Dryer System - Rules of Thumb for Maximized Performance
By Archie Johnson
Successful car wash operators everywhere know that in addition to their customers wanting their vehicles clean, they expect them to be dry as well, really dry. Living up to that expectation can be a challenge. It starts with having a dryer system that’s correctly configured and installed. If your dryer is more than 10 years old, it may be time to replace it with a more efficient one.
Choosing a dryer system for your car wash is a major undertaking and certainly not one to be taken lightly. Do some research by first identifying your specific requirements and, second, finding solutions that will meet those requirements. Even though many car washes have similar drying issues, addressing your specific needs will go a long way to improve the quality of your drying which will satisfy more of your customers. And that’s what will bring them back again and again.
THE RIGHT BALANCE
There are a number of things that affect how dry vehicles are when they exit a car wash. Probably the most critical one is having the right balance of chain speed to the number of air producers on a dryer. As a rule of thumb, there should be one nozzle for each 15 cars-per-hour increment of chain speed. For example, if you run your conveyor at 90 cars per hour, you should have a minimum of six nozzles, for 120 cars per hour conveyor speed, eight nozzles, etc. Keep in mind, this formula is general in nature and other variables can also affect how well a dryer performs.
Obviously, planning and building a new car wash allows more flexibility in planning a dryer system. On the other hand, retrofitting one in an existing building always has fixed conditions that must be dealt with. Some of the critical ones are available power to run the dryer, amount of drip space, and floor space allotted for the dryer. Upgrading to a new and more efficient dryer in an existing building can be easily accomplished with help from the manufacturer.
Most dryer manufacturers offer both 10-hp and 15-hp air producers. Even though they both require approximately the same operating space, a 15-hp producer will generate 12 percent to 15 percent more cubic feet per minute (CFM) and air velocity than a 10-hp unit and dry noticeably better. When line space is marginal, overall dryer performance can be maximized by using as many 15-hp producers as possible. If the available power can only handle a few 15-hp nozzles, they should always be put on top because of the distance the air must travel to dry hoods, windshields, and trunks of cars.
Manufacturers offer several dryer options that should be considered. When floor space is an issue, performance-enhancing options can improve drying without needing more floor space. For example, oscillating top nozzles used in place of stationary ones can cover nearly twice as much area. Then there’s the “flip” nozzle that changes the air stream direction to dry the back of vehicles. These particular options add to a dryer’s performance without requiring additional floor space.
A dual-port or flip nozzle (top) and an oscillating nozzle (bottom).
Another effect of chain speed is how much water is lost when vehicles pass through the drip area. After leaving the last rinse arch, vehicles should have enough time in the drip space to allow most of the water to run off. Using the right rinse additive certainly helps, but dryers can still only do so much. If a lot of water is left on vehicles going into the dryer, chances are they’re going to come out wet. There’s one obvious solution to this problem, and it’s not a good one: that is to slow down the conveyor, which, of course, will reduce throughput.
There’s one contributing factor to this problem that has to be addressed: While regular soft water beads up and strips off easily, spot-free or reverse-osmosis water tends to cling to surfaces making it harder to remove. However, a high-quality rinse additive formulated for spot-free water will go a long way to solve that problem. It’s safe to say that most operators think that the benefits of spot-free water outweigh the extra chemical needed to help dryers remove it from vehicles.
Every tunnel operator knows the biggest single consumer of electricity is the dryer system. It’s not uncommon for car wash facilities to have dryer systems in excess of 100 hp. That means the single most expensive function in processing a vehicle through a car wash facility is probably drying that vehicle. A large portion of that cost can be due to constantly starting the dryer motors.
During their initial start-up, “inrush” power surges can be three to four times the power used by a motor after it reaches full rpm. Adding to that problem, in many areas electrical rates are based on peak power so it’s important to keep it as low as possible.
An air-on-demand nozzle with intake open (top) and intake closed (bottom).
There are two tested and proven ways to reduce a dryer’s electrical power usage. One way is by slow-starting the motors with a VFD or variable frequency drive. Simply put, this device reduces inrush current during motor start-up by starting the motor with a low frequency and increasing the frequency slowly until the motor reaches full RPM. The other method that’s gaining popularity is closing off the intake of a running air producer, which causes a 50 percent drop in motor load. This simple device opens allowing airflow when a vehicle enters the dryer and closes as the vehicle exits, much like how a rinse arch operates. Although each system functions differently, both systems reduce power consumption significantly.
Dryers are a critical component of any car wash, particularly in exterior washes where the customers can judge its performance from the driver’s seat. Make sure your dryer meets their expectations and you’ll have more satisfied customers and a better bottom line.
Archie Johnson is the owner of The Dryer Pros and can be reached at (602) 272-2940 or email@example.com.