KROHNE H250 M9 Safet V2 EN - Manual (Page 10)

7
SAFETY-RELATED CHARACTERISTICS
10
H250 M9
www.krohne.com 06/2013 - 4000656702 MA H250-M9 SIL R03
Safety-related characteristics
7.1 Assumptions
The following assumptions have been made during the Failure Modes, Effects and Diagnostic
Analysis of the variable-area flowmeter H250/M9 with switching contact output.
• Failure rates are constant, wear out mechanisms are not included.
• Propagation of failures is not relevant.
• The time to restoration after a safe failure is 8 hours.
• All modules are operated in low demand mode of operation.
• External power supply failure rates are not included.
• The stress levels are average for an industrial outdoor environment and can be compared to
the Ground Fixed classification of MIL-HNBK-217F.
Alternatively, the assumed environment is similar to:
IEC 60654-1, Class C (sheltered location) with temperature limits within the manufacturer´s
rating and an average temperature over a long period of time of 40°C.
• Humidity levels are assumed within manufacturer´s rating.
• Only the switching contact output is used for safety applications.
7.2 Specific safety-related characteristics
Under the assumptions described in 7.1 and the definitions given in section 4 the following tables
show the failure rates according to IEC 61508:
Based on the construction of the H250/M9 this device is specified as a type A device according to
IEC 61508 with a HFT (Hardware Failure Tolerance) = 0 and a classification as SIL (Safety
Integrity Level): 1.
1 The switching contact output is connected to a fail-safe NAMUR amplifier (e.g. Pepperl +
Fuchs KF**-SH-Ex1). Failure rates of the amplifiers are not included.
PFD
AVG
was calculated for three different proof test times using the Markov modeling.
The PFD
AVG
value in brackets mean, that the calculated PFD
AVG
values are within the allowed
range for SIL 2 according to table 2 of IEC 61508-1 but do not fulfil the requirement to not claim
more than 35% of this range, i.e. to be better than or equal to 3.50E-03.
The PFD
AVG
value (not in brackets) mean, that the calculated PFD
AVG
values are within the
allowed range for SIL 2 according to table 2 of IEC 61508-1 and do fulfil the requirement to not
claim more than 35% of this range, i.e. to be better than or equal to 3.50E-03.
System SFF T
PROOF
PFD
AVG
λ
SD
λ
SU
λ
DD
λ
DU
H250/M9
connected to a
standard switching
amplifier
54% 1 year 5.04E-04 0 FIT 81 FIT 55 FIT 115 FIT
5 years 2.52E-03
10 years (5.03E-03)
H250/M9
connected to a fail-
safe switching
amplifier 1
57% 1 year 3.35E-04 0 FIT 50 FIT 55 FIT 77 FIT
5 years 1.67E-03
10 years 3.34E-03
MA_H250_M9_SIL2_R03_en_656702_PRT.book Page 10 Wednesday, June 26, 2013 9:08 AM