There are various pump types that can be configured for metering applications. In this post, we will focus on two specific types – diaphragm pumps and peristaltic pumps. Both types of metering pumps will typically provide many years of reliable, efficient use. When you’re deciding which one to use, you need to know how each type works and what the maintenance will be to make the best decision for your needs.
Diaphragm pumps have a flexible membrane, or diaphragm, that vibrates to create suction to move fluid in and out of the pumping chamber. These types of pumps do not require any seals. Peristaltic pumps, also known as hose pumps, function by using a roller device that moves the liquid through a hose or tube with a milking action. The fluid that is being pumped doesn’t come into contact with the outside environment or the pump since it is all contained within the tube. Each type of pump comes with its own advantages and disadvantages. Let’s take a look at the pros and cons of each.
Diaphragm Metering Pumps
Using diaphragm metering pumps require you to be knowledgeable about pump valves, proper priming, and adjustment characteristics. However, once you have a good understanding of how the pump works, using and maintaining a diaphragm pump shouldn’t be difficult.
Advantages of Diaphragm Metering Pumps
There are various important advantages that diaphragm metering pumps offer. Firstly, they are less expensive to operate long-term, as long as proper maintenance is performed regularly. You’ll also find that they are more energy-efficient. This is because they are designed to use more motor torque on the forward stroke, but significantly less on the backstroke. Diaphragm pumps are ideal for pumping harsh, damaging liquids or chemicals because they rarely leak or damage the surrounding area. Lastly, diaphragm pumps that are correctly sized are better than other options because they can overcome standing pressure in the flow line.
Diaphragm Metering Pump Maintenance Tips
While diaphragm metering pumps are less expensive and more energy-efficient than other pumps, they need the liquid being pumped to be clean and free of particulates in order to function optimally. This is due to the fact that diaphragm pumps have check valves on both the intake and discharge sides of the pump. If those valves become clogged in any way, the pump will not have accurate metering, and there will be a loss of suction (prime).
Additionally, it can be difficult to prime diaphragm pumps against pressure. In other words, they work best without back-pressure. That means you have to set diaphragm pumps to maximum stroke to overcome any back-pressure. Some of these types of pumps have bleed valves to remove sludge and trapped air, and a feed-rate mechanism that adjusts the inflow. Don’t get confused with air operated diaphragm pumps which don’t have bleed valves.
Peristaltic Metering Pumps
Peristaltic pumps work by alternating compression and relaxation of a hose/tube. This type of metering pump is a great option when the fluid you’re pumping is being pumped in a high-pressure system and has particulate matter or trapped gases.
Advantages of Peristaltic Metering Pumps
Peristaltic metering pumps are easy to use and can operate efficiently even with dirty or thick liquids because there are no check valves that might become clogged. They can also handle higher back-pressures, are easier to prime, and they maintain good suction for most fluids.
Peristaltic Metering Pump Maintenance Tips
The hose or tube on the pump becomes weakened over time until it degrades, and the flow rate diminishes over time because of the constant squeezing (this is called fatigue). It’s not only the hose and feed rate that diminish over time, but also the pump motor. The motor on a peristaltic pump is constantly under a load which uses more power and consumes more energy.
The fatigue aspect of the pump hoses means there is always a possibility that the hose may leak or rupture. To help prevent this from happening, manufacturers rate hoses for a specific number of hours that they should be used. Be sure to not overestimate the useful lifespan of the hoses, as this could increase the risk of leaks or tears.
Ideal Applications for Diaphragm and Peristaltic Metering Pumps
As you can see from the differences between each type of metering pumps, there are some needs that are better met by one type or the other. Diaphragm pumps will work most effectively with clean liquids and harsh chemicals in low-pressure applications. Conversely, peristaltic pumps perform more effectively with thick or dirty fluids that contain particulate material, trapped gases or bubbles, especially in high-pressure applications, but the hose must be monitored to prevent leaks.
Final Thoughts
With some research and the differences above, you have some valuable information that will help you determine which type of metering pump is best for your needs. You’ll also need to have a good understanding of the pump’s maintenance requirements and its operating parameters.