How to configure a diaphragm pump with confidence – Part 1

Graco’s online selector tools assist you in configuring a pump in a few clicks.

Correct configuration is key to the safe and reliable operation of a double diaphragm pump. Making the right choice can significantly reduce the overall cost of the pump – while making the wrong choice can give you a pump that is too expensive or not properly working for your requirements.

However, pump selection is a notoriously challenging procedure as it depends on many factors.

One of these is the fluid that’s being pumped. Selecting the right pump depends on the properties of the fluid, such as its solid content, pH level, viscosity, density and specific gravity. Is the material abrasive or corrosive? At what temperature is it being pumped? All these considerations have a major impact on the compatibility of the fluid with the pump. 

Then there’s the actual application. What flow rate is needed, where is the feed tank relative to the pump, and what is the overall suction length, vertical rise, and discharge distance? All these play a role in determining the inlet and outlet hose diameter. Is a pump with ATEX certification necessary, for use in a potentially explosive environment?

Further complicating matters is the fact that a pump is a combination of components: body, seat, balls, rings, diaphragm, to name just a few. And you need to select the right material for each component. 

Finally, commercial considerations have to be taken into account, including capital costs, operating costs and maintenance costs. It’s often a delicate balance between getting the performance and efficiency you want, at a price you can afford.

But before you get totally overwhelmed, help is at hand. To help you select and configure a diaphragm pump, Graco has broken down the process into three easy-to-follow steps. Each step has its own online guide, freely accessible to everyone on the Graco website:

• Step 1. Chemical compatibility guide
• Step 2. Materials of construction guide
• Step 3. Diaphragm pump selector

Step 2 – Materials of construction guide

This is a chart that displays the technical specifications of 17 materials. Depending on the two or three materials that you have just selected from step one, it’s now possible to look more deeply into their characteristics. 

The first column indicates the temperature range at which a material functions effectively. This is important for two reasons. Firstly, for a plastic it gives an indication of its flexibility. When the temperature of many common plastics decreases, flexibility is typically greatly reduced, and the plastic may become brittle with low failure stresses. Secondly, for some applications – notably those involving food & beverages – a pump is cleaned at high temperatures, maybe with steam or hot water. So choosing a material with an operating range that peaks at say 65oC is not going to be satisfactory, as it will melt at 100oC.

Another column indicates the specific gravity of the material. This is important when selecting a material for a pump’s balls. If you are pumping a fluid with a viscosity equal to or lower than water, a ball with a low specific gravity is fine. But when pumping a high viscosity material like Barbecue Sauce, you need a heavier ball to ensure an efficient close-out between ball and seat in a diaphragm pump.

As mentioned above, cost is often an over-riding issue. The chart has a column that gives an indication of the price level of each material, from one (least expensive) to three (most expensive).

The chart also indicates the availability of a material for a pump’s seat, ball and diaphragm, as well as whether that material is suitable for chemicals, high temperatures, and abrasive fluids. The far-right column summarizes which applications each material is most suitable for, and why. 

By now you should have been able to narrow down the materials that are the best fit for a diaphragm pump’s body, seat, balls and diaphragm with respect to your specific application.

Now that you know which materials of a pump are compatible with the fluid you wish to pump (and the cleaning agent if relevant), and you understand the properties of those materials and their suitability for your specific application, it’s time to go to step three.

Need help configuring your pump?

We hope that these three steps have simplified the process of selecting and configuring a diaphragm pump. If you require further assistance, or would like to see a demonstration of a Graco diaphragm pump, please fill in the contact form below.