15 Hazop Study

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

HAZOP STUDY

SHEET 1 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 2 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

CONTENTS

1.0

Introduction

2.0

Guideline for HAZOP

3.0

Guide- Word HAZOP Methodology

-

APPENDIX A- COMMON HAZOP DEVIATIONS AND CAUSES

-

APPENDIX B- WORH SHEET REPORT

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 3 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

HAZOP STUDY 1.0

Introduction This work procedure has been prepared to provide a guideline for GUIDE-WORD HAZOP study based on HAZOP software (diadem's PHA-pro 5or 6). A HAZOP study identifies hazards and operability problems. A HAZOP study is a formal systematic procedure used to review the design and operation of a potentially hazardous process facility. HAZOP is based on the principle that several experts with different backgrounds can interact and identify more problems when working together than when working separately and combining their results. The HAZOP concept is to review the plant in a series of meetings, during which a multidisciplinary team methodically "brainstorms" the plant design, following the structure provided by the guide words and the team's experience. The primary advantage of this brainstorming is that it stimulates creativity and generates ideas. This creativity results from the interaction of the team and their diverse backgrounds. The best time to conduct a HAZOP is when the design is fairly firm. At this point, the design is well enough defined to allow meaningful answers to the questions raised in the HAZOP process. Also, at this point it is still possible to change the design without a major cost impact. However, HAZOP can be done at any stage of the design (Basic or detail design) after the design is (in that stage) nearly firm.

2.0

Guideline for HAZOP The following steps shall be followed in doing a HAZOP study:  Select the team  Obtain the necessary data (HAZOP DATA BASE)  Arrange the necessary meetings  Carry out the team review  Record the results It is important to recognize that some of these steps can take place at the same

CHAGALESH CONSULTING ENGINEERS time.

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 4 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

CHAGALESH CONSULTING ENGINEERS 2.1

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 5 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Select the team A team of people under the guidance of chairman or leader, who is experienced in the HAZOP methodology, performs the study. The team will consist of, as a minimum: -

Process engineer Safety engineer Mechanical/machinery engineer Instrument engineer Piping engineer QHSE representative Operations supervisor (if required) Maintenance supervisor (if required) Engineers from other disciplines (if required)

There will also be a HAZOP secretary responsible for recording the sessions using the HAZOP software provided. The team leader most important job is to keep the team focused on the key task: to identify problems, not necessarily to solve them.

In some situations, due to project requirements and/or other problems, HAZOP Study may be done by a third party (or company), or the chairman may be selected from outside of the contractor’s project team. Suitablity of the selected company or person for performing or leading the HAZOP Study should be checked by the process section (process PSL and process head section) and verified by the engineering manager, based on the audit form No. F/GE/29.

CHAGALESH CONSULTING ENGINEERS 2.2

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 6 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Obtain the necessary data (HAZOP DATA BASE) The data requirements associated with each unit are: -

2.3

General site layout drawing A list of all hazardous materials present onsite (raw materials, intermediate, by-products and final products) Process Flow Diagram (PFD) for each unit Piping instrumentation diagram (P&ID) for each unit Control system description Emergency Shut-down system (ESD) philosophy and/or diagram Vent and Blow-down system philosophy Drainage Philosophy Mechanical data sheets for the major vessels and equipment items (if required) Safety philosophies for leak detection, fire detection and protection, Emergency Plans and accident records

Arrange the necessary meetings Once the data have been assembled the team leader is in a position to plan meetings. The first requirement is to estimate the team-hours needed for the study. As a general rule, each individual part to be studied, e.g., each main pipe into a vessel, will take an average of fifteen minutes of the team time. For example, a vessel with two inlets, two exits, and a vent should take one and a half hours for those elements and the vessel itself. Thus, an estimate can be made by considering the number of pipes and vessels. Another way to make a rough estimate is to allow about three hours for each major piece of equipment. After estimating the team-hours required, the team leader can arrange meetings. Ideally, each session should last no more than three hours (preferably in the morning). Longer sessions are undesirable because their effectiveness usually beings to fall off. Under extreme time-pressure, sessions have been held for two consecutive days, but such a program should be attempted only in very exceptional circumstances, (for example, when the team is from out of town and travel

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 7 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

every day is not acceptable). With large projects, it has been found that often the team cannot carry out all the studies within the allotted time. It may therefore be necessary to use several teams and team leaders. One of team leaders should act as a coordinator to allocate sections of the design to different teams and to prepare time schedules for the study as a whole. 2.4

Carry out the team review The detail description of this step has been provided in chapter 3, GUIDEWORD HAZOP methodology.

2.5

Record the results It is essential that an adequate record of the HAZOP sessions are kept, both to ensure that any necessary HAZOP recommendations or actions can be properly followed up and to allow effective use of the generated HAZOP libraries for any subsequent study required. A secretary will be provided by chairman to attend and record all meetings. This Secretary will have good command of both the Farsi and English languages, some technical qualifications to fully understand the discussions, and who has gained experienced in the use of the software provided. Subsequent to the meetings a HAZOP report will be issued which contains all the Administration, Nodes, Deviations, Worksheets, Recommendations and Analysis Result, which are generated automatically by the software provided (diadem's PHA- PRO 5r6), together with the necessary back up information, and ranking of the Recommendations according to their importance. One sample of filled worksheet of this software which will be produced during HAZOP study are provided in appendix B. All documents used in the study, particularly the P&ID's, PFD's, etc., will be carefully filed for future reference.

CHAGALESH CONSULTING ENGINEERS

3.0

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 8 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Guide- Word HAZOP Methodology Guide Word Hazard and Operability (HAZOP) is a qualitative method that identifies design faults, potential hazards and operating problems. This technique applies guide words to process parameters to create deviations from the design intention. The deviations apply to specific items, known as nodes. Risk analysis use Guide Word HAZOP to identify process or operational hazards as well as unacceptable risk situations. This methodology is applied mainly to P&ID's, related drawings and specifications to analyze for hazards during most modes of operation. Using the approach requires a multi-disciplinary team with members experienced in HAZOP, plant design, operation and maintenance. Guide Word HAZOP is relevant for continuous processes, batch processes and written procedures, such as operating instructions. The technique is used for new designs, existing process, revamp cases and plant modifications.

Following paragraphs describe this methodology step by step: 3.1

Identify a NODE, which is a section of plant on the P&ID at which the process parameters are investigated for deviations. You should assign nodes on a functional basis to reflect a specific function. Most nodes will be of the line type, but other categories include vessels, compressors, tanks, reactors and so on. Typical examples of nodes include:  Transference or heating of a material  Increasing the potential energy by mechanical means such as a pump  Separation of phases You may find it beneficial to join several types of nodes to form a single compound node, such as line + pump + Heat Exchanger. Doing so may help you to avoid repetition and to maintain continuity and focus. The nodes are points where the process parameters (pressure, temperature, flow, etc.) have an identified design intent. Between these nodes are found the plant components (pumps, vessels, heat exchanger, etc.) that cause

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 9 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

changes in the parameters between nodes. While the study nodes should be identified before the meetings, it is to be expected that some changes will be made as the study progress due to the learning process that accompanies the study. It's better that the team leader establish nodes prior to any meeting. 3.2

Define the design intent (normal operating parameters and/or conditions) for each node. The intention defines how the plant is expected to operate in the absence of deviations at the study nodes. It is better to specify design conditions/parameters (design intents) before the meeting together with nodes definition. Like nodes it is to be expected that some changes will be made as the study progress.

3.3

Identify a deviation (or list all possible deviations) from design intent or operating conditions. This can be done by interactively applying guide words. The guide words shown in table 1 are the ones most often used in a HAZOP study.

Table 1- Overview of Guide Words

Guide word

Meaning

Deviation example

No, none

Negation of design intent No flow

More, high

Quantitative increase (above design intent)

More flow

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 10 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Less, low

Quantitative decrease (below design intent)

Less flow

Part of

Qualitative decrease (below design intent)

Part of stream composition is missing

More than, as well as

Qualitative increase (above design intent)

More components present than there should be (more impurities, contaminants)

Reverse

Logic opposite of design intent

Reverse flow

Other than, including sooner/later

Alternative mode (what else can happen)

Start-up, shut-down, power failure, leak, rupture and so on

Each guide word is applied to the process variables (parameters) at the point in the plant (node) which is being examined to create deviation, so: Guide word + parameter = deviation Guide words are applicable to both the more general parameters (e.g., react, transfer) and the specific parameters (e.g., pressure, temperature). With the general parameters, meaningful deviations are usually generated for each guide word; moreover, it is not unusual to have more than one deviation from the application of one guide word. For example, "More reaction" could mean either that a reaction take place at a faster rate, or that a greater quantity of product results. With the specific parameters, some modification of the guide words may be necessary. In addition, it is not unusual to find that some potential deviations are eliminated by physical limitation. For example if the design

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 11 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

intention of a pressure or temperature is being considered, the guide word "more" or "less" may be the only possibilities. There are other useful modifications to guide words such as:  SOONER or LATER for OTHER THAN when considering time.  WHERE ELSE FOR OTHER THAN when considering position, source, or destination.  HIGHER and LOSER for MORE and LESS when considering elevation, temperatures or pressures. When dealing with a design intention involving a complex set of interrelated plant parameters (e.g., temperatures, reactions rates, composition, or pressure), it may be better to apply the whole sequence of guide words to each parameter individually, than to apply each guide word across all of the parameters as a group. A deviation can be considered meaningful if it has a credible cause and can result in harmful consequences to production, personnel, the environment and/or equipment. It is better to define a preliminary list of deviations for each node before the meeting. It's clear that this list may change as the study progress. Common HAZOP deviations and causes are specified in appendix A.

CHAGALESH CONSULTING ENGINEERS 3.4

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 12 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Assign causes to each deviation For each deviation, list all possible causes for the deviation from the design intention. These are the reasons why deviation might occur. Once a deviation has been shown to have a credible cause it can be treated as a meaningful deviation. These causes can be hardware failures, human errors, an unanticipated process state (e.g., change of composition), external disruptions (e.g., loss of power), etc.

3.5

Assign consequences to each cause For each cause, identify the potential consequences. These are the results of the deviations should they occur (e.g., release of toxic materials). If you want, you can rank each consequence by frequency/likelihood in terms of severity for:  Fire  Explosion  Toxicity  Environmental release (leakage, spillage)  Personnel safety loss  Production loss  Capital loss Following is description of each value in Risk Ranking: U: N: C: A:

3.6

Unacceptable Not desirable, risk control measures to be introduced within a specified time period Acceptable with control, risk control measure are in place Acceptable, no risk control measures are needed

Assign safe guards to each cause For each cause, identify the safeguarding measure to prevent the cause from occurring or mitigate the associated consequences.

CHAGALESH CONSULTING ENGINEERS 3.7

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 13 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

Propose recommendations For each cause, propose recommendations intended to meet acceptable criteria for risk, production requirements and so forth. When suggesting recommendations, be sure to take into account the consequence(s) and the safeguard(s) currently in place.

3.8

Repeat steps 3 to 7 until all possible and applicable deviation for the specified node have been exhausted and the team is satisfied that all meaningful deviations have been discussed.

3.9

Mark in the master P&ID drawings the sections covered plus a reference of the recommendation(s) made.

3.10 Go back to step 1 and repeat the process for another section (node) of plant.

CHAGALESH CONSULTING ENGINEERS

INTERNAL WORK PROCEDURE ISSUED BY THE PROCESS SECTION

SHEET 14 OF 14 DATE : 30.07.84 REV. 0 NO.P/PR/35

APPENDIX A- COMMON HAZOP DEVIATIONS AND CAUSES Deviation Cause NO FLOW

REVERSE FLOW

MORE FLOW LESS FLOW MORE LEVEL LESS LEVEL MORE PRESSURE LESS PRESSURE MORE TEMPERATURE LESS TEMPERATURE COMPOSITION CHANGE MORE TIME LESS TIME WRONG TIME ABNORMAL OPERATION MAINTENANCE IGNITION SPARE EQUIPMENT SAFETY ENVIRONMENT

Blockage- wrong routing- incorrect slip plate- incorrectly fitted check valve- pipe rupture- equipment failure- incorrect pressure differential- isolation in error- etc. Defective check valve- siphon effect- incorrect pressure differential- 2 way flow- emergency venting- incorrect operationin line spare equipment- etc. Increased pump capacity- increased suction- reduced delivery head- greater density- exchanger tube leaks- cross connections open- control failures- etc. Line restrictions- filter blockage- defective pumps- vessel blockage- orifice plates- density or viscosity changes. Outlet blocked or isolated- inflow greater than outflow - control failure- instrumentation failure- etc. Inlet flow stops- leak- outflow greater than inflow - control failurefaulty level measurement- drainage- etc. Surge problems- connection to high pressure system - gas breakthrough (not vented) thermal overpressure- positive displacement pumps PCV open- etc. Vacuum conditions- condensation- gas dissolving in liquid restricted line/pump- leak- drainage- etc. Ambient conditions- tube exchanger failure- cooling lossdepressurization of liquefied gases - joule- Thomson effects- etc. Ambient conditions- reduced pressure – tube exchanger failure heating loss- control failure etc. Isolation valve leak- tube exchanger leak- phase change- wrong feed stock- inadequate QA- etc. Batch step(s) missed. Step does not occur when it should. Flow or activity occurs when it should not. Purging- flushing- start up- ESD- sampling- etc. Isolation failure- drainage purging- slip plates- access- trainingrescue- permit to work- lifting and handling- etc. Grounding arrangements – hot work- hot surfaces- auto – ignition- flame arrester failure- incorrect electrical classificati onetc. Installed/non installed - spare availability- specification changetest run of spare equipment- etc. Fire & gas detection- fire fighting response- ESD- CCTVtoxicity- emergency planning- noise- compliance with regulations/standards- etc. Ecological(physical & biological) degradation, Water, Air or Soil pollutions, socioeconomic impacts