1. Understanding Water Hammer Ohio AWWA State Conference Presentation September 17, 2004 Dan Barr, PE

2. What Is Water Hammer?

3. What Is Water Hammer?

4. What Is Water Hammer? Webster says “ A concussion or sound of concussion of moving water against the sides of a containing pipe or vessel.” Also known as Surge Events or Fluid Transients

5. Valve Closure

6. System Dynamics of Valve Closure

7. Pump Start

8. Why Should I Care About Water Hammer?

11. Air Valve Caused Surge Air pocket

12. Air Valve Caused Surge Air is quickly expelled out of valve.

13. Air Valve Caused Surge Water hits valve and is immediately stopped.

14. Air Valve Caused Surge Secondary transient starts

15. Water Column Separation High point in main

16. Water Column Separation Low pressure wave arrives causing potential vacuum conditions

17. Water Column Separation High pressure wave arrives later and forces vacuum pocket closed

18. Water Column Separation Secondary transient wave started

21. Air Valves: Controlled Column Rejoining a lot of air Low pressure wave hits and valve lets air in quickly to prevent vacuum.

22. Air Valves: Controlled Column Rejoining a little air High pressure wave arrives and tries to push out air. Small orifice prevents this and cushions the pressure wave.

23. Air Valves: Controlled Column Rejoining Water comes to a stop with no transient

25. Questions and Answers