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Mobrey™ Magnetic Level Switches
Functional Safety Manual
Functional Safety Manual
M310/FSM, Rev BA
April 2017
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Functional Safety Manual
M310/FSM, Rev BA
Contents
1Section 1: Contents
2Section 1: Introduction
1.1 Scope and purpose of the safety manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Skill Level Requirement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Safety messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.4 Terms, abbreviations, and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.5 Documentation and standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3Section 2: Product Description
2.1 Operation principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Level switch purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Contents
April 2017
4Section 3: Designing a Safety Function
Using the Level Switch
3.1 Safety function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Environmental limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Application limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Design verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.5 SIL capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5.1 Systematic integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5.2 Random integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5.3 Safety parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6 Connection of the level switch to the SIS logic solver . . . . . . . . . . . . . . . . . . . . . . . 9
3.7 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5Section 4: Installation and Commissioning
4.1 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2 Physical location and placement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3 Electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Contents
6Section 5: Operation and Maintenance
5.1 Proof-test requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2 Repair and replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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Functional Safety Manual
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5.3 Notification of failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.4 Useful lifetime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
AAppendix A: Proposed Proof-test Procedure
A.1 Suggested proof-test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
A.2 Proof-test coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
BAppendix B: Level Switches Certified to IEC 61508
B.1 List of Level Switches Certified to IEC 61508. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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Section 1 Introduction
1.1 Scope and purpose of the safety manual
This safety manual contains the information to design, install, verify and maintain a Safety Instrumented
Function (SIF) utilizing the Mobrey Magnetic Level Switch.
The manual provides the necessary requirements to enable the integration of the horizontal point-level
float switch when showing compliance with the IEC 61508 or IEC 61511 functional safety standards.
It indicates all assumptions that have been made on the usage of the level switch. If these assumptions
cannot be met by the application, the Safety Integrity Level (SIL) capability of the product may be
adversely affected.
Note
For product support, use the contact details on the back page.
Introduction
April 2017
1.2 Skill Level Requirement
System design, installation and commissioning, and repair and maintenance shall be carried out by
suitably qualified personnel.
1.3 Safety messages
Procedures and instructions in this section may require special precautions to ensure the safety of the
personnel performing the operation. Information that raises potential safety issues is indicated by a
warning symbol ( ). Refer to the following safety messages before performing an operation preceded
by this symbol.
Failure to follow these guidelines could result in death or serious injury.
Make sure only qualified personnel perform the installation.
Explosions could result in death or serious injury.
Verify that the operating environment of the level switch is consistent with the
appropriate hazardous locations certifications.
Do not remove the level switch covers in explosive atmospheres when the circuit is alive.
Electrical shock can result in death or serious injury.
Avoid contact with the leads and terminals. High voltage that may be present on leads can
cause electrical shock.
Make sure the main power to the level switch is off, and the lines to any other external
power source are disconnected or not powered while wiring the level switch.
Introduction
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Introduction
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1.4 Terms, abbreviations, and acronyms
Table 1-1. Terms, Abbreviations, and Acronyms
Term Definition
Basic safety Freedom from unacceptable risk of harm
BPCS Basic Process Control System – a system which responds to input signals from the
process, its associated equipment, other programmable systems and/or an
operator and generates output signals causing the process and its associated
equipment to operate in the desired manner but which does not perform any
safety instrumented functions with a claimed SIL greater than or equal to 1.
Functional Safety Manual
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Fail Safe State State where the switch output is in the state corresponding to an alarm
Fail Dangerous Failure that does not respond to an input from the process (i.e. not switching to
Fail Dangerous
Detected
Fail Dangerous
Undetected
Fail No Effect Failure of a component that is part of the safety function but that has no effect on
Fail Safe Failure that causes the switch to go to the defined fail-safe state without an input
FIT FIT is the abbreviation for Failure In Time. One FIT is 1x10-9 failure per hour
FMEDA Failure Modes, Effects and Diagnostic Analysis
Functional Safety Part of the overall safety relating to the process and the BPCS which depends on
HFT Hardware Fault Tolerance
Low demand Mode of operation, where the frequency of demands for operation made on a
PFD
AVG
SFF Safe Failure Fraction – a fraction of the overall random failure rate of a device that
SIF Safety Instrumented Function – a safety function with a specified SIL which is
SIL Safety Integrity Level - a discrete level (one out of four) for specifying the safety
condition. In this condition, the switch contacts will normally be open.
the fail-safe state).
Failure that is dangerous but is detected.
Failure that is dangerous and that is not detected.
the safety function.
from the process.
the correct functioning of the Safety Instrumented System (SIS) and other
protection layers.
safety-related system is no greater than twice the proof test frequency.
Average Probability of Failure on Demand
results in either a safe failure or a detected dangerous failure.
necessary to achieve functional safety. Typically a set of equipment intended to
reduce the risk due to a specified hazard (a safety loop).
integrity requirements of the safety instrumented functions to be allocated to
the safety instrumented systems. SIL 4 has the highest level of safety integrity,
and SIL 1 has the lowest level.
SIS Safety Instrumented System (SIS) – an instrumented system used to implement
2
one or more safety instrumented functions. An SIS is composed of any
combination of sensors, logic solvers, and final elements.
Introduction
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1.5 Documentation and standards
Introduction
April 2017
.
This section lists the documentation and standards referred to by this safety manual
Table 1-2. Associated Documentation
Documents Purpose of documents
IEC 61508-2: ed2, 2010 Functional Safety of Electrical/Electronic/Programmable Electronic
Exida EM 10/08-36 R001 FMEDA Report Version V1, Revision R2 for the Mobrey magnetic
IP101 Mobrey magnetic level switch Product Data Sheet
M310 Mobrey magnetic level switch Instruction leaflet
Safety-Related Systems
level switch with a F84 Float
Table 1-3. Associated Standards
Standards Purpose of standards
IEC 61508: ed2, 2010 Functional Safety of electrical/electronic/programmable electronic
IEC 61511
(ANSI/ISA 84.00.01-2004)
safety-related systems
Functional safety - Safety instrumented systems for the process industry
sector
Introduction
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Introduction
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4
Introduction
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Functional Safety Manual
s
N
s
N
Contact B-B
Contact A-A
Pushrods
Float
Magnet
Float
Cross-section of the Level Switch
s
N
s
N
Contact B-B
Contact A-A
Pushrods
Float
Magnet
Float
Cross-section of the Level Switch
M310/FSM, Rev BA
Section 2 Product Description
Note
For all product information and documentation downloads, see the on-line
Mobrey Magnetic Level Switch web page at Emerson.com/Mobrey.
2.1 Operation principle
The level switch is designed to open or close a circuit (“switch”) as a changing liquid level within a vessel
passes the level of the float (the Switch Point).
When the process fluid level is below the Switch Point, contacts B-B are made and contacts A-A are open
(Figure 2-1 on page 5).
When the process fluid level is above the Switch Point, contacts A-A are made and contacts B-B are open
(Figure 2-2 on page 5).
Product Description
April 2017
Figure 2-1. Level Decreases – Float Pivots Downwards
Figure 2-2. Level Increases –Float Pivots Upwards
Product Description
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Product Description
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2.2 Level switch purpose
Mobrey magnetic level switches are ideal for high and low liquid level alarm, overfill alarm, and pump
control duties.
Figure 2-3. Application Example: High and Low Level Alarm
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2.3 Ordering information
Level switch models fitted with options listed Appendix B: Level Switches Certified to IEC 61508 of this
manual have been externally assessed and certified to IEC 61508.
A copy of the third party SIL certificate can be ordered using the part number MBY-CERT-SIL-L2049.
Note
For all product information and documentation downloads, see the on-line
Mobrey Magnetic Level Switch web page at Emerson.com/Mobrey.
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Product Description
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Designing a Safety Function Using the Level Switch
Section 3 Designing a Safety Function
Using the Level Switch
Note
For all product information and documentation downloads, see the on-line
Mobrey Magnetic Level Switch web page at Emerson.com/Mobrey.
3.1 Safety function
A change in liquid level through the operating range of the float causes the switch to operate. It may be
used in high level or low level safety related applications. In either case, it is recommended to use the set
of contacts (A-A or B-B) which are Open in the Fail Safe State.
April 2017
3.2 Environmental limits
The designer of the SIF (Safety Instrumented Function) must check that the level switch is rated for use
within the expected environmental limits. See the Mobrey Magnetic Level Switch Product Data Sheet
environmental limits.
3.3 Application limits
It is very important that the SIF designer checks for material compatibility by considering process liquids
and on-site chemical contaminants. If the level switch is used outside the application limits or with
incompatible materials, the reliability data and predicted SIL capability becomes invalid.
The construction materials of a level switch are specified in the product data sheet and the product
reference manual (see Table 1-2 on page 3). Use the model code on the product label, and the ordering
information table and specification in these product documents, to find out the construction materials.
3.4 Design verification
A detailed Failure Modes, Effects and Diagnostics Analysis (FMEDA) report for the Mobrey Magnetic Level
Switch is available from Emerson. This report details all failure rates and failure modes as well as
expected lifetime.
Note
The FMEDA report is available from the Mobrey Magnetic Horizontal Float Switches web site page at
Emerson.com/Mobrey
and this safety manual.
. In the Documents section, there are SIL documents including the FMEDA report
for
The achieved Safety Integrity Level (SIL) of an entire Safety Instrumented Function (SIF) design must be
verified by the designer using a PFD
proof-test effectiveness, any automatic diagnostics, average repair time, and the specific failures rates of
all equipment included in the SIF.
Designing a Safety Function Using the Level Switch
calculation considering the architecture, proof-test interval,
AVG
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Designing a Safety Function Using the Level Switch
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Each subsystem must be checked to assure compliance with minimum Hardware Fault Tolerance
(HFT) requirements. When using the level switch in a redundant configuration, a common cause
factor of at least 5% should be included in the safety integrity calculations.
The failure rate data listed in the FMEDA report is only valid for the useful lifetime of the level switch.
Failure rates increase after this useful lifetime period has expired. Reliability calculations based on
the data listed in the FMEDA report for mission times beyond the lifetime may yield results that are
too optimistic, i.e. the calculated SIL will not be achieved.
3.5 SIL capability
3.5.1 Systematic integrity
The Mobrey level switch has met manufacturer design process requirements of Safety Integrity
Level 2 (SIL 2). These are intended to achieve sufficient integrity against systematic errors of design
by the manufacturer.
A Safety Instrumented Function (SIF) designed with the Mobrey level switch must not be used at a
SIL higher than the statement without “prior use” justification by the end-user, or verification of
diverse technology in the design.
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3.5.2 Random integrity
The Mobrey level switch is a type A device according to Table 2 of the standard IEC 61508-2.
Using Route 2H assessment criteria, the device Random Capability has been determined as SIL 2.
3.5.3 Safety parameters
The failure rates given here are valid for the useful lifetime of the product, as described in the section
“Useful lifetime” on page 13.
Note
The FMEDA report is available from the Mobrey Magnetic Horizontal Float Switches web site page at
Emerson.com/Mobrey
report and this safety manual.
Table 3-1. Failure Rates for Level Switch, 4-contact Versions – Types D and P
Failure category
Fail Safe Detected 0 0
Fail Safe Undetected 88 117
Fail Dangerous Detected 0 0
Fail Dangerous Undetected 243 214
. In the Documents section, there are SIL documents including the FMEDA
Failure rate (FIT)
Maximum detection Minimum detection
(1)
No Effect 34 34
1. FIT is the abbreviation for Failure In Time. One FIT is 1x10
8
-9
failure per hour.
Designing a Safety Function Using the Level Switch
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Table 3-2. Failure Rates for Level Switch, 6-contact Versions – Types D6, P6, H6, and B6
Designing a Safety Function Using the Level Switch
April 2017
(1)
Failure category
Failure rate (FIT)
Maximum detection Minimum detection
Fail Safe Detected 0 0
Fail Safe Undetected 168 197
Fail Dangerous Detected 0 0
Fail Dangerous Undetected 327 298
No Effect 34 34
1. FIT is the abbreviation for Failure In Time. One FIT is 1x10
-9
failure per hour.
Table 3-3. Failure Rates according to IEC 61508, 4-contact Versions – Types D and P (FIT)
Device
Level switch, maximum detection 0 88 0 243
Level switch, minimum detection 0 117 0 214
1. FIT is the abbreviation for Failure In Time. One FIT is 1x10
(1)
SD
-9
failure per hour.
SU
DD
DU
Table 3-4. Failure Rates according to IEC 61508, 6-contact Versions – Types D6, P6, H6, and B6 (FIT)
Device
Level switch, maximum detection 0 168 0 327
Level switch, minimum detection 0 197 0 298
1. FIT is the abbreviation for Failure In Time. One FIT is 1x10
(1)
SD
-9
failure per hour.
SU
DD
DU
3.6 Connection of the level switch to the SIS logic solver
The Mobrey level switch should be connected to the safety-rated logic solver which is actively
performing the safety function as well as automatic diagnostics (if any) designed to diagnose potentially
dangerous failures within the level switch. The Mobrey Magnetic Level Switch Reference Manual
gives
installation details for the level switch.
3.7 General requirements
The system and function response time shall be less than the process safety time. The Mobrey level
switch will change to its defined safe state in less than this time with relation to the specific hazard
scenario.
All SIS components, including the Mobrey level switch must be operational before process start-up.
The user shall verify that the Mobrey level switch is suitable for use in safety applications by confirming
the level switch nameplate and model number are properly marked.
Personnel performing maintenance and testing on the Mobrey level switch shall first be assessed as
being competent to do so.
Results from periodic proof tests shall be recorded and periodically reviewed.
The Mobrey level switch shall not be operated beyond the useful lifetime as listed in the section
“Useful lifetime” on page 13 without undergoing overhaul or replacement.
Designing a Safety Function Using the Level Switch
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Designing a Safety Function Using the Level Switch
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Designing a Safety Function Using the Level Switch
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Installation and Commissioning
Section 4 Installation and Commissioning
Note
For all product information and documentation downloads, see the on-line
Mobrey Magnetic Level Switch web page at Emerson.com/Mobrey.
4.1 Installation
The Mobrey Magnetic Level Switch (“level switch”) must be installed as described in the installation
section of the product manual M310
the specification section.
The Mobrey level switch must be accessible for physical inspection.
4.2 Physical location and placement
. Check that environmental conditions do not exceed the ratings in
April 2017
The Mobrey level switch shall be accessible with sufficient room for cover removal and electrical
connections, and allow for manual proof-testing to take place.
The switch point is determined by the location of the level switch, and consideration must be given to
allow the safe proof-testing of the level switch by forcing liquid to put the switch into its Fail Safe State.
4.3 Electrical connections
Wiring should be adequately rated and not be susceptible to mechanical damage. Electrical conduit is
commonly used to protect wiring.
Installation and Commissioning
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Installation and Commissioning
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Installation and Commissioning
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Operation and Maintenance
Section 5 Operation and Maintenance
5.1 Proof-test requirement
During operation, a low-demand mode SIF must be proof-tested. The objective of proof-testing is to
detect failures within the equipment in the SIF that are not detected by any automatic diagnostics of the
system. Undetected failures that prevent the SIF from performing its function are the main concern.
Periodic proof-tests shall take place at the frequency (or interval) defined by the SIL verification
calculation. The proof-tests must be performed more frequently than or as frequently as specified in the
SIL verification calculation in order to maintain the required safety integrity of the overall SIF.
A sample procedure is provided in Appendix A: Proposed Proof-test Procedure.
Results from periodic proof tests shall be recorded and periodically reviewed.
5.2 Repair and replacement
April 2017
Repair procedures in the product manual M310 must be followed.
5.3 Notification of failures
In cas e of mal fun cti on of th e sy ste m or SIF , th e Mobrey Magnetic Level Switch (“level switch”) shall be put
out of operation and the process shall be kept in a safe state by other measures.
Emerson must be informed when the level switch is required to be replaced due to failure. The occurred
failure shall be documented and reported to Emerson using the contact details on the back page of this
functional safety manual. This is an important part of Emerson’s SIS management process.
5.4 Useful lifetime
According to the Section 7.4.9.5 of IEC 61508-2, a useful lifetime based on experience should be
assumed.
Although a constant failure rate is assumed by the probabilistic estimation method (see FMEDA report),
this only applies provided that the useful lifetime
lifetime, the result of the probabilistic calculation method is therefore meaningless as the probability of
failure significantly increases with time. The useful lifetime is highly dependent on the subsystem itself
and its operating conditions.
This assumption of a constant failure rate is based on the bath-tub curve. Therefore, it is obvious that the
PFD
the calculation is limited to the useful lifetime of each component.
calculation is only valid for components that have this constant domain and that the validity of
AVG
(1)
of components is not exceeded. Beyond their useful
Based on general field failure data and manufacturer component data, a useful life period of
approximately 10 to 15 years is expected for the Mobrey level switch. When plant experience indicates a
shorter useful lifetime than indicated here, the number based on plant experience should be used.
1. Useful lifetime is a reliability engineering term that describes the operational time interval where the failure rate of a device is relatively constant. It is not a term which covers
product obsolescence, warranty, or other commercial issues.
Operation and Maintenance
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Operation and Maintenance
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Operation and Maintenance
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Proposed Proof-test Procedure
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Appendix A Proposed Proof-test Procedure
A.1 Suggested proof-test
According to Section 7.4.3.2.2 (f) of the standard IEC 61508-2, proof-tests shall be undertaken to reveal
dangerous faults which are undetected by diagnostic tests. This means that it is necessary to specify how
dangerous undetected faults which have been noted during the Failure Modes, Effects, and Diagnostic
Analysis can be detected during proof-testing.
The suggested proof-tests (Table A-1 and Table A-2) consist of switch operation tests in-situ.
Table A-1. Suggested Proof-test (Low Level Alarm)
Step Action
1 Inspect the accessible parts of the level switch for any leaks or damage
2 Bypass the safety function and take appropriate action to avoid a false trip
Disable any filling mechanism and drain the vessel to force the switch to the fail-safe state and
3
4
confirm that the Safe State was achieved and within the correct time. INDEPENDENT PRECAUTIONS
MUST BE TAKEN TO ENSURE THAT NO HAZARD CAN RESULT FROM THIS OPERATION.
Reinstate the filling mechanism so that the vessel refills and confirm that the normal operating state
of the switch was achieved.
5 Remove the safety function bypass and otherwise restore normal operation
Table A-2. Suggested Proof-test (High Level Alarm)
Step Action
1 Inspect the accessible parts of the level switch for any leaks or damage
2 Bypass the safety function and take appropriate action to avoid a false trip
Disable any drain mechanism and fill the vessel to force the switch to the fail-safe state and confirm
3
4
5 Remove the safety function bypass and otherwise restore normal operation
that the Safe State was achieved and within the correct time. INDEPENDENT PRECAUTIONS MUST
BE TAKEN TO ENSURE THAT NO HAZARD CAN RESULT FROM THIS OPERATION.
Reinstate the drain mechanism so that the vessel refills and confirm that the normal operating state
of the switch was achieved
A.2 Proof-test coverage
The proof-test coverage for the tests listed in the section “Suggested proof-test ” are in Table A-3.
Table A-3. Proof-test Coverage
15
Safety function
4-contact versions – types D and P 84%
6-contact versions – types D6, P6, H6, and B6 88%
Proof-test coverage
Proposed Proof-test Procedure
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Proposed Proof-test Procedure
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Proposed Proof-test Procedure
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Level Switches Certified to IEC 61508
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Manual Supplement
Appendix B Level Switches Certified to
IEC 61508
B.1 List of Level Switches Certified to IEC 61508
Tables B-1, B-2, and B-3 list all Mobrey Magnetic Level Switch options that are certified to IEC 61508.
In general, this is the entire range with the exception of the marine versions, pneumatic switch
mechanisms, and some floats. Refer to product data sheet IP101
for the full specifications.
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Level Switches Certified to IEC 61508
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Manual Supplement
Level Switches Certified to IEC 61508
M310, Rev BA
Table B-1. Level Switches for General Purpose Applications (Stainless Steel Wet-side)
Model Product description
S Switch
Flange (head) Flange (head)
36 Mobrey A 431 EN 1092-1 PN 16 (DN 125)
190 Mobrey A 417 EN 1092-1 DN 65 PN 40 (DN 65)
440 3 in. ASME B16.5 Class 150 RF 418 EN 1092-1 PN 40 (DN 80)
441 4 in. ASME B16.5 Class 150 RF 419 EN 1092-1 PN 40 (DN 100)
424 3 in. ASME B16.5 Class 300 RF 433 EN 1092-1 PN 40 (DN 125)
425 4 in. ASME B16.5 Class 300 RF 434 EN 1092-1 PN 40 (DN 150)
489 3 in. ASME B16.5 Class 600 RF 488 EN 1092-1 PN 63 (DN 80)
490 3 in. ASME B16.5 Class 900 RF 435 EN 1092-1 PN 63 (DN 100)
428 EN 1092-1 PN 16 (DN 65) 436 EN 1092-1 PN 63 (DN 125)
429 EN 1092-1 PN 16 (DN 80) 437 EN 1092-1 PN 63 (DN 150)
430 EN 1092-1 PN 16 (DN 100)
Switch mechanism
D Electrical: 2 independent Single Pole Single Throw (SPST) contact sets
P As Type D but with gold plated contacts
April 2017
D6 Electrical: 2 independent circuits of double pole changeover contact sets
P6 As Type D6 but with gold plated contacts
H6 As Type D6 but with gold plated contacts and hermetically sealed moving parts
B6 As Type H6 but approved for Zone 2 areas
Enclosure/housing
A Aluminum alloy
Float
F84 General purpose e.g. high/low alarm, 316 SST
F93 Shrouded for dirty liquids, 316 SST
F96 General purpose e.g. high/low alarm, 316 SST
F98 General purpose e.g. high/low alarm, 316 SST
F185 General purpose e.g. high/low alarm, Alloy 400
F104/+ Cranked arm: horizontal or vertical, 316 SST
F106 General purpose e.g. high/low alarm, 316 SST
F107 General purpose e.g. high/low alarm, 316 SST
Typical Model Number: S 36 D A / F84
Level Switches Certified to IEC 61508
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Table B-2. Level Switches for General Purpose Applications (Aluminum Bronze Wet-side)
Model Product description
S Switch
Flange (head)
01 Mobrey A flange
Switch mechanism
DB Electrical: 2 independent Single Pole Single Throw (SPST) contact sets
PB As Type DB but with gold plated contacts
D6B Electrical: 2 independent circuits of double pole changeover contact sets
P6B As Type D6B but with gold plated contacts
Float
F84 General purpose e.g. high/low alarm, 316 SST
F93 Shrouded for dirty liquids, 316 SST
F185 General purpose e.g. high/low alarm, Alloy 400
F104/+ Cranked arm: horizontal or vertical, 316 SST
Typical model number: S 01 DB / F84
Manual Supplement
M310, Rev BA
Table B-3. Level Switches for Hazardous Area Applications
Model Product description
S Switch
Flange (head)
250 Mobrey G, 316 Stainless Steel
275 Mobrey G, Gunmetal
256 3 in. ASME B16.5 Class 150 RF
257 4 in. ASME B16.5 Class 150 RF
278 6 in. ASME B16.5 Class 150 RF
251 3 in. ASME B16.5 Class 300 RF
254 4 in. ASME B16.5 Class 300 RF
260 3 in. ASME B16.5 Class 600 RF
261 3 in. ASME B16.5 Class 900 RF
253 EN 1092-1 PN 40 (DN 80)
255 EN 1092-1 PN 40 (DN 100)
269 EN 1092-1 PN 40 (DN 125)
272 EN 1092-1 PN 63 (DN 80)
268 EN 1092-1 PN 63 (DN 100)
270 EN 1092-1 PN 63 (DN 125)
271 EN 1092-1 PN 63 (DN 150)
19
Level Switches Certified to IEC 61508
Page 24
Manual Supplement
Level Switches Certified to IEC 61508
M310, Rev BA
Switch Mechanism
D Electrical: 2 independent Single Pole Single Throw (SPST) contact sets
P As Type D but with gold plated contacts
D6 Electrical: 2 independent circuits of double pole changeover contact sets
P6 As Type D6 but with gold plated contacts
H6 As Type D6 but with gold plated contacts and hermetically sealed moving parts
Enclosure / Housing
A Aluminum alloy
G Gunmetal
X Use ‘AX’ or ‘GX’ for applications with ambient temperatures –4 to –76 °F (–20 to –60 °C)
Float
F84 General purpose e.g. high/low alarm, 316 SST
F185 General purpose e.g. high/low alarm, Alloy 400
F96 General purpose e.g. high/low alarm, 316 SST
F98 General purpose e.g. high/low alarm, 316 SST
F104/+ Cranked arm: horizontal or vertical, 316 SST
April 2017
F106 General purpose e.g. high/low alarm, 316 SST
F107 General purpose e.g. high/low alarm, 316 SST
Typical model number: S 250 D A / F84
Level Switches Certified to IEC 61508
20
Page 25
Page 26
Functional Safety Manual
M310/FSM, Rev BA
April 2017
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