How do you select a pump for a difficult service with high temperature, low NPSH, and viscous fluid?

Systematic approach: determine fluid properties at operating temperature (viscosity affects performance derating per HI standards), calculate NPSHa accounting for vapor pressure at temperature, apply viscosity corrections to pump curves. Options to improve NPSHa: raise vessel level, reduce suction piping losses, use oversized suction line, cool suction fluid, or use inducer impeller. For high viscosity: consider positive displacement pumps (screw, gear), or oversized centrifugal with viscosity correction. May need jacketed pump for temperature control. Seal selection critical for high temperature.