Is cavitation eroding your bottom line?

When a fluid's pressure drops below its vapor pressure it changes state from a liquid state into a gaseous state. Then as the pressure recovers or increases over the fluid's vapor pressure, these bubbles collapse forming supersonic fluid micro jets that erodes material in proximity. The bubble collapse can also create shock waves of up to 100,000 psi.

Left uncontrolled, cavitation damage can affect the performance of equipment, cause failures and be very costly to repair.

If you have ever seen a propeller spinning under water you would likely have seen bubbles that seem to magically be expelled from the propeller even though it is no where near the surface of the water. That is cavitation. The propeller on the left shows signs of cavitation damage on the edge of its blades. This occurs when gas bubbles collapse near the surface of the metal and make millions of microscopic pock marks on its surface from the micro jets mentioned above.

In industry, such as oil and gas, a choke valve will drop pressure by means of flowing fluid through a variable orifice or Vena Contracta (choke point). When this pressure drop occurs at the Vena Contracta the pressure drop can dip greatly before recovering. If that pressure dip drops below a fluids vapor pressure and recovers, then cavitation will occur.

Over time, this will damage valve parts and the valve's body to such an extent that it can breach fluid, including hydrocarbons, outside of the valve. This poses a threat to workers and the environment.

Master Flo Valve, an oil and gas choke valve manufacturer has engineered a special choke trim for these applications that feature several methods to avoid cavitation and its costly damage. First by using an impingement technology that directs high velocity fluid streams in on themselves. This greatly reduces cavitation by creating additional back pressure that reduces the sharp dip in pressure produced by the choking action of the Vena Contracta.

Secondly, a double walled choke trim takes two separate drops of pressure that lighten the force in which each pressure drop occurs. Finally, this "dual-cage" as it is called, is made of a tough grade of stainless steel, so that any cavitation that does occur is less likely to damage its surface. Together, these innovations reduce and prevent cavitation from occurring in the valve and have saved operators thousands of dollars in damage and lost production.

Recently, Master Flo engineers have optimized their "dual-cage" design to increase capacity by as much as 3-fold. This means that they can now provide the same amount of flow capacity while using much smaller valves to do so. In some cases this will saves clients over 50% on the price of there valves. To learn more about Master Flo's anti-cavitation valves or their premier anti-erosion choke valves visit www.masterflo.com

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