Toshiba LF434 - Manual (Page 135)

TOSHIBA
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Knipty pipe alj^rtn
If the deicctor pipe is not filled with fluid, The following nicssiige appears.
Design piping so th<U Ihe detector pipe is alway?j filled with the fluid to be measured. If the
empty alarm enable/disablc status is set to OFl-, this function is disabled. See 8.2.13,
'4impty Pipe Alarms."'
Alarm message Description Corrective action
EWFTY
Detector pipe is not filled
with fluid. Arrange piping so that the
detector pipe is always
filled with fluid.
Precautionary notes on using the empty pipe alarm
(1) The flowmeter detects an empty pipe condition by monitoring the impedance and signal
level between the flow signal lines connected 1o a pair of electrodes. Therefore, the
following factors may trigger an erroneous empty pipe alarm:
• Opening or loose conncciion of flow signal lines
• The fluid to he measured carrying a lot of bubbles
• Contamination of the electrode with non-conductive deposits
(2) If the llowmeter is not grounded properly or if it is in an environment where high
electrical noise exists, the empty pipe alarm may not function properly, Under these
conditions, Ihe reliability of flowmeter accuracy itself is not high. Try to ground the
flowmeter securely to an independent good ground and relocate the cable runs to
prevent noise from entering into the flowmeter circuit,
(3) If the fluid still remains in the detector pipe or the imernal wall of the detector pipe is
contamitiaied with electrically conductive deposits, the iinpedanee between the signal
lines will not go high and the empty pipe alarm may not w'ork. In this kind of event, try
to use other means to detect an enpty pipe condition (such as a pump stop signal or a
signal from a valve).
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