Operation; Homogeneous Redundancy - Siemens SITRANS F Additional Operating Instructions

SITRANS FX330
SAC8: Inspection intervals
The definition of the maximum proof test intervals (for details refer to
proof test
responsible for adjusting the proof test intervals if the deployment conditions deviate from the
reference conditions.
SAC9: Modification
The flowmeter must not be manipulated.
SAC10: Repair
Repair of the flowmeter must only be done by manufacturer's personnel or personnel authorised
by the manufacturer. Exceptions regarding replacement with spare parts are shown in chapter
"Service" in [N1]. In all other cases, send the flowmeter to the manufacturer for repair (for
instructions refer to chapter "Returning the device to the manufacturer" in [N1]).

2.2.5 Operation

SAC11: Operational limits
The operational limits as shown in [N1] in the chapter "Technical data" must be observed. To
prevent unintentional trigger of the safety reaction, a permanent operation near the operational
limits should be avoided.
SAC12: Supervision of failure current
If a safety critical failure has been detected, the device outputs a failure current on the current
output (4...20 mA). The operator must supervise both failure currents
(< 3.6 mA and > 21 mA).
In case of the occurrence of any failure current the operator has to ensure that the safety loop
reacts according to relevant application specific norms (e.g. the safety loop must be prevented
from automatically resuming operation after failure notification disappears).

2.2.6 Homogeneous redundancy

SAC13:
The logic subsystem must compare the current values transmitted by the two flowmeters (or
one dual version respectively) permanently. In case of a difference greater than 4% of the
measurement range over a time interval greater than 30 seconds, the devices must be regarded
as non-safe, or defect respectively.
SAC14:
The two flowmeters (or one dual version respectively) must be operated independently. Any
hazardous re-activeness from the logic subsystem (for details refer to
10) on the two measurement devices must be excluded. This means at least:
• Current loops are independently driven.
• Current loops are installed in a way that failures affecting both lines at a time (common
cause) can be avoided.
• The logic subsystem must provide an appropriate low failure rate.
10/2017 - A5E40875009-AB EN
SPECIFICATION OF THE SAFETY FUNCTION
on page 19) are calculated for operation under reference conditions. The operator is
www.siemens.com/flow
Operation modes and
Operation modes
on page
2
9