring and system components for signs of deterioration and loose connections. This includes the motor control center operating the drying system. Check the electrical and thermal overload protection for the motor. If a time-delay is used, its amp capacity should be about 125 percent of the full-load amperage (FLA) shown on the nameplate of the motor. Larger sized over-current protection may permit motor burnout. If the motor is equipped with a reset button overload protection, check to make sure it is not stuck.

All motors should be totally enclosed, and an electrical disconnect may be required within sight of, or in the immediate vicinity of every motor. A motor which is not totally enclosed offers an avenue for moisture penetration and requires routine greasing of the provided zerks. Cast body motors with fins dissipate heat more effectively than rolled motors, thus increasing the life of the motor.

A direct-drive fan is mounted directly on the motor shaft and presents the least maintenance. However, if a belt is employed, the routine checking of belt condition is one of the primary, and often over-looked maintenance problems. These must be regularly adjusted or replaced if full air movement is to be achieved, and efficiency maintained.

Knowing and understanding the type of fan and its capabilities is important. One-piece fans, precisely machined and balanced, generally pose little risk. Conversely, fans with welded fins are susceptible to repeated torque stress and the strains of pressure buildup. Sometimes, in an effort to reduce noise, the manufacturer reduces the size of the inlets and outlets. Improperly sized outlets on centrifugal fans increase air backpressure and add stress to both the fan and motor leading to failures; therefore, examining for stress fractures should be part of the routine maintenance.

Should your drying system contain moving parts, i.e. oscillating outlets operated by air cylinders or electronic eyes, special attention needs to be paid. Very often, check the air lines for leaks and the eyes for cleanliness. Staring down the tunnel, customers are keen enough to realize when something is not working properly. Predictably, when consumer’s “catch” dysfunctional equipment before they bid farewell, they tend to be more critical of the wash overall.

Check fan housings, air inlets and delivery systems for dirt buildup, blockages and corrosion. Choking off the air supply may lead to poor performance, overheating and failures. Debris inducted in the system will ultimately end up on the vehicle. Following manufacturer’s instructions, take the relatively small amount of time required to wash down the exterior of your dryer (and the surrounding area). Remember the dryer provides the visual frame for the exiting, and hopefully clean car.

PL: What advice would you give a carwash owner interested in replacing an older drying system?

CD: In addition to replacing the drying system, the owner may be upgrading the entire facility to increase car count and/or converting to an express wash to reduce labor. In either case, higher horsepower may be required. Insuring the facility has both adequate space and electrical to accommodate a new dryer will guarantee a smooth transition. Additionally, newly enforced neighborhood restrictions on sound can no longer be an after-after thought. And, last but not least, request and verify references on the system you intend to purchase – experience is always the best teacher.