Preventing Water Hammering in Food and Beverage Applications
Hydraulic shock, commonly known as water hammer, causes a slamming or banging noise through vibration in piping. These vibrations wreak havoc in many production systems, and are especially prevalent in the food and beverage industry, where Clean In Place (CIP) applications require quick valve closures for maximum accuracy.
Though the noise can be irritating, the true danger of water hammer is that process equipment, piping, and instrumentation are not designed to withstand repeated vibrational shock from piping. Instead of replacing expensive components, Matrix Technologies can mitigate water hammer through thorough investigation, intelligent design, and experienced equipment installation.
Water Hammer Cause
Water Hammer is created when fluid velocity or direction changes rapidly in piping. The flowing fluid’s energy creates a transient acoustic pressure wave similar to a train wreck: if the engine stops suddenly, the other cars keep moving forward slamming into one another. This wave energy is transferred into the piping and equipment causing harmful vibrations and the hammering noise.
Stopping flow quickly in any manner will cause a pressure wave to a certain degree. However, severe water hammer occurs when the pressure exceeds the pressure specifications of the system. This wave pressure (Ps) is described by the relationship of fluid specific gravity (s), fluid velocity (v), and valve closure time (t) as demonstrated in the equation:
For example, water flowing at 6 ft/sec with a valve closing time of 1 sec adds 360 lb/in2 of pressure to a system. If the steady state system pressure is 40 lb/in2, then the system must be designed for ten times the normal operating pressure! Thus, decreasing fluid velocity or increasing valve closure time is instrumental in reducing damage. However, in CIP applications fluid velocity is often unalterable, so only valve closure time remains. Increasing this time will help mitigate the problem, but increasing time isn’t always possible or practical.
Solution: Three Chamber Divert Valves
If investigating the process determines that the design parameters require high fluid velocities and quick valve closures, the next step is to mitigate the problem through technology using three chamber divert valves. Traditional divert valves with one inlet at the bottom of the valve fail to mitigate the pressure increase of the valve closing and can actually exacerbate the pressure increase. Instead, a three chamber divert valve helps absorb the pressure wave’s energy by always closing against the flow of the fluid. Though just as versatile as the traditional divert valve, these valves are higher priced. However, the cost is offset many times by safeguarding expensive equipment and piping.
Lastly, it is important that the valve is installed correctly. The valve can correctly divert fluids while actually being installed backwards. That is, the valve stem will close rapidly with the fluid flow creating additional vibration. It is often difficult to inspect a valve after installation, so it is essential that the craft installing the valve understands its mechanics and function.
How Matrix Helps
We at Matrix Technologies are your partners in specifying your next CIP system, ensuring that your high value process equipment is undamaged by water hammer. Our experts identify possible water hammer events and use adept industry knowledge and experience to make your next project a success.
Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To discuss a project, or learn more about our Process Engineering Services, contact Khalil Omran, Senior Process Engineer in the Engineering Services Division.
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Multidiscipline Engineering – Process Design