Guidelines for Engineering Design for Process Safety E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 686

Veröffentlichungsjahr: 2012

Beschreibung

This updated version of one of the most popular and widely used CCPS books provides plant design engineers, facility operators, and safety professionals with key information on selected topics of interest. The book focuses on process safety issues in the design of chemical, petrochemical, and hydrocarbon processing facilities. It discusses how to select designs that can prevent or mitigate the release of flammable or toxic materials, which could lead to a fire, explosion, or environmental damage. Key areas to be enhanced in the new edition include inherently safer design, specifically concepts for design of inherently safer unit operations and Safety Instrumented Systems and Layer of Protection Analysis. This book also provides an extensive bibliography to related publications and topic-specific information, as well as key information on failure modes and potential design solutions.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Acronyms and Abbreviations

Glossary

Acknowledgments

Foreword

Preface

Chapter 1: Introduction

1.1 Engineering Design for Process Safety Through the Life Cycle of the Facility

1.2 Regulatory Review / Impact on Process Safety

1.3 Who Will Benefit From These Guidelines?

1.4 Organization of this Book

1.5 Other CCPS Resources

1.6 References

Chapter 2: Foundational Concepts

2.1 Understanding the Hazard

2.2 Risk-Based Design

2.3 Intentional Unsteady State Condition Evaluation

2.4 Unintentional Unsteady State Issues

2.5 Non-Linearity of the Design Process

2.6 References

Chapter 3: Basic Physical Properties/Thermal Stability Data

3.1 Basic Physical Properties

3.2 Flammability Data

3.3 Reactivity / Thermal Stability Data

3.4 References

Chapter 4: Analysis Techniques

4.1 Hazard Identification

4.2 Hazard Analysis Techniques

4.3 Risk Assessment

4.4 Reliability / Maintainability Analysis

4.5 References

Chapter 5: General Design

5.1 Safeguarding Strategies

5.2 Inherently Safer Design

5.3 Basic Process Control Systems

5.4 Instrumented Safety Systems

5.5 Process Design / Process Chemistry

5.6 Plant Siting and Layout

5.7 Materials of Construction

5.8 Corrosion

5.9 Civil / Structural / Support Design

5.10 Thermal Insulation

5.11 Human Factors In Design

5.12 Site Security Issues

5.13 References

Chapter 6: Equipment Design

6.1 Vessels

6.2 Reactors

6.3 Mass Transfer Equipment

6.4 Heat Transfer Equipment

6.5 Dryers

6.6 Fluid Transfer Equipment

6.7 Solid-Fluid Separators

6.8 Solids Handling And Processing Equipment

6.9 Fired Equipment

6.10 Piping and Piping Components

6.11 Material Handling and Warehousing

6.12 Utility Systems

Chapter 7: Protection Layers

7.1 Ignition Control

7.2 Instrumented Safety Systems

7.3 Pressure / Vacuum Relief Systems

7.4 Equipment Isolation / Blowdown

7.5 Effluent Disposal Systems

7.6 Emergency Response Alarm Systems

7.7 Fire Protection

7.8 Deflagration/Detonation Arresters

7.9 Explosion Suppression

7.10 Specialty Mitigation Systems

7.11 Effluent Handling/Post-Release Mitigation/Waste Treatment Issues

7.12 References

Chapter 8: Documentation to Support Process Safety

8.1 Process Knowledge Management

8.2 Engineering Design Package

8.3 Operating / Maintenance Procedures

8.4 Asset Integrity / Reliability / Predictive Maintenance Data

8.5 References

Index

GUIDELINES FOR ENGINEERING DESIGN FOR PROCESS SAFETY

This book is one in a series of process safety guideline and concept books published by the Center for Chemical Process Safety (CCPS). Please go to www.wiley.com/go/ccps for a full list of titles in this series.

Copyright © 2012 by American Institute of Chemical Engineers, Inc.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey. All rights reserved.Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

Guidelines for engineering design for process safety. — 2nd ed.p. cm.Includes bibliographical references and index.ISBN 978-0-470-76772-6 (hardback)1. Chemical plants—Safety measures. I. American Institute of Chemical Engineers. Center for Chemical Process Safety.TP155.5.G765 2012660’.2804—dc232011041436

It is sincerely hoped that the information presented in this document will lead to an even more impressive safety record for the entire industry. However, the American Institute of Chemical Engineers, its consultants, the CCPS Technical Steering Committee and Subcommittee members, their employers, their employers’ officers and directors, and Aon Energy Risk Engineering, and its employees do not warrant or represent, expressly or by implication, the correctness or accuracy of the content of the information presented in this document. As between (1) American Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee members, their employers, their employers’ officers and directors, and Aon Energy Risk Engineering, and its employees and (2) the user of this document, the user accepts any legal liability or responsibility whatsoever for the consequences of its use or misuse.

ACRONYMS AND ABBREVIATIONS

ACGIH

American Conference of Government Industrial Hygienists

ACI

American Concrete Institute

ACS

American Chemical Society

AEGL

Acute Emergency Guideline Levels

AGA

American Gas Association

AIChE

American Institute of Chemical Engineers

AIHA

American Industrial Hygiene Association

AISC

American Institute of Steel Construction, Inc.

AISI

American Iron and Steel Institute

AIT

Autoignition Temperature

ALARP

As Low as Reasonably Practical

ANSI

American National Standards Institute

APC

Air Pollution Control

APFA

American Pipe Fittings Association

API

American Petroleum Institute

ARC

Accelerating Rate Calorimeter

ASM

American Society for Metals

ASME

American Society of Mechanical Engineers

ASSE

American Society of Safety Engineers

ASNT

American Society of Nondestructive Testing

ASTM

American Society for Testing and Materials

AWS

American Welding Society

BLEVE

Boiling Liquid Expanding Vapor Explosion

BPCS

Basic Process Control System

Btu

British Thermal Units

BTX

Benzene, Toluene and Xylene

CAA

Clean Air Act

CAAA

Clean Air Act Amendments

CCPS

Center for Chemical Process Safety

CEM

Continuous Emissions Monitor

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act

CFR

Code of Federal Regulations

CGA

Compressed Gas Association

CIA

Chemical Industries Association

CMA

Chemical Manufacturers Association

COT

Coil Outlet Temperature

CRT

Cathode Ray Tube

CSTR

Continuous-Flow Stirred-Tank Reactor

CWA

Clean Water Act

DAF

Dissolved Air Flotation

dBA

A-Weighted Decibel Level

DCS

Distributed Control System

DDT

Deflagration to Detonation Transition

DIERS

Design Institute for Emergency Relief Systems

DIPPR

Design Institute for Physical Property Data

DOT

Department of Transportation

DOE

Department of Energy

DPC

Deflagration Pressure Containment

DSC

Differential Scanning Calorimeter

DTA

Differential Thermal Analysis

EEGL

Emergency Exposure Guidance Level

EJMA

Expansion Joint Manufacturers Association, Inc.

EPA

Environmental Protection Agency

EPRI

Electric Power Research Institute

ERPG

Emergency Response Planning Guidelines

ERS

Emergency Relief System

ERD

Emergency Relief Design

ESCIS

Expert Commission for Safety in the Swiss Chemical Industry

ESD

Emergency Shutdown Device

ECT

Eddy Current Testing

FBIC

Flexible Intermediate Bulk Containers

FEED

Front-End Engineering and Design

F&EI

Fire and Explosion Index

FMEA

Failure Modes and Effects Analysis

FMECA

Failure Modes, Effects and Criticality Analysis

FMEDA

Failure Modes, Effects and Diagnostic Analysis

FMEC

Factory Mutual Engineering Corporation

FRP

Fiber Reinforced Plastic

GFCI

Ground Fault Current Interrupter

GPM

Gallons per Minute

GSPA

Gas Processors Suppliers Association

HAZOP

Hazard and Operability Study

HEI

Heat Exchanger Institute

hp

Horsepower

HSE

Health and Safety Executive

HVAC

Heating, Ventilation, and Air Conditioning

IChemE

Institute of Chemical Engineers

ICI

Imperial Chemical Industries

IEEE

Institute of Electrical and Electronics Engineers

IDLH

Immediately Dangerous to Life or Health

IGC

Intergranular Corrosion

IPL

Independent Protection Layer

IRI

Industrial Risk Insurers

ISA

Instrument Society of America

ISGOTT

International Safety Guide for Oil Tankers and Terminals

ISO

International Standards Organization

ISS

Independent Safety System

kA

kiloampere

kV

kilovolt

LEL

Lower Explosive Limit

LFL

Lower Flammable Limit

LNG

Liquefied Natural Gas

LOC

Limiting Oxygen Concentration

LOPA

Layer of Protection Analysis

LPG

Liquefied Petroleum Gas

mA

milliampere

MAWP

Maximum Allowable Working Pressure

MCC

Motor Control Center

MEC

Minimum Explosible Concentration

MIE

Minimum Ignition Energy

mJ

millijoule

MOC

Management of Change

MSDS

Material Safety Data Sheet

MSS

Manufacturers Standardization Society

MT

Magnetic Particle Testing

NACE

National Association of Corrosion Engineers

NAS

National Academy of Science

NBIC

National Board Inspection Code

NEC

National Electrical Code

NEMA

National Electrical Manufacturers Association

NESC

National Electrical Safety Code

NDE

Nondestructive Examination

NFPA

National Fire Protection Association

NIOSH

National Institute of Occupational Safety and Health

NOAA

National Oceanic and Atmospheric Administration

NPCA

National Paint and Coatings Association

NPDES

National Pollutant Discharge and Elimination System

NPSH

Net Positive Suction Head

NRC

National Research Council

NSPS

New Source Performance Standards

NTIAC

Nondestructive Testing Information Analysis Center

OSHA

Occupational Safety and Health Administration

PAC

Protective Action Criteria

PCB

Polychlorinated Biphenyl

PEL

Permissible Exposure Limit

PES

Programmable Electronic System

PFD

Process Flow Diagram

PFR

Plug Flow Reactor

PLC

Programmable Logic Controller

P&ID

Piping and Instrumentation Diagram

PHA

Process Hazard Analysis

PID

Proportional Integral Derivative

POT

Pass Outlet Temperature

ppm

parts per million

pS

picoSiemen

PS

Process Safety

PSA

Pressure Swing Adsorption

PSD

Process Safety Device

PSV

Pressure Safety Valve

PSS

Process Safety System

PT

Liquid Penetrant Testing

PVRV

Pressure-Vacuum Relief Valve

QRA

Quantitative Risk Analysis

REST

Reactivity Evaluation Screening Tool

RC

Reactor Calorimeter

RCRA

Resource Conservation and Recovery Act

RP

Recommended Practice

RSST

Reactive System Screening Tool

RT

Radiographic Testing

RTD

Resistance Temperature Detector

SCAPA

Subcommitee on Consequence Assessment and Protective Actions

SCBA

Self-Contained Breathing Apparatus

SCC

Stress Corrosion Cracking

scf

Standard Cubic Foot

SCR

Silicon Conductor Rectifier

SAE

Society of Automotive Engineers

SFPE

Society of Fire Protection Engineers

SIF

Safety Instrumented Function

SIS

Safety Instrumented System

SLOD

Significant Likelihood of Death

SLOT

Specified Level of Toxicity

SOL

Safe Operating Limit

SPCC

Spill Prevention Control and Countermeasures

SPEGL

Short-Term Public Emergency Guidance Level

SRS

Safety Requirement Specification

SSPC

Steel Structures Painting Council

TEEL

Temporary Emergency Exposure Limits

TEMA

Tubular Exchanger Manufacturer Association

TLV

Threshold Limit Value

TOC

Total Organic Compounds

TSCA

Toxic Substance Control Act

UBC

Uniform Building Code

UEL

Upper Explosive Limit

UFL

Upper Flammable Limit

UL

Underwriters Laboratory Inc.

UPS

Uninterruptible Power Supply

UT

Ultrasonic Testing

UVCE

Unconfined Vapor Cloud Explosion

VOC

Volatile Organic Compound

VP

Vapor Pressure

VSP

Vent Size Package

WEEL

Workplace Environmental Exposure Limit

GLOSSARY

Administrative Controls

Procedural mechanisms, such as lockout / tagout procedures, for directing and / or checking human performance on plant tasks.

Auto-ignition Temperature

The autoignition temperature of a substance, whether solid, liquid, or gaseous, is the minimum temperature required to initiate or cause self-sustained combustion, in air, with no other source of ignition.

Basic Event

An event in a fault tree that represents the lowest level of resolution in the model such that no further development is necessary (e.g., equipment item failure, human failure, or external event).

Basic Process Control System (BPCS)

The control equipment which is installed to support normal production functions.

Batch Reactor

Reactor in which all reactants and solvents are introduced prior to setting the reaction conditions (temperature, pressure). Products are only taken from the reactor upon conclusion of the reaction process. Both heat generation and concentrations in the batch reactor vary during the reaction process.

Boiling Liquid-Expanding Vapor Explosion (BLEVE)

A type of rapid phase transition in which a liquid contained above its atmospheric boiling point is rapidly depressurized, causing a nearly instantaneous transition from liquid to vapor with a corresponding energy release. A BLEVE is often accompanied by a large fireball if a flammable liquid is involved, since an external fire impinging on the vapor space of a pressure vessel is a common BLEVE scenario. However, it is not necessary for the liquid to be flammable to have a BLEVE occur.

Bonding

The process of connecting two or more conductive objects together by means of a conductor.

Car Seal

Metal or plastic cable used to fix a valve in the open position (car seal open) or closed position (car seal closed). Proper authorization, controlled via administrative procedures, must be obtained before operating the valve. The physical seal should have suitable mechanical strength to prevent unauthorized valve operation.

Catastrophic Incident

An incident involving a major uncontrolled emission, fire or explosion that causes significant damage, injuries and / or fatalities onsite and have an outcome effect zone that extends into the surrounding community.

Combustible

Capable of burning.

Combustible Liquid

A term used to classify certain liquids that will burn on the basis of flash points. The National Fire Protection Association (NFPA) defines a combustible liquid as any liquid that has a closed-cup flash point above 100°F (37.8°C) (NFPA 30). There are three subclasses, as follows:

Class II liquids have flash points at or above 100°F (37.8°C) but below 140°F (60°C).

Class III liquids are subdivided into two additional subclasses:

- Class IIIA are those having flash points at or above 140°F (60°C) but below 200°F (93.4°C).

- Class IIIB are those having flash points at or above 200°F (93.4°C).

The Department of Transportation (DOT) defines “combustible liquids” as those having flash points of not more than 141°F (60.5°C) and below 200°F (93.4°C).

Common Mode Failure

An event having a single external cause with multiple failure effects which are not consequences of each other.

Continuous Reactors

Reactors that are characterized by a continuous flow of reactants into and a continuous flow of products from the reaction system (e.g., Plug Flow Reactor (PFR) and the Continuous Stirred Tank Reactor (CSTR)).

Continuous Stirred Tank Reactor (CSTR)

A reaction vessel in which the feed is continuously added and the products continuously removed. The vessel (tank) is continuously stirred to maintain a uniform concentration within the vessel.

Critical Event

A critical event is an event with a specified, high consequence such as an event involving an offsite community impact, critical system damage, a severe injury or a fatality.

Critical Event Frequency

The frequency of occurrence of a critical event.

Deadheading

A blockage on the discharge side of an operating pump which results in the flow reducing to zero and an increase in the discharge pressure. The energy input from the deadheaded pump increases the temperature and pressure of the fluid in the pump.

Deflagration

The chemical reaction of a substance in which the reaction front advances into the unreacted substance at less than sonic velocity. Where a blast wave is produced that has the potential to cause damage, the term explosive deflagration may be used.

Deflagration to Detonation Transition (DDT)

The transition phenomenon resulting from the acceleration of a deflagration flame to detonation via flame-generated turbulent flow and compressive heating effects. At the instant of transition a volume of precompressed, turbulent gas ahead of the flame front detonates at unusually high velocity and overpressure.

Design Institute for Emergency Relief Systems (DIERS)

Institute under the auspices of the American Institute of Chemical Engineers founded to study relief requirements for reactive chemical systems and two-phase flow systems.

Detonation

A release of energy caused by the propagation of a chemical reaction in which the reaction front advances into the unreacted substance at greater than sonic velocity in the unreacted material.

Distributed Control System (DCS)

A system which divides process control functions into specific areas interconnected by communications (normally data highways), to form a single entity. It is characterized by digital controllers and typically by central operation interfaces.

Dow Fire and Explosion Index (F&EI)

A method (developed by Dow Chemical Company) for ranking the relative fire and explosion risk associated with a process. Analysts calculate various hazard and explosion indexes using material characteristics and process data.

Emergency Relief Device

A device that is designed to open during emergency or abnormal conditions to prevent rise of internal fluid pressure in excess of a specified value. The device also may be designed to prevent excessive internal vacuum. The device may be a pressure relief valve, a nonreclosing pressure relief device, or a vacuum relief valve.

Emergency Shutdown Device

A device that is designed to shutdown the system to a safe condition on command from the emergency shutdown system.

Emergency Shutdown System

The safety control system that overrides the action of the basic control system and shuts down the process when predetermined conditions are violated.

Equipment Reliability

The probability that, when operating under stated environment conditions, process equipment will perform its intended function adequately for a specified exposure period.

Explosion

A release of energy that causes a pressure discontinuity or blast wave.

Fail-Safe

Design features which provide for the maintenance of safe operating conditions in the event of a malfunction of control devices or an interruption of an energy source (e.g., failure direction of a motor operated value on loss of motive power).

A feature incorporated for automatically counteracting the effect of an anticipated possible source of failure. A system is fail-safe if failure of a component, signal, or utility, initiates action that return the system to a safe condition.

Failure

An unacceptable difference between expected and observed performance.

Failure Mode and Effects Analysis (FMEA)

A systematic, tabular method for evaluating and documenting the effects of known types of component failures.

Fire Point

The minimum temperature at which a flammable or combustible liquid, as herein defined, and some volatile combustible solids will evolve sufficient vapor to produce a mixture with air that will support sustained combustion when exposed to a source of ignition, such as a spark or flame.

Fireball

The atmospheric burning of a fuel-air cloud in which the energy is mostly emitted in the form of radiant heat. The inner core of the fuel release consists of almost pure fuel whereas the outer layer in which ignition first occurs is a flammable fuel-air mixture. As buoyancy forces of the hot gases begin to dominate, the burning cloud rises and becomes more spherical in shape.

Flammability Limits

The range of gas or vapor amounts in air that will burn or explode if a flame or other ignition source is present. Importance: The range represents an unsafe gas or vapor mixture with air that may ignite or explode. Generally, the wider the range the greater the fire potential. See also Lower Explosive Limit / Lower Flammable Limit and Upper Explosive Limit / Upper Flammable Limit.

Flammable Liquid

Any liquid that has a closed-cup flash point below 100°F (37.8°C), as determined by the test procedures described in NFPA 30 and a Reid vapor pressure not exceeding 40 psia (2068.6 mm Hg) at 100°F (37.8°C), as determined by ASTM D 323, Standard Method of Test for Vapor Pressure of Petroleum Products (Reid Method). Flammable liquids are classified as Class I as follows:

Flash Fire

The combustion of a flammable vapor and air mixture in which flame passes through that mixture at less than sonic velocity, such that negligible damaging overpressure is generated.

Flash Point

The temperature at which the vapor-air mixture above a liquid is capable of sustaining combustion after ignition from an external energy source.

Fugitive Emissions

Those emissions which could not reasonably pass through a stack, chimney, vent or other functionally-equivalent opening.

Grounding

The process of connecting one or more conductive objects to ground so that each is at the same potential as the earth. By convention, the earth has zero potential. In practice, grounding is the process of providing a sufficiently small resistance to ground so that a static hazard cannot be created at the maximum credible charging current to a system. Grounding may be referred to as “earthing” in Europe.

Hazard

An inherent chemical or physical characteristic that has the potential for causing damage to people, property, or the environment. In this document it is the combination of a hazardous material, an operating environment, and certain unplanned events that could result in an accident.

Hazard Analysis

The identification of undesired events that lead to the materialization of a hazard, the analysis of the mechanisms by which these undesired events could occur and usually the estimation of the consequences.

Hazard and Operability Study (HAZOP)

A systematic qualitative technique to identify process hazards and potential operating problems using a series of guide words to study process deviations. A HAZOP is used to question every part of a process to discover what deviations from the intention of the design can occur and what their causes and consequences may be. This is done systematically by applying suitable guidewords. This is a systematic detailed review technique, for both batch and continuous plants, which can be applied to new or existing processes to identify hazards.

Hazard Identification

The identification of causes that lead to hazardous events and an estimation of the event consequence.

Hazardous Material

In a broad sense, any substance or mixture of substances having properties capable of producing adverse effects to the health or safety of human beings or the environment. Material presenting dangers beyond the fire problems relating to flash point and boiling point. These dangers may arise from, but are not limited to, toxicity, reactivity, instability, or corrosivity

Human Factors

A discipline concerned with designing machines, operations, and work environments so that they match human capabilities, limitations, and needs. Includes any technical work (engineering, procedure writing, worker training, worker selection, etc.) related to the human factor in operator-machine systems.

Inert Gas

A nonflammable, nonreactive gas that can be used to render the combustible material in a system incapable of supporting combustion.

Inherently Safer

A condition in which the hazards associated with the materials and operations used in the process have been reduced or eliminated, and this reduction or elimination is permanent and inseparable.

Interlock System

A system that detects out-of-limits or abnormal conditions or improper sequences and either halts further action or starts corrective action.

Intrinsically Safe

Equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture or hazardous layer.

A protection technique based upon the restriction of electrical energy within apparatus and of interconnecting wiring, exposed to a potentially explosive atmosphere, to a level below that which can cause ignition by either sparking or heating effects. Because of the method by which intrinsic safety is achieved, it is necessary to ensure that not only the electrical apparatus exposed to the potentially explosive atmosphere but also other electrical apparatus with which it is interconnected is suitably constructed.

Likelihood

A measure of the expected frequency with which an event occurs. This may be expressed as a frequency (e.g., events per year), a probability of occurrence during a time interval (e.g., annual probability), or a conditional probability (e.g., probability of occurrence, given that a precursor event has occurred).

Limiting Oxygen Concentration (LOC)

The limiting oxygen concentration (LOC) is that concentration of oxygen, below which a deflagration (flame propagation in the gas, mist, suspended dust, or hybrid mixture) cannot occur. For most hydrocarbons (where oxygen is the oxidant and nitrogen is the diluent) the LOC is approximately 9 to 11 vol% oxygen. The LOC for dusts is dependent on the composition and particle size distribution of the solid. Values of LOC for most organic chemical dusts are in the range of 10 to 16 vol% oxygen, again where nitrogen is the diluent.

Lower Flammable Limit (LFL)

That concentration of a combustible material in air below which ignition will not occur. It is often, interchangeably called Lower Explosive Limit (LEL) and for dusts, the Minimum Explosible Concentration (MEC).

Minimum Explosible Concentration (MEC)

The lowest concentration of combustible dust necessary to produce an explosion.

Minimum Ignition Energy (MIE)

Initiation of flame propagation in a combustible mixture requires an ignition source of adequate energy and duration to overcome heat losses to the cooler surrounding material. Dust and vapor clouds may be readily ignited if exposed to electric discharges that exceed the minimum ignition energy (MIE) for the combustible mixture.

Mitigation

Reducing the risk of an accident event sequence by taking protective measures to reduce the likelihood of occurrence of the event, and / or reduce the magnitude of the event and / or minimize the exposure of people or property to the event.

Net Positive Suction Head (NPSH)

The net static liquid head that must be provided on the suction side of the pump to prevent cavitation.

Oxidant

Any gaseous material that can react with a fuel (gas, dust, or mist) to produce combustion. Oxygen in air is the most common oxidant.

Piping and Instrumentation Diagram (P…ID)

A diagram that shows the details about the piping, vessels, and instrumentation.

Plug Flow Reactor (PFR)

A plug flow reactor is a tubular reactor where the feed is continuously introduced at one end and the products continuously removed form the other end. The concentration / temperature in the reactor is not uniform.

Pool Fire

The combustion of material evaporating from a layer of liquid at the base of the fire.

Pressure Relief Valve (PRV)

A relief valve is a spring-loaded valve actuated by static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over opening pressure. A relief valve is normally used with incompressible fluids.

Pressure Safety Valve (PSV)

A safety valve is a spring loaded pressure relief valve actuated by static pressure upstream if the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids.

Process Flow Diagram (PFD)

A diagram that shows the material flow from one piece of equipment to the other in a process. It usually provides information about the pressure, temperature, composition, and flow rate of the various streams, heat duties of exchangers, and other such information pertaining to understanding and conceptualizing the process.

Process Hazard Analysis (PHA)

An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate recommendations are developed. Occasionally, quantitative methods are used to help prioritized risk reduction.

Process Safety

A discipline that focuses on the prevention of fires, explosions, and accidental chemical releases at chemical process facilities.

Process Safety Management (PSM)

A management system that is focused on prevention of, preparedness for, mitigation of, response to, and restoration from catastrophic releases of chemicals or energy from a process associated with a facility.

Process Safety System (PSS)

A process safety system comprises the design, procedures, and hardware intended to operate and maintain the process safely.

Programmable Electronic System (PES)

A system based on a computer connected to sensors and / or actuators in a plant for the purpose of control, protection or monitoring (includes various types of computers, programmable logic controllers, peripherals, interconnect systems, instrument distributed control system controllers, and other associated equipment).

Programmable Logic Controller (PLC)

A microcomputer-based solid-state control system which receives inputs from user-supplied control devices such as switches and sensors, implements them in a precise pattern determined by instructions stored in the PLC memory, and provides outputs for control or user-supplied devices such as relays and motor starters.

Purge Gas

A gas that is continuously or intermittently added to a system to render the atmosphere noncombustible. The purge gas can be inert or combustible.

Quenching

Rapid cooling from an elevated temperature, e.g., severe cooling of the reaction system in a short time (almost instantaneously), “freezes” the status of a reaction and prevents further decomposition or reaction.

Risk Based Process Safety

The CCPS’s process safety management system approach that uses risk-based strategies and implementation tactics that are commensurate with the risk-based need for process safety activities, availability of resources, and existing process safety culture to design, correct, and improve process safety management activities.

Runaway Reactions

A thermally unstable reaction system which exhibits an uncontrolled accelerating rate of reaction leading to rapid increases in temperature and pressure.

Safety Instrumented System (SIS)

The instrumentation, controls, and interlocks provided for safe operation of the process.

Safety Layer

A system or subsystem that is considered adequate to protect against a specific hazard. The safety layer:

Is totally independent of any other protective layers.

Cannot be compromised by the failure of another safety layer.

Must have acceptable reliability.

Must be approved according to company policy and procedures.

Must meet proper equipment classification.

May be a noncontrol alternative (e.g., chemical, mechanical).

May require diverse hardware and software packages.

May be an administrative procedure.

Semi-Batch Reactor

In a semi-batch reactor, some reactants are added to the reactor at the start of the batch, while others are fed continuously during the course of the reaction.

Source Term

For a hazardous material and / or energy release to the surroundings associated with a loss event, the release parameters (e.g., magnitude, rate, duration, orientation, temperature, etc.) that are the initial conditions for determining the consequences of the loss event. For vapor dispersion modeling, it is the estimation, based on the release specification, of the actual cloud conditions of temperature, aerosol content, density, size, velocity and mass to be input into the dispersion model.

Task Analysis

A human error analysis method that breaks down a procedure or overall job description into individual work tasks.

Unconfined Vapor Cloud Explosion (UCVE)

When a flammable vapor is released, its mixture with air will form a flammable vapor cloud. If ignited, the flame speed may accelerate to high velocities and produce significant blast overpressure.

Upper Flammable Limit (UFL)

The highest concentration of a vapor or gas (the highest percentage of the substance in air) that will produce a flash of fire when an ignition source (heat, arc, or flame) is present. See also Lower Flammable Limit. At concentrations higher then the UFL, the mixture is too “rich” to burn.

Valve Failure Positions

In the event of instrument air or electrical power failure, valves either Fail Closed (FC), Fail Open (FO), or Fail in the last position (FL). The position of failure must be carefully selected so as to bring the system to, or leave the system in a safe operating state.

Vapor Cloud Explosion (VCE)

The explosion resulting from the ignition of a cloud of flammable vapor, gas, or mist in which flame speeds accelerate to sufficiently high velocities to produce significant overpressure.

Vapor Density

The weight of a vapor or gas compared to the weight of an equal volume of air; an expression of the density of the vapor or gas. Materials lighter than air have vapor densities less than 1.0 (example: acetylene, methane, hydrogen). Materials heavier than air (examples: propane, hydrogen sulfide, ethane, butane, chlorine, sulfur dioxide) have vapor densities greater then 1.0.

Importance: All vapors and gases will mix with air, but the lighter materials will tend to rise and dissipate (unless confined). Heavier vapors and gases are likely to concentrate in low places - along or under floors, in sumps, sewers and manholes, in trenches and ditches - and can travel great distances undetected where they may create fire or health hazards.

Vapor Pressure

The pressure exerted by a vapor above its own liquid. The higher the vapor pressure, the easier it is for a liquid to evaporate and fill the work area with vapors which can cause health or fire hazards.

Venting

Emergency flow of vessel contents out of a vessel. The pressure is controlled or reduced by venting, thus avoiding a failure of the vessel by overpressurization. The emergency flow can be one-phase or multi-phase, each of which results in different flow characteristics.

ACKNOWLEDGMENTS

The American Institute of Chemical Engineers (AIChE) and the Center for Chemical Process Safety (CCPS) express their appreciation and gratitude to all members of the Engineering Design for Process Safety, Second Edition and their CCPS member companies for their generous support and technical contributions in the preparation of these Guidelines. The AIChE and CCPS also express their gratitude to the team of authors from Aon Energy Risk Engineering.

SUBCOMMITTEE MEMBERS:

Committee Chairman

, Pete Lodal

Eastman Chemical

Mark Davis

Eli Lilly

Americo Diniz

Braskem

Edward Dyke

Merck

Brad Fong

3M

S. Ganeshan

Toyo Engineering India Ltd

Bala Chaitanya Gottimukkala

CB&I Lummus

Chantell Lang

CB&I Lummus

Darrin Miletello

Bayer CropScience

Mikelle Moore

Buckman

Mike Moosemiller

BakerRisk

Perry Morse

DuPont

Keith Pace

Praxair

Jack Philley

Baker Hughes

Ravi Ramaswamy

Reliance Industries Limited

Ron Riselli

Nexen

Sheri Sammons

TPC Group

Narayanam Sankaran (Sank)

UOP / Honeywell

Kevin Shaughnessy

Dow Chemical

Gill Sigmon

Honeywell

James Slaugh

Lyondell Basell

Gary Solak

Bayer Material Science

Angela Summers

SIS-TECH Solutions

Scott Wallace

Olin

CCPS Staff Consultant

:

Dave Belonger

CCPS wishes to acknowledge the contributions of the Aon Energy Risk Engineering staff members who wrote this book, especially John Alderman, Christy Franklyn, and Donna Pruitt.

Before publication, all CCPS books are subjected to a thorough peer review process. CCPS gratefully acknowledges the thoughtful comments and suggestions of the peer reviewers. Their work enhanced the accuracy and clarity of these guidelines.

Although the peer reviewers have provided many constructive comments and suggestions, they were not asked to endorse this book and were not shown the final draft before its release.

Peer Reviewers

:

Zaheer Ahmed

Baker Hughes

Jeff Fox

Dow Corning

Stan Grossel

Process Safety and Design Consultant

Dave Krabacher

Cognis Corporation

Haluk Kopkalli

Honeywell Specialty Materials

Brook Vickery

Flint Hill Resources

FOREWORD

Engineers like to think of their discipline as a rigorous application of scientific and mathematical principles to the problem of creating a useful object. To a certain extent, this is an appropriate description of the tools of engineering – those techniques that we use to translate a concept in the mind of the designer into a physical object. But, where does that mental image of the object to be built come from? At its heart, engineering is intuitive, and an art form. The engineer / designer’s accumulated experience, and that of others, is applied to a defined problem. By intuitive and creative problem solving processes, the engineer develops and refines a conceptual design, and uses the mathematical and scientific tools of engineering to translate a mental concept into reality.