Instruction Manual Supplement
D104215X012
DLC3100 SIS Digital Level Controller
April 2018
8
Table 7. Failure Rates for Fisher 249 Displacer Sensors with DLC3100 Digital Level Controller
Failure Category
High Trip
Failure Rate (FIT)
Low Trip
Failure Rate (FIT)
Fail Safe Detected, λ
SD
38 39
Fail Safe Undetected, λ
SU
10 8
Fail Dangerous Detected, λ
DD
570 568
Fail Detected (detected by internal diagnostics) 342 340
Fail High (detected by logic solver) 77 77
Fail Low (detected by logic solver) 151 151
Fail Dangerous Undetected, λ
DU
61 63
No Effect 205 205
Annunciation Detected 34 34
SFF 91.0% 90.7%
Application Limits
D Safety Instrumented Function design verification must be done for the entire collection of equipment used in the
Safety Instrumented Function including the DLC3100 SIS digital level controller. The SIS must fulfill the
requirements according to the Safety Integrity Level, especially the limitation of average Probability of Failure on
Demand (PFDavg).
D The DLC3100 SIS digital level controller can only be used for Level or Interface applications.
D The system response time is dependent on the entire final element subsystem. The user must verify the system
response time is less than the process safety time for each final element. The DLC3100 SIS digital level controller
safety function has a fault reaction time upon fault detection of < 1 second plus the mean time to repair.
D Measurement signal used by logic solver must be the analog 4-20 mA signal proportional to the fluid level.
D The logic solver must recognize both high/low alarms. If the logic solver loop uses IS barriers, caution must be
taken to ensure the loop continues to operate properly under the low alarm condition.
D Safe failure in which 4-20 mA current is driven out of range (<3.6 mA or > 21 mA).
D Device Response Time: less than 1 second
D When using the DLC3100 SIS in redundant applications, the owner-operator of the facility should institute
common causes training and more detailed maintenance procedures specifically oriented toward common
cause defense.
Environmental Limits
D Operating ambient temperature: -40_C to 80_C (-40_F to 176_F)
D Humidity: tested per IEC61298-3 Section 6
D Electromagnetic Compatibility: tested per IEC61326-3-2
D Vibration: tested per ISA 75.13 and FTEP 3B1
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