Fuji Electric Time Delta-C FSV-2, Instruction Manual

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6.5.4. Error in measured value
Status Probable cause Troubleshooting
 Connection between main unit and
sensor units (upstream,
downstream) are inverted.
Connect properly. The reading appears with
“-” (minus).
 Flow of fluid is reversed.
 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.
 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.
 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)
 Error in piping specifications
 Sensor is mounted on
welding.
 Error in sensor mounting
dimensions
 Error in acoustic coupler at
the time of mounting the
sensor
 Error in connection of the
sensor cable.
Upon checking, remove the sensor,
apply acoustic coupler, and slightly off
position the sensor.
Sensor mounting is poor
 Mounting dimension
 The sensor is coming off the
pipe.
 Mount the sensor in parallel with
pipe, allowing correct sensor unit
spacing.
 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.
 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.
 Raise the level of the pump well.
 Check the shaft seal of the pump.

Retighten the flange of negative
pressure pipe.

Arrange so that fluid doesn’t fall into
the pump well.
Move the sensor to the location where
air bubbles have not entered.
 Inlet side of the pump
 Upstream side of the valve
(Continued on next page.)