Positive Displacement Pumps: A Buying Guide for Facility Managers

Executive buying summary

Positive displacement pumps are essential for transferring fluids accurately and at controlled pressures, often in applications requiring precise dosing or high viscosity handling. Selecting the right pump involves balancing performance requirements with factors such as material compatibility, energy efficiency, and maintenance needs. Total cost of ownership is influenced by factors like energy consumption, service intervals, and the potential for downtime. A key risk to avoid is selecting a pump unsuitable for the fluid’s properties, leading to premature failure and process disruption.

• Careful consideration of the fluid being pumped is paramount to ensure material compatibility and prevent damage.
• Energy efficiency should be a significant factor in the decision-making process, impacting long-term operational costs.
• Compliance with relevant safety standards, such as the Supply of Machinery (Safety) Regulations 2008, is essential for legal operation and user safety.
• Thorough validation and commissioning are critical to ensure the pump performs as expected and meets process requirements.
• A comprehensive service and maintenance plan is vital to maximise pump lifespan and minimise unexpected downtime.

Equipment types compared

Key features to look for

• Flow Rate & Pressure Range: Ensure the pump's capabilities align with the application’s specific needs to avoid underperformance or over-sizing. Ask for performance curves demonstrating flow versus pressure.
• Material Compatibility: Verify that all wetted parts are compatible with the fluid being pumped to prevent corrosion or degradation. Request material certificates and chemical resistance data.
• Sealing System: Evaluate the sealing system's effectiveness and suitability for the fluid's properties, particularly for hazardous or volatile materials. Inquire about seal materials and leakage rates.
• Drive System: Consider the motor’s efficiency and suitability for the pump’s power requirements. Confirm the motor's compliance with ecodesign minimum efficiency requirements.
• Noise Levels: Assess the pump’s noise emissions, especially in environments where noise pollution is a concern. Request noise emission data and consider vibration dampening measures.
• Ease of Maintenance: Look for designs that facilitate easy access to components for routine maintenance and repairs. Ask about recommended maintenance schedules and spare part availability.
• Control System Integration: Ensure the pump can be integrated with existing control systems for automated operation and monitoring. Confirm compatibility with standard communication protocols.
• Safety Features: Verify the presence of safety features such as overload protection, pressure relief valves, and emergency shut-off mechanisms. Confirm compliance with PUWER regulations.

Pros and cons of each equipment type

Reciprocating Pumps (Piston/Plunger)

Pros: High pressure capabilities, precise flow control, suitable for high viscosity fluids.

Cons: Relatively high maintenance requirements, pulsed flow can be problematic in some applications, higher upfront cost.

Rotary Lobe Pumps

Pros: Gentle pumping action suitable for shear-sensitive fluids, handles solids well, relatively low maintenance.

Cons: Lower pressure capabilities compared to reciprocating pumps, can be noisy, limited flow rates.

Gear Pumps (External/Internal)

Pros: Compact size, relatively simple design, cost-effective for many applications.

Cons: Can be noisy, limited to lower viscosity fluids, potential for internal leakage.

Progressive Cavity Pumps

Pros: Excellent for handling fluids with solids, self-priming, consistent flow.

Cons: Rotor and stator wear can be a concern, longer lead times, potential for clogging.

Screw Pumps

Pros: Suitable for high viscosity and shear-sensitive fluids, smooth and consistent flow, relatively quiet operation.

Cons: Higher upfront cost, more complex design, potential for wear in high-solids applications.

Which facilities each type suits

• Reciprocating Pumps: Chemical processing plants, high-pressure cleaning systems, hydraulic power units.
• Rotary Lobe Pumps: Food and beverage processing, pharmaceutical manufacturing, wastewater treatment.
• Gear Pumps: Lubrication systems, hydraulic circuits, fuel transfer.
• Progressive Cavity Pumps: Sludge handling, wastewater treatment, oil and gas extraction.
• Screw Pumps: Polymer processing, viscous chemical transfer, paint and coating applications.

Buyer's checklist

1. Fluid Analysis: Conduct a thorough analysis of the fluid’s properties (viscosity, solids content, temperature, chemical compatibility).
2. Flow & Pressure Requirements: Define precise flow rate and pressure requirements for the application.
3. Regulatory Compliance: Verify compliance with all relevant regulations (Supply of Machinery (Safety) Regulations 2008, ATEX/UKEX if applicable).
4. Site Assessment: Evaluate the installation location for space constraints, power supply, and accessibility.
5. Risk Assessment: Conduct a risk assessment to identify potential hazards and implement appropriate safeguards.
6. Commissioning & Validation: Develop a comprehensive commissioning and validation plan to ensure proper operation.
7. Training: Ensure personnel receive adequate training on pump operation, maintenance, and safety procedures.
8. Service & Maintenance Plan: Establish a service and maintenance plan with the supplier, including preventative maintenance schedules.
9. Spare Parts Availability: Confirm the availability of spare parts and their lead times.
10. Lifecycle Cost Analysis: Consider the total cost of ownership, including energy consumption, maintenance, and potential downtime.