Screw Pumps - Modern Twists on a Classic Device

To design an effective screw pump device (Archimedes screw), designers have to work within external constraints, including: i) Radius of the screw’s outer cylinder, ii) Total length from the bottom to the top and iii) Slope of the screw pump.

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This week, we¦re looking at modern implementations of that classic hydraulic engineering device v the Archimedes Screw.

An Archimedes screw has many uses, but was most commonly used throughout history to move water uphill. As someone turned the crank manually, the screw blades forced water upwards along the threading, and thereby transport water uphill. Once the water reaches the top, the screw design releases the water into a trough.

The device itself is a simple design. It is a screw inside a tube. But this simple device has been refined over time and even today it appears in many modern devices.

To design an effective screw pump device, designers typically have to work with a number of fixed (external÷ constraints, including:

  • The radius of the screw¦s outer cylinder
  • The total length from the bottom to the top
  • The slope of the screw pump

The design challenge then is to come up with the most efficient internal parameters, including:

  • The radius of the screw¦s inner cylinder
  • The pitch of each blade, and
  • The number of blades to lift the water

Optimizing these parameters takes some serious algorithms, and some seriously smart engineers.

The design challenges mount when you consider more mundane design constraints, such as cost and manufacturability. And when you consider moving contents other than water. Designers have overcome these constraints to insert screw pumps into all sorts of devices from snow blowers to truck loaders to materials handling applications.

Our last story comes from a group of engineers at Van Beek in the Netherlands. They design screw conveyors that get installed into modern assembly lines.

They deliver thousands of screw conveyors each year that move everything from food and chemicals to pharmaceuticals and sythetics. And all of the machines are made-to-order. That means that every one of the design constraints we talked about earlier have to be optimized for each machine. Worse yet, the assembly line dimensions (the given constraints) often change after the screw conveyor design has been started. To meet this challenge, the Van Beek engineering team uses direct modelling software to make multiple fast design iterations to produce top quality screw conveyors as fast as possible. It¦s a lot easier and a lot more accurate than doing the math.