172
Reference Manual
00809-0100-4026, Rev HA
Section 8: Safety Instrumented Systems (4-20 mA Only)
November 2014
Safety Instrumented Systems (4-20 mA Only)
8.5.3 Amplitude threshold
For amplitude thresholds, verify that:
the Amplitude Threshold is at least 50 % greater than the amplitude of disturbances.
For example, if the amplitude of disturbance is 1000 mV, the Amplitude Threshold
should be at least 1500 mV.
the Amplitude Threshold has an amplitude of at least 100 mV
the Amplitude Threshold is set to 20-50 % of the signal amplitude of the product
surface
Amplitude Thresholds should be verified with the measured product in the tank. It is not
recommended to register any false echo areas. For more information on Amplitude Thresholds,
see “Echo tuning” on page 83, “ATC” on page 84, and “Analyzing the measurement signal” on
page 132.
8.5.4 Write protection
A Rosemount 5400 Series transmitter can be protected from unintentional configuration
changes by a password protected function. It is recommended to use write protection
described in “Write protecting a transmitter” on page 152.
8.5.5 Site acceptance
After the installation and configuration, proper operation of the transmitter should be verified.
A site acceptance test is therefore recommended. The proof test outlined in this section can be
used for this. Note that re-verification of the transmitter operation is recommended if the
configuration is changed.
8.6 Operation and maintenance
8.6.1 General
The Rosemount 5400 Series QS option must be tested at regular intervals to confirm that the
overfill and empty tank protection function result in the desired system response. The required
proof test intervals are dependent on the configuration of the transmitter and the process
environment. It is the responsibility of the operator/owner of the system to determine the
sufficient time interval and verify it is followed. See the FMEDA
(1)
report for additional details or
references.
If the overfill and empty tank protection function cannot be tested by a controlled filling to the
response height, suitable simulation of the level must be used to make the level sensor respond.
The following proof test is recommended. If an error is found in the safety functionality, the
measuring system must be switched out of service and the process held in a safe state by means
of other measures. Proof test results and corrective actions taken must be documented at
www.emersonprocess.com/rosemount/safety.
(1) The Rosemount 5400 Series FMEDA report is accessible at www.emersonprocess.com/rosemount/safety/PriorUse.htm.
To Next Page
Loading...
