• October 16, 2018
  • Tim Wolstencroft
  • Blog

Whether it’s for agriculture, construction, mining, municipal, quarrying or tunnelling applications, properly selecting an industrial pump is important for achieving cost effectiveness. After all, the pump will be in regular operation and in fact crucial in carrying out important aspects of a certain application.

That’s why here in this guide we’ll discuss some of the most important considerations when selecting a pump. We’ll talk about both general and specific considerations and applications. Let’s start.

What are the characteristics of the fluid to be pumped?

That’s the first question we should be asking. The equipment to be used for pumping water will be different for pumping oil or slurry. They have different viscosities (resistance to flow) and specific gravities (the “heaviness” of the fluid).

As a result, the pumps will have varying performance requirements. It will be more difficult to pump a viscous liquid such as oil and slurry than a less viscous fluid such as water. In fact, the entire design of the pumping system could be totally different for each case. As a consequence, the costs can widely differ for each application.

Aside from the viscosities and the specific gravities of the fluids to be pumped, another important characteristic is the physical and chemical composition of the fluid. Will solids be present when pumping the fluid? What are the pH levels? Should we be worried about corrosion and abrasion? Should we also consider the potential damage to the solids being transported along with the fluid?

For instance, transporting tomatoes with the use of water as the medium requires some level of sensitivity. The goal is to transport tomatoes to the next step of the supply chain (e.g. packaging, dicing) at an acceptable rate while minimising damages to the goods. The requirements in that application will be different compared to let’s say transporting potatoes (potatoes could be tougher than tomatoes).

Aside from the presence of solids, we also have to consider abrasion and corrosion. The contact of the solids with the pump’s internal parts will result to gradual or sudden abrasion. This then results to the pump’s loss of or declining performance. For instance, when the impeller vanes (crucial parts of the pump) are worn down, the pump in general will lose its power or effectiveness to pump the fluid (together with the solids) at the originally specified rate. It’s a similar case when corrosion occurs. Corrosion also eats away the pump’s parts thereby also affecting the pump’s performance. Corrosion occurs gradually or eventually because this chemical process requires water, oxygen and the substrate (the metallic parts of the pump). As a result, submersible pumps can be more prone to corrosion.

To address this issue about corrosion, almost all the parts (or the parts that are constantly in contact with the fluid) are made from materials that resist corrosion. Another way to accomplish this is by applying a suitable coating to protect the metal underneath. For example, the rotors of mine dewatering pumps could be made from hard chrome plated stainless steel. The skid frame (related to mounting the pump) could be made from galvanised structural mild steel. Both of those examples are about applying a protective coating to the metal underneath.

The result is longer-lasting parts which then translates to lower maintenance requirements and lower costs for repairs and replacements. This is an important aspect in harsh environments (high acidity, salinity, constant contact with water).

What’s the desired flow rate?

We’ve discussed the importance of identifying what type of fluid to be pumped and its characteristics. Next is we’ll talk about how fast (or in what volume) the fluid should be pumped.

As you might have already realised, the fluid’s characteristics has a direct effect on the desired flow rate. We mentioned earlier viscosities and specific gravities (two important characteristics of fluids). The “heaviness” and the resistance to flow of fluids will have a huge effect on achieving the desired flow rate for our application.

For instance, centrifugal pumps are ideal for irrigation applications. It’s a low-viscosity application (just water is being pumped) wherein the desired flow rate can be easily achieved. But for high-viscosity applications, the performance could be really different or far from cost effective. That’s because the mechanism of how centrifugal pumps work depend on the conversion of rotational kinetic energy into hydrodynamic energy of the fluid flow. That rotational energy heavily depends on the impeller’s speed and size. Handling fluids of higher viscosities could make it harder for the impeller to rotate and transport the fluid.

That’s why for high-viscosity applications, facilitating fluid movement can better be achieved by using positive displacement pumps. These pump systems can achieve constant flow rate even when facilitating the transport of high-viscous liquids. This is possible because positive displacement pumps don’t rely on the impeller’s capability. Instead, it’s a cycle of trapping and then forcing the liquid in each cycle. In each cycle, the positive displacement pump moves the fluid at the same speed (hence, the constant flow rate). As a result, positive displacement pumps are commonly chosen for handling difficult liquids (high-viscous liquids and fluids that contain solids).

Achieving the desired flow rate may heavily depend on the mechanism of the pump system. There are advantages and disadvantages to choosing any type of pumps. This is an everyday engineering problem wherein we have to balance the tradeoffs and understand the limitations.

That’s why pump selection is one of the final decisions to be made on a project whether it’s for mining, agriculture or construction application. For instance, we have to first understand the soil and the crop before choosing an agricultural pump system and its specifications. Another example is in mine dewatering. We first have to understand the hydrogeological profile of the site before selecting a pump with a specified flow rate. We also have to analyse the immediate environment where the pump will be placed and how it will be used (e.g. submerged, also take note of corrosion).

Customisation, compatibility and other factors

Each site or project is unique. As a result, they often require different pumps and specifications. Often, pump engineers create a tailored pump system or package to address the unique requirements of a site or project.

For example, you have to consider the following when irrigating a farmland:

  • Land area & terrain (slopes)
  • Risks of erosion and runoff
  • Type of crop (growth rate, water requirements)
  • Location of the water source
  • The area’s weather patterns (rainfall, wind)

Strong winds can reduce the effectiveness of the pump and sprinkler systems (the wind will carry away the water). Too much water (flow rate is too high) can result to agricultural runoff. This event will carry away the nutrients from the soil.

The goal in efficient crop irrigation is to ensure plants get sufficient amounts of water and in equal distribution. Although the design of the sprinkler system is a huge factor in this, the pump’s specifications and installation also contribute to whether efficient crop irrigation will be achieved or not.

It’s a similar case in mine dewatering applications. The goal is to control groundwater and surface water levels to achieve better geotechnical stability. Each mining site is different because of the varying hydrogeological profiles. Add to that the varying conditions and environments of the sites. The different levels of salinity, acidity and even the presence of solids will affect the selection or design of the pump system.

We also mentioned earlier about transporting food items such as tomatoes. Transporting fruits and vegetables also have varying requirements. The goal here is to minimise physical damages to the goods. As a result, we have to consider the goods to be transported and the rate it should be done.

These are all important considerations. The key here is to have a pump system that exactly suits your application. The one-size-fits-all approach is not applicable to industrial settings. To achieve the optimal outcome (and save on operating costs for the long term), the crucial and regular aspects of the project should be tailored.

This is what we do here at Tru-Flo Pumping Systems. Through the 20+ years, we have sold and serviced more than 21,000 pumps. As a leading global pump manufacturer, we’ve successfully tailored our solutions to achieve optimal outcomes and low operating costs for each project or site. More than 70 skilled professionals and experienced support staff are providing their expertise to clients. This is to meet the diverse client demands and come up with the most cost-effective and optimal sets of methods and technologies. Contact us today for more information.