Fluid Temperature Control and Thermally Efficient Equipment
by: By John Courier

Section: Features-Summer 2023

Photo: SURASAK_PHOTO/shutterstock

Present equipment is not set up to accurately handle, control and monitor the temperatures and flow rates. Backup equipment is too big and expensive to operate and current proportioners cannot control the heat, especially when the lines are not even insulated.

To optimize mixing of the A and B side chemicals, their viscosity at the gun should be closely matched when heated to the same temperature. At room temperature the viscosity of the A-side is about 275 cps (centipoise) and reduces to 200 cps at 130° F. Conversely, the B-side has a viscosity between 600-1200 cps as room temperature that reduces to about 350 cps at 130° F.

This difference in viscosity of the A and B side at the gun can often result in a foam that has 1-2% excess A-side which can increase airborne isocyanates above safe levels.

More heat is needed to B-side chemicals to better control flow rate at the proportioner, better match viscosities at the gun and optimize spray ratios. This can begin by installing a 400-watt heater at the foot valve of the B resin pump can. A way to make resin heaters more efficient is to replace steel fire rods and springs with aluminum counterparts. Aluminum has superior heat transfer properties and can reduce spring spacing and reduce pressure loss in these heaters.
So, what is the future of equipment in SPF Rigs? Major changes will happen to our equipment soon. The need for onsite backup equipment is important, but at a high cost to the contractor.

Reduced Power Demand

Proportioners should be designed to operate with less wattage. Present proportioners are not insulated and lose heat from the preheaters to the heated hoses; aluminum manifolds mounted on a cold aluminum chassis lose 25% of the heat without insulation.


An unheated resin hose in winter will lose significant heat long before it gets to the meter if not spraying constantly. Summer heat could cause problems. Proper insulation of your supply hoses from the drums to the proportioner is vital to maintaining proper temperatures through your system. Strategically placed low wattage heaters and insulation can reduce the size of your generator, fuel consumption and maintenance costs and still give ample heat to the spray gun.

If you feel heat from your hose outside in the winter laying on the ground; you’re lacking insulation on the spray Hose! Too many amps are being used to heat our present-day systems with a demand for huge generators with higher operating costs.

Fire rods that heat the chemicals directly can cause damage to the chemicals as well as destroying the outside jackets of the fire rods, not to mention the pressure losses they cause. They cause 100 #’s pressure loss in every 18 inches of steel springs.

Without insulation of the manifold and tubes, massive preheaters draw huge amperage. Once the fluids leave the preheaters in small metal lines with no insulation, the fluids cool or heat back to ambient temperature quickly.

The 15,000-watt preheaters and 40 KVA generators with substantial costs per day for fuel are not efficient in our systems. We heat our 500 lb. drums with little 500-watt blankets that only draw 4.16 amps on 120 volts. This is useless with uninsulated supply hoses. We need to control the temperatures of both fluids from the drum to the gun with less amperage draw than we are presently using. See SPFA TT – G10. The contractor can do a great deal in controlling temperatures now. Heat tracing your supply line from the drum to the proportioner alone will control the beginning heat to the system.

Pump lube systems
Most ISO A pump lube systems are a failure in design and fluids used. Any contractor can fix this problem by installing a small peristaltic pump and eliminating plasticizers that react and set up with ISO A.


Hydraulic pumps

Electrical directional control components are costly to troubleshoot and are not needed. Hydraulic reciprocating pumps have been available for over 40 years with fewer components, more reliability and faster directional change. They can also eliminate air transfer pumps by using a driver pump technology, which can simplify your whole setup. For example, the paint industry uses simple hydraulic paint pumps.


Generators and compressors

Using a rotary screw type compressor eliminates current surges compared to piston compressors. This can reduce the size, KW, fuel consumption, and accessory components mounted to the generator. Using the hydraulics from the proportioner for a hydraulic drum mixer can reduce the CFM draw off your compressor allowing a smaller compressor. With air meters the fluids can over pressure the air pumping system causing problems; running a larger air system also costs much more to operate. If you switch between shore power and generators, keep a wired rotary screw compressor and hydraulics on the proportioner. I propose to go green with a generator that gets rid of all LP, gas and diesel type generators that contaminate our air and cost too much to operate!

Unheated gun flex whips with mini-Y strainers
You can reduce maintenance time and costs by taking the screens out of the gun and installing separate mini-Y strainers just after the manifold valves. You can shut off the valves, clean the screens, and be back running in a few minutes without wasting time taking the gun off or apart. The gun without screens operates cleaner and better all day. When screens get full, they restrict flow and split and allow dirt to get into the rest of the gun.


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