Safe Failure Fraction; Installation; Switches; Changing Switch Position - Emerson Rosemount 3144P Reference Manual

Rosemount 3144P
SAFE FAILURE
FRACTION

INSTALLATION

Switches

Changing Switch
Position
7-2
The Safe Failure Fraction calculation for the combination of the 3144P and
the process sensor must consider the effects of the transmitter's process
sensor diagnostics. The 3144P FMEDA report should be consulted for
calculated transmitter failure rates. Sensor failure data may be found in
various references, or may be based on the user's experience history. A copy
of the FMEDA can be found at www.rosemount.com/safety.
No special installation practices are necessary with the 3144P in a PU Safety
Instrumented System. However, a full review of the Failure Mode and Security
switches is required. Follow the standard installation requirements (see
Section 2: Installation).
Failure Mode Switch
The transmitter monitors itself during normal operation using an automatic
diagnostic routine. If the diagnostic routine detects a sensor failure or a failure
in the transmitter electronics, the transmitter goes into high or low alarm,
depending on the position of the failure mode switch.
The analog alarm and saturation values that the transmitter uses depend on
whether it is configured to standard (set by the factory) or NAMUR-compliant
operation. These values are also custom-configurable in both the factory and
the field using the 375 Field Communicator. The limits are:
21.0 ≤ I ≤ 23 for high alarm
•
3.5 ≤ I ≤ 3.75 for low alarm
•
The values for standard and NAMUR operation are as follows:
Characteristics Standard Operation
21.75 mA ≤ I ≤ 23.0 mA
Fail High
I ≥ 20.5 mA
High Saturation
I ≤ 3.90 mA
Low Saturation
I ≤ 3.75 mA
Fail Low
Transmitter Security Switch
The transmitter is equipped with a write-protect switch that can be positioned
to prevent both accidental and deliberate change of configuration data.
The Failure Mode and Security switches are located on the top center of the
electronics module (see Figure 7-1). The electronics module is on the
electronics side of the transmitter housing. For transmitters with LCD
displays, the electronics module is located behind the LCD display faceplate.
Without a LCD display
1. If the transmitter is installed, set the loop to manual.
2. Remove the housing cover on the electronics side of the transmitter. Do
not remove the transmitter cover in explosive atmospheres when the
circuit is live.
3. Set the switches to the desired position (see Figure 7-1).
4. Replace the transmitter cover. Both transmitter covers must be fully
engaged to meet explosion-proof requirements.
5. Set the loop to automatic control.
Reference Manual
00809-0100-4021, Rev EA
March 2007
NAMUR-Compliant Operation
21.0 mA ≤ I ≤ 23.0 mA
I ≥ 20.5 mA
I ≤ 3.8 mA
I ≤ 3.6 mA