Diaphragms on Air Operated Double Diaphragm Pumps
A double diaphragm pump is also called a positive displacement pump which utilizes two flexible diaphragms, connected by a shaft, which move back and forth. The diaphragms work as separation of the air one side and the medium on the opposite side of the diaphragm.
The diaphragms, in most common AODD pump designs, maintain a seal at two points:
- At the center diaphragm hole by tightening the inner and outer diaphragm plates to the main shaft, capturing the diaphragm. When properly torqued, a leak-free seal is created. Torque may vary per brand.
- A seal also occurs at the outer circumference of the diaphragms, usually at the molded-in sealing bead or from sealing grooves on the inner air chamber and/or outer fluid chamber. The seal occurs from the compression created when the outer chamber bolts (bolted pumps) or the large clamp band assemblies (clamp style pumps) are tightened.
Diaphragms Maintenance is key
As part of a general maintenance program, diaphragms should be replaced regularly, according to the manufacturer’s recommendations. The efficiency, lifetime and stability of a diaphragm in an AODD pump is dependent on its compressed air supply. The compressed air supply must be at the same or a higher pressure than the fluid to be pumped, with a maximum of 0.3bar (4.35PSI) in difference. This tends to limit the use of AODD pumps to only low pressure applications.
Diaphragm pumps will move nearly any kind of fluid in multiple industries like:
- Coating & Glue
- Food & Beverage
- Oil & Gas
- Printing & Painting
- Pulp & Paper
- Sanitary Steel & Metal
Every industry or solution has it own selection requirements if it comes to diaphragm material. They come in a variety of materials (availability may vary per manufacturer) and designs to meet specific application needs such as chemical compatibility, temperature, abrasion resistance, and certification requirements.
Most common used materials supplied by Thinqk Pump Parts:
An excellent general purpose diaphragm for use in non-aggressive applications such as water-based slurries, well water or sea water. Exhibits excellent flex life and low cost.
Color Code: Green (common color) Different OEM intent to use brand specific color
Excellent for applications involving petroleum/oil-based fluids such as leaded gasolines, fuel oils, non-synthetic hydraulic oils, kerosene, turpentines and motor oils.
Color Code: Red (common color) Different OEM intent to use brand specific color
Excellent for use in applications requiring extremely cold temperatures. May also be used as a low cost alternative when pumping dilute acids or caustics
Color Code: Blue (common color) Different OEM intent to use brand specific color
Excellent for use in applications requiring extremely hot temperatures. May also be used with aggressive fluids such as aromatic or chlorinated hydrocarbons and highly aggressive acids. PTFE would normally be used with these aggressive fluids as its flex life is better than Viton®. However, in applications involving suction lift outside the range of PTFE, Viton® will be the preferred choice for highly aggressive fluids
Color Code: Silver or White (common color) Different OEM intent to use brand specific color
An excellent general purpose diaphragm for use in non-aggressive applications. This material exhibits exceptional flex life and durability. Wilden’s least expensive diaphragm
Color Code: Clear
Excellent choice as a low cost alternative to PTFE in many acidic and caustic applications such as sodium hydroxide, sulfuric or hydrochloric acids. Exhibits excellent abrasion resistance and durability at a cost comparable to neoprene
Color Code: Cream (common color) Different OEM intent to use brand specific color
Exhibits excellent abrasion resistance, flex life and durability. This material is FDA approved for food processing applications. An outstanding general purpose diaphragm as well.
Color Code: Cream (common color) Some brand use alternative color
Excellent choice for applications requiring high oil resistance that meets or exceeds that of nitrile (Buna-N). This material exhibits exceptional performance for a variety of fluids
Color Code: Black
Excellent choice when pumping highly aggressive fluids such as aromatic or chlorinated hydrocarbons, acids, caustics, ketones and acetates. Exhibits good flex life compared to a standard rubber diaphragm
Color Code: white. (Compound diaphragms: light blue)
Can we help you?
For questions on Diaphragms to service your AODD Pumps please contact our Team of professionals at Thinqk Pump Parts. We are more than happy to assist you with your needs.
To reduce your downtime we stock most common diaphragm sizes and materials used in the Diaphragm Pump industry. Parts ship worldwide from our semi-automated warehouse located in the Netherlands.
Thinqk Diaphragms Pump Parts, original quality at a better price