Instruction Manual Supplement
D104215X012
DLC3100 SIS Digital Level Controller
April 2018
10
Decommissioning Guidelines
When decommissioning a DLC3100 SIS instrument, proper procedures must be followed. Decommissioning includes
the following steps:
1. Avoid personal injury or property damage from sudden release of process pressure or bursting of parts. Before
proceeding with any decommissioning procedures:
D Always wear protective clothing, gloves, and eyewear to prevent personal injury or property damage.
D Do not remove the sensor from the process while the vessel is still pressurized.
2. Bypass the sensor subsystem or take appropriate action to avoid a false trip
3. Bypass the safety function of the level measurement or take appropriate action to avoid a false trip.
4. Disconnect the electrical wiring to and from the DLC3100 SIS instrument.
5. Remove the DLC3100 SIS instrument, mounting parts from the sensor assembly.
Application
The DLC3100 SIS digital level controller can be applied to most process or storage vessels, bypass chambers, and
interfaces up to the unit pressure and temperature ratings. The DLC3100 SIS with 249 sensor can be used for liquids,
clean or dirty, light hydrocarbons to heavy acids to meet the safety system requirements of IEC61508.
Benefits
The DLC3100 SIS provides the following benefits to operation:
D Suitable for use in environments up to SIL 2 (Safe Failure Fraction = 92.2%) as independently assessed (full
assessment) by exida.com as per IEC61508/61511-1.
D Continuous self-test with > 21 mA or < 3.6 mA fault indication fully compliant with NAMUR NE-43.
D Intrinsic Safe, Explosion-proof approvals.
D Two-wire, loop-powered transmitter for level, interface measurement.
Proof testing
According to section 7.4.5.2f of IEC61508-2, proof tests must be undertaken regularly to reveal dangerous faults
which are undetected by diagnostic tests. Proof test coverage is a measure of how many undetected dangerous
failures are detected by the proof test. It is a testing of safety system components to detect any failures not detected
by automatic online diagnostics followed by repair of those failures to an equivalent as-new state. A proof test is a test
that is manually initiated. It is an effective way to reduce the PFDavg of the DLC3100 SIS instrument. As part of the
test, the capability of the SIF to achieve the defined safe state must be verified. The Safety Function must be verified.
The proof test interval must be established for the SIF based on the failure rates of all the elements within the function
and the risk reduction requirements. This determination is a critical part of the design of the SIS. A proof test will
detect 95% of possible dangerous failures undetected in the DLC3100 SIS digital level controller with Fisher 249
displacer sensors. Proof testing is a vital part of the safety lifecycle and is critical to ensuring that a system achieves its
required safety integrity level throughout the safety lifecycle.
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