How to Choose a Diaphragm Pump – A Complete Guide

Diaphragm pumps are a great option for delivering high volumes of material at relatively low pressures. They typically resist wearing as they do not have a piston moving through a cyclinder but a simple rubber diaphragm or diaphragms that are displaced side to side allowing material to be sent (more on diaphragm vs piston pumps can be found here). So you may have finally decided a diaphragm pump is the right choice for your pumping needs, now it is time to learn how to properly select a diaphragm pump.

Factor 1 to Determine for Choosing a Diaphragm Pump – Pump Volume Requirements

Diaphragm pumps can pump material ranging from a gallon per minute up to hundreds of gallons per minute depending on the overall size of the diaphragm pump and the speed at which it is operating. An important fact when choosing a diaphragm pump is to ensure that you try to select a pump that will run at about 50% of its maximum potential capacity under normal use. Having the pump run at half of its maximum capacity will ensure the pump runs for a long time without need of much maintenance. Any diaphragm pump should list its operating capacity in Gallons per minute either in the service manual or on the sales sheet (see below for example).

Factor 2 in Choosing a Diaphragm Pump – Drive Type for Displacement Pump

There are a variety of options available to drive the diaphragm of a diaphragm pump back and forth enabling it to pump material. Common drive options for diaphragm pumps include electric drive or air driven pumps. The drive will be important because it can impact where the pump will operate and the if the diaphragm pump can be safely used. Electric drive diaphragm pumps will be able to run anywhere electric is available but are typically not a safe solution for areas where hazardous levels of flammable materials are present (like in paint areas).  In contrast air operated diaphragm pumps will work anywhere where compressed air can be provided to drive a diaphragm and are safe even around paints and similar materials because air doesn’t provide a source of ignition.

Factor 3 when Choosing a Diaphragm Pump- Materials the pump is composed of

Diaphragm pumps are offered in a variety of material builds. In general, the most common options that are available for diaphragm pump materials include the material that the ball and seat of the pump are made of, and the material that the pump body is made of. There is a lot to be considered but in general common options for coatings includes stainless steel ball and seats and PTFE diaphragm materials. Stainless steel will be more wear resistant but expensive while PTFE is more cost effective but may not hold up to abrasive materials as well.  Additionally stainless will tend to be more resilient to heat.

Factor 4 when Choosing a Diaphragm Pump – The Pumps Performance Curve for Air Operated Diaphragm Pumps

Any diaphragm pump will have a performance curve which will give you a lot of additional detail on the pump. Common information that a diaphragm pump performance curve will address will include how much volume (CFM) of air the pump will require at various operating levels and how much as well as how far the material can be supplied at various operating levels of the pump. Below we have taken a sample pump curve and broken down the components that are shown. The important thing to know for your particular diaphragm pump is that you have the proper amount of air for your pump to operate and that the pump will be able to deliver material at the rate you want and over the distance you need to deliver material. As an example, the chart below shows a pump performance curve. On the right side of the chart is the distance you want to move material, on the left side is the pressure the pump will need to be run at, along the bottom is the gallons per minute of material you will want to deliver. You will select a distance you need to deliver material over (in our example 40 feet), then you will select how many GPM you need to deliver (20 in the example). Next, move up from GPM to find the solid line that corresponds with pumping material the distance you want it to be moved. This line will be curved and you will follow the curve to the left to find the pressure required to deliver material a given distance at a given GPM.  In our example to move 20 GPM of material with this pump over 40 feet will require 60 PSI. Finally, you will locate the nearest curved dotted line on the diaphragm pump curve to find the CFM required for this level of performance which would be 20 CFM. The important thing to check is that the diaphragm pump your considering will be able to supply the amount of material you want (remember you will typically want the pump to be running at about 50% capacity at most to reduce wear though the curve will show higher operating rates as options), over the distance you want, and you have the air you need to run the pump.

Ultimatley a diaphragm pump is a great way to deliver large volumes of material quickly and effectively. To ensure you get great results from your diaphragm pump, consider the four factors we discussed here to look at when choosing a diaphragm pump. By following this simple advice you will be able to ensure you select a diaphragm pump that will last and perform well. If you need further advice on diaphragm pumps contact us today.