PPS Impels Automotive Pump Design

• chemical- & temperature-resistant

• dimensionally stable

When developing new water pumps for cars made by US automakers, Airtex Products needed to find a material that would have the mechanical integrity and dimensional stability to resist continual immersion in aggressive coolant solution at temperatures up to 130°C. Curt Ulm, director of engineering at Airtex, says “Today’s glycol ‘long-life coolants’ contain organo-acid inhibitors that prevent particulate formation and so extend coolant life to 100,000 miles. Unfortunately, those inhibitors can attack aluminum and many plastics. In developing the impellers for these pumps, we considered resins such as polyphthalamide and several nylon derivatives, but these did not perform as well as PPS.” 

The water pumps, which are 4- to 15-in. dia. and 3.5- to 8-in. wide, circulate coolant through the radiator and engine at rates of 30 to 100 gal/min. The pumps are powered by a belt off the crankshaft and operate when a thermostat indicates engine temperatures above threshold value. The impellers are 2.5- to 4-in. dia. and 0.2- to 1-in. wide, and rotate at rates as high as 8,000 rpm. “Impellers made of Fortron PPS are practically trouble-free,” comments Curt Ulm, director of engineering at Airtex. “This is impressive because they must retain their size and strength in a tough chemical environment.”

Ulm says Fortron PPS from Ticona withstands the mechanical stresses of rapidly changing rpm’s in this high-heat, acidic environment. “The polymer’s dimensional stability keeps the impellers from deforming under the high rotational torque and uneven pressures in the pump. This can involve a 30 to 40 psi differential across the face of the impeller.” Design flexibility was also important, enabling “new geometries that promote efficient interaction between the impeller and the fluid…[helping] fit our pumps into the underhood space auto designers define for them,” concludes Ulm.

For more information:
Airtex Products, Fairfield, IL  www.rsleads.com/203df-243

Ticona, Summit, NJ  www.rsleads.com/203df-245