HAZOP (Hazard and Operability) study

HAZOP (Hazard and Operability Study) is the prefered method for systematic hazard identification of process installations. The risk identification is a standard part of a safety management system.

The HAZOP method

IEC 61882 HAZOP standard
HAZOP standard (IEC61882)

The HAZOP method (Hazard and Operability Analysis), also called hazard identification, failure analysis, safety study or HAZID (Hazard Identification), is the standard method for identifying and evaluating process deviations. The HAZOP standard (standard IEC 61882) is usually followed.

The HAZOP method works with guide words for the different process parameters (for example: more pressure, less temperature). The method comes from the chemical industry and was introduced to ICI by Bert Lawley in 1974.

Most companies in the process industry require a HAZOP to be performed at the design stage and upon changes in the installation (Management of Change). HAZOPs are also performed periodically for existing installations.

Knowledge and experience in applying the HAZOP method and the ability of the chairman to make the team think outside of the usual thinking patterns are essential for the desired result of the HAZOP study.

Old HAZOP (1985)
Old HAZOP from 1985.

Hazop preparation

For the execution of a good HAZOP, a good preparation is important. The following points are important:

HAZOP node
The installation is divided into studie sections (nodes)
  • Determine the scope of the HAZOP. For example, a new installation /project or a periodic HAZOP.
  • Put together a multidisciplinary HAZOP team.
  • Determine the HAZOP chairman.
  • Ensure as-built or ready for construction design drawings (P&IDs)
  • Divide the installation to HAZOP’s into study parts (nodes).
  • Determine the relevant parameters such as: flow, pressure, temperature, level, etc.
  • Determine the relevant guide words such as: more, less, reversed, high, low, etc.
  • Make sure that important information is easily and quickly accessible during the HAZOP. Think of information m.b.t.. chemicals (Chemical maps and SDSs), incident reports, information m.b.t. process automation, photos of the installation, design data, etc.

The HAZOP session

On the basis of the design drawings (P&IDs), certain nodes and the parameter/guide word combinations, the HAZOP is used to look for deviations that can lead to dangerous and/or undesirable situations. Among other things, you can talk about Loss Of Containment scenarios.

HAZOP worksheet
HAZOP worksheet

For each node the purpose (design intent) of the specific part of the installation is determined. Next, the parameter/guide word combinations are used to investigate which deviations can occur and what the possible causes and consequences are. The deviations, causes and possible consequences are documented in the HAZOP worksheets. If relevant, existing measures (safeguards) are described and recommendations are made where necessary.

The results of the HAZOP sessions are presented in a report that includes the worksheets and a list of recommendations.

Multidisciplinary team

What ensures that a HAZOP study is well executed? Not the HAZOP software or the size of the HAZOP team. A HAZOP study falls or falls among the HAZOP participants who are part of the HAZOP team.

An experienced operator, the process engineer who knows all the ins and outs of his process, the maintenance engineer with knowledge and experience of the materials, pumps, appendages etc. of his installation. Supplemented by skilled engineers from other disciplines. A safety expert (HSE) with knowledge of the substances used, knows about any incidents, contacts with the government etc.

Of course, a competent and experienced chairman (or facilitator) should not be missed. He must maintain the balance between undisturbed brainstorming and progress, achieving the right detail and working with the HAZOP team to identify potential hazards and objectify gut feelings.

HAZOP worksheet inclusief risicobeoordeling
HAZOP worksheet including risk assessment.

It is wise to also assess the risks of the identified scenarios during a HAZOP study. Carrying out a risk assessment determines the need for (further) protections and their necessary reliability.

Nowadays, the risk assessment is often carried out using the LOPA methodology in combination with, for example, a risk matrix. The framework for this is set in the LOPA expenditure of CCPS.

An alternative method is SIL classification using a risk graph.

Consiltant BV

Consiltant supplies experienced and knowledgeable HAZOP facilitators. Our employees can guide you throughout the HAZOP process. Consiltant prefers to use HAZOP Manager, Lihou Technical Software Services software package to facilitate HAZOP studies and other equivalent identification and evaluation studies.

Consiltant BV has extensive experience with various different types of processes and installations. Examples are:

  • Hydrogen installations (including PEM and alkaline electrolysers)
  • Biogas installations (i.e. sewage treatment plants)
  • Membrane installations (i.e. food industry)
  • CIP- installations (i.e. food industry)
  • Storage and distribution of (dangerous) chemical substances
  • Utilities (including steam systems, cooling towers and ammonia cooling installations)
  • Installations with solid substances (risk of dust explosions)
  • Various chemical processes
  • Various pilot projects and R&D projects
  • Sectors:
    • Chemical industry
    • Oil & gas, production and storage companies
    • Utilities companies
    • Food industry
    • Automotive industry
    • Rail infrastructure