sil & partial stroke testing solutionstation

8/13/2019 SIL & Partial Stroke Testing Solutionstation

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SIL & Partial StrokeTesting Solutions

Permission granted for ISA Houston Section Website



© Metso2

OSHA 29 CFR 1910.119

“Process Safety Management (PSM) of Highly HazardousChemicals”

EPA 40 CFR 68“Chemical Accident Prevention Provisions”

• Hazards must be identified and appropriate measures takento protect employees, the community and the environment.

• Compliance requires use of “generally accepted goodengineering practice.”




© Metso

Safety valve as part of the Safety InstrumentedSystem (SIS)

3

FT

Distributed Control

System (DCS)Inputs Outputs

Reactor

PT1A

PT1B

Safety System

Inputs Outputs




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Process Control System

(BPCS)

Safety Instrumented System

(SIS)

• Controls the process• Dynamic

• Failures “revealed”.

• Reduces risk• Passive

• Failures “hidden”

• To reduce risks associatedwith abnormal operation,availabil i ty must be high(probability of failure ondemand, PFD , must be low)

• Availability confirmed bytesting.




© Metso

Safety instrumented system (SIS) for processindustries

• SIS monitors the process and ensuressafety by taking process to safe state

when unconventional condition occur• Safety engineers have been challenged to

comply string safety requirements

• Intelligent ESD valve solutions help to

reach the most demanding safety solutiontargets for final elements with minimuminvestment.




© MetsoUNCLASSIFIED

Safety Standards To Comply With...

Safety

System

• IEC 61508: Functional Safety of Electrical /Electronic / Programmable Electronic Safety-Related Systems

• IEC 61511: Functional Safety InstrumentedSystems for the Process Industry Sector

• More redundant systems or more testing neededthan before

• This leads to very high CAPEX (capital expense)and OPEX (operating expense) unless the latesttechnology is utilized




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One study has shown

that valves can

represent as much

as 50% o f all SIS

failures.

One study has shown

that valves can

represent as much

as 50% o f all SIS

failures.

50%o f al l SIS fai lures

as much as

OREDA:Analysis of Safety Loop Failures




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0

0

1

1

2

3

3

0

0

1

1

2

3

3

4

0

1

1

2

3

3

4

4

0

P3 P2 P1

D1

D2

D3

D4

E1

E2

E1

E2

A1

A2

A1

A2

D - Extent of Damage

• D1: slight injury

• D2: severe injuries or one death

• D3: death of several persons

• D4: multiple deaths

E - Exposure Time

• E1: seldom to relatively frequent

• E2: frequent to continuous

A - Hazard Avoidance

• A1: possible under certain conditions

• A2: hardly possible

P - Probability to occur

• P1: very low

• P2: low

• P3: relatively high

Consequence only method: D

Risk matrix method: D + P Permission granted for

ISA Houston Section Website



© MetsoUNCLASSIFIED

“Off-line diagnostics”

(= periodic maintenance)

Validation - PFD for Component

Where:

λ d = dangerous failure rate = 1/MTBFd

MTBFd = mean time between dangerous failures

MTTR = mean time to repair

DC = diagnostic coverage factor

TIa = test interval for automatic testing

TIm = test interval for manual testing (= maintenance period)

“On-line diagnostics”

(= testing)




UNCLASSIFIED



© Metso

UNCLASSIFIED

SIL vs. Probability of Failure on Demand

Difference between SILs is

an order of magnitude!

PFD = Probability to Fail on DemandWhat is the chance that the system fails




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I10-5 to 10-4

Probability of failure to

perform its design

function on demand

10-4 to 10-3

10-3 to 10-2

10-2 to 10-1

4

3

2

1

Low demand Mode: Frequency of demand no greater than once per year andno greater than twice the proof check frequency

Safety Availability

(1-PFD) X 100%

99.99% to 99.999%

99.90% to 99.99%

99.00% to 99.90%

90.00% to 99.00%

(IEC /ISA)

(IEC/ISA)

(IEC/ISA)

(IEC/ISA)

Safety Integrity Level

(SIL)(How reliable the SIS needs to be to reduce

a particular r isk to an acceptable level)




© Metso

Validation - Calculating PFD

MTBFd = 50 years

SIL 3

SIL 2

SIL 1

Where, λ d = dangerous failure rate

TI = testing interval (shutdown interval)




© Metso

Validation - PFD with diagnostic coverage

MTBFd = 50 years, DCF = 75%

SIL 3

SIL 2

SIL 1




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Motivation to use partial valve stroke testing

• Safety valve proof testing is mandatory activity in accordance of

IEC 61511 standard

- Interval is defined according to the safety requirement of the plant

- BUT interval can be influenced with• Product selection (hardware fault tolerance reduction)

• PST implementation (online testing of critical components)

15

Maximizedproduction with

PST

…and at the same timesafety is improvedwith intelligent PST

valve stickinghigher needed torque




© Metso

What is a safety valve?

• ESD (emergency shut down)valves or ESV (emergencyventing) valves operating in

demanding environment

• Part of Safety InstrumentedSystem (SIS)

• Defense against processupsets

• Operating only in trip situation

16Permission granted for ISA Houston Section Website



© Metso19

A solution to the dilemma:

“Run longer, test more often.”

?

Bypass

Partial strokeShutdown

Demand for

Uptime

Demand

for testing




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Partial Stroke Testing Options

• Mechanical Jammer

• Instrumentation Based Custom Panel

• Redundant Solenoids

• Digital Positioner + solenoid

• Control System Based Solution

• PST with an Intelligent Safety Valve Controller




© Metso


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Jammer Based Solution

• Safety loop disabled during PST

• No real diagnostics information from the PST

• Testing requires manual work -> higher testing

costs• Human interaction always required for PST ->

safety risk

• The safety solenoid is tested only during PST

• Full stroke test needs to be done manually




© Metso


Instrumentation Based Solution

•Complicated system with multiple potential failurecauses

•Safety loop usually disabled during PST

•No real diagnostics information from the PST•Testing requires manual work -> high testing costs

•Human interaction always required for PST ->safety risk

•In most cases the safety solenoid is not tested

•Full stroke test needs to be done manually




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Redundant Solenoids

• PST not available or it requires difficult, manualconfiguration

• No diagnostics

• The solenoids can not be tested automatically• Full stroke test needs to be done manually




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Positioner + Solenoid

•Higher nuisance trip rate

•Solenoid can not be testedautomatically

•Manual testing and interpretation of

test results




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Control System Based Solution

•Use DCS to initiate and Monitor PST

•Solenoid and Limit Switch configuration

•Diagnostics Limited to timing of PST

•Limited Safety Features




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Intelligent PST Solution

• Safety loop enabled during PST

• Diagnostics information from PST Possibility to optimize ESD valvemaintenance

• Automated PST -> no testing costs

• Seamless Communication with DTMor EDDL

• HART Based


P i l S k T i O i



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Intelligent PST Solution - continued

• Human interaction not required for

PST more effective use ofmaintenance resources

• Emergency trip captured

• Self documentation

• Improves safety while making lifeeasier with safety valves

• 3rd part certification (i.e. TÜV, Exida)




© Metso

Potential Issues with Conventional PST

• Human interaction is typicallyrequired

• The safety system must bedisabled during testing

• Testing creates high costs due tohuman factors


P t ti l I ith C ti l PST



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Potential Issues with Conventional PST

• Testing intervals are long

• Little or no diagnosticsinformation is received when thetests are being performed

• Safety solenoid valve might notbe tested at all

• Complex instrumentation is oftenrequired for conducting the tests


R t I t t i t lli t PST



© Metso

Recent Improvements to intelligent PST

• High Pneumatics Capacity- Improve SIL level by limiting need for

pneumatic accessories with lower PFD values

• Internal pneumatics test

- Improve PFD of valve controller with internaltesting that doesn’t move the valve

• PST stroke randomizer- Prevent buildup on the safety valve by

randomizing the stroke size

• Integrated Limit Switches

• Emergency trip test

- Report safety test figures• Full interoperability with all major safety

systems and asset management systems


E l f Di ti ith I t lli t PST f



© Metso

Example of Diagnostics with Intelligent PST forpredictive maintenance• Load factor and breakaway pressure

- Trends collected from partial stroke tests

- Results shown test based not time based

• Enables predictive maintenance- Potential valve failures can be detected in advance


The valve is in original condition



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0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 %

Actuator outputtorque

Needed valve torque

The valve is in original condition

0 %

10 %

20 %

30 %

40 %50 %

60 %

70 %

80 %

90 %

100 %

Load factor trend for 10 latest PST's

FULLY OPENFULLY CLOSED

T O R Q U E

WARNING LIMIT


When the needed valve torque exceeds the



© Metso

0 %

10 %

20 %

30 %

40 %50 %

60 %

70 %

80 %

90 %

100 %

Load factor trend for 10 latest PST's

0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 %

Actuator outputtorque

Needed valve torque

qavailable actuator output torque, the valve is stuck

FULLY OPENFULLY CLOSED

T O R Q U E

WARNING LIMIT


With less instrumentation, It can be easier, safer and more reliable



© Metso

, ,

34

ESD ball valve with:

• PST Device

• Inductive proximity

switches or positiontransmitter

• Filter regulator

• Volume booster ¾”

• ASCO solenoid valve

• Mounting panel

• Tandem mounting

• Tubing and fittings

Not Needed:Cv of SMARTPST Device

Not needed,

internal SOV

Not needed

Not needed

Less tubing andfittings, since SOVand booster can be

omitted


General Feature Summary of Intelligent PST



© Metso

• Pneumatic capacity [Cv]

• PST• 100% Safety action test• Pneumatics test• Solenoid needed for trip

• Local user interface• Single and double acting• Energized to trip configuration• Full diagnostics included

• Plug-in needed• Diagnostics storage• PST speed control• Time stamping

• LCP Option• Continuous Power Option

35

• Max 6.4 Cv

• Manual, auto & variable stroke• Yes

• Yes

• No

• Yes• Yes

• Yes, with SOV

• Yes

• No, DTM free of charge• In the device

• Limiting execution time

• Based on AM system

• Yes

• Yes

General Feature Summary of Intelligent PST




© Metso36

Seamless Integration into Control Systems

YokogawaCentum/PRM

ABB800xA

FoxboroIA

HoneywellExperion

Rockwell

MetsoDNA

EmersonDELTA V/AMS

Emerson375 Field Communicator

EDDL

DD




© Metso37

Configuration and Testing Using Software Tools

• Automated Intervals

•Pushbuttons

•DTM

•EDD- Emerson AMS

•HART DD- 375 HART handheld


Future of Partial Stroke Testing



© Metso

Future of Partial Stroke TestingFieldbus based PST

• FOUNDATION for SIF (Safety Instrumented Functions) has just beenintroduced to industry, only demo devices and systems exist

• Current Configuration of some devices allows for ESD activity tocome from Current Safety Systems while communication is FF toDCS or Asset Management System


TRAINING



24 VDC DO from Safety System




mA




24 VDC

mA

RCI


Thank You

sil & partial stroke testing solutionstation

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