Have you assessed your shop's air quality lately?
Some would say that quality compressed air remains the lifeblood of the collision repair facility. Loss of this vital pneumatic supply will bring any shop to its knees, stopping all operations of production. Only the loss of electricity would have a larger impact.However, most facilities treat the air supply as if it will always be there and never change. What is changing however, is the requirement for larger volumes and a cleaner, higher quality of this supply.
New, ultra-thin finishes, high-volume, low-pressure (HVLP) spray equipment, universal use of pneumatic tools, and more technicians on the line will require a complete review and assessment of this vital supply system.
Compressors
Repair facilities continue to undersize the compressor that supplies this lifeblood of air to the shop. Don't think of horsepower and price when choosing a compressor. Horsepower is only a part of the equation; cfm displacement is the major factor. Compressors use two ratings: Free air displacement is the calculated output, based on piston bore, diameter and pump rpm. And sustained cfm is the volume of air leaving the receiver or tank; this is the number to apply to your needs.Further complicating your decision are factors such as: Single- or multi-stage pumps, pulley or direct drive, piston or screw pumps, horizontal or vertical tank, tank or receiver size and electrical power requirements. The best recommendation is to contact a compressor supply company and have a representative survey your facility, review the data you have developed and then evaluate the options you have.
Pumps are either single-stage or multi-stage. In a single-stage pump, air is compressed once and sent to the receiver. In a multi-stage pump, air is compressed then sent to a second piston and re-compressed.
Pump units can be in single- or multi-piston design, or in a screw style design, which compresses like a turbo or super charger. One factor to consider is that almost all collision repair tools require no more than 100 psi pressure. Many single-stage/multi-piston pumps will provide proper air for your use. The screw design pumps very high volumes of air and creates less of a temperature increase during the compression.
Belt or direct drive refers to the method of turning the pump. Standard compressors mount the motor and pump parallel and connect them with drive belts. Direct drive connects the pump directly to the output shaft of the motor. Direct drive is used for high volume applications like jackhammers or construction. However, models now exist for the collision repairer.Receiver or tank size and shape become important for two reasons: Vertical tanks work best in facilities with limited floor space. Also, the tank size and dimension is most often determined by pump output and user air volume requirements. Generally, there are limited choices.
Power requirements are dictated by the motor size needed to efficiently turn the pump. If your facility has or could have three-phase electricity, use it. Motors will be smaller, power rates are more economical and start up torque is higher.
Unfortunately, compressors create a condition that is not palatable in collision repair-hot air with moisture. When the air is compressed, its temperature rises dramatically. When this hot air cools down, any moisture (humidity) in the air turns to a condensate. This liquid can settle to the bottom of the tank-or if still contained in the hot air, can continue down the main line where cooling and condensation occurs. This condition causes severe internal tool wear and paint problems, including blistering and dirt in the finish.Tank drains allow for the removal of moisture buildup in the tank. Unfortunately, most shops have a poor schedule for opening these drains. Purchase a "float" style or electrically activated self-drain to eliminate this problem. Also, installing an aftercooler or refrigerated air cooler will almost completely eliminate these problems. These units, when installed shortly after the compressor chills the air, collect the condensate and release it out of a drain.
Dos and Don'ts about Compressors
Locate the compressor in a room with ample fresh air supply and ventilation. Also, plum for outside air supply if needed. Do not locate the compressor above an office or a supply room-heat rises, so the compressor will start out compressing hot air, increasing the volume of condensate.Pressure settings should be adjusted to meet your needs. Ideal pressure settings are 90 psi low and 120 psi high. Do not over work the pump by creating a higher pressure than needed. These settings lower the compressed air temperature, which lowers the condensation factor. The compressor will operate more efficiently at the lower pressure settings.
Develop a maintenance check chart, following the manufacturer's recommendations, and place it on a clipboard located near the compressor. Routinely check and sign off on these activities-assign this task to a specific person.
Pipe Size Selection and Location
Ideally, airline plumbing should be done using stainless steel. Although more expensive, this material does not deteriorate, has a smooth finish on the surface and develops less internal buildup of contaminates. Stainless steel dissipates heat at an acceptable level. Galvanized or black iron pipes, as well as copper, are also acceptable materials. Avoid using PVC plastic pipe. This material, although easy to work with, has some disadvantages. Plastic expands and contracts at a high rate. This may cause droops in the lines, fittings to come apart, and subject materials to cracking or breaking from external forces.Properly routing and locating your mainline piping will have a positive role in providing cooler, cleaner air. Hot air leaving the compressor storage will continue to cool as it travels down the lines. Condensation will form on the inside of the pipe and travel along with the flow of air. Install drip legs with manual or self drains regularly along the main line. Secondary or take-off lines are plumbed to exit the main line from the top, which helps avoid the moving condensate from falling into the secondary line, exit from the side of the secondary line and install an air transformer. Extend the secondary line below the transformer and install a manual ball valve drain at the bottom of the secondary line. At the end of the mainline, install a ball valve allowing for a full line blow out.
Water in the air is a major and constant problem. Even dry regions of our country can have high humidity conditions and suffer from condensation in the airflow.
Plan ahead; begin with an after-cooler or refrigerant dryer at the compressor, plumb in drop legs, and if needed install desiccant dryers along the way. Additional considerations to a successful air system include:
- Avoid plumbing in the warm upper areas or ceiling of the facility. Mid wall height or lower is preferred.
- Plan your supply system so the air provided to the painting area has traveled the farthest and cooled down the most. Provide larger hoses and fittings for use with HVLP spray equipment (3¼8 in.).
- Design the routing to minimize the number of joints, fittings and angles; each of these will create internal resistance known as "line drop."
- Remember that lube, oil and filter are as important to the compressor as to your motor vehicle.
- Shut down and drain your system each week. If possible, leave it down over the weekends.
Remembering that this simple air supply system is the lifeline of your shop. It is critical that it be valued higher than all other equipment. Thoughtful planning, selection and installation of the air supply will reap benefits for years.
