Pumps for viscous masses: Which pump is most suitable for transporting a viscous, homogeneous molten soap mass in process plants?

Introduction / Context:
Molten soap is a viscous liquid that benefits from smooth, continuous pumping with minimal pulsation and good volumetric efficiency. Selecting the proper pump type improves product quality and energy efficiency while reducing shear-related issues.

Given Data / Assumptions:

• Fluid: viscous molten soap, relatively homogeneous and lubricating.
• Need: steady flow, good suction characteristics, self-priming if possible.
• Solids content minimal; moderate temperatures.

Concept / Approach:
Gear pumps (external or internal gear) are classic positive displacement rotary pumps for viscous liquids such as syrups, oils, and molten soaps. They provide near-constant flow proportional to speed, handle high viscosities, and maintain good efficiency where centrifugal pumps lose head.

Step-by-Step Solution:
Match fluid to pump class: viscous → positive displacement rotary.Shortlist options: gear, lobe, screw; among given choices, gear pump fits best.Select gear pump for molten soap transfer.

Verification / Alternative check:
Pump selection guides consistently recommend gear or screw pumps for viscous, clean liquids due to favorable performance curves at high viscosity.

Why Other Options Are Wrong:

• Diaphragm/reciprocating: better for slurries or metering; can be pulsatile and less ideal for hot viscous melts.
• Centrifugal/axial: efficiency drops with viscosity; poor choice for thick, slow-moving liquids.

Common Pitfalls:
Choosing centrifugal pumps for high-viscosity service and then encountering inadequate head/flow and overheating.

Final Answer:
Gear pump (positive displacement, rotary)