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Balancing your tunnel

October 11, 2010
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For maximum performance and profitability in your tunnel, it is important that you understand how your equipment and chemistry work together to clean a vehicle. For instance, using too little product might save you money, but at the cost of return customers. Using too much product will not necessarily clean a vehicle any better than using the proper amount, yet will unnecessarily increase costs.

This does not only apply to chemical products. Running your conveyor too fast may cause cleaning issues as well as staffing concerns. Running your conveyor too slow may increase chemical costs but not cleaning efficiency.

In today’s market there are three basic types of tunnels: friction, touch free and hybrid. Each type has its own need for a chemical balance for the best performance and this should be kept in mind when tuning your tunnel.

Speed, time and weather
An important aspect of balancing any tunnel is conveyor speed. For years there has been a never ending debate in the tunnel industry regarding conveyor speed. Generally, operators tend to run conveyors at a much higher rate than necessary. It should be set to handle the amount of cars that are normally done at the wash if it has been properly staffed.

The other factors involved are:
  • The day of the week;

  • Weather conditions; and

  • Time of day.
On a slow day you can allow for greater spacing and maybe do with less staff. At high volume, space the cars as close as you are able to handle with the staff on hand.

If you are running too fast, it may require higher chemical concentrations to get maximum cleaning. If run too slowly, raising dilution ratios may not be able to achieve a good cost per car.

Keep in mind, any changes in conveyor speed done after a wash has been set up will require adjustment of the chemical dilutions. Once you have arrived at the speed you can live with, set it and don’t change it. Once the speed is set, you can work on balancing your chemicals.

Regardless whether or not you have a gauge to set your conveyor speed, I would recommend checking the rate manually. The formula for calculating conveyor speed is:

(Time * 2 ) * 60 = cars per hour (CPH)

To arrive at the time portion of the formula, time a roller for a distance of 10 feet. Most conveyors are designed with 10-foot sections, so you should be able to use the welds on the conveyor as a guide.

Friction cleaning process
The equipment configuration and form of friction used in a friction tunnel wash varies a great deal. There are still a few carwashes using brushes, but most washes use some form of cloth or closed cell foam type material or a combination of both as their friction media.

Normally a friction wash contains some form of friction on all sides of the vehicle. On the top you may see a mitter curtain, mitters or a top brush. On the sides you may see some form of side brush or high pressure. Many also have wrap around units to clean fronts and backs of vehicles. In today’s tunnel market, there is some form of friction in at least 90 to 95 percent of washes.

In balancing a standard friction set up, there are three basic elements that must be considered:
  • Speed of the conveyor;

  • Type of friction media used; and

  • Chemical application.
As was previous discussed, how fast the conveyor is run has a major effect on cleaning as well as chemical application and usage.

In a traditional friction set up there is normally a pre-soak, followed by the application of a shampoo. What products you choose should provide a chemical balance.

When choosing your cleaning products, balance is key to removing the various types of soils you are dealing with. There are two different categories of soils: organic and inorganic. In simple terms, organic soils originate from a living source such as vegetation or animal matter. They are best removed with an alkaline or high pH product. Inorganic soils originate from a man made or synthetic, non-living source. For example, brake dust, mineral deposits, road salt, clay and abraded asphalt or concrete. They are best removed by acidic or low pH products.

Low pH products do a better job on glass and chrome and aid in the drying process. The vast majority of the matter you encounter will be organic soil, so you will use a closer balance between high and low pH products than low pH in a friction tunnel. (In hybrid and touch free tunnels, an operator will use more high pH product than low pH.)

If you use a high pH or alkaline pre-soak, it would be important to use an acidic or low pH shampoo. If you use low pH presoak, a high pH shampoo would most likely be your best choice.

If you are using the dense foam material, it is also important that the shampoo you select provides good lubricity but not necessarily high foam. Too much foam can cause the media to glide over the foam without making any contact with the vehicle’s surface defeating the purpose of friction cleaning.

Touch-free cleaning process
In a touch-free conveyor carwash the vehicle is washed by a combination of mostly low-pressure chemical application and high-pressure water rinses rather than brushes or cloth or foam. Generally, the chemical solutions are heated (from 110 degrees to 130 degrees Fahrenheit) before application to enhance their cleaning ability.

After the chemical application, high-pressure water (usually 800 to 1200 psi) is applied at an angle (anywhere from 10 degrees to 45 degrees) to rinse the chemical and loosened soils from the surface of the vehicle. Angles are used in rinsing to increase impingement or degree of contact with the surface to “peel” or push the chemicals and loosened soils from the surface.

There are two basic methods utilized in touch-free washing, and both involve two steps. One is the application of a high alkaline product followed by the application of another alkaline. The other method is the application of both a high alkaline and low pH product.

The two-step process involving the high and low pH products is the most common method found in tunnels. The rationale for this approach is that the low and high pH products attack a greater range of surface soils than the two step alkaline approach. I have heard arguments as to which product — high or low pH — should be applied first. Some say the high pH should be applied first since it will be neutralized if the application of low pH is used first. Others say the low pH should be applied first to get better cleaning of glass and chrome. My personal preference is the latter, but I have seen both methods used effectively. Most operators that employ the two-step alkaline do so because of a reluctance to use a low pH product in the wash process. If that is your choice, I would recommend increased dwell time, a stronger chemical dilution ratio or a higher solution temperature to compensate for cleaning inorganic soils.

The appropriate selection of the products used is critical in the cleaning process. As mentioned previously a residual high pH may also have an effect on the drying process. High residual alkalinity may also create difficulties for your sealant or protectant. On the other hand, a slightly acidic or neutral surface residual will enhance the drying process.

In addition to an awareness of what the residual effects cleaning products may have on drying, the flexibility of choice of cleaning products and the relationship of cost per car can make the difference between cost and performance.

Hybrid cleaning process
The hybrid carwash blends the best features of friction and touch free washing. In the typical hybrid carwash you will find a limited amount of friction, usually some form of mitter or top brush and possibly a side brush. Also involved in the process will be some form of two-step chemical application followed by high pressure. The exception would be the new exterior express tunnels that utilize two-step chemistry as well as extensive friction. Normally, two pre-soaks are applied followed by a shampoo. Once again most will use both an acidic and alkaline presoak rather than two alkaline applications.

In a hybrid tunnel, especially with a short conveyor, I would highly recommend that you use a low pH shampoo for better drying results. In today’s market, the hybrid technique is found in most of the washes using some form of friction. It is especially popular in short tunnel configurations (85 feet or less) due to the length of time devoted to the cleaning process.

Fixing your tunnel’s unique quirks
As you can tell by now, balancing a tunnel by taking into the considerations all of these cleaning factors is no easy task. If you are lucky enough to have a well trained chemical rep, some of this work may already have been done for you. The true professional rep develops a feel for the cleaning process and often can make a positive effect on cleaning by making the proper adjustment in their customer’s tunnel.

Each tunnel has its unique “quirks” that need to be dealt with on an individual basis. As an operator there is no substitute for gaining an understanding and experience with what works best in your tunnel.

Ron Holub has been in the carwash industry for almost 30 years. He has worked for several national carwash chemical companies, owned a carwash and detail supply company, and served as a general manager for a national carwash chain. He currently works for Townco Washing Systems in the Atlanta area and can be reached at

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