POLY - Discharge Gear Pump POLY high-pressure gear pump for the discharge of medium to high viscosity media from the reactor. The extra large inlet opening guarantees an even flow of product to the gearwheels even under vacuum or extremely low NPSH conditions. Offered with either a round inlet port, by means of which the suction flange of the pump is directly connected to the outlet flange of the reactor or as a low NPSH version, where the pump is connected between the pump and reactor flanges, in order to achieve an even larger and shorter inlet port. Technical Features Housing Non-alloyed and alloyed steels · cast steel · with optional surface coating Gears Nitrated steel · tool steel · special steel · with optional surface coating · helical gearing · herringbone gearing Friction Bearings Tool steel · NiAg (nickel-silver) · Al-bronze · special materials · with optional surface coating Shaft Seals (Vacuum) viscoseal · stuffing box · combination of viscoseal and stuffing box · double-action, buffered mechanical seal Heating Systems Heat transfer oil · steam Application Examples Polymer processing There are two types of Poly: a) Standard design: The suction flange is also the fastening flange to the reactor. b) The Low NPSH design: In this case, the fastening flange is designed as an alifning flange and is seated on the delivery side of the pump. The pump is clamped between the aligning flange and the reactor flange. This design provides an extremly large and short suction opening, promotin product flow. The opening can be circular, squate or rectangular. Low NPSH Version The loss of pressure on the suction side of the pump is dependent upon a number of factors. Parameters like viscosity and flow rate are largely predetermined by the process. According to the Hagen-Poiseuille equation, the pressure loss is linearly proportional to the length of the inlet path and inversely proportional to the fourth power of the diameter. The unique WITTE low NPSH version utilises this knowledge and offers an extremely large diameter, short suction inlet. With the Low NPSH version, the connecting flange is foreseen as a loose flange and is located on the pressure side of the pump. The pump itself is connected between the loose flange and the reactor flange. This configuration allows an extremely large diameter, short suction inlet to be incorporated into the housing. The shape of the inlet is variable and can for example be round, quadratic or square. Due to the fact that the pressure losses at the suction side have been reduced to a minimum, even critical applications can be reliably realised, e.g. discharging high viscosity or foaming melts.