Process Cooling Pumping Systems Analysis

Abstract

An analysis of the mill water pumping systems at a North American manufacturing facility was conducted late las year and the following issues were observed:

1. Overpumping – Both systems were overpumped to a significant degree against their calculated design conditions. As observed, each system was running +1 pump more than required to meet the requirement. System 1 was overpumped by 25%, or 1100 GPM, and System 2 was overpumped by 37%, or 1850 GPM. Both systems may provide adequate heat rejection while operating three pumps each.

2. Check Valve induced Pump Failure – While attempting to take readings, both systems exhibited check valve failure to hold. This failure causes significant short-circuiting of water to the cold well, causing flow instabilities, surging, and low pressure alarms. Finally, water flow reversals cause significant and premature damage to vertical turbine pumps not equipped with non-reversing ratchets. It is advisable to revise operational sequence to eliminate pump staging to minimize future pump failures.

3. High Pressure Differentials – Observed end of system pressure differentials were in excess of 50 PSIG with adjacent equipment served requiring 15-17 PSIG differential. High pressure differentials will result in velocity erosion and premature valve/heat exchanger failure, and should be addressed immediately to minimize additional equipment damage and potential system shutdown.