Fault Outside The Functional Safety - ABB 2600T Series Operating Instruction

FAULTS OUTSIDE THE FUNCTIONAL SAFETY
The redundant algorithms and the electronics are designed to detect all the internal hardware faults therefore the transmitter
diagnostic is not able to detect faults related to the process and to the installation configuration. In the following table the known
weaknesses resulting from the transducer FMEA (Failure Mode and Effect Analysis) are listed.
failure
Assembled material at the pipes of the transmitter,
blockage of pipe.
Application outside specified temperature range.
Excess of temperature
Assembled gas at the transmitter, if the transmitter
is mounted above the process line
Overload pressure, high peak pressure pulses in
process lines
Penetration of hydrogen, diaphragm crack in
applications with hydrogen process medium.
Thin walled diaphragm, leaky diaphragm in
applications with abrasive medium.
Thin walled diaphragm, leaky diaphragm in
applications with corrosive medium.
Higher diaphragm stiffness, crack in application
with contamination of metal ions
Mechanical damage through cleaning, damage
of the coating, corrosion.
Other considerations
The alarm levels of the transmitter (down-scale or up-scale)
can be selected by the user. For some faults (e.g. crystal
breakdown), the output will latch at 22 mA even if the down
scale alarm level is selected.
- 8 -
failure effect
∆p-level
measurement is wrong
wrong measurement
insensitive, wrong
measurement
wrong measurement after
compression stress
insensitive measurement,
breakdown
wrong measurement,
breakdown
wrong measurement,
breakdown
insensitive
measurement
faulty or insensitive
measurement, breakdown
Comments
Piping should be periodically
inspected and cleaned.
The transmitter should operate
inside the specified temperature
ranges.
Transmitter should be installed
properly as specified in this
manual.
The transmitter should operate
inside the specified temperature
ranges.
Hydrogen service allowed with the
application of a special grace on
diaphragms or by using gold
plated diaphragms.
Transmitter manual specifies the
preventive periodic maintenance.
Appropriate materials should be
selected for corrosive
applications.
Appropriate materials should be
selected for particular
applications.
Transmitter manual specifies
correct maintenance
procedures.