Fluid pumps are at the core of PDT’s business; our design and manufacturing expertise has been developed during decades of support to the airborne cooling system market and has evolved to encompass pumping solutions for a wide range of fluids and power sources. PDT pumps are running around the clock in a variety of applications, from airborne cooling systems in demanding military applications to scientific spacecraft in use on Mars.

Capitalizing upon the skills developed in the design and production of circulating pumps, PDT has expanded our product line to include fuel pumps for small turbine engines used in missiles and auxiliary power units. PDT also provides lubrication and scavenge pumps for mechanical gear systems.

Positive Displacement Pumps

Positive displacement pumps work by trapping a fixed amount of fluid and then forcing that trapped volume from the inlet to the outlet port. These pumps deliver a consistent flow regardless of the discharge pressure. 

Power Options	Fluid Options	Applications
Motor Driven (A.C. or D.C) Shaft Driven	Hydraulic Fluid JP-10 PAO DIESEL Jet-A COOLANOL Lubrication Oil	Fuel Pumps Coolant Pumps Refrigerant Pumps Lube and Scavenge Pumps

Centrifugal Pumps

Centrifugal pumps use a rotating impeller to impart velocity to the fluid, converting kinetic energy to pressure energy as the fluid exits the impeller and slows down in the pump casing.

Power Options	Fluid Options	Applications
Motor Driven (A.C. or D.C) Shaft Driven	PAO Water Fuels EGW/PGW Flouirinert CO2 (liquid) CFC-11 (liquid) R-134A (liquid) Therminol	Fuel Pumps Coolant Pumps Refrigerant Pumps

Selecting the Optimal Pump

Pump selection is dependent upon a few key variables:

• Flowrate
• Pressure rise (head)
• Operating fluid
• Fluid pressure and temperature operating ranges
• Available power source

PDT uses these inputs, along with information about the system and/or vehicle application, to select the optimum pump for each installation. Pumps broadly fall into two types: dynamic or positive displacement. Among each type there exist several variations which are selected based on the variables listed above and other considerations for the intended usage of the pump. PDT currently designs and supplies centrifugal (dynamic) pumps as well as gear and gerotor (positive displacement) pumps.

The performance of centrifugal pumps is characterized by a pronounced inverse relationship between flowrate and pressure rise; that is, as the outlet restriction on the pump discharge is increased, the flow developed by the pump falls markedly. Positive displacement pumps display this effect as well, but to a much smaller degree. It is common for a positive displacement pump to have less than 25% decrease in flow over a discharge pressure range of several hundred psig. All pumps are typically sized for a nominal or rated performance point where efficiency is optimized. In a properly designed system, the rated performance point of the pump will coincide with the main operating condition, where the system will spend most of its functional life and overall efficiency is paramount.

Although most of the pumps produced by PDT are driven by an electric motor, shaft-driven pumps are typically used in engine or gearbox lubrication systems. PDT can supply either motor-driven or shaft-driven pumps, depending upon the needs of the application.

 



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