Fault Tracing; General; Interchangeability; Fault Tracing Procedure - ABB PFTL 101 User Manual

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Pressductor PillowBlock Load Cells, Horizontal Measuring PFTL 101, User Manual

Fault Tracing

General

It is important to be thoroughly familiar with the description of operation in
2 Description before starting fault tracing.

Interchangeability

The load cells are factory calibrated and can be replaced directly with another load cell of the same
type. The only adjustment required after load cell replacement is zero adjustment in the control
unit.

Fault Tracing Procedure

The measuring equipment can be divided into four parts:
• The mechanical installation.
• The load cell.
• The junction boxes and the cabling.
• The control unit (see the control unit manual).
The fault symptoms indicate in which part the fault lies.
• Faults in the mechanical installation often result in an unstable zero point or incorrect sensi-
tivity.
If a fault follows something else in the process, such as temperature, or can be linked
to a particular operation, it probably originates from something in the mechanical installation.
• Load cells are extremely robust and can withstand five times their nominal load in the meas-
uring direction. If a load cell has nevertheless been so overloaded that its data have been
altered, this is probably due to an event in the mill, such as web/strip breakage. On exces-
sive overload the first thing that happens is that the zero point shifts.
• Problems such as interference or unstable zero point may be caused by wiring faults. Some
malfunctions may be due to the proximity of cables that cause interference. Incorrect instal-
lation, such as imbalance in a cable or screens earthed at more than one end may cause the
zero point to become unstable. Cables are subject to mechanical wear, and should be
checked regularly. The junction box should also be checked, especially if it is subject to
vibration.
• A fault in the control unit usually causes intermittent loss of a function. It is unusual for the
control unit to cause stability problems. Faults in connected units may affect the operation of
the control unit. For further details see the control unit manual.
6 Fault Tracing
3BSE009965R0401 en Rev E