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Table 1
Pulsar
®
Model Number
Intrinsically Safe
R86-51XX-aXX
R86 is energy limited but
(a=0, 1, A, C or D)
not isolated from current
loop.
Explosion Proof
R86-51XX-aXX
R86 is galvanically isolated
(a=3 or B)
from current loop.
The R86 is classified as a Type B
2
element according to
IEC 61508, having a hardware fault tolerance of 0)
Table 2
SIL vs. PFDavg
Safety
Target Average
Integrity Level
probability of failure
(SIL)
on demand (PFDavg)
4
≥10
3
≥10
2
≥10
1
≥10
Table 3
Minimum hardware fault tolerance
Type B sensors, final elements and non-PE logic solvers
Hardware Fault
Tolerance (HFT)
SFF
0
Not
None: <60%
Allowed
Low: 60% to <90% SIL 1
Medium: 90% to <99% SIL 2
High: ≥99%
SIL 3
58-651 Pulsar
®
Model R86 SIL Functional Safety Manual
1.0
1.1
1.2
1.3
-5
to <10
-4
-4
to <10
-3
-3
to <10
-2
-2
to <10
-1
1
2
SIL 1
SIL 2
SIL 2
SIL 3
SIL 3
Introduction
Product Description
The Pulsar
Model R86 Pulse Burst Radar Level
®
Transmitter is a loop-powered, 24 VDC level transmitter
based on Pulse Burst Radar technology. For Safety
Instrumented Systems usage, it is assumed that the 4–20 mA
output is used as the primary safety variable. The analog
output meets NAMUR NE 43 (3.8 mA to 20.5 mA
usable), and the transmitter contains self-diagnostics and
can be programmed to send its output to a user-selected
failure state, either low or high upon internal detection of
a failure. The device can be equipped with or without an
LCD display. Table 1 lists the versions of the PULSAR
Model R96 that have been considered for the hardware
assessment.
Theory of Operation
PULSAR Model R86 is a top-mounted, downward-facing
pulse burst radar transmitter operating at 26 GHz. Unlike
true pulse devices that transmit a single, sharp (fast rise-
time) waveform of wide-band energy, the PULSAR Model
R86 emits short bursts of 26 GHz energy and measures the
transit time of the signal reflected off the liquid surface.
Distance is calculated utilizing the equation:
Distance = C × Transit time/2, then developing the Level
value by factoring in application-specific configuration.
The PULSAR Model R86 is classified as a Type B device
according to IEC 61508.
Determining Safety Integrity Level (SIL)
Tables 2 & 3 define the criteria for the achievable SIL
against the target mode of operation in Demand Mode
Operation.
Table 2 shows the relationship between the Safety Integrity
Level (SIL) and the Probability of Failure on Demand
Average (PFDavg).
Table 3 can be used to determine the achievable SIL as a
function of the Hardware Fault Tolerance (HFT) and the
Safe Failure Fraction (SFF) for the complete safety system
(type B – complex components as per IEC 61508 Part 2) of
which the level transmitter is one component.
3
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