CHAPTER 8

HAZOP STUDY OF STRIPPER

SUMMARY

In this chapter, it reviews about the hazop study of stripper. It describes the

parameters need to be used and control during the process begins. HAZOP is a formal

procedure that offers a great potential to improve the safety, reliability and operability

of process plants by recognizing and eliminating potential problems at the design

stage. It is not limited to the design stage, however. It can be applied anywhere that a

design intention (Perry’s Handbook, 1998). When using the operability study

technique to vet a process design, the action to be taken to deal with a potential hazard

will often be modification to the control system and instrumentation, the inclusion of

additional alarms, trips or interlock. If major hazard are identified, major design

changes may be necessary, alternatives processes, material and equipment. In order to

have a safe process successfully producing to specification to the required product, a

sound control system is necessary but not sufficient(Coulson & Richardson’s, 1999).

8.1 INTRODUCTION

In this project, the safety procedure will be used to study the safety of the plant

designed. HAZOP study is a structured and systematic examination of a planned or

existing process or operation in order to identify and evaluate problems that may

represent risks to personnel or equipment, or prevent efficient operation. This

procedure is preferred since it is a formal systematic examination of a processing

plant for identifying hazards, failure and operability problems and assessing the

consequences. This leads to fewer lapses in safety, quality and production provided

that the plant is installed according to the design and maintained in appropriate

condition. A HAZOP is carried out as a team activity. The HAZOP can also be used

as a check on the operability of an existing plant. The procedure for a HAZOP study

is to apply a number of guide words to various parts of the process design intention,

which tells us what, the process is, expected to do.

The advantages of HAZOP study to the design application:

Early identification of problems areas when conceptual design stage.

Identifies need for emergency procedures to mitigate.

Provide essential information for safety case, such as on the hazards identified

and effectiveness of safety systems.

Through examination of hazard and operability problems when applied at

detailed stage.

Meets legislative requirements.

Identifies need for commissioning, operating and maintenance procedures for

safe and reliable operations.

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8.2 Parameters and guide words

The key feature is to select appropriate parameters which apply to the design

intention. These are general words such as flow, temperature, pressure, level, time,

concentration and reaction. It can be seen that variations in these parameters could

constitute deviations from the design Intention. A set of guide words to each

parameter for each section of the process was applied in order to identify deviations.

These guide words are given below and are applied to the stripper unit operations to

be considered.

Guide Word Meaning Comment

No or NotThe complete negation of

these intentions

No part of the intentions is

achieved but nothing else

happens.

More or LessQuantitative increases or

decreases

These refer to quantities

and properties such as flow

rate and temperature as

well activity likes “HEAT”

As well as A qualitative increases

All the design and

operating intentions are

achieved together with

some additional activity.

Part of A qualitative decreaseOnly some of the attention

achieved; some are not.

The following words are used in a special way, and have the precise meanings

given below:

i. Intention: the intention defines how the particular part of the process was

intended to operate and the intention of the designer.

ii. Deviations: these are departures from the designer’s intention which are

detected by the systematic application of the guide words.

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iii. Causes: reasons why, and how, the deviations could occur. Only if a

deviation can be shown to have a realistic cause is it treated as meaningful.

iv. Consequences: the results that follow the occurrence of a meaningful

deviation.

The table below shows the typical HAZOP process parameter that could

be considered during the measurement of the HAZOP study.

Typical Hazop Process Parameter

Pressure

Temperature

Flow

Level

Time

Composition

pH

Reaction

Heating

Cooling

Mixing

Addition

Data

Information

Separation

Viscosity

Voltage

Frequency

Speed

Density

Solubility

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Type of vessel: Stripper

Temperature: 180⁰C

Pressure: 2.75Pa

Guide

Word

Deviation Possible Causes Consequences Actions

Required

None No Flow - No flow in

stream

coming to

the column

- Quality and

amount of

product will

suffer.

- Install low

level

alarm

- Line

fracture

- Accidental

discharge to

the

environment

(aromatics

are

flammable

material).

- Plant shut

down.

More

of

Flow - LCV fails

open in

error

- Overfills

- Incomplete

separation of

non-

aromatics

from solvent

+ aromatics

- Install

high level

alarm and

check

sizing.

Pressure - Isolation

valve close

in error

- Full pump

delivery

- Isolation

valve

close in

error

Temperatu

re

- Higher

pressure in

transfer

- Degradation

of the solvent

quality will

- High

Temperat

ure Alarm

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line become

significant

ms.

(HTA).

Less of Flow - Leaking

flange of

valve

- Material

discharge to

the

environment

- Isolate

- that part

of the

plant

Others Maintenan

ce

- Equipment

Failure

- Line cannot

be

completely

drained or

purged

- Install

alarms.

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REFERENCES

Charles A.Wentz, Safety, Health, And Environmental Protection, McGraw Hill, 1998

Coulson and Richardson’s. Chemical Engineering Design, Volume 6. Butterworth

Heinemann. 2000.

Green W. Don & Perry Robert H. Perry’s Chemical Engineers’ Handbook. Seventh

Edition Kansas. McGraw Hill, 1997.

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