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SMARTLINE® RM77
9.1 General notes
The device agrees with these conditions in the IEC 61508 standard:
The device operates in high
demand or continuous mode of
operation
The device is a type B system
The device has a hardware fault
tolerance of zero (HFT = 0)
1 This agrees with IEC 61508 Part 4, section 3.5.16
9.2 Assumptions
FMEDA is applicable for the conditions that follow:
• Use of the device agrees with its design and performance characteristics. This includes
ambient and process conditions.
• Installation of the device must agree with the instructions and the requirements of the
application.
• We can ignore wear of mechanical parts. Failure rates are constant.
• Failures that follow one after the other are put in the same group as the failure that is the
source of the problem.
• The HART
used during safety operation mode.
• All components that are not part of the safety function and cannot influence the safety
function (feedback immune) are not included.
• Only the analog output (4...20 mA) is used for safety applications.
• The Mean Time to Recovery after safe failure is 72 hours (MTTR = 72 h).
• If necessary, the device can operate as a safety-related system in a low-demand mode of
operation.
• External power failure rates are not included.
INFORMATION!
The FMEDA of the device was calculated with the exida tool FMEDA v7.1.17, with the
configuration that follows:
Database SN 29500
•
Ambient temperature is 40
•
T[Proof] is from 1 to 10 years (87600 hours)
•
T[Repair] is 72 hours
•
T[Test] is 24 hours (all internal test functions are done a minimum of one time during this
•
period)
34-VF-25-105 iss.1 GLO April 15 US
Condition
1
®
protocol is only used for set-up, calibration and diagnostic purposes. It is not
C
°
The device continuously measures the distance to the surface of the
product in the tank. If electrical power is not available or is not
sufficient, the device will not measure. The safety function is
continuously available to keep the device in a safe state.
The device uses programmable electronics embedded in complex
components (a microcontroller). It is not possible to find all the
failure modes for this type of component.
The device does not have hardware redundancy.
www.honeywell.com/ps
TECHNICAL DATA
Description
9
35
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