Dwyer UXF3 - Manual (Page 124)

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6.6.4. Error in measured value
Status Probable cause Troubleshooting
z Connection between main unit and
sensor units (upstream,
downstream) are inverted.
Connect properly. The reading appears with
“-” (minus).
z Flow of fluid is reversed.
z Straight pipe length is inadequate. Move the sensor to the place where the
length of 10D can be assured on
upstream side and 5D on downstream
side.
z Pump, valve or others which
disturb the flow are located nearby.
Mount the instrument with a clearance of
30D or more.
Measured value
fluctuates though flow
rate is constant.
z Pulsation exists in flow. Set the damping to increase the response
time.
Measured value is held because ultrasonic wave cannot be propagated into a pipe.
1. Incomplete installation
Measured value remains
the same though flow
rate is changing. (LED lit
in red)
z Error in piping specifications
z Sensor is mounted on
welding.
z Error in sensor mounting
dimensions
z Error in silicone appliance at
the time of mounting the
sensor
z Error in connection of the
sensor cable.
Upon checking, remove the sensor,
apply silicone filler, and slightly off
position the sensor.
Sensor mounting is poor
z Mounting dimension
z The sensor is coming off the
pipe.
z Mount the sensor in parallel with
pipe, allowing correct sensor unit
spacing.
z Mount the sensor properly so that it
is kept in close contact with the pipe.
2. Problem on pipe or fluid
{ Pipe not filled with fluid Locate a place which is completely
filled on the same piping line, and shift
the sensor there.
z Attach the sensor to the lowest place
on the pipeline.
{ Bubbles present in the fluid
Bubbles are introduced if reading
is normal when flow is stopped.
If mounted immediately
downstream a valve, a cavitation
causes the same phenomenon
as when bubbles are introduced.
Eliminate ingress of bubbles.
z Raise the level of the pump well.
z Check the shaft seal of the pump.
z Retighten the flange of negative
pressure pipe.
z Arrange so that fluid doesn’t fall into
the pump well.
Move the sensor to the location where
air bubbles have not entered.
z Inlet side of the pump
z Upstream side of the valve
(Continued on next page.)
Bulletin F-107-UXF3