What Is a Snake Pump?
A snake pump is a type of pump that moves liquid using a distinctive spiral shaft (rotor) rotating inside a tube shaped like a snake.
Also known as a uniaxial, eccentric screw pump, it serves as an alternative to other pumps, such as plunger pumps, for discharging challenging materials like highly viscous substances or those containing solids.
Uses of a Snake Pump
Snake pumps efficiently discharge and pump fluids containing viscous and concentrated materials or solids, generating strong internal propulsive force. They are used for slurries (muddy plasma, a high-viscosity liquid mixture of minerals and sludge), processed foods (like fish and ground meat) unsuitable for conventional pumps, fibrous liquids, and cosmetics manufacturing.
In the automotive industry, they are employed for pumping highly viscous liquids and mixtures such as lubricants, abrasives, and silicone resins.
Principle of the Snake Pump
Classified as a rotary pump within positive displacement pumps, snake pumps consist of a metal rotor (male thread) and an elastic material stator (female thread). The screw-like twisted rotor rotates within the stator, pumping liquid without pulsation and at a consistent volume.
The sealed helical space created by the rotor’s tangent line within the stator facilitates the transfer of liquid from the suction to the discharge side through piston motion, as the rotor rotates and reciprocates.
The discharge volume, adjustable by rotor speed, varies with rotation speed. Discharge pressure, on the other hand, can be altered by modifying the rotor and stator length, with longer components providing higher pressure if space permits.
How to Select Snake Pumps
Selecting the appropriate snake pump depends on its intended application, considering the following factors:
1. Discharge Volume
The discharge volume, influenced by rotor shape and diameter, can also be adjusted through rotor speed. However, consistent high-speed operation can lead to abrasion and is limited by liquid viscosity, necessitating the selection of a model suitable for the intended discharge volume.
2. Liquid Properties
Liquid properties, particularly viscosity and wear, significantly affect allowable rotor speed and discharge volume. High-viscosity liquids permit lower rotor speeds. Conversely, single-phase fluids allow higher speeds due to lower wear, while fluids with hard solid particles necessitate slower speeds.
3. Type of Fluid
The stator’s elastic materials, varying in rubber and resin types, should be chosen based on resistance to substances in the pumped fluid. Incorrect selection can cause critical failures, such as stator damage or melting.
4. Discharge Pressure
Discharge pressure correlates with the rotor-stator length and the number of spirals. Higher pressure requires longer equipment, which may be constrained by space availability.
Other Information on Snake Pumps
Disadvantages of Snake Pumps
A significant disadvantage of snake pumps is the constant contact between the rotor and stator, leading to wear. Dry operation can quickly damage the rotor, and discharged debris from rotor damage, especially in the food industry, can result in contamination and serious issues.