Hazop Procedure

THE PROCEDURE FOR HAZARD

AND OPERABILITY (HAZOP) STUDY

THE PROCEDURE FOR HAZARD AND OPERABILITY (HAZOP) STUDY



Table of Contents

1. PURPOSE ....................................................................................................................... 3

2. APPLICABLE CODES AND STANDARDS ...................................................................... 3

3. HAZOP STUDY TEAM COMPOSITION .......................................................................... 3

4. TECHNICAL INTRODUCTION ........................................................................................ 4

5. REFERENCE DOCUMENTS .......................................................................................... 6

6. ANALYSIS PROCEDURE ............................................................................................... 6

7. RISK CHARACTERIZATION ......................................................................................... 11

8. FORMS USED .............................................................................................................. 13

9. SCHEDULE AND LOCATION ....................................................................................... 14

ATTACHMENT : SAMPLE OF HAZOP WORKSHEET



1. PURPOSE

This procedure describes the procedure of the HAZOP (Hazard and Operability) Study.

The HAZOP yields a qualitative description of the hazards and operability problems,

provides ranking of hazardous situations and indicates recommendations for reducing or

eliminating hazards and operability problems in the plant.

2. APPLICABLE CODES AND STANDARDS

The following code and standards are referred to as useful guidelines in the application

of this procedure.

(1) QP.GDL - S - 001 : QP Guide for Hazard & Operability Studies

(2) OSHA Legislation on Process Safety Management of Highly Hazardous Chemicals

(29 CFR 1910.119)

(3) American Petroleum Institute (API) Recommended Practice No. 750

(4) Center of Chemical Process Safety (CCPS) of the American Institute of Chemical

Engineers (AIChE), Guidelines for Hazard Evaluation Procedures

3. HAZOP STUDY TEAM COMPOSITION

In performing a HAZOP Study, the proper selection of team participants is very

important. The study team should consist of personnel who are knowledgeable in the

process technology and experienced in the operations of the process. The team

should have the necessary technical expertise to answer most questions raised during

the review. The chairman will be independent of the Contractor and Company will

review and approve of his curriculum vitae prior to the HAZOP meeting.

The HAZOP Study team includes the following;

(1) Chairman who has experiences in leading HAZOP Study of similar plant

(2) Scribe

(3) Process Engineer who has experiences in design of similar plant

(4) Operating Engineer who has experience in operation of related plant

(5) Piping Engineer

(6) Electrical Engineer

(7) Mechanical Engineer

(8) Instrument Engineer



(9) Safety Engineer

(10) Environmental Engineer

(11) Licensor Representatives

(12) COMPANY Representatives

Of these personnel, several are often only part-time participants but remain on call for

assistance.

4. TECHNICAL INTRODUCTION

4.1 The HAZOP Study will be performed during the process plant’s detailed design or

during operating the existing process plant.

4.2 There are two principal advantages of using the HAZOP Study during the process

plant’s detailed design.

(1) It can identify potential hazards and operability problems at a time when they can

be corrected at minimal cost and disruption.

(2) It can help the development team identify and/or develop operating guidelines

that can be used throughout the life of process.

4.3 The HAZOP Study shall be performed based on the following sequence.

(1) The Piping and Instrument Diagrams (P&IDs) for HAZOP Study will contain all

requirements for Start-up, S/D, catalyst regeneration, Vendor, APC, LIMS, all

modes of operation and so on.

(2) P&IDs will be reviewed by COMPANY, CONTRACTOR, Licensors (if applicable)

(3) The comments of P&IDs review will be incorporated in the P&IDs.

(4) The HAZOP Study will be performed for these P&IDs, which are incorporated the

comments of P&IDs review, and necessary changes incorporated in the detailed

design.

4.4 This is a simple, structured methodology for hazard identification. It is an

investigation technique that is designed to inspire imaginative thinking (or

brainstorming) by a team of experts to identify hazards and operational problems

while examining a process or system in a thorough and systematic manner.



4.5 This involves a systematic, methodical examination of design documents that

describe the facility. This is performed by a multidisciplinary team to identify

hazards or operability problems by evaluating deviations from design intents.

4.6 As each hazardous situation or operability problem is identified, the potential

causes, effects and possible corrective/preventive measures will be listed in the

final HAZOP report.

4.7 In HAZOP Study, an experienced leader systematically steers the team through

the system components identified in the design documents by using a set of

“guide words” to identify deviations from the design intents of key parameters.

These guide words are used on specific, defined areas of the plant design(called

nodes) that encompass a common set of process parameters that are relevant to

the goals of the HAZOP Study.

4.8 A systematic method of identifying nodes is used on the P&IDs for the process

unit to focus the attention of the HAZOP team and to provide sufficient

documentation for later reviews. The team then identifies possible causes of

deviations, and the resulting consequences. Any realistic causes and

consequences are qualitatively prioritized, using a risk ranking matrix. Some

findings may result in corrective actions, and other findings may prove to be not of

concern at all, given the goals of the HAZOP Study.

4.9 A basic premise for a HAZOP Study is that the process does not have inherent

hazards or operating problems when the unit is operating with process parameters

within ranges specified by the unit design. These parameters are defined by the

basic design documents for the unit such as the process flow diagrams, P&IDs,

equipment specifications, operating procedures, etc. In other words, if there are

no deviations from the expected norm, by definition, there are no hazards or

operability problems.

4.10 A related premise for the HAZOP study is that the safety / environmental rules and

regulations are followed by operating and maintenance personnel. This means

that the facility safety features are not bypassed, or process guarantee are not

exceeded and maintenance is not performed without proper administrative

controls so that the facility does not endanger anyone. It also means that the

equipment is tested, inspected, and maintained according to approved policies

and that the operators are trained to operate the unit in accordance with approved

written operating procedures.



5. REFERENCE DOCUMENTS

The following documents or information are necessary to perform the HAZOP Study;

(1) Piping and Instrumentation Diagrams (P&ID)

(2) Process Flow Diagrams (PFD)

(3) Overall Plot Plan including existing facilities, Process Plot Plan & Offsite Plot Plan

(4) Process Description

(5) Codes, Regulations and Plant Design Criteria including design specification to be

applied.

(6) Material Safety Data Sheets (MSDS)

(7) Equipment Data Sheet

(8) Safety Valve Data Sheet

(9) Safety Valve Load Calculation Sheet

(10) Interlock Logic Description

(11) Hazardous Area Classification

(12) Cause & Effect Chart for process and Fire & Gas system

(13) Fire & Gas Detection Drawings.

(14) Tie-in Summary

(12) Operating Procedure

6. ANALYSIS PROCEDURE

The sequence of activities followed during a HAZOP Study is as follows.

6.1 Introduce Team Members : A short biographical sketch by each team member

that identifies the skills and experience that each brings to meet the expectations

of the study.

6.2 Conduct HAZOP Orientation

6.2.1 HAZOP Methodology

A presentation is made by the team leader of the methodology to be used in the

HAZOP Study. This establishes a common starting basis for the team that is

necessary to conduct an effective HAZOP Study. This is done by guiding the

team members through an example or two of a typical HAZOP session.



6.2.2 Purpose of HAZOP Study

A presentation of the overall purpose of the HAZOP Study is made to focus the

efforts of the team members.

6.2.3 Scope of HAZOP Study

For the established purpose of the HAZOP Study and the properties the

hazardous materials present, a general discussion is conducted of the hazards

present within the process and areas of the plant where hazards could exist.

6.2.4 Establish the Risk Ranking Matrix

The parameters of the risk matrix are discussed by the team for subsequent use

in classifying hazards identified during the HAZOP Study.

6.2.5 Process Description

The process engineer presents an overall explanation of the plant’s process so

that all team members have a clear understanding of the basic operations of the

plant. This also acquaints the team members with typical scenarios that may

lead to a hazardous condition, based on the limiting release rates or spill sizes.

6.3 Conduct HAZOP Study

The HAZOP Study sequence is presented in figure 1. A systematic node by node

review is performed of the systems and equipment contained within the HAZOP

scope. Nodes are selected in the sequence of the process itself. A sample of

specific guide word/parameter phrases or deviations used is given in Table 1.

Table 2 is the guide word/parameter deviation matrix provided to team members

during the study that reflects deviations in Table 1.

6.4 Issue Preliminary Data Reports

A draft, unedited listing of all node information developed to date during the

HAZOP Study is provided daily for use by management in tracking HAZOP

progress.



6.5 Issue an Interim HAZOP Report

An abbreviated report is prepared by the team leader and submitted immediately

following completion of the study. This report provides timely notification to

project management of any unacceptable hazards that were identified during the

HAZOP meetings.

6.6 Issue the HAZOP Report

This HAZOP report will be issued as a formal report after review and comment by

the other members. This report shall summarize as a minimum :

(1) Executive Summary

(2) Purpose of HAZOP

(3) Scope of HAZOP

(4) Methodology of HAZOP Study

(5) Process Description

(6) Safety Data for Materials used in the Plant

(7) Summary of Findings & Recommendations

(8) HAZOP Worksheets

(9) P&IDs marked HAZOP Nodes



Table 1. Deviation Listing

The following deviation will be used during the HAZOP study for each node identified on P&IDs.

Operating Deviations Other Deviations

More Flow Less Flow No Flow Back Flow Higher Pressure Lower Pressure Vacuum Higher Temperature Lower Temperature Higher Level Lower Level No Level Utility Failure

Wrong Percentage Contaminants Wrong Material Poor Separation Higher Reaction Rate Lower Reaction Rate Other Reactions Hardware Failure (H/Ex Tube rupture) (Sight-glass) (Gaskets) (Hoses) (Corrosion) (Single Valve Leakage)



Figure 1. HAZOP Study Sequence

1. Select P&ID.

2. Select study node (equipment, segment of lines and equipment) and identify on master drawing.

3. Define design intent using pertinent process parameters.

4. Select process parameter.

5. Select guideword described deviation in design intent.

6. Identify and record causes.

7. Identify and record consequences.

8. Evaluate and record severity of consequence (see

consequence severity table).

9. Identify and record safeguards or protection provided to reduce likelihood or severity of consequences.

10. Evaluate and record frequency of cause and consequences

(see likelihood table)

11. Record risk level (see risk ranking matrix table).

12. Record the recommendation to mitigate and prevent the consequences, if risk rank is 1 or 2.

13. Repeat for each guideword applicable to parameter.

14. Repeat for each parameter for study node.

15. Mark study node completed on P&ID when all appropriate

parameters considered.

16. Repeat for each study node.

17. Repeat for each P&ID.



Table 2. The Guide Word / Parameter Deviation Used in a HAZOP Study

Guide Word

Design Parameter

More Less None Reverse Part Of As Well As Other Than

Flow More flow Less flow No flow Back flow Wrong

percentage

Contaminant

Wrong material

Pressure Higher

pressure Lower

pressure Vacuum

Temperature Higher

temperature

Lower temperatu

re

Mixing Excessive

mixing Poor

mixing No mixing Foaming

Level Higher level

Lower level

No level

Reaction Higher

reaction rate

Lower reaction

rate

No reaction

Reverse reaction

Incomplete reaction

Side reactions

Wrong reaction

Time Too long Too short Wrong time

Sequence Step too

late Step too

early Step left

out Step

backwards

Part of step left

out

Extra action

included

Wrong action taken

Other parameters : Hardware Failure ; pH ; heat capacity ; number of phases ; flash

point ; viscosity ; static charge ; specific concentration ; etc.

7. RISK CHARACTERIZATION

7.1 Risk Ranking

During the initial stages of the HAZOP study, Team leader establishes a risk-

ranking matrix with severity rankings and frequency rankings to allow for a

qualitative assessment of the consequences of each hazard. This matrix allows

the HAZOP team to screen each identified hazard and to assign a ranking and

recommend suitable measures to eliminate/mitigate high ranked hazards.

To accomplish this qualitative assessment of risk, each hazard event is ranked

through a team consensus judgment in two ways : first, deciding the severity of

the consequences of the event, and second, deciding the expected frequency or

likelihood of the scenario resulting in the consequences identified for the hazard.



Table 3 presents the consequence severity and event likelihood used in ranking

the hazards found in HAZOP Study performed. Table 4 portrays how the

relationship between severity and likelihood rankings is used to assign risk

rankings to each hazard, and risk rank definitions used in ranking the hazards

found in the HAZOP Study.

7.2 Severity and Likelihood

To establish the severity of the consequences of an event, the HAZOP team’s

familiarity with the process is used to estimate the consequence severity for the

potential of worker injury and/or death from toxic exposure, fire or explosion. In

assigning a frequency to the hazard scenarios, the team uses operational and

maintenance experience to recall similar process deviations and excursions,

especially those that required immediate operator’s action for mitigation.

Table 3. Assignment of Severity and Likelihood Categories

Consequence Severity Category

Public Worker Property

A Major release of AHM Loss of life Major fire or explosion and/or loss of production

B Moderate release of AHM Severe injury or disability

Moderate fire or explosion and/or loss of production

C Small release or AHM Loss time injury but no disability

Small equipment damage or loss of production

D Very small release of AHM with no significant offsite impact

First aid injury but no disability

Minor equipment damage or minor loss of production

E Not a significant hazard Not a significant hazard

Not a significant hazard

AHM : Acutely Hazardous Material

Consequence Likelihood Category

1 Likely; may occur as often as once in an operating year in any similar plant

2 May occur; frequency between once a year and once in 10 operating years or at least once in 10 similar plants operated for 1 year

3 Not likely; frequency between once in 10 years and once in 30 operating years or at least once in 30 similar plants operated for 1 year

4 Very unlikely; frequency of less than once in 30 year or less than once a year in 30 similar plants operated for 1 year

5 Not probable



Table 4. Risk Ranking Matrix

Risk Categories

Severity of Likelihood of Consequence

Consequence

1 2 3 4 5

A 1 1 2 3 NP

B 1 2 3 4 NP

C 3 3 4 4 NP

D 4 4 4 4 NP

E NH NH NH NH NH ※ NH (No Hazard), NP (No Probable)

Risk Decision Criteria

Risk Rank

Recommendation

1 Unacceptable - should be mitigated to risk rank 3 or lower as soon as possible

2 Undesirable - should be mitigated to risk rank 3 or lower within reasonable period

3 Acceptable with controls - verify that procedures, controls, and safeguards are in place

4 Acceptable as is - no action is necessary

7.3 Recommendation

HAZOP Study team shall recommend addition, deletion or modification to be

made in plant for mitigating or eliminating the consequences of hazard events

identified during the HAZOP Study.

8. FORMS USED

8.1 Microsoft Excel program will be used for recording and documenting the HAZOP

Worksheets.

8.2 HAZOP Study information is recorded onto Worksheets (a sample Worksheet is

attached), showing the deviations resulting from the combinations of guide words

and process parameters, causes and any resulting consequences, risk ranking,

and suggested actions to prevent or mitigate the consequences. Each

Worksheet has a banner at the top that identifies the company, facility, date of the

review session, the node and parameter reviewed, and the design intention of the

Incre

asi

ng

Increasing



process parameter. The drawings are identified in the node description.

8.3 The HAZOP team shall identify possible means of reducing the severity or

likelihood associated with a deviation, or a possible plant improvement. In

addition, the team indicates the organization or group that shall be responsible for

implementing the recommendation in the “By” column.

8.4 The “Recommendation” column is also used to identify additional information

needed for completing the review of a particular deviation. Wherever applicable,

consequences of a particular deviation are worded such that obtaining the

information would confirm the scenario.

8.5 The “Comments” column is used to record drawing corrections that are required

for evaluation of the node and to document any assumptions made by the team in

developing the HAZOP scenarios.

9. SCHEDULE AND LOCATION

The HAZOP Study will be performed on all P&IDs at CONTRACTOR’s offices, Seoul,

Korea. The schedule of HAZOP Study is as follow:

HAZOP for Utility & Offsite : May 17, 2004 ~ May 21, 2004

Wrap up meeting for Utility & Offsite : May 24, 2004

HAZOP for Process 1 & 2 : May 31, 2004 ~ June 11, 2004

Wrap up meeting for Process : June 14 ~ 15, 2004

ATTACHMENT 1 : Sample of HAZOP Worksheet

Unit Area 3 Unit 64 Kerosene/ Gas Oil Hydrotreater Unit P&ID No. 7J48N-64-00-30-003, 7J48N-64-00-30-017, 7J48N-64-00-30-018 Node P64-3 Description Reactor charge heater (6401B) Date : 24. July. 1999

Deviation Cause Consequences S Safeguard L R Recommendations Comments By

Flow To use approximately approximately 1,350 Nm3/hr fuel gas.

More Flow (Fuel gas)

PV-009 sticks open, mismanaged open or bypass mismanaged open or TIC-008 malfunctions.

Increased heater firing. Possible tube damage. Potential heater fire. Increased coking and possible catalyst damage in reactor.

A TAH-009A/B. TAH-055/056 (skin temperature). TI-053. FAH-036 (fuel gas line). Multiple reactor temperature indicators.

4 3 See previous recommendation for multiple thermocouples in Node 1.

More Flow (Pilot) PCV-001 malfunctions or misoperated.

Possible pilot flameout. Potential heater explosion at start-up.

A BAL-001A-C. Start-up procedure. PI-067.

4 3

Less Flow (Fuel gas)

PV-009 fails closed, sticks closed, mismanaged closed or manual valve mismanaged closed or TIC-008 malfunctions or XV-002/065 fails closed.

Reactor upset. Off-spec products. Possible flameout.

C PALL-064. FAL-063. TI-009A/B. Multiple reactor temperature indicators. Valve position indicator for XV-002/065.

3 4

Less Flow (Fuel gas)

XV-068/ 069 fails open. Fuel gas vented to atmosphere. C Valve position indicator. 3 4 Consider locating vent downwind of ignition sources. Also consider a hydrocarbon detector.

LGEN

Less Flow (Pilot) PCV-001 malfunctions or misoperated or manual valve or strainer plugging or XV-001/070 fails closed.

Possible pilot flameout. Heater shutdown.

C PALL-057. BAL-001A-C. Start-up procedure. PDI-138. Valve position indicator for XV-001/070.

2 3 Consider a low pressure alarm on PI-067.

LGEN

Wrong Flow (Nitrogen)

XV-066 fails open. Loss of main burners. Heater shutdown. Possible backflow of nitrogen to fuel gas drum. Upset in entire fuel gas system.

C Valve position indicator. 3 4 Consider a restriction orifice (RO) to restrict nitrogen pressure to prevent backflow.

LGEN

SAMPLE

Documents

Hazop Procedure