Screw Pump vs. Gear Pump

Pumps are machines that convey fluids or pressurize them, and are mainly used to convey water, oil, slurries, acid and alkali liquids, emulsions, suspensions, gas mixtures and liquid metals, etc. They are common conveying equipments in mining, chemical and metallurgical industries, and different pumps differ in their structural appearances, load-bearing capacity, service life and application areas.There are many types of pumps, but we will only discuss two of them here: screw pump and gear pump. Understanding the difference between them is important for the correct choice of the desired product, which can effectively improve the service life and performance of mechanical equipment.

The Structural Difference between Screw Pump and Gear pump

Screw pump is the use of spiral vane rotation, so that the body of water along the axial spiral rise of a pump. Composed of shaft, spiral vane, shell.Screw pump belongs to the rotor type volumetric pump, suitable for conveying high-viscosity fluids, solid suspensions, highly abrasive slurry, solid, liquid, gas three-phase mixtures, such as extremely sensitive and susceptible to centrifugal damage to the fluid medium.

The earliest prototype and principle of the screw pump is Archimedes proposed Archimedes screw. Screw pump is the use of screw rotation to transport the fluid medium. Simple structure, easy to manufacture, larger flow, small head loss, high efficiency, easy to repair and maintenance, but low head, low speed, need to set up variable speed device.

Gear pumps are a component of machine lubrication, oil supply or other liquid systems, a type of hydraulic pump. It is rotary type. There are 2 or more gears meshing in the gear box, under the action of rotation from one side of the inhalation of fluid and then discharged to the other side. Its vibration and noise is slightly larger than the screw pump, can be used as a substitute for the screw pump type. Its role is to make the oil or other fluid medium with a certain pressure and flow and flow direction.

Gear pumps are also known as volumetric devices and displacement pumps, i.e., like a cylinder piston, when one tooth enters the fluid space of another tooth, the fluid is mechanically displaced. Since the fluid is incompressible, the fluid and the teeth cannot occupy the same space at the same time, so the fluid is excluded under the action of the gear pump.

Due to the continuous engagement of the teeth, this phenomenon occurs continuously, thus providing a continuous discharge at the outlet of the pump, the same amount being discharged with each revolution. As the drive shaft rotates uninterruptedly, the fluid is discharged uninterruptedly. The flow rate of a gear pump is directly related to the rotational speed.

The Difference between the Working Mode of Screw Pump and Gear Pump

Screw pumps rotate by placing two or more rotors with helical vanes in intermeshing helical grooves in the pump body, and through the action of the intermeshing helical teeth, the liquid is pressed from the suction inlet into the pump chamber, and then discharged to the outlet.

Screw pumps have relatively simple structure, small size, good sealing and low noise. Screw pumps are mainly used in the transportation of high viscosity liquids, such as petroleum, chemical, food, pharmaceutical and other industries. Gear pump, on the other hand, place two or more gears (gears are generally cylindrical gears or internal gears) in the pump body, and through the mutual meshing of the gears, the medium is pressed into and out of the pump body.

Gear pumps use meshing gears to suck and compress the media, equipment operation process noise. However, it works efficiently and conveys a stable flow rate. Gear pumps are mainly used in thin media transportation, such as fuel transportation, oil presses and so on.

Application Scenarios of Screw Pump and Gear pump

Screw pumps are suitable for conveying high viscosity, volatile, corrosive and particle-containing media. Therefore, screw pumps are widely used in petroleum, chemical, food, pharmaceutical and other industries. At the same time, due to the good sealing of the screw pump, it is also widely used in the refrigeration system of the screw chiller.

Gear pumps are suitable for conveying relatively thin media. Gear pumps can mix different kinds of liquids together for transportation, as well as filtration and condensation. Therefore, gear pumps are widely used in the field of fuel and lubricant transportation, especially in ships, petrochemical and agricultural machinery.

Advantages and Disadvantages of Screw pump and Gear Pump

• Characteristics of  screw pump: Compact structure, flow, pressure, basically no fluctuations, and higher pressure, than the gear pump running smoothly, vibration, low noise, long life, high efficiency, applicable to liquid varieties, viscosity, the use of stainless steel arc pump.
• Disadvantages of screw pump: High manufacturing process requirements, the working characteristics of the more sensitive to changes in viscosity, the flow rate of the transport medium is small.
• Characteristics of gear pump: Reliable mechanism, stable operation, low cost, can transport non-corrosive oil and other viscous media, the pump itself comes with a safety valve, arc gear pumps, conveying medium pressure.
• Disadvantages of gear pump: Unsuitable for conveying liquids containing solid particles and high volatile, low flash point liquids, berth gear pumps. Long time running gear pump gears are easy to wear. Conveying medium flow rate is small.

Summary

Screw pumps and gear pumps are pumps, but they are very different in structure and working mode. Screw pumps are suitable for conveying high viscosity, volatile, corrosive and particle-containing media, gear pumps are suitable for conveying relatively thin media. Different application scenarios require the selection of different pumps to achieve the best results.