Table of Contents
Advertisement
4 Meter selection and Installation
4.1
Selecting the correct meter size
The complete PD 340 Flow Transmitter family has a very large measuring range. It is nor-
mally recommended that a particular transmitter size is selected so that it will operate in the
upper half of its measuring range. This is due to the fact that the influence of zero point error
is relatively higher at low flow rates. This applies to any flow transmitter on the market. How-
ever, it is possible to use the PD 340 even at very low flow rates, whilst still obtaining high
accuracy. Flow measurement down to 1 % of maximum flow rate for the Flow Transmitter is
now possible (100:1 turndown), when the linearizing function is enabled (refer to
function
in section 1).
Practical examples from different installations indicate that actual expected operational flow
rates do vary. It is therefore recommended that the calculated maximum flow rate should not
exceed 90 % of the specified maximum flow rate for the selected Flow Transmitter. Excep-
tions may be made if the flow rate is well known and very stable.
As a rule, a Flow Transmitter with a pipe dimension equal to the rest of the piping system
should be selected.
The size of the meterhead should be selected according to the maximum flow rate. This
maximum flow rate must be the absolute maximum flow rate during operation, cleaning,
startup etc. The smallest possible transmitter is then chosen for that maximum flow rate. This
will ensure optimum measurement accuracy. If the metering section is smaller than the pipe-
work in the installation, the connecting pieces should be tapered.
A Flow Transmitter should not be installed in a pipe construction where the pipes are smaller
than the pipes in the connections.
If two products are mixed before measuring, the mixed product must be a homogenous liquid
before entering the Flow Transmitter to ensure maximum accuracy.
The Flow Transmitter is available in 5 different sizes as shown in the table below:
Max. flow rate:
C 25
3
8 m
/h
20 m
Note:
The max. flow rate for the Flow Transmitter must NEVER be exceeded, otherwise
the meterhead may be damaged.
Manual
C 38
C 51
3
3
/h
40 m
/h
Flow Transmitter, PD 340
C 63
C 76
3
3
80 m
/h
120 m
/h
502 010 05
Linearizing
17/55
Advertisement
Table of Contents
