Flow Measurement Accuracy

PROBLEM:

Inaccurate flow measurements

Lack of space for proper installation

Trapped fluids in dangerous chemical concentrations

SOLUTION:

BENEFITS:

Accurate flow measurements

More compact pipe layout

Eliminates trapping of chemical species

Technology breakthrough reduces inlet 'Flowmeter' runs

The CRV® provides a uniform elbow exit velocity profile, without swirl, allowing the close coupling of pipe elbows to meters.

Distortion and separated flow always accompany the fluid exiting a pipe elbow. Long meter-runs are required to allow the viscous forces to re-establish a steady equilibrium flow distribution before they encounter the measuring instrument. The CRV® is a set of stationary vanes, in a cylindrical body, which is positioned upstream of the elbow. The CRV® will precisely rotate the flow about its axis to compensate for the rotation caused by the elbow. The CRV® produces a uniform and non-turbulent flow at the exit of the elbow, and allows the length of the meter-run to be dramatically reduced. Elimination of the separated pulsating flow also increases the accuracy of the meter system.

The conventional need for pipe meter-runs

Three examples of meter-run requirements:

For a plain elbow, standard meter-runs are up to 30 diameters long, depending upon the type of fluid being measured (see example A below).

Tubular flow straighteners, used to homogenize the separated, non-uniform flow from elbows, still require at least 20 pipe diameters in length for settling velocity distortion (see example B below).

The CRV® prevents the formation of separation and cross flow in the elbow. Now the meter-run can be as short as 1 diameter (see example C below).

Benefits from the use of a CRV®

It is not always convenient to provide a long meter-run, especially when metering instruments are added to an existing piping system. The use of a CRV® eliminates the need for long meter-runs, and provides a steady, uniform flow which results in consistent accurate flow measurements for all types of meters.

FLOW METERS

Continuous Emission Monitor (CEM)

CEM is an EPA requirement for all power plants. A poor stack piping design will result in fluctuations, inaccurate pollutant readings, and burst phenomena (see Figure 1). This is a result of the separated flow caused by the ducting elbows in the stacks.

This separated flow impairs the user and prevents an accurate assessment of the emissions by the local EPA. This separated flow burst phenomenon is much like a vortex along a river bank, which traps debris, and then without notice, the debris is suddenly discharged. The results can be disasterous.