Air operated diaphragms pumps (also known as pneumatic diaphragm pumps, AODD pumps, AOD pumps) are used for endless applications in mining, industrial and general plant service. Air operated diaphragm pumps are especially used where electricity isn't available, or in explosive or flammable areas. They are also used for chemical transfer, de-watering underground coal mines, food manufacturing or where the liquid being pumped has a high solids content or high viscosity.
How AOD Pump Works
Air operated diaphragm pumps are a type of reciprocating diaphragm pump which contains two diaphragms driven by compressed air. Air section with shuttle valve applies air alternately to the two diaphragms, each diaphragm has a set of check/ball valves.
What to consider when selecting the proper diaphragm material:
• Chemical resistance • Estimated flex life • Temperature limitations • Abrasion resistance • Cost
Diaphragm pressure limits
Rubber diaphragms can handle a maximum positive inlet pressure of 25-40 PSIG dependent upon pump size, pump design and diaphragm material. Teflon diaphragms are limited to 4.3 PSIG (10') positive inlet pressure due to their poor flexibility and low tolerances for mechanical stress. Back up diaphragms may be used in connection with Teflon diaphragms to help extend Teflon diaphragm life in severe applications. Typically, rubber diaphragms can operate under any amount of vacuum, however Teflon diaphragms are generally limited to 16'' HG.
Typical diaphragm materials
Rubber compounds
BUNA N (NBR) Temperature range: -12°C to 85°C Excellent for oil / petroleum based fluids
NEOPRENE (CR) Temperature range: -18°C to 85°C Good for abrasive materials
NORDEL (EPDM) Temperature range: -40°C to 100°C Good for extremely cold applications Good resistance to acids and caustics
VITON (FPM) Temperature range: -30°C to 120°C Excellent for aggressive fluids such as aromatic or chlorinated hydrocarbons and acids Good for high temperature applications
Note: for estimated diaphragm cycle life, consult pump manufacturer.
Thermoplastic compounds
SANTOPRENE (TPO) Temperature range: -23°C to 110°C Good for abrasive materials Good resistance to acids and caustics Good for high temperature applications
HYTREL (TPE) Temperature range: -18°C to 120°C Excellent general purpose / durable diaphragm Long life in non-aggressive applications
TEFLON Temperature range: -4°C to 100°C Excellent choice for pumping highly aggressive fluids Can have good life if abrasives are not present Back up rubber diaphragm may be used
Elastomers may be available in FDA compliant material for use with food, pharmaceutical and cosmetic applications. Note: for estimated diaphragm cycle life, consult pump manufacturer.
Often customers call us about diaphragm cycle life and the first few questions we ask are:
What pump are they using?
What chemicals are they using and at what temperature?
Is it a suction lift application or a flooded suction?
At what flow rate are they operating the pump?
After discussing these questions we find that several customers are running the pump at full throttle instead of selecting a larger pump in the beginning process of the pump selection. Operating a larger pump at half throttle would extend the diaphragm life, consume less air consumption and overall provide less wear and tear on the equipment. For more information on the diaphragm pump from the producer Yamada click here or contact us!