Endress+Hauser Nivotester FTL325P - 7.4 Operating elements

Nivotester FTL325P Design
Endress+Hauser 17
• Minimum level monitoring (dry running protection, MIN detection)
A maximum of one safety function – either MAX detection or MIN detection of a level –
may be performed with a 3-channel Nivotester unit.
A device combination with non-functional safety functions is only possible in accordance
with version VI.
3.3.1 Other safety-related characteristic values
Please note the following in relation to the Declarations of Conformity with safety-related
characteristic values.
• A common cause factor β = 10 % has been assumed in the calculations specified.
• For multi-channel systems, the PFD
avg
values already contain common cause failures for the
specific wiring scheme.
• The PFD
avg
values only apply to the particular wiring scheme for which the values have been
calculated. They are not a suitable basis for making calculations for other wiring schemes.
The use of NC contacts instead of NO contacts, in particular, is not permitted for operation
according to SIL specifications.
• The wiring scheme shows the number of devices and the switching of the contacts in the
level relays (contact open in demand mode).
• If there are several devices in a wiring scheme, all the devices have the same settings
shown.
• The Declarations of Conformity show safety-related values and wiring options for the
measuring system.
• FIT = Failure in Time, 1 FIT = 10
-9
1/h
3.3.2 Common cause errors
Where HFT=1, the failure rates are based on an analysis in accordance with
DIN EN 61508-6: 2011-02, Table D.4, "Using the β-factor to calculate the probability of
failure in an E/E/PE safety-related system due to common cause failures".
The calculation gives a β-factor of 10 %.
This factor is based on the failure rates indicated above.
If additional measures are implemented during installation to prevent common cause errors
as defined in Table D.1, the β-factor can possibly be reduced to 5 %.
Possible measures are:
• Sensors installed in a physically separate location
• Cable routed separately between the Liquiphant and Nivotester
• Separate protection from environmental influences:
• Impact
• Sunshine
• EMC protection and/or overvoltage
• Use of different sensor materials
• Combination of high-temperature and normal version