GE PT878GC User Manual download pdf (Page 40)

April 2004

3-8

Obtaining the Transducer Spacing

1. Using the measured OD and the pipe wall thickness, program

the PT878GC (discussed in Chapter 4, Programming Site

Data) to determine the required transducer spacing.

2. To determine the PT878GC correction factor, calculate the

mean inside pipe diameter (ID) and the pipe ID at the

transducer locations. Then divide the square of the mean ID

by the square of the ID at the transducer location, as shown in

the equations below, where OD

is the outside diameter at a

given point, and W

is the wall thickness at a given point (as

shown in Figure 3-6 on the previous page).

(3-1)

(3-2)

3. Program the value into the PT878GC.

Note: See Chapter 4, Programming Site Data, pages 4-3 to 4-16,

for more details on programming.

Based on the pipe OD, proceed to the appropriate section:

• If the pipe is < 12” (300 mm), see the section Installing the V

Series Clamping Fixture and Transducers on the next page.

• If the pipe is > 12” (300 mm), go to Installing the PI Fixture

and Transducers on page 3-12.

mean ID OD

+()–()OD

+()–()

+()–()OD

+()–()

(

) 4⁄

for non-concentric pipe

Mean ID

()

ID at transducer location()

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GE PT878GC User Manual Page 40