Safety Considerations Guide for Triconex General ... - ICEWeb

Safety Considerations Guide for Triconex General ... - ICEWeb Safety Considerations Guide for Triconex General ... - ICEWeb

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26 Chapter 2 Application Guidelines Table 4 describes the operating requirements for handling maintenance overrides when using Triconex communication capabilities. Table 4 Operating Requirements for Maintenance Override Handling Operating Requirements Maintenance overrides are enabled for an entire controller or for a subsystem (process unit). Controller activates an override. The operator should confirm the override condition. Controller removes an override. DCS Operator, Maintenance Engineer Operator, Maintenance Engineer Operator, Maintenance Engineer Responsible Person TriStation 1131 Software Maintenance Engineer, Type Approval Maintenance Engineer, Type Approval Maintenance Engineer Additional Recommendations These procedures are recommended in addition to the recommendations described in the tables on page 25 and page 26: • A DCS program should regularly verify that no discrepancies exist between the override command signals issued by a DCS and override-activated signals received by a DCS from a PES. This figure shows the procedure: Safety-Instrumented System Controller Sensors Safeguarding Application Program Actuators Hard- Wired Switch Maintenance Override Handling (Application Program) Operator Warning Distributed Control System Inputs Engineering Workstation Figure 6 PES Block Diagram Safety Considerations Guide for Triconex General Purpose v2 Systems

Guidelines for Triconex Controllers 27 • Use of the maintenance override capability should be documented in a DCS or TriStation 1131 log. The documentation should include: — Begin- and end-time stamps of the maintenance override. — Identification of the maintenance engineer or operator who activates a maintenance override. If the information cannot be printed, it should be entered in a workpermit or maintenance log. — Tag name of the signal being overridden. — Communication packages that are different from a type-approved Modbus should include CRC, address check, and check of the communication time frame. — Loss of communication should lead to a warning to the operator and maintenance engineer. After loss of communication, a time-delayed removal of the override should occur after a warning to the operator. • For more information about maintenance override operation, please see the TÜV web site at http://www.tuv-fs.com/m_o202.pdf. Safety Controller Boundary The boundary of the safety controller includes the External Termination Panels (ETPs) and interconnecting cables. Triconex safety controllers must be used with approved ETPs and cables only. The use of unapproved, unauthorized cables and/or ETPs compromises the TÜV safety certification and potentially the ability of the logic solver to respond to safety demands. False trips resulting from the use of unapproved components can cause end-user economic loss. CAUTION When using fanned-out interface cables or third-party ETPs—such as those from P&F or MTL—please consult the Invensys Global Customer Support (GCS) center for the safety-boundary impact of using such cables or ETPs. Background IEC 61508 and IEC 61511 define a programmable electronic Safety Instrumented System (SIS) as consisting of sensors, logic solvers, and final control elements, as shown in this figure. Sensors Logic Solver Final Elements Figure 7 Simplified SIS Together, these elements implement Safety Instrumented Functions (SIF) of the target Safety Integrity Level (SIL). In order to implement a safety-certified SIF, the system designer must choose safety-certified loop elements, including sensors, final elements, logic solvers, and other interconnecting components. Safety Considerations Guide for Triconex General Purpose v2 Systems

<strong>Guide</strong>lines <strong>for</strong> <strong>Triconex</strong> Controllers 27<br />

• Use of the maintenance override capability should be documented in a DCS or<br />

TriStation 1131 log. The documentation should include:<br />

— Begin- and end-time stamps of the maintenance override.<br />

— Identification of the maintenance engineer or operator who activates a maintenance<br />

override. If the in<strong>for</strong>mation cannot be printed, it should be entered in a workpermit<br />

or maintenance log.<br />

— Tag name of the signal being overridden.<br />

— Communication packages that are different from a type-approved Modbus should<br />

include CRC, address check, and check of the communication time frame.<br />

— Loss of communication should lead to a warning to the operator and maintenance<br />

engineer. After loss of communication, a time-delayed removal of the override<br />

should occur after a warning to the operator.<br />

• For more in<strong>for</strong>mation about maintenance override operation, please see the TÜV web<br />

site at http://www.tuv-fs.com/m_o202.pdf.<br />

<strong>Safety</strong> Controller Boundary<br />

The boundary of the safety controller includes the External Termination Panels (ETPs) and<br />

interconnecting cables. <strong>Triconex</strong> safety controllers must be used with approved ETPs and cables<br />

only. The use of unapproved, unauthorized cables and/or ETPs compromises the TÜV safety<br />

certification and potentially the ability of the logic solver to respond to safety demands. False<br />

trips resulting from the use of unapproved components can cause end-user economic loss.<br />

CAUTION<br />

When using fanned-out interface cables or third-party ETPs—such as<br />

those from P&F or MTL—please consult the Invensys Global Customer<br />

Support (GCS) center <strong>for</strong> the safety-boundary impact of using such cables<br />

or ETPs.<br />

Background<br />

IEC 61508 and IEC 61511 define a programmable electronic <strong>Safety</strong> Instrumented System (SIS) as<br />

consisting of sensors, logic solvers, and final control elements, as shown in this figure.<br />

Sensors<br />

Logic<br />

Solver<br />

Final<br />

Elements<br />

Figure 7<br />

Simplified SIS<br />

Together, these elements implement <strong>Safety</strong> Instrumented Functions (SIF) of the target <strong>Safety</strong><br />

Integrity Level (SIL). In order to implement a safety-certified SIF, the system designer must<br />

choose safety-certified loop elements, including sensors, final elements, logic solvers, and other<br />

interconnecting components.<br />

<strong>Safety</strong> <strong>Considerations</strong> <strong>Guide</strong> <strong>for</strong> <strong>Triconex</strong> <strong>General</strong> Purpose v2 Systems

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