Chapter 22 - Insertion (Sampling) Flow Measurement

Most flow measurements are made by meters that are installed in-line such that
all of the fluid passes through the meter body. Insertion (sampling) flow measurement
is a different technique because the meter is inserted into the pipe and the
flow rate is inferred from the measurement at a point in the flow stream.
There are both similarities and differences between in-line and insertion techniques.
On the one hand, fluid properties, pipe flow phenomena, and the basic
principles of flow sensing are the same. There are significant differences, however,
in operating principles, installation, and applications.

Where Can an Insertion Meter Be Used?

An insertion meter can be used in most flow measurement applications. Insertion
meters are available that utilize most of the traditional flow sensing technologies
(i.e., turbine, vortex, magnetic, dP). The range of fluid conditions (i.e.,
pressure, temperature, fluid type) under which insertion meters operate is similar
to that of in-line meters. The performance of the sensing techniques is likewise
similar.

Why Are Insertion Meters Used?
The applications in which an insertion meter may be a better choice than an inline
meter can be divided into three categories:

1. Applications in which an insertion meter is the only option. This is the
   case of large line sizes for which in-line meters are unavailable. Another
   example is an application where the process cannot be shut down for
   meter installation.
2. Applications in which the insertion meter is a more economical option.
   Installations in intermediate pipe sizes are suited to either in-line or insertion
   meters, but the insertion meter may be more economical.
3. The unique operation of an insertion meter can sometimes provide a better
   solution. For example, the velocity range of an insertion meter can be
   changed by installing a different sensor.

Most flow measurements are made by meters that are installed in-line such that
all of the fluid passes through the meter body. Insertion (sampling) flow measurement
is a different technique because the meter is inserted into the pipe and the
flow rate is inferred from the measurement at a point in the flow stream.
There are both similarities and differences between in-line and insertion techniques.
On the one hand, fluid properties, pipe flow phenomena, and the basic
principles of flow sensing are the same. There are significant differences, however,
in operating principles, installation, and applications.