Appendix D. Measuring P and L Dimensions
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DigitalFlow™ Multipurpose Ultrasonic Liquid Flowmeter Startup Guide (1- and 2-Channel)
D.1 Measuring P and L (cont.)
Use Figure 19 to properly measure the coupling length. Typically, the transducer face is positioned just outside the
inside diameter (ID) of the pipe, or slightly retracted inside the coupling.
Figure 19: Determining the Pipe Coupling Length
Use the following formula to determine the P dimension:
[ID + 2(WT)]/(cos MA) = 2 (CL–FD) = P dimension
For example, given the following:
•
inside diameter (ID) = 48”
•
wall thickness (WT) = 3/8”
•
installed coupling length (CL) = 2.0”
•
a transducer face depth (FD) = 1.75”
•
mounting angle (MA) = 45°
The P dimension would be: [48 + 2(3/8)]/(0.7071) + 2(2.0–1.75) = 69.4”
