3
57-657 SIL Certified Safety Manual for ECLIPSE Model 706
1.0
Introduction
1.1
Product Description
The ECLIPSE Model 706 High Performance Guided Wave
Radar Level Transmitter is a two-wire, loop-powered
24 VDC level transmitter based on Guided Wave Radar
(GWR) technology.
NOTE: For Safety Instrumented Systems usage, it is assumed that the
4–20 mA output is used as the safety variable.
The analog output from the Model 706 meets the NAMUR
NE 43 standard (3.8 mA to 20.5 mA usable). The transmitter
contains self-diagnostics and is programmed to drive the
output to a user-selected failure state, either low or high,
upon internal detection of a diagnostic indicator. The device
can be equipped with or without an optional non-interfering
graphic liquid crystal display (LCD).
Table 1 indicates the version of the ECLIPSE Model 706
transmitter that has been certified for SIL 2/3 applications.
1.2
Theory of Operation
Guided Wave Radar is based upon the principle of TDR
(Time Domain Reflectometry). TDR utilizes pulses of electro-
magnetic energy transmitted down a wave guide (probe).
When a pulse reaches a liquid surface that has a higher
dielectric constant than the air (
ε
r
= 1) in which it is traveling,
a portion of the pulse is reflected. The transit time of the
pulse is then measured via ultra high-speed timing circuitry
that provides an accurate measure of the liquid level. The
amplitude of the reflection depends on the dielectric con-
stant of the product. The higher the dielectric constant, the
larger the reflection.
1.3
Determining Safety Integrity Level (SIL)
Safety Instrumented System designers using the Enhanced
ECLIPSE Model 706 must verify their design per applicable
standards, including IEC 61511-1.
Three limits must be met to achieve a given SIL level:
1. The PFD
AVG
numbers for the entire Safety Instrumented
Function (SIF) must be calculated. Table 2 shows the rela-
tionship between the Safety Integrity Level (SIL) and the
Probability of Failure on Demand Average (PFD
AVG
).
2. Architecture constraints must be met for each subsystem.
Table 3 can be used to determine the achievable SIL as a
function of the Hardware Fault Tolerance (HFT) and the
Table 3
Minimum hardware fault tolerance
Type B sensors, final elements and non-PE logic solvers
SFF
Hardware Fault
Tolerance (HFT)
0
1
2
None: <60%
Not
Allowed
SIL 1
SIL 2
Low:
60% to <90%
SIL 1
SIL 2
SIL 3
Medium: 90% to <99%
SIL 2
SIL 3
High:
≥
99%
SIL 3
Table 2
SIL vs. PFDavg
Safety
Integrity Level
(SIL)
Target Average
probability of failure
on demand (PFDavg)
4
≥
10
-5
to <10
-4
3
≥
10
-4
to <10
-3
2
≥
10
-3
to <10
-2
1
≥
10
-2
to <10
-1
1
Transmitters:
Model 706, 706-512*-*** (HART)
Hardware Version (or later)
Analog Board 030-9160-001 Rev K
Digital Board 030-9159-001 Rev AC
Wiring Board 030-9165-001 Rev F
Software Version (or later)
Model 706 HT 1.0hA.hex
2
Probes:
All ECLIPSE probes can be utilized.
Refer to I/O Manual 57-606 for
complete probe offering.
Table 1
Enhanced ECLIPSE Model Numbers
