Using Smart Positioners in Emergency Shutdown Applications

Customer : Saudi Aramco Customer : Saudi Aramco Technical Presentation on Technical Presentation on Fisher DVC6000-ESD Smart Fisher DVC6000-ESD Smart Positioners in Emergency Positioners in Emergency Shutdown ApplicationsShutdown Applications

Using Smart Positioners in Using Smart Positioners in Emergency Shutdown ApplicationsEmergency Shutdown Applications

Basic Concepts Historical methods Smart Positioners to the Rescue Installation Conclusion

What is a Safety Instrumented System?What is a Safety Instrumented System?

DefinitionDefinition

An SIS is a set of components such as sensors, An SIS is a set of components such as sensors, logic solvers, and final control elementslogic solvers, and final control elementsarranged for the purpose of taking the process arranged for the purpose of taking the process to a safe stateto a safe state when predetermined when predetermined conditions are violated.conditions are violated.

What is a Safety Instrumented System What is a Safety Instrumented System (SIS)?(SIS)?

(Hardware and Software)

Logic solver

Sensor Logic Solver Final ControlElement

What is a Safety Instrumented System What is a Safety Instrumented System (SIS)?(SIS)?

Dike Passive protection layer

Emergency response layerPlant andEmergency Response

ProcessValue Normal behaviour

BasicProcessControlSystem

Process control layer

Safety Through Layers of ProtectionSafety Through Layers of Protection

OperatorIntervention

Process control layer

Process alarm

ProcessShutdown

Trip level alarm

SafetyInstrumentedSystem

Safety layerEmergencyShut Down

Prevent

Mitigate

x x

Relief valve,Rupture disk Active protection layer

What is SIL?What is SIL?

SIL is a way of quantifying risk.

NO SIL

Ris

k

SIL1

SIL2

SIL3

SIL4

What Is SIL? – Safety Integrity LevelWhat Is SIL? – Safety Integrity Level

RISK

FrequencyConsequence

or

SIL Is Directly Related To RiskSIL Is Directly Related To Risk

Safety Integrity Level

SIL 4

SIL 3

SIL 2

SIL 1

Probability of failure on demand per year

(Demand mode of operation)

Risk Reduction Factor

>=10-5 to <10-4

>=10-4 to <10-3

>=10-3 to <10-2

>=10-2 to <10-1

100000 to 10000

10000 to 1000

1000 to 100

100 to 10

PFD 1/PFD

Safety Integrity LevelsSafety Integrity Levels

Valve50%

Sensor35%

Logic Solver

15%

What Components Cause More Faults?

SIS Faults – Investigation Uncovers SIS Faults – Investigation Uncovers CluesClues

(Hardware and Software)

Sensor

SIS Faults – Where Do They Happen?SIS Faults – Where Do They Happen?

Final ControlElement

Logic Solver

Typically operate in one position - only move upon an emergency

Without mechanical movement, unreliability inherently increases

Frequent testing ensures valve availability upon Demand

Historically, expensive, labor intensive pneumatic testing methods required

Why does the ESD valve account Why does the ESD valve account for 50% of failures?for 50% of failures?

Aramco Existing Pneumatic Test Aramco Existing Pneumatic Test Methods (costly and complicated)Methods (costly and complicated)

Limitations to existing pneumatic test Limitations to existing pneumatic test panelpanel

Local testing and Hard Stop Requires bypass Shutdown and Test Restricted analysis Expensive & Complex Limit Switch and time Signal to Allow Partial

Stroke

Smart Positioners to the Rescue-Smart Positioners to the Rescue-FeaturesFeatures

Partial Stroke Diagnostics Vent Actuator Pressure Collect pressure, travel data and analyze Supply and output pressure sensors Documentation (Compare and Storage) Full stroke valve signatures for seat load details

Smart Positioner or Digital Valve Controller (microprocessor-based instrument)

Smart Positioners to the Rescue-Smart Positioners to the Rescue-CapabilitiesCapabilities

Partial Stroke Test criteria– Configurable valve travel

– Valve returns to normal operation, if diagnostic fails

– If “valve is stuck”, alert operator

– Don’t exhaust all the air

– Configurable Speed of Stroke

– Demand Overrides Partial Stroke Test

Without partial valve stroke testing – Without partial valve stroke testing – SIL2SIL2

With partial valve stroke testing – With partial valve stroke testing – SIL3SIL3

Doing The MathDoing The Math

PFD avg = [(DF)(d) (TI/2)]p + [(DF)(d) (TI/2)]F

Assumptions: DF 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

Full Stroke Testing Only

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

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

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

= [(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 still maintaining the same PFD!

Continuous Check of Device Integrity– In case of problem, provide alert

Smart Positioners to the Rescue -Smart Positioners to the Rescue -CapabilitiesCapabilities

Manual Initiation of Automated testing – Remote companion software

– Handheld

– Remote push button

On Demand, digital valve controller continues to communicate


Step Response Test– Initiated via Companion software

– Provides analysis of overshoot, hysteresis, dead time and travel time.

– This data can be utilized to extrapolate valve stroking time

Modular

Construction


Encapsulated & Potted electronics

Pneumatic relay - mechanical beam

Solution Proposal:Solution Proposal:Point to Point Mode ApproachPoint to Point Mode Approach

Digital Valve Controller

Travel Feedback

Logic Solver

24V DCSolenoid Valve

Exhaust

S

ESD Valve/Actuator

4-20 mA DC

Supply Pressure

Solution Proposal:Solution Proposal: Multi-drop Mode Approach Multi-drop Mode Approach

Digital Valve Controller

Travel Feedback

Logic Solver

24V DCSolenoid Valve

Exhaust

S

ESD Valve/Actuator

Supply Pressure

Line Conditioner

ConclusionConclusion Increased System Availability Safety Defaults Predictive Maintenance System Audit Documentation Valuable Time Saving Reduced Cost Of Ownership

Installed BaseInstalled BaseSaudi Aramco - Yanbu Saudi Aramco ShedgumSaudi Aramco, Berri Gas PlantSaudi Aramco, Haradh Gas Plant ICI - Runcore plant - UK Doffasco - Canada TiWest - Australia SCECO - Riyadh - S. Arabia Huntsman Chemicals-BeaumontDuPont-Washington Works- USADOW Chemicals, Freeport - USAQP (Qatar Petroleum) - Qatar ORC, OmanAnd more…

Using Smart Positioners in Using Smart Positioners in Emergency Shutdown Emergency Shutdown ApplicationsApplications

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Using Smart Positioners in Emergency Shutdown Applications

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