Air Operated Double Diaphragm Pumps play a crucial role in various industries such as chemical processing, lubrication, ceramics, and wastewater treatment. One of the primary challenges faced by users of Diaphragm Pumps is the premature wear of the pump’s diaphragms, which can result in failures and subsequent loss of fluid flow and pressure.
Chemical Compatibility
The diaphragms, as well as other components such as balls and seats, that contact the fluid in the diaphragm pump must be compatible and resistant to chemical attack. Premature diaphragm failures indicate chemical attack when there are signs of bubbling, cracking, or discoloration of the diaphragm. It is crucial to thoroughly review the application and select chemical compatible materials to prevent this issue. Selection compatible materials can be accomplished by consulting the diaphragm pump manufacturer’s chemical compatibility guide or reaching out to the manufacturer for technical support.
Dry Running
It is common for diaphragm pumps to empty a tank or drum of fluid and start running dry. While it is safe to operate the diaphragm pump in this manner, the diaphragms’ lifespan is diminished because the pump cycles faster when running dry. Additionally, the compressed air used to operate the diaphragm pump is consumed and wasted. To prevent dry running, it is recommended to use liquid level controllers on the fluid tank or install a stroke sensor on the diaphragm pump to monitor pump speed. Utilizing a stroke sensor or other cycle counting methods will allow the creation of a specific preventative maintenance program for the application.
Abrasive Fluids
The continuous pumping of highly abrasive fluids, such as inks or slurries, can lead to wear on the diaphragms and other components that contacts the fluid. Typically, wear occurs between the diaphragm and the outer fluid piston. To minimize the impact of abrasion, it is necessary to reduce the pump speed. This can be achieved by adding an air pressure regulator and lowering the air pressure. If a high discharge pressure is necessary and the air pressure cannot be reduced, it is recommended to choose a larger-sized diaphragm pump to decrease the required operating speed.
Pumping Solids without Suspension
Diaphragm pumps are frequently utilized for pumping fluids that contain suspended solids. However, if the solids are not properly suspended, they may accumulate in the pump’s fluid chamber, obstructing the movement of the diaphragms and causing damage to both the diaphragms and, in certain cases, the connecting rod of the pump. Additionally, solid particles can settle around the ball valve seats, resulting in inadequate diaphragm pump performance. To avoid blockages, it is advisable to regularly flush the pump and install a filter screen of the appropriate size on the suction side.
High Inlet Fluid Pressure
When the inlet pressure exceeds 10 psi (0.69 bar), it can lead to diaphragms imploding and breaking. In severe instances, the diaphragms may rub against the air chamber, exacerbating the problem. This issue commonly occurs in applications where the diaphragm pump is fed from a tall tank or when the fluid has a relatively high density. To prevent this problem, consider adding a pressure-reducing valve at the diaphragm pump’s inlet or reducing the maximum amount of fluid in the tank. Check this article for review the Pivot Series reliability.
High Inlet Air Pressure
Diaphragm failures may result from over-pressurization of the air side in a diaphragm pump. When the pump encounters excessive air pressure, the diaphragms balloon and rupture. Typically, metallic pumps have a maximum inlet pressure of 8 bar (120 psi), whereas non-metallic pumps have a maximum inlet pressure of 7 bar (100 psi). Installing an air pressure regulator can effectively reduce the pressure at the diaphragm pump’s air inlet, avoiding diaphragm failures and other potential issues.
Improper Temperature Range
To prevent premature pump failure and associated diaphragm failures, it is necessary to observe the specified temperature working ranges, which depend on the materials of the diaphragm pump. When diaphragms are exposed to high temperatures, they often exhibit discoloration along with signs of cracking or bubbling. To eliminate this issue, it is recommended to either replace the diaphragm pump with a new one or use repair kits that include materials capable of withstanding the fluid temperatures of the application.
MATERIAL |
TEMPERATURE RANGE |
PTFE (Teflon®) |
(5°C – 105°C), (41°F – 221°F) |
BUNA-N |
(10°C – 80°C), (50°F – 176°F) |
ACETAL |
(10°C – 90°C), (50°F – 194°F) |
HYTREL® |
(10°C – 90°C), (50°F – 194°F) |
SANTOPRENE® |
(-29°C – 135°C), (-20°F – 275°F) |
FKM (VITON®) |
(-40°C – 176.7°C), (-40°F – 135°F) |
POLYPROPYLENE |
(10°C – 80°C), (50°F – 176°F) |
PVDF (Kynar®) |
(-12.2°C – 107.2°C), (10°F – 225°F) |
Hytrel® is a registered trademark of the DuPont Company, Viton® & Teflon® of the Chemours Company and Santoprene® of the Monsanto Company, licensed for Advanced Elastomer Systems, L.P. Kynar® is a registered trademark of Arkema, Inc. Hastelloy® is a registered trademark of Haynes International, Inc.
