Eliminating Water Hammer

This Benshaw white paper explains how to protect pumping systems from damaging pressure surges caused by water hammer. It covers the physics behind pressure spikes, the role of valve closure timing, pump and system curve behavior, and how electronic motor control technologies like soft starters and variable speed drives can mitigate or eliminate water hammer.

Key Points

  • Understanding Water Hammer: Water hammer occurs when a sudden change in flow—such as a rapid valve closure or pump stop—creates a pressure surge capable of damaging pipes, valves, and pumps.
  • Valve Closure and Prevention: Proper control of valve closure time can significantly reduce the intensity of pressure surges, emphasizing prevention over mitigation.
  • System and Pump Curves: The relationship between flow rate, pressure, and system design determines how sensitive a system is to speed changes; steep curve pumps offer better control.
  • Advanced Control Features: Modern soft starters with direct acceleration and deceleration control—like AuCom’s XLR-8 technology—allow precise customization for different system profiles.
  • Causes and Calculations: The paper outlines the science behind pressure waves in piping systems and provides formulas for calculating additional pressure resulting from flow interruption.
  • Electronic Speed Control: Soft starters and variable speed drives (VSDs) manage pump acceleration and deceleration, reducing the mechanical and hydraulic stresses that trigger water hammer.
  • Choosing Between Soft Starters and VSDs: Soft starters are cost-effective and efficient for systems not requiring continuous speed control, while VSDs provide greater flexibility for variable flow needs.
  • Key Takeaway: Preventing water hammer through careful design, valve timing, and intelligent motor control ensures longer equipment life, reduced maintenance, and system reliability.