When to use Positive Displacement Pumps

Head (pressure) development is independent of pump speed

In instances where a process application necessitates different head conditions, the impact on capacity is minimal. Consequently, positive displacement pumps are unable to function against a closed discharge line without risking damage to the pump, prime mover, piping, or other associated process equipment. To address this issue, it is essential to install a bypass pressure relief valve on the pump or discharge line.

Power requirements vary directly with Head (pressure)

Provided that speed stays constant, power requirements are determined by the capacity pumped, dynamic head and efficiency.

Self- Priming

Typically, the majority of positive displacement pumps are designed to be self-priming. Nevertheless, each specific type may exhibit certain constraints related to this functionality, such as speed, viscosity, and the capacity to prime under dry conditions. In general, all of these pumps will require an additional priming to ensure proper lubrication.

Ability to handle fluids containing entrained gases or vapours

Typically, the majority of positive displacement pumps are designed to be self-priming. Nevertheless, each specific type may exhibit certain constraints related to this functionality, such as speed, viscosity, and the capacity to prime under dry conditions. In general, all of these pumps will require an additional priming to ensure proper lubrication.

Pump in either direction of rotation

Various types of Rotary PD pumps can operate efficiently in both directions by merely altering the direction of rotation, allowing for delivery on the gland or suction on the gland in the case of progressive cavity type pumps.

Good suction capability

In general, rotary positive displacement pumps exhibit superior suction capabilities, with the net positive suction head (NPSH) required by the pump rising as the pump speed increases. At lower operational speeds, the NPSH requirements remain minimal. This characteristic can be particularly beneficial when handling volatile fluids.

Accurate Proportioning

Reciprocating piston or diaphragm pumps can be employed for precise metering or proportioning tasks by adjusting either the stroke length, the frequency of the strokes, or a combination of both.

Step 8: Replace the O-ring And Cover

Replace the O-ring on the locating face and then align the cover with the rest of the unit, by making sure the holes for the screws align.

Air-Operated Double Diaphragm (AODD) Pumps:

AODD pumps operate by utilizing compressed air to oscillate diaphragms, thereby generating a pumping motion. These pumps are highly adaptable and capable of managing a diverse array of fluids, such as abrasive, viscous, and shear-sensitive substances. Their capacity to function without damage when running dry, along with their ability to accommodate solids, renders them ideal for numerous industrial applications.

Electrically Operated Double Diaphragm (EODD) Pumps:

EODD pumps function in a manner akin to AODD pumps; however, they utilize an electric motor rather than compressed air. This distinction allows for enhanced control over the pump’s performance and diminishes the dependence on an air supply. EODD pumps are characterized by their energy efficiency and are particularly suitable for applications that demand reliable and regulated fluid delivery.

Peristaltic Pumps

Peristaltic pumps operate by employing a flexible tube along with rotating rollers to generate a compressive motion that facilitates the movement of fluid. This configuration guarantees that the fluid interacts solely with the inner surface of the tube, rendering these pumps ideal for applications that require sterility or are sensitive to contamination. They are extensively utilized in the medical, pharmaceutical, and food processing sectors owing to their accurate dosing abilities and their gentle treatment of sensitive fluids.

Applications

1. Pharmaceuticals: In the pharmaceutical industry, Positive Displacement Pumps are essential for precise dosing and handling of sensitive fluids. Their ability to maintain sterility and handle high-viscosity liquids ensures the integrity of pharmaceutical products.
2. Food Processing: Positive Displacement Pumps are used to transfer ingredients, syrups, and finished products in food processing. Their gentle pumping action preserves the quality and texture of food products, making them ideal for handling delicate or shear-sensitive materials.
3. Chemical Processing: The chemical industry benefits from Positive Displacement Pumps’ ability to handle corrosive, abrasive, and high-viscosity fluids. Their robust construction and consistent flow rate make them suitable for transferring a wide range of chemicals.

Advantages

• Precision: Positive Displacement Pumps offer precise flow control, making them suitable for applications requiring accurate dosing and fluid handling.
• Versatility: These pumps can handle various fluids, including high-viscosity, shear-sensitive, and abrasive materials.
• Consistency: Positive Displacement Pumps maintain a constant flow rate, regardless of pressure changes, ensuring reliable performance.
• Self-Priming Capability: Many Positive Displacement Pumps can self-prime, reducing the need for additional equipment.

Disadvantages

• Pulsation: Some Positive Displacement Pumps, especially diaphragm pumps, can produce pulsating flow, which may require dampening mechanisms in certain applications.
• Maintenance: Regular maintenance is necessary to ensure optimal performance and longevity, particularly for pumps handling abrasive or corrosive fluids.
• Cost: Initial costs and energy consumption for Positive Displacement Pumps can be higher compared to centrifugal pumps, depending on the application and operating conditions.