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    Standards

    Certification

    Education & Training

    Publishing

    Conferences & Exhibits

    PARTIAL STROKE TESTING

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    Top Customer Issues Regarding Safety

    Production Uptime Tests are known to cause outages Some types of tests require outages

    Regulatory compliance HSE and OSHA and others are turning up the heat New customer guidelines on the horizon include 29CFR part 1910

    Easy and safe integration of PAS and SIS

    Control, alarms, configuration Elimination of SIS tests as they are manpower intensive potentially dangerous

    An incident with two fatalities due to the by-pass valve being left open after aSIS test

    Increase the confidence that the SIS will perform on demand Easy Maintenance with increasingly fewer staff

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    PFD Calculation : Simple Math

    = (1) (d) (1/2) = 0.5 (d)

    PFD avg = [(DC)(d) (TI/2 ]p + [(1-DC)(d) (TI/2)]F

    Assumptions: DC is 70% for partial stroke and 100% for full stroke

    TI is 4x/yr for partial and 1x/3 yrs for full

    Adding Partial Stroke Testing

    = [(0.7)(d) (0.25/2)] + [(1-0.7) (d) (3/2)]= 0.09 (d) + 0.45 (d) = 0.54 (d)

    Conclusion: Partial Stroke Testing enables extending the full-stroke

    testing interval to 3 years and sti ll maintaining the same PFD!

    Full Stroke Testing Only

    PFD avg = [(DC)(d) (TI/2)]

    Assumptions: DC is 100% and TI is 1x / yr

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    Analysis of safety loop failures

    (Source: OREDA)

    42%

    50%

    8%

    Safety Systems

    Sensors

    Final Elements

    Does the Final Control Element lead potential SIS loop failures?

    Is there Empirical Evidence or Field Experience that suggests the Final

    Control Element must be tested?

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    Why does the SIS valve

    account for over 50% of failures

    Valves in SIS Applications typically operate in one staticposition all the time and only move upon an emergency

    situation. The problem: the valve being in a static position without

    mechanical movement for long periods of time, inherently

    increases unreliability. To ensure availability on demand, SIS valves must have

    regular testing

    Until recently, SIS valves could only be tested through

    expensive, labor intensive pneumatic testing methods

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    Test Methods

    The primary objective of testing is to reduce the Probability ofFailure on Demand (PFD)

    OFF LINE

    Total StrokeProcess Down

    ON LINE

    Total StrokeByPass In Service

    Component Test

    Partial Stroke

    Solenoid (SOV)

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    The power of partial stroke testing Increase SIL Level

    Implementation of Partial Stroking on Final Control Element can increase orachieve desired SIL level

    Validation of SIS

    Partial Stroking Validates the proper operation of the FCE Final Control Elements are commonly untested and are inherently unreliable

    Maintains SIL Level Safely extend turnaround times

    1/PFD(t)

    Time

    Test Interval

    Without testing the PFD increases

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    Current Test Methods

    Manual Interlock Pneumatic Panel

    Solenoid PanelBypass Valve

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    ISA S84.01-1996: A Safety Instrumented System is a distinct,

    reliable system used to safeguard a process to prevent a

    catastrophic release of toxic, flammable, or explosive chemicals

    What is a Safety Instrumented System?

    How can we

    Prevent the

    Catastrophe?

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    SIS Tests Options

    Low Risk

    Process Availability

    Manual Interlockor J ammer

    Device

    Solenoids withLimit Switches

    Reduces Chance forHuman Error

    Low Complexity

    Low OPEX

    Known Valve

    Performance

    Automated

    Low CAPEX

    IntelligentPositioner

    By-PassValves

    SolenoidPulsing

    Panels

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    (Hardware and Software)

    Logic solver

    Sensor Logic Solver Control

    Element

    What is a Safety Instrumented System?

    SIS Loop Sub-components

    IEC61511: Safety Instrumented System (SIS)

    Instrumented system used to implement one or more safetyinstrumented functions. A SIS is composed of any combination ofsensor (s), logic solver (s), and final elements(s)

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    Separation of BPCS from SIS is Recommended. If you share any

    loop elements, all SIS Requirements flow to BPCS

    - Do you see any common

    elements between BPCS and SIS?

    Basic Process Control System (BPCS) vs.

    Safety Instrumented System (SIS)Control Safety

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    IEC 61511 - End-user/Integrator Standard

    Applies to the Entire Loop

    Effects of:Weather

    Corrosion

    IEC 61511

    Wiring

    ImpulseLines

    Piping

    Power

    Loop Components

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    IEC 61508 - Applies to Component

    Manufacturers Not the Entire Loop

    IEC 61508

    Sensors

    Final ControlElements

    Logic

    Solver

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    Overview of SIS Industry Standards

    Manufacturers &

    Suppliers of Devices

    IEC61508

    Sections 2&3

    Manufacturers &

    Suppliers of Devices

    IEC61508

    Sections 2&3

    Safety Instrumented

    Systems Designers,

    Integrators & Users

    IEC61511

    Safety Instrumented

    Systems Designers,

    Integrators & Users

    IEC61511

    Process Sector

    Safety Instrumented Systems

    Process Sector

    Safety Instrumented Systems

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    Process Hazards and Risk Review

    (IEC 61511 Section 8) Purpose

    Identify the possible hazards including fault conditions andreasonable foreseeable misuse

    Assessment

    Human Injury/loss of life

    Loss of Assets

    Environmental Impact Typical process/tool

    HAZOPS Analysis

    Output of HAZOPs will determine required risk reduction - Safety

    Integrated Level

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    SIL applies only to the entire LOOP / SIF

    PFDFCE

    PFDPLC

    PFDSensor

    Loop SIL equals:PFDFCE + PFDSensor +PFDPLC

    Individual PFD =Risk that the:

    transmitter reads a

    false safe flow?

    control system

    wont shut down

    if flow is unsafe?

    Valve (FCE) stays

    open?

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    SIS Design and Engineering

    (IEC 61511 Section 11)

    Separation of BPCS and SIS

    Human Interface System Design

    Shut Down and Start-up design

    Requirements of Components and Subsystems

    Fault Tolerance

    Sensor Speed

    Proof Testing Intervals

    Wiring Practices

    System Interface Maintenance

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    Other Considerations for Optimizing Safety Consider real-world common causefailures:

    Performance (even with redundancy)

    Practices (selection, installation, maintenance)

    Hardware/sensor/interface failures

    Select devices with best performance

    Installed performance under real-world conditions

    Dynamic response to match application

    Experience minimizes common causefailures Has the vendor field-proven this device?

    Has the user site-proven this device?

    Is the user familiar with this device?

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    What is the Future Direction ?

    Certified

    PIU

    Certified

    PIU

    Today 2007

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    Limitations to traditional testing methods

    Panels:

    Expensive, up to 10-15K per panel (not including labor cost/hr.)

    Test procedures are complex Labor-intensive testing

    Solenoid Pulsing

    Doesnt Validate or Test Valve Movement; Only tests the solenoiditself

    Coil burnout due to increased cycling

    increased risk to process disruption

    By-Pass valves

    Testing is expensive and time consuming; Testing becomes

    infrequent

    Cost of by-pass deters economic feasibility for valves in larger sizes

    Piping and space

    100% diagnostic coverage and can not be replaced by partial stroke

    technology

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    Limitations to traditional testing methods

    Solenoids w/ Limit Switches

    No validation testing on Limit Switches (test is only as reliable as

    the limit switches) Can take you to spurious trip if coil does not energize in

    time(burnout)?

    No ability to collect friction data or valve stickage(no

    diagnostics) Calibration/Set up for this solution is expensive and time

    consuming

    Manual Interlock or J ammer device

    Has the jammer been removed? Is the FCE available? No data or validation

    manual and labor-intensive testing

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    Summary of Savings

    Elimination of By-Pass Valve, Piping, Wiring

    4Cooper-Cameron Full-Bore API rated / Bettis / Solenoid / Limit Switch

    Assembly Cost: $5000 Estimated Piping & Wiring Savings: $750

    Estimated Total CAPEX savings: $5750

    Elimination of Full Stroke Testing & By-Pass Valve Procedures over3 year run-time

    Field Technician Hours saved: 10 hrs X $60/hr = $600

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