September 17, 2020
Understanding and Troubleshooting Centrifugal Pumps
By Bridget Minner
Choosing the right type of pump to meet your industrial plant’s needs is crucial to maintaining efficiency and prolonging the life of your machinery. Pumps are classified by the purpose they serve and the way they are built to operate. The most commonly used types of pumps are classified as centrifugal, reciprocating, and rotary. Centrifugal pumps are particularly notable, as they are widely used across different industries and typically preferred. What exactly is a centrifugal pump, though? Let’s take a look.
The Advantages and Usage of a Centrifugal Pump
A centrifugal pump is a machine that moves and pressurizes liquids using spinning blades. Centrifugal pumps are known for their simple design and ability to provide a constant, smooth flow of liquids. They are known to be cost-effective and well-suited for large volumes. They work best with thin liquids that flow easily such as water or certain oils. Numerous industries including but not limited to oil, pharmaceutical, waste management, and agriculture utilize centrifugal pumps.
How does it work?
A centrifugal pump consists of spinning blades inside of a spiral-shaped case. The blades are typically spun by an outside motor, and the case is sealed to prevent leakage. Liquid continuously enters the pump at the center of the case where pressure is low. It then moves onto the spinning blades. As the blades spin rapidly, the liquid increases in pressure and begins to quickly move away from the center of the pump towards the inner edge of the case. This energizing force that pushes the liquid away from the center of the spinning blades is the defining characteristic of a centrifugal pump known as centrifugal force. Once the liquid hits the inner edge of the case, it flows along the spiral shape until it is discharged.
Important to Know
You must fill the pump’s case with liquid prior to operating the pump. Additionally, you cannot reverse the direction that the blades of a centrifugal pump spin. You will notice the blades are curved. The blades must spin in the direction that allows the liquid to flow along the top of the curve on each blade. Otherwise, liquid will be cupped underneath each curve if the spin is reversed. This will reduce the efficiency of your pump and potentially shorten its life.
Options to Meet Your Needs
You still might be wondering whether or not a centrifugal pump is best suited for your unique needs. We know one size doesn’t fit all. Every industry and every plant has unique operating conditions. Fortunately, centrifugal pumps come in a variety of sizes, styles, and designs to accommodate a wide range of industries. For example, certain types of centrifugal pumps use a multi-stage system where liquid is carried through a series of connected pumps. Additionally, some pumps allow liquid into the casing through two points of entry rather than one. This type of customization also extends to the blades themselves. There are three types of blades:
Open– The blade is completely exposed. This is the simplest type and works best with liquids containing minimal solids.
Semi-open– A plate covers one side of the blade. This type can accommodate liquids containing sediment and other solids.
Closed– The blade is covered by a plate on each side. Use this option if promoting efficiency is your primary focus.
Though the centrifugal pump is credited with being particularly simple in design, we have some tips to help you navigate common issues that might arise.
1. The liquid isn’t being pumped.
Don’t forget that the case of the pump must be filled with liquid prior to starting the machine. If you completed this step but the issue persists, check for any obstructions and ensure the blade is spinning in the correct direction.
2. The pump isn’t producing a strong flow or pressure.
Make sure the case is sealed properly, as there might be an air leak. Also check for clogs in the piping.
3. The bearings are hot.
Lubrication and alignment are key. Inspect the machine for proper lubrication and alignment of the pump and motor.
4. The pump vibrates.
If the pump and motor are not properly aligned, they will be susceptible to vibrations that can hinder the smooth flow of liquids. It is also important to inspect the blades for obstructions and possible damage.
5. The pump stopped shortly after starting.
Check for air pockets and leaks in the piping. If you do not identify any issues there, it is possible you need to add more liquid to the case.
6. The motor seems to be working too hard and is struggling.
Be sure that none of the rotating parts of the machine are bumping against each other or dragging while the pump is operating. Verify that all parts of the machine are assembled correctly and make adjustments accordingly.
7. The seal is leaking.
Tighten or replace the seal.
Now that you understand the basics of centrifugal pumps, feel free to connect with us about troubleshooting questions.