Liquid or Slurry? Which pump should you use?

If you're looking to install a pump, your first consideration should be its purpose. What do you need your pump to do?

We can break this down into:

• What type of medium do you need to transport or process?
• How far do you need to move it?
• What volume and at what flow rate will be required?
• What power source do you have available? – electricity, compressed air etc.

In this post we're going to focus on the first point. By understanding the type of material, whether solid or liquid or viscous, you will be able to identify the type of pump you need.

Flowable Liquids vs Slurry Mediums

Anything that needs to be pumped has a viscosity. For instance, water is 1 cPs while a much thicker liquid like a fruit pulp can be about 5,000 cPs. If it’s a slurry from a mine, this also is viscous to some degree. Slurry will also have a solids percentage which has to be taken into account. A general rule of thumb is, ‘if you can pour it, you can pump it’. There is a list of typical viscosities here.

Pumps for Different Mediums

Your first step should be to understand the nature of the product you are wanting to process or transport via a pump. If the medium pours easily without chunks of solid material present, then we can happily describe this as a liquid. But the real test is how viscous the liquid is. Likewise, if there are solids present, then this medium will require different equipment. There is a stark difference between pumping water which is thin and extremely fluid as opposed to oil or grease which is thick, or an abrasive medium which contains solids.

Let's take a look at three common mediums and the pumps you might need:

• Water: This is the simplest medium to transport. It's easy to move around because it has low viscosity. Therefore either a centrifugal style pump, which includes submersible pumps, or even a pneumatic pump for dewatering, will suit your needs. 
• Oil: Now things get trickier. When a medium becomes oily, it's still a liquid, but because it has higher viscosity you're going to need a different style of pump. It needs to be able to withstand increased friction. Something like a gear or lobe pump which can handle higher viscosities. However, these pumps cannot run dry, so if your system needs a pump that may run dry at some point, you'll need a tube or diaphragm pump.
• Slurries and Abrasives: These mediums have deposits within them which are solid. Pieces of rock, metal, or other minerals etc. There are two considerations here. The first is to make sure that your pump is powerful enough to transport such medium, the second is to ensure that the pump is durable enough to withstand the abrasive nature of the medium. A peristaltic hose pump or a heavy duty slurry pump is ideal for such a situation.