G-type screw pumps have a very wide range of applications; in standard industrial sectors, they can be used for almost any liquid transfer task. However, while they are the optimal choice for some applications, they may be less suitable for others—where, although usable, they might lead to inefficiency or inconvenience. For details regarding specific application fields and functions, please refer to our previous article, "The Functions of G-type Screw Pumps"; we will not repeat that information here. Today, as a manufacturer of G-type screw pumps, Shanghai Shenyin Pump Manufacturing Co., Ltd. would like to discuss the selection process. An incorrect choice can lead to reduced efficiency or damage to the pump itself in minor cases, or disrupt the entire production process in severe cases; thus, the importance of proper selection cannot be overstated. We hope you find this information useful.
I. Selecting the pump speed: The flow rate of a G-type screw pump is linearly related to its rotational speed. Compared to low-speed models, high-speed screw pumps offer increased flow rates and discharge heads but require significantly higher power. High speeds accelerate wear between the rotor and stator, inevitably leading to premature pump failure; furthermore, the short stator-rotor length typical of high-speed pumps makes them highly susceptible to wear, thereby shortening their service life. By using a reduction gear or a variable-speed drive to keep the speed within a reasonable range—below 300 revolutions per minute—the pump's service life can be extended several times over compared to high-speed operation.
II. Considering pump quality: There is a wide variety of screw pumps on the market today. Imported pumps generally feature sound designs and high-quality materials, but they come with high prices, potentially inadequate service, expensive spare parts, and long lead times, all of which can disrupt normal production. Most domestically produced pumps are imitations of imported models, resulting in inconsistent quality. When selecting a domestic product, one should weigh the cost-performance ratio and prioritize models that feature low rotational speeds, long lead (pitch), high-quality drive components, and a long rated service life. III. Prevent debris from entering the pump body: Solid debris mixed into wet sludge can damage the rubber stator of the screw pump; therefore, preventing debris from entering the pump chamber is crucial. Many wastewater treatment plants install macerators, screens, or strainers upstream of the pump to block debris. Screens must be cleared promptly to prevent clogging.
IV. Avoid dry running: Screw pumps must never operate without material flow. If this occurs, dry friction causes the rubber stator to overheat rapidly and burn out. Consequently, the proper functioning of macerators and clear, unobstructed screens are essential conditions for the normal operation of the screw pump. To address this, some screw pumps are equipped with dry-run protection devices; because screw pumps possess self-priming capabilities, a vacuum forms in the chamber when the material supply is interrupted, and a vacuum-sensing device triggers the pump to stop.
V. Maintaining Constant Discharge Pressure: The screw pump is a type of rotary positive-displacement pump. If the discharge outlet becomes obstructed, the pressure rises—potentially exceeding the preset limit—causing a sharp increase in motor load. This places loads on the drive mechanism components that exceed their design specifications; in severe cases, it can lead to motor burnout or the breakage of drive parts. To prevent damage, a bypass relief valve is typically installed at the pump outlet to stabilize discharge pressure and ensure normal operation.
Selection of G-Series Screw Pumps
We hope this proves helpful to you.