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COATINGSPRO ROOF COATINGS 2016 21 truck with an increased gross vehicle weight (gvw). e main component of the equipment is the propor- tioner, or sprayer, and you have a lot to think about. Choosing a Proportioner e spray equipment is the most expensive cost when build- ing a mobile SPF rig. is consists of the proportioner, heated hose, spray guns, feed pumps, circulation systems, and possibly an agitator depending on the type of foam you choose. When choosing a proportioner, there are several features to consider: • Flow rate: This is the main factor in choosing a propor- tioner that is right for your needs. Portable sprayers for small jobs and touch-ups have flow rates as low as 8 lbs. (3.6 kg) per minute (approximately 0.8 gallon, or 3.0 L, per minute). Larger proportioners typically found in commer- cial roofing have flow rates around 40–50 lbs. (18.1–22.7 kg) per minute. When using these larger pumps you can support larger tip (also known as mix chamber) sizes. A larger tip means you can move faster, increasing produc- tivity. To prevent material waste when doing small jobs or detail portions of a larger job, you can use smaller tips, reducing the flow rate and improving control. Using smaller tips on large pumps does not hurt the equipment. • Power: There are three power sources to choose from that drive the sprayer's pumps: electric/direct drive, electric/ hydraulic, and pneumatic. Electric/direct drive is the most efficient in transferring horse power into gallons per minute, so it is the best value; however, equipment with this drive are restricted in flow rate to 30 lbs./min. (13.6 kg/min.) as there are limitations to how much torque the direct drive transmission can handle. For higher flow rates, electric/hydraulic systems go up to 50 lbs./min. (22.7 kg/min.) and are the most common sprayers for roofing contractors to increase production. Pneumatic systems can handle high flow rates also; however, they are ineffi- cient in transferring horsepower to gallons per minute, and they are typically not as effective in mobile applica- tions. Pneumatic systems require a large air compressor to operate and can have issues with motor freeze up in humid conditions with inadequate moisture removal equipment. • Heaters: The proportioners have large electric heaters to heat the A and B components to spray temperatures commonly between 125–140° F (51.7–60.0° C). As the flow rate increases from the pumps, the heaters have less contact time with the material, requiring the heaters to have more power and increased wattage. Low flow proportioners have 6,000 watt (6 kw) heaters Rig For Commercial Roofing When choosing a proportioner, the most expensive part of a mobile SPF rig, there are several features to consider. The necessary flow rate and power source for the jobs are two of the considerations.