01

Define the complete operating envelope

Record the required normal, minimum and maximum dose, injection-point pressure, suction conditions and operating schedule. Size against the maximum credible back pressure—not only the normal gauge reading—and confirm the pump can still operate accurately at the minimum required output.

  • Minimum, normal and maximum flow
  • Normal and maximum discharge pressure
  • Continuous, batch or intermittent operation
  • Required turndown and control signal
  • Ambient and fluid temperature

02

Characterise the chemical

Chemical name alone is not enough. Concentration, temperature, viscosity, vapour pressure, dissolved gas, solids and crystallisation tendency can change material compatibility and suction performance. Confirm wetted materials using current chemical-resistance data and obtain written confirmation for severe service.

  • Concentration and temperature
  • Specific gravity and viscosity
  • Solids content and particle behaviour
  • Toxicity, flammability and containment needs
  • Tendency to gas, freeze, settle or crystallise

03

Choose the pumping principle

Packed plunger liquid ends suit compatible fluids and can be attractive for high-pressure service, but packing wear and controlled leakage must be considered. Diaphragm liquid ends isolate the process fluid from the drive and are generally preferred where containment, hazardous chemicals or leakage control are important.

  • Plunger: robust, direct displacement and high-pressure capability
  • Mechanical diaphragm: simple chemical feed at moderate duties
  • Hydraulic diaphragm: containment and demanding process service

04

Design the system around the pump

A correct pump can still perform poorly in an incorrect system. Review suction-line diameter and length, flooded suction, calibration arrangement, relief protection, back-pressure control, pulsation damping and injection-point design. Confirm that every pressure-containing component is rated for the maximum possible pressure.

  • Suction strainer only where appropriate
  • Relief valve returning to a safe destination
  • Back-pressure valve where stable differential pressure is required
  • Calibration pot or verified flow-measurement method
  • Pulsation dampener where piping or instruments require it

Frequently asked questions

Should a dosing pump be oversized?

Allow a sensible engineering margin, but avoid extreme oversizing. A pump that normally operates near the bottom of its adjustment range can lose useful control resolution.

What information is essential for a quotation?

Provide the chemical and concentration, required flow range, suction conditions, discharge pressure, temperature, materials preference, control method and hazardous-area requirement.

Technical references

Use the current applicable standard, manufacturer manual and project specification for final engineering.

VK Pumps metering-pump product range Petrox–VK metering-pumps brochure