www.miinet.com
Moore Industries-International, Inc.
- 118 -
User’s Manual
238-760-00K
May 2019
Functional Safety Dual Input Smart HART® Temperature Transmitter
STZ
SECTION 7
Section 7 - STZ in Safety Instrumented Systems
The STZ is designed for use as an element of a safety instrumented system as defined by
IEC61508-4 paragraph 3.4.1.
This user manual contains all of the information needed to configure, install, operate and
maintain this product. For safety applications the STZ must only be used in accordance with this
information and the restrictions and limitations as detailed below.
Functional Safety Description
The STZ has been certified, by exida ® to IEC61508:2010 for systematic integrity up to SIL3
and for random integrity up to SIL2 (HFT=0). This means that an STZ is approved for single use
in Safety Instrumented Systems (SIS) up to SIL2 and in a redundant architecture (1oo2, 2oo3,
etc.) up to SIL 3. It is classified as a Type B device according to IEC 61508. Therefore, table 2
in IEC61508-1 and table 3 in IEC61508-2 provide the Safety Failure Fraction (SFF) and PFD
AVG
requirements for a given SIL rating.
The STZ is a programmable transmitter which accepts one or two RTD, thermocouple, millivolt,
resistance or potentiometer as inputs. It has one loop current output and HART communication
modulated on the output current signal. The device is loop powered. For safety systems, the
STZ performs as a transmitter which processes the input signal(s) and sets the 4-20mA output
current according to its configuration. The HART signal is not part of the safety path.
Failure Rate Data
The STZ FMEDA report (Moore Industries’ Document No: 700-702-39) provides the failure data
required for calculations to use the STZ as part of a Safety Instrumented System.
Product life
For the STZ, the components have a useful lifetime of 50+ years. However, IEC 61508-2,
section 7.4 states that a useful lifetime based on experience has more weight than the calculated
figures; Note 3 in the section comments that the useful lifetime of a transmitter is most often
within 8 to 12 years.
Installation
No special installation is required in addition to the standard installation practices in this user
manual. Refer to the specifications table of this user manual for ambient conditions and required
power input.
Prior to use in a safety function, the user must validate the operation of the device offline (see
bench check in Section 2)