A Cheng Rotation Vane (CRV®) will prevent pipe burst, increase a plant’s safety & reduce a plant’s down time. A CRV® placed prior to an elbow creates a uniform more efficient flow to eliminate turbulence, vibration, erosion, cavitation to insure plant & worker safety.

Problem: Pipe Thinning & Pipe Bursting

A recent accident involving a bursting steam pipe in a nuclear power plant killed four people. Pipe bursting is caused by corrosion and erosion of areas inside the pipe, which cause the pipe walls to thin down and eventually burst under pressure. Commonly cavitation erosion occurs downstream of an elbow in piping systems and is caused by sudden flash of liquid into vapor bubbles followed by immediate collapse of the bubbles; the subsequent shock-wave generated by the flashing and collapsing of vapor or dissolved gas creates a stress erosion on the pipe wall.

 

Solution: CRV® Plant & Worker Safety

As fluid flows through an elbow, the centrifugal forces are inversely proportional to the radius of the elbow’s curvature as shown above. A vacuum is created on the inside radius of the elbow and a high stagnation pressure appears on the outside pipe wall.

With a pre-rotation of the fluid by CRV® set of stationary vanes, the measurement of this same pressure distribution shows that the stagnation pressure and the vacuum condition have been removed. With the pre-rotation of the fluid, the streamlines carry the particulates as if they are in a straight length of pipe, thus preventing erosion.

A CRV® placed prior to the bend would have prevented the erosion shown at the outlet of the elbow. It has been determined that if the flow streamlines travel an equal distance when going around the bend of an elbow, the fluid will not be subject to acceleration or flashing.