201205 Presentation

7/29/2019 201205 Presentation

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A Case Study: Updating a Refinery Boiler

Controls utilizing ISA 84 Standard for

Safety Instrumented Systems

Permission granted for ISA Houston Section Website


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Presenters

Alan Sharkey Audubon

Chuck Laughter Audubon

Matt Hufford Wilson Mohr

Steve Papp - Wilson Mohr



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Agenda

Functional Safety Life Cycle Overview

Case Study of Boiler in Refinery

HAZOP

LOPA PFD/SIL Determination

SRS Development

SIS Implementation Phase

Operation & Maintenance Phase

Q&A



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Process Safety Management

ISA 84

IEC 61508/11

NFPA

API



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Safety Life Cycle Flow-Chart



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Hazard ID and Risk Assessment



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HAZID/HAZOP Objectives

Identify Hazards and Hazardous events of the process and

associated equipment

Task Required For each hazard identified , determine the consequence /severity

level, the deviation, the initiating cause(s), and the safeguards(s)

Note: Safe design should be developed as far as reasonably

practical before reliance is placed on the SIS to reduce risk



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LOPA

Objectives Identify required mechanical, operational & safety instrumented

functions (SIF) protection layers for each consequence carried intoLOPA

For each SIF determine the associated SIL & and risk reduction

target

Tasks required

Review hazard identification, for each hazard assign risk reductioncredits

Assign target PFD (SIL x) to each SIF

Note: Client will most likely have own risk graph and acceptablelevels of risk



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SRSDefinition of SRS: Function design requirements of the SIS

Minimum Requirements

SIS System architecture (sensor, logic solver & end control elements

System hardware standards

Spare capacity, loading & expansion

Specify testing interval(s)

I/O requirements

I/O signal types and field interfaces

System communications

Equipment and field termination/marshalling cabinet design

requirements Operator MOS Override requirements (HSW/KSW/Status Panel)

Optional Items

Preliminary SIL verification calculations



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Det ai l Designing of SIS Objectives To design, procure and test the SIS equipment to meet the SRS

Detailed specification of hardware; data sheets, etc

Provide SIS detailed design drawings; loop diagrams, etc.

Application software functional logic design and development. Construct SIS following approved procedures designed to reduce

systematic faults.

Verify compliance to SRS; confirm testing intervals are satisfied.

Provide procedures to operate and maintain the SIS. To validate, through inspection and testing, that the designed,

built & configured SIS logic solver, application software (SIFs) &

associated hardware meets in all respects the requirements as

stated in the SRS (FAT).



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Ins ta l la t ion & Comm iss ion ing Objectives Install and commission the SIS according to design

documentation so that it is ready for final system validation.

Commission and check calibration of the SIS components

To integrate and test the SIS (SAT)

To validate, through inspection and testing, that theinstalled & commissioned SIS & its associated SIFs meets

in all respects the requirements as stated in the SRS.



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Operat ion & Main tenanc e Objectives To ensure that the functional safety of the SIS is maintained

during operation and maintenance

SIS documentation is maintained

To control maintenance and testing activities, so that the

design intent of SIS is retained over the asset life



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Management o f Change Objectives To control all SIS modifications, so that safety integrity of

the SIS is maintained over the asset life.

To ensure that any SIS changes are properly planned,designed reviewed, approved and tested prior to

implementation.



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Case Study of Refinery SRU

HAZOP

LOPA

SRS

SIS

Operations & Maintenance



15/21

SIS Implementation

-Customer Timing

-Plant Control

Infrastructure

-CorporateSpecifications

-S84 vs NFPA 85

-CustomerAwareness

-MaintenanceRestrictions

Practical Considerations

-Concurrent

Development Cycle

-Vendor

Restrictions

-Conflicting

Requirements

-Needs dont match

capabilities

Impact on Cycle

QualificationsResulting

Complications



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SIS Implementation

- Customer Timing:

- 2 Year Turnaround Schedule

- Confecting Requirements

- Corporate Spec for S84

- Plant Spec for NFPA 85

- Concurrent design cycle required

- Forced SIL Target

- Commitment to Amend Mechanical design

- Preselected Control Vendor



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SIS Implementation

- RedundantProcessors UtilizingIndependent Tasks

- Shared Power &Comm Backbone

- DedicatedRedundant Analog &Digital Inputs on SISI/O

- SIS & BMS OperateTotally independently

- SIS Processes SIF

and Controls SafetyRelay Only

- MFT Circuit is theInterlockingMechanism Betweenthe Two Systems



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SIS Implementation

DCS Controlled

Combustion Circuit

with BMS Dump

Vale on IP

Backup Nitrogen

System on IA

Single Block with

Vent on Headers

Low Fire Light off on

Individual Burner Trains

2of3 Voting on all

NFPA Recommended

SignalsDouble Block and

Bleed on all

Individual Trains



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SIS Implementation



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SIS Implementation



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Quest ions?

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