Identifying Opportunities to Optimize Pump Life Cycle Performance

Pumping system optimization has the potential for significant reductions in life-cycle-cost (LCC). Through plant assessments, the best few applications can be identified and prioritized for system improvements. Mechanical modification and variable speed control, where applicable, will allow pump operation near the best efficiency point (BEP) for a given head and flow. Operation near BEP offers significant improvements in pump and process reliability as well as energy savings. Variable speed control has the potential to lower LCC in the range of 20 to 60%. Also, speed control can lower process variability for additional improvements in material usage.

The application of intelligent drives, in lieu of a standard variable frequency drives, provides embedded condition monitoring and mechanical fault protection to prevent catastrophic failures. Also, real-time monitoring allows predictive maintenance to schedule repairs before process operation is negatively affected.

Engineering Strategies to Improve Pump System Performance

At existing plants, about 20% of installed centrifugal pumps offer 80% of the potential life cycle cost savings. In general, the best candidates for energy reduction exceed 40 HP. Although, lower HP pumps with high maintenance cost are also good candidates for optimization. As a rule of thumb, systems with static heads less than half of the pump’s total dynamic head are viable candidates for speed control. Overall, pump system performance is affected by several factors:

• Efficiency of the pump as well as other system components
• Efficiency of drives (Motor and VFD)
• Efficient pump control (e.g. variable hydraulics, on-off control
• Overall system design (sizing and balancing measures)
• Effectiveness of piping systems (e.g. reduced frictional pressure losses, matching of pump and system characteristic)
• Appropriate maintenance cycles

Plantwide assessments identify the following process modifications that offer the most potential for efficiency improvements:

• Motor efficiency via new replacement or upgrade
• Best match between component size and load requirement
• Use of speed control instead of throttling or bypass mechanisms
• Reduced load on the motor through improved process and systems design

Symptoms that indicate opportunity for pump optimization:

• Presence of cavitation noise
• Throttled valve-controlled systems
• Bypass (recirculation) lines normally open
• Multiple parallel pump system with same number of pumps always operating
• Constant pump operation in a batch environment or frequent cycle batch operation in a continuous process