B-144-12-E
16
9.2 Operating Precautions
(1) When changing flowrates
In applications where the flowrate varies or
where shutoff valve opening and closure takes
place in batch operation, avoid rapid changes
in flowrate across the meter.
As a rule of thumb, one second per 25
millimeters (1") in connecting pipe diameter
is acceptable as the permissible changes in
flowrate.
Operating the meter at flowrates in excess
of the maximum allowable flowrate will nullify
the guaranteed accuracy,
reduce the meter
life and may result in faulty conditions, such
as the seizure of bearings or the rotor-to-
measuring chamber contact.
(2) Where the temperature of metered fluid
changes
Avoid rapid temperature changes in the meter.
Temperature changes of the fluid in the meter
should be held within 3
°
C per minute.
Extra care should be used particularly when
making a flow measurement in batch operation
without the provision of heat tracing of the
piping where the fluid temperature differs from
atmospheric temperature.
If rapid temperature changes are anticipated,
heat trace the piping assembly as well as the
meter.
(3) Liquids of low steam pressure
Temperature and pressure of LPG, polyvinyl chloride monomers or anything with low viscosity and
low steam pressure that are too ready to vaporize should strictly be controlled.
During operation, the temperature of bearings in the meter is usually higher than that of the metered
fluid. Vapors around the bearings can be causes of faulty conditions, including generation of unusual
noise and bearing seizure.
(4) Corrosive liquids
When you make a measurement of highly corrosive liquids, such as nitric acid and sulfuric acid,
appropriate materials should be used for tanks and piping assembly. Heterogeneous materials
originally contained in the metered fluid or corrosive substances dissolved from tanks and pipes of
inappropriate materials may lead to costly downtime, as a result of locked rotors, for example, when
they are allowed into the measuring chamber.
Excessive flow
Rapid Flow Variation
Take Precautions
Against Bearing Seizure !
Rapid Temperature
Changes
