VP instruments VPFlowScope M probe, Руководство пользователя, Страница: 15 / 48

Mechanical installation 15
© 2016 Van Putten Instruments BV | MAN-VP-SMPR-UK | Revision:1600 | Date:23-03-2016
6.2 Piping table
At least 20 times the pipe diameter upstream and at least 5 times the pipe diameter downstream
needs to be applied, to avoid any distortion of the flow profile. This is a general rule, check the piping
table below for your application. The table shows the amount of length upstream or downstream
depending on the installation. If applicable in front of the meter, use given upstream length. If
applicable in behind the meter, use given downstream length.
Gas flow in pipes follows certain rules,
which must be observed for optimal measurement results. For some exceptions the upstream length
needs to be longer, or can be shorter.
If possible, you can always choose a longer upstream length, as these are minimum
values. The up- and downstream lengths are used industry wide as guidelines, but will
never be a guarantee for obtaining the “true value”. So always be careful and try to build
up your own experience from practical measurements
Piping table
The following table provides a guideline for proper distances between upstream or downstream
objects and the VPFlowScope M probe. The upstream length is the length between the last non-
straight object and the VPFlowScope M probe. If the upstream length is straight, and the distortion is
downstream of the VPFlowScope probe, you can use the column "downstream length" as a
guideline. In very complex situations, with multiple up- and downstream objects, you should consider
another location. This table is a practical guideline and is not exact science. Practical situations can
have multiple sources of distortion, therefore VPInstruments does not take any responsibility for the
correctness.
Picture Description
Upstream
length
2
Downstream
length
2
Effect
Single elbow
30 * D
1
10 * D
1
Distorted flow profile
Complex feed-in
situation (header)
40 * D
1
10 * D
1
Flow profile will be
distorted
Double elbow, multiple
elbows following each
other
40 * D
1
10 * D
1
Distorted p
swirl