A screw spindle pump, also known as a double screw pump or twin screw pump, moves fluid by means of two counter-rotating, interlocking screws moving the medium axially through the pump. The screws do not touch each other and are synchronized via an external gearbox, ensuring low-pulsation, structure-friendly movement. We therefore frequently use screw spindle pumps in highly viscous and hygienic applications.
01.What is the difference between a screw spindle pump and a worm pump?
Although both pump types belong to the positive displacement pumps and are often mentioned in the same breath, they operate fundamentally differently. A screw pump moves fluid radially via an eccentrically rotating rotor that does make contact with the stator. A screw spindle pump moves fluid axially via two contactless, interlocking screws. Because there is no contact between the screws, mechanical wear in the fluid circuit of a screw spindle pump is generally lower than in a screw pump.
02.Operating principle of screw spindle pumps
The operating principle step by step
Suction
The two spindles rotate in opposite directions. Due to the screw geometry, new chambers with increasing volume are continuously formed on the suction side, creating negative pressure. The fluid is drawn in. As a result, the pump is self-priming with a low NPSHr.
Containment and transport
The fluid is enclosed in the sealed chambers between the spindles and the inner wall of the pump housing. Due to continuous rotation, these chambers move axially towards the discharge side. The fluid is carried along without turbulence or shear forces.
Squeeze out
On the discharge side, the volume of the chambers decreases, and the fluid is pushed into the system under pressure. Because chambers are formed simultaneously on both sides of the spindles, the flow is virtually completely pulsation-free.
03.Wat betekent het "2-in-1"-concept bij een schroefspindelpomp?
A screw spindle pump combines two characteristics that often exist separately in other pump types: a high self-priming capacity and the ability to continue operating during temporarily low or fluctuating fluid flow, for example in the event of foam formation or a partially filled suction line. This makes the pump type suitable for applications where other positive displacement pumps encounter problems more quickly.
04.Why is the contactless design important for hygienic applications?
Because the screws do not touch each other, no metal-on-metal contact occurs in the fluid circuit, which minimizes the risk of particle formation in the product. Combined with a CIP/SIP-compatible pump housing, this makes the screw spindle pump suitable for the food, pharmaceutical, and cosmetics industries, where EHEDG and 3-A guidelines apply.
| Feature | Wangen twin screw pump | Progressive cavity pump |
|---|---|---|
| Direction of movement medium | Axial | Radially, via chambers between rotor and stator |
| Contact between moving parts | No, synchronized via gearbox | Yes, the rotor is touching the stator |
| Wear part | Screws, bearings, gearbox | Stator (elastomer) |
| Self-priming capacity | Very high | Good, but usually lower |
| Viscosity range | Very broad, from thin to extremely viscous | Wide, but more limited at the top |
Screw spindle pumps can typically handle a viscosity range many times wider than an average centrifugal pump, making the pump type particularly suitable for processes with varying product viscosity.