2600T Series Pressure transmitters | SOI/266-XC Rev. I 23
8 Safety manual (Rev. I)
8.19 Safety-related parameters for HART digital communication IEC 61508 SIL2 certified transmitters
The Safety 266 pressure transmitters product meets the SIL2 requirements of IEC 61508 in low as well as high demand mode of
operation. The total PFD in low demand mode for 10 years proof test interval in the worst case is less than the 35% of the range defined
in IEC 61508-1. The relevant numbers are stated in the table below.
266DXX, 266VXX,
266PXX, 266HXX,
266NXX
266MXX, 266CXX,
266JXX, 266RXX
(range R)
266MXX, 266CXX,
266JXX, 266RXX
(except range R)
266GXX, 266AXX 266GXX, 266AXX
(only range C and F
sold before May 2012)
266GXX, 266HXX
(only range Z)
λdd
2.62E-07 4.11E-07 3.94E-07 4.05E-07 4.13E-07 3.72E-07
λdu
6.82E-08 6.87E-08 6.85E-08 6.85E-08 6.90E-08 8.06E-08
λsd
3.37E-07 2.45E-07 2.39E-07 2.40E-07 2.40E-07 2.50E-07
λsu
3.01E-07 3.55E-07 3.53E-07 3.42E-07 3.18E-07 3.46E-07
HFT
0 0 0 0 0 0
T1
1 year / 10 years (8760h / 87600h)
SFF
92.95% 93.63% 93.51% 93.51% 93.37% 92.32%
Total Failure Rate
9.68E-07 1.08E-06 1.06E-06 1.06E-06 1,04E-06 1.049E-06
MTBF
118 106 108 108 110 109
MTTR
8 hours
DC
D: 79% D: 86% D: 85% D: 86% D: 86% D: 82%
S: 53% S: 41% S: 40% S: 41% S: 43% S: 42%
PFD (1 year)
2.99E-04 3.01E-04 3.00E-04 3.00E-04 3.02E-04 3.53E-04
PFH (1 year)
6.82E-08 6.87E-08 6.85E-08 6.85E-08 6.90E-08 8.06E-08
PFD (10 years)
2.98E-03 3.00E-03 2.99E-03 2.99E-03 3.01E-03 3.52E-03
PFH (10 years)
6.82E-08 6.87E-08 6.85E-08 6.85E-08 6.90E-08 8.06E-08
Testing time
< 20 s < 20 s < 20 s < 5 s < 70 s <20s
ROM check time
< 30 s < 30 s < 30 s < 30 s < 70 s <30s
Important. A diaphragm-seal-equipped pressure transmitter features different safety parameters if compared to the abovementioned ones. The intrinsic
safety failure rates of diaphragm seal should be added to the ones of the pressure transmitter (as per above table). The values represent the worst case and
may be slightly different (nearly negligible) depending on the type of diaphragm seal. As a reference, you may want to consider the below value:
One diaphragm seal configuration Two diaphragm seal configuration
λdd
0.46E-08 0.92E-08
λdu
1.38E-08 2.75E-08
λs
0 0
Note. The above failure rates have to be added to the transmitter ones in case you selected a transmitter equipped with one or two diaphragm seals. The
above table shows the dangerous failures only because the diaphragm seal system does not generate any safe failure. In order to calculate the Safety
Failure Fraction (SFF) and Diagnostic Coverage (DC) of a diaphragm-seal-equipped pressure transmitter, please use the followiong formulas:
SFF = DC =
λs + λ
dd
λ
d
+ λs
λ
dd
λ
dd
+ λ
du
Important. Values listed here above and instructions given in chapter 12 are valid only for HART digital communication and 4 ... 20 mA IEC 61508 SIL2
certified pressure transmitters (digits T and 8 under the “Output” option within product codes). Therefore safety instructions cannot be considered as valid
in case the transmitter features Standard or Advanced HART (digits H, 1, L, 7), PROFIBUS PA (digits P, 2) or FOUNDATION Fieldbus (digits F, 3)
communication protocols.
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