Choosing the Right Diaphragm for an AODD Pump

When it is time to choose or replace the diaphragm on an air-operated double diaphragm pump, there are a number of factors to take into consideration. You will want a diaphragm that performs the best in your specific application, whether you are pumping wastewater or highly aggressive chemicals, while also seeking a cost-effective solution. Here, we offer some guidelines on choosing the right diaphragm for your AODD pump to ensure safe, efficient operations.

The Material of the Diaphragm

You will need to consider the diaphragm’s compatibility with the fluid being pumped and the temperature of the application. This will depend on whether you are pumping water, aggressive acids, chemicals or caustics, or highly abrasive materials. Extreme temperatures, hot or cold, will also have a bearing on the material of the diaphragm. Consult chemical compatibility guides and seek expert advice to ensure you make the right choice.

The materials used in diaphragms can be broadly placed into three main groups; rubber, TPE, and PTFE.

Rubber

• Neoprene – Perfect for nonaggressive chemical applications.
• Buna-N – Also called nitrile, Buna-N is widely used for petroleum or oil-based fluids.
• EPDM – Excellent for very cold temperatures.
• Viton® – Suitable for very hot temperatures, harsh chemicals and aggressive fluids and acids.

Thermosplastic Elastomer (TPE)

• Polyurethane – Good general purpose diaphragm for nonaggressive chemical applications.
• Wil-Flex™ – Ideal for acidic and caustic fluids and versions are available for use in food and beverage applications.
• Saniflex ™ – Excellent for food processing applications.
• Geolast® – The equivalent of Buna-N, Geolast is suitable for petroleum industry applications.

Polytetrafluooethylene (PTFE)

Also known as Teflon®, polytetrafluoroethylene is one of the most chemically inert compounds available. PTFE has excellent flex life and good abrasion resistance. As well as water and wastewater, it is suitable for applications involving ketones and aldehydes, acetates, aromatic hydrocarbons, chlorinated hydrocarbons, oil and gas, with temperature operating limits of 4º to 104ºC. A back up diaphragm is needed with a PTFE diaphragm because it is inflexible.

Resistance to Abrasion

The above is a basic summary of diaphragm materials. Keep in mind that different materials will provide different levels of resistance to abrasion. Consider how much wear and friction will occur from being in contact with solids and particles in the fluid being pumped when choosing the right diaphragm.

Flex Life

In addition, different materials will have a varying flex life. This will determine how long the diaphragm can stay in place before a replacement is needed or repairs are required, which will have implications on ongoing maintenance costs.

Sanitary Standards

When choosing the right diaphragm for an AODD pump, talk to a technician at Allied Pumps about the capacity of the equipment to pump the required distance, the hardware configuration of the pump, and whether it is intermittent or continuous pump operation. We take into account diaphragm material, temperature limits, abrasion resistance, chemical compatibility and flex life and can advise you on the best diaphragm material for your application according to your budget and specific requirements.