Common Causes of Diaphragm Pump Valve Failures: A Guide to Troubleshooting and Prevention

Ⅰ.Overview of Fluid Operation in Pneumatic Diaphragm Pumps and Illustrative Video on the Wear of Ball Valve Components.

The air operated double diaphragm pump has chambers on both the left and right sides, each equipped with a set of diaphragms. The diaphragms separate the chambers into two spaces: one for air pressure and the other for fluid. Additionally, there are four sets of ball valve components on both sides of the chambers, which are designed as check valves to control the direction of fluid delivery.

As shown in Figure 1, when compressed air enters the A air pressure chamber, the A diaphragm is pressurized and pushed outward, creating a pumping stroke. Simultaneously, the fluid is pressurized and delivered through the ball valve components and the discharge pipe from the liquid outlet. (At this time, the ball valve below the A section is closed, and the one above is open.)

There is a common shaft connecting the two diaphragms. As the A-side diaphragm is pushed outward, the B-side diaphragm contracts inward, performing the opposite suction stroke. The fluid is drawn in through the liquid inlet using the siphon principle. (At this time, the ball valve below the B section is open, and the one above is closed.)

When the diaphragms reach the end of the designed stroke, the pump's internal switch is activated to control the main air valve, switching the direction of compressed air intake. This enables the pneumatic power to switch to the other chamber for pressurization. The chambers on both sides will continue the alternating pumping and suction actions, utilizing this principle to achieve fluid delivery.

Therefore, if there is wear in the valve components, it may cause pump delivery failures.

Learn more: DEMONSTRATIVE VIDEO: POSSIBLE OUTCOMES OF BALL VALVE PARTS ABRASION

Ⅱ.Common Causes of Diaphragm Pump Valve Components Failures:

The valve components (#5~#10) in the air operated double diaphragm pump are crucial mechanisms for achieving efficient pump delivery, as they determine the direction and efficiency of fluid transportation. Wear of the valve components can result in a decline in pump performance (at this point, the pump may continue to operate but with irregular frequency and an inability to effectively transport fluids) or even lead to pump shutdown. The following are common situations and root cause analyses that may lead to valve component failures:

(1) Abrasive Solid Particles: The presence of hard substances in the conveyed fluid over an extended period can result in wear of the valve components. Severe wear of the ball cover, ball, and ball seat may cause the valve to dislodge from its original position or become stuck, leading to fluid backflow prevention failure or blockage, causing abnormal pump delivery.

(2) Operation under High Pressure: Operating the pump under high-pressure conditions may subject the valve components to higher fluid pressure, making them more prone to damage or deformation.

(3) Inappropriate Conveyed Fluid: If the material of the valve components selected for the pump is incompatible with the chemical properties of the conveyed fluid, corrosion or adhesion leading to solidification may occur. This can damage the material of the valve components, resulting in material deterioration, brittleness, deformation, or erosion.

(4) Overheating or Overcooling: Extreme temperature conditions in the pump's operating conditions or environment require consideration of the suitability of the valve component materials. Temperature variations can cause material expansion, contraction, or deterioration, affecting normal operation and service life.

(5) Oversized Particles or Impurities: Pumps of different specifications and designs have size limits for applicable particles. Ingesting oversized particles or impurities can cause the valve components to jam, preventing normal operation and affecting the pump's suction and delivery efficiency.

(6) Fluid Deposition or Solidification: When the fluid contains substances with a relatively high specific gravity that tend to settle or fluids that develop solidifying characteristics over time, deposition or solidification on the valve components may occur. This can lead to the valve components becoming stuck due to deposits or solidified fluid, preventing normal operation and causing the pump to malfunction or jam.

III. Improving Wear on Valve Components

Here are solutions for common causes of valve component failures. Before selecting pump specifications and materials, it is advisable to ensure compatibility between the fluid and material specifications. If there are concerns about material selection, feel free to contact us via phone or email with information on the chemical properties of the conveyed fluid, and we will respond promptly.

(1) Abrasive Solid Particles:

Choose materials for valve components with higher hardness or better toughness based on the characteristics of hard or sharp-edged particles in the fluid to increase the components' lifespan.

(2) Operation under High Pressure:

Operate the pump at the lowest pressure that meets the flow rate requirements, installing an air pressure regulator to control input pressure. Lower operating pressures significantly extend the pump's lifespan. If the fluid has high viscosity or requires elevated output pressure, it is also recommended to operate the pump at the lowest pressure that meets the specified conditions.

(3) Inappropriate Conveyed Fluid:

Consider the chemical properties of the fluid, such as solvents, pH values, or adhesive characteristics, when selecting material for valve components to avoid corrosion and prolong component life.

(4) Overheating or Overcooling:

Choose materials that can withstand extreme temperatures if the fluid itself experiences high or low temperatures. Improve environmental temperature conditions or adjust fluid temperature before pump operation.

(5) Oversized Particles or Impurities:

Install a filter with an appropriate aperture size at the suction end of the pneumatic diaphragm pump to prevent the intake of oversized particles or impurities, avoiding valve component failures. Especially when the fluid container or trough is an open-type structure or space, there is often the risk of debris such as wood shavings, plastic bags, plastic pieces, or cigarette butts being drawn in. In such cases, it is strongly recommended to install protective measures.

(6) Fluid Deposition or Solidification:

Use a mixer to suspend particles effectively in the fluid before transport, and flush the pump chamber and valve components after pumping to keep them clean. For fluids with solidification tendencies, use a solvent for thorough cleaning after pump operation.

(7) Regular Replacement of Consumables:

Despite selecting suitable valve materials, observe the frequency of consumable replacement. Replace consumables early based on replacement frequency to prevent unplanned production line downtime and associated costs.

For any further inquiries or assistance, please don't hesitate to contact us.

Ⅳ.Material Introduction and Applications of Ball Cover, Ball Valve, and Ball Seat

The ball valve components of the pneumatic double diaphragm pump consist of a ball seat, ball cover, and ball valve. These components are typically made of different materials to adapt to various application requirements and fluid characteristics. The following is a brief introduction to the common materials used for ball valve components and their applications:

🔸Aluminum Alloy:

Aluminum alloy's main advantages lie in its lightweight, high strength, and superior corrosion resistance. It is commonly used in the structural components of the ball cover to provide strong support and durability. Aluminum alloy is effective in handling fluids with lower corrosiveness in certain applications.

🔸Stainless Steel:

Stainless steel is a highly corrosion-resistant material with excellent chemical corrosion resistance and high-temperature resistance. It is typically used in manufacturing crucial components of the ball valve to ensure the purity and safety of the fluid. Stainless steel is common in applications that involve corrosive or high-temperature fluids.

🔸Polypropylene (PP):

Polypropylene is a lightweight and corrosion-resistant plastic material commonly used in manufacturing the ball seat or other fluid-contact components of the pump. It exhibits good resistance to some corrosive fluids but may not be suitable for handling specific high-temperature or highly corrosive fluids.

🔸Polyethylene (PE):

Polyethylene is the most widely used thermoplastic material, known for its strength, good insulation, cold resistance, excellent impact resistance, and resistance to acids and alkalis.

🔸Polyurethane (PU):

Polyurethane is a chemical material with properties between rubber and plastic, combining rubber-like elasticity with the high strength of plastic. PU elements exhibit good physical and chemical properties, including excellent wear resistance, wide elongation, high tensile strength, and breathability.

🔸Chloroprene Rubber (Neoprene):

Neoprene exhibits excellent heat resistance, flame resistance, resistance to acids and alkalis, wear resistance, and resistance to mineral oils and many chemicals.

🔸Santoprene®:

Santoprene® is a thermoplastic rubber known for its excellent elasticity, wear resistance, and corrosion resistance. It is used in manufacturing ball covers and ball seats to enhance effective sealing performance and wear resistance.

🔸PTFE:

PTFE is a non-adhesive material that is particularly useful in handling viscous fluids. It prevents fluid adherence to the internal components of the pump, reducing the risk of dirt and blockages. PTFE has excellent resistance to many chemicals and corrosive fluids, making it an ideal choice for handling corrosive fluids.

🔸Bakelite:

Bakelite features characteristics such as non-absorbency, non-conductivity, high temperature resistance, high strength, hard surface, and brittleness. It is an excellent insulating material but is not resistant to oil and chemical corrosion.

Selecting the appropriate material depends on the specific requirements of the application, including the nature of the handled fluid, operating environment, temperature range, and chemical corrosiveness. Choosing the right material based on these requirements ensures the safe and reliable operation of the pump in various applications.

Please feel free to contact us for more information:

E-mail: service@tdspump.com

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2023-12-25