HAZOP STUDY

A HAZOP survey is one of the most common and widely accepted methods of systematic qualitative hazard analysis. It is used for both new or existing facilities and can be applied to a whole plant, a production unit, or a piece of equipment It uses as its database the usual sort of plant and process information and relies on the judgment of engineering and safety experts in the areas with which they are most familiar. The end result is, therefore reliable in terms of engineering and operational expectations, but it is not quantitative and may not consider the consequences of complex sequences of human errors.

          The objectives of a HAZOP study can be summarized as follows:

1)                  To identify (areas of the design that may possess a significant hazard potential.

2)                  To identify and study features of the design that influence the probability of a hazardous incident occurring.

3)                  To familiarize the study team with the design information available.

4)                  To ensure that a systematic study is made of the areas of significant hazard potential.

5)                  To identify pertinent design information not currently available to the team.

6)                  To provide a mechanism for feedback to the client of the study team's detailed comments.

 A HAZOP study is conducted in the following steps:

Table 7.1: HAZOP Guide Words and Meanings

Guide Words	Meaning
No Less More Part of As well as Reverse Other than	Negation of design intent Quantitative decrease Quantitative increase Qualitative decrease Qualitative Increase Logical opposite of the intent Complete substitution

 7.1:HAZOP Study of Storage Tank for Ethylene Oxide

  A HAZOP study is to be conducted on ethylene oxide storage tank, as presented by the piping and instrumentation diagram shown in fig.

In this scheme, ethylene oxide is unloaded from tank trucks into a storage tank maintained under pressure until it is transferred to the process. Application of the guide words to the storage tank is shown in Table along with a listing of consequences that results from process deviation. Some of the consequences identified with these process deviations have raised additional questions that need resolution to determine whether or not a hazard exists.

Piping and instrumentation diagram

Deviations from operating conditions	What event could cause this deviation	Consequences of this deviation on item of equipment under consideration	Process indications
Level: Less More Temperature: Less More	Tank runs dry Rupture of discharge line V-3 open or broken V-1 open or broken Tank rupture (busting of vessel) Unload too much from column Reverse flow from process Temperature of inlet is colder than normal Temperature of inlet is hotter than normal  External fire	Pump cavitates Reagent released Reagent released Reagent released Reagent released Tank overfills Tank overfills Possible vacuum Region released Tank fails	LIA-1 FICA-1 LIA-1, FICA-1 LIA-1 LIA-1 LIA-1 LIA-1 LIA-1