Centrifugal Pumps 101

When heading to the jobsite, a typical equipment checklist usually includes earth movers like excavators, wheel loaders and backhoes, but what about the supporting cast of machines? Crews dealing with excavation or any other sort of construction work can encounter groundwater that impedes earth moving operations. This obstacle calls for the use of a pump to transport liquids and get the ball rolling for work to begin.

“Before any excavation, trenching or grading can begin on a construction project, such as laying or relining pipelines, groundwater must be removed,” explains Kirsten Stroud, marketing manager for Thompson Pump. “Too much moisture in the material will slow or prevent construction operations and will leave the project site without the necessary preparation for further building or compaction.”

When water does becomes an issue — whether it’s to supply water to a project or dewater a jobsite — a centrifugal pump is the most common choice for construction work. This type of pump is popular because it’s very durable and offers an efficient method for moving water that doesn’t contain a lot of trash. Since water is a constant challenge, contractors are almost forced into using centrifugal pumps on a frequent basis.

“[They] are popular because they are a necessary evil of the construction industry,” says Thomas Aldridge Jr., Sales Engineer for Griffin Dewatering. “They are one of the most widely used tools because nature keeps producing water and in order to perform most construction, that water has to be moved.”

For applications where clean water must be moved, centrifugal pumps offer the best and most inexpensive means to do so. As the name implies, centrifugal force drives the operation of a centrifugal pump by moving water away from the center in a circular motion. An impeller within the pump drives this centrifugal force.

With each rotation of the impeller, velocity is increased, which causes the liquid to move into the volute. The velocity is reduced within the volute and its energy is converted to pressure energy — allowing the fluid to be quickly forced from the pump.

Hansen Webel, manager of centrifugal pumps for Gorman-Rupp, further explains: “When the impeller rotates in the volute, velocity energy is imparted on the fluid as it moves from the center eye of the impeller to the impeller vane tips. The increased pressure of the fluid causes it to flow, rise to a higher level or do both, while simultaneously reducing pressure at the impeller eye and allowing more liquid to enter the pump.”

Centrifugal pumps have narrow impeller vanes, making clear water that is virtually free of debris the only type of water this pump is able to handle. Obviously there is always a chance that seemingly clear water will contain at least a small amount of debris. This is why these pumps are equipped with a strainer, which acts as a safety net and stops unforeseen debris from entering the intake hose. For water that may contain debris that could clog or damage a centrifugal pump, a trash pump would be the best option.

Typically in the construction market, a pump must be paired with a priming system. This addition will help to rapidly create the low pressure area, as well as to handle the air that is a by-product in the system — enabling a crew to move water more efficiently.

Before You Buy

After deciding that a centrifugal pump is the right fit for your job, the next step is finding a reliable manufacturer and dealer for the purchase. There’s a variety of manufacturers to choose from including Griffin, Gorman-Rupp and Thompson Pump, to name a few. These companies offer a diverse selection of centrifugal pumps and priming systems ideal for utility work.

When choosing a manufacturer, Stroud recommends doing your homework and picking one with pump-specific, knowledgeable employees. This core group will be able to address any concerns you may have and help you select the right pump for your needs.

“Be sure to choose a manufacturer that is a member of the Contractor’s Pump Bureau [CPB] with the Association of Equipment Manufacturers [AEM],” she adds. “This certifies that the pump has been designed and manufactured in conformance with CPB pump standards.”

After-sale support is also important to consider when making a pump purchase. Webel suggests that buyers should inquire how long a company has been in business and ask for references from past customers. These can be an indication of how much factory support is available in terms of expertise, education, manufacturing capabilities and repair parts availability.

“If the user has issues or questions down the road, there is no substitute for partnering with a quality world-class pump company,” says Webel. “Saving a few dollars on the front end of a pump purchase by ignoring this advice will often end up costing the equipment owner much more down the road. The old adage that ‘You get what you pay for’ is certainly true when purchasing a pump.”

Although finding a pump system can seem overwhelming, the biggest consideration to take into account is the application it’s expected to perform in and the desired outcome of its use. This requires looking at the liquid the pump will encounter and matching a unit accordingly. Aldridge points out that when purchasing a pump, it is important to know what the requirements for the equipment will be from both a performance and operational standpoint.

“Performance should be defined based on how much fluid needs to be moved, where it is being moved from and to and the resistance it has to overcome for that,” says Aldridge. “It should also be determined what is being pumped. From an operational standpoint, it is important to look at ease of maintenance, transportation, setup and general usability.”

To help simplify the purchasing process, Stroud offers several questions to address with an equipment dealer:

What do you need to accomplish with the pump?

What type of liquid will you be pumping?

Is there any solid matter in the liquid you’re pumping?

What is the distance the fluid will be pumped?

How quickly does the liquid need to be moved?

Is noise an issue where you will be working?

What type of hose will be used?  

Protecting Your Investment

Like with any piece of machinery with moving parts, maintenance is necessary to keep a pump running in tip-top shape. Since centrifugal pumps are very durable pieces of equipment, they should not require excessive amounts of maintenance as long as they are sized and used properly.

Routine preventative maintenance should be performed after every eight hours of operation and include a thorough check of the engine fluid levels and the fuel system, says Stroud. Prior to performing maintenance, it’s important to always shut down the unit and allow it to cool.

Webel adds, “When performing maintenance on a pump, the user should ensure that new seals and gaskets are installed as required and that any regular maintenance items such as wear rings or bearing oil chambers have been properly inspected and serviced as necessary.”

According to a recommended 250-hour maintenance schedule, pumps should undergo several advanced assessments, replacements and lubrications. Although the pump requires minimal maintenance, Stroud mentions that the use of the pump in dusty, dirty, wet or otherwise adverse conditions may require more frequent inspection and maintenance.

Pam Kleineke is associate editor of Compact Equipment, based in Brecksville, Ohio.