When is a HAZOP become necessary for an existing plant?

Many industrial plants are operated successfully for many years. During this time, sensors and pumps are replaced, piping is modified, control systems are modernized, and entire plant components are optimized. Each individual change has clear objectives: to make the plant more reliable and efficient and to ensure its long-term viability.  

However, as a facility ages, a crucial question often arises: Does the facility’s safety assessment still reflect its current condition?
Especially with older existing plants, it becomes apparent that the original design and the plant’s current condition no longer match in many respects and details. Components, sensors, and actuators have been replaced, processes have been adapted, and the documentation has not always been fully updated to reflect these changes. Older plants often lack the documentation required for a complete HAZOP, or the documentation only partially reflects the plant’s current condition.

This issue comes into focus, at the very latest, when major renovations are planned, a safety inspection is due, or authorities and experts require documentation.

Not every change should be classified in the same way

In practice, terms such as “replacement,” “modernization,” “optimization,” and “retrofit” are often used interchangeably. From a safety perspective, however, these measures can have different implications and must be handled accordingly.

From a safety perspective, replacing components (e.g., a pump) with technically equivalent models or replacing a measuring device as part of routine maintenance must be assessed quite differently than, for example, the integration of an additional heat exchanger, the adjustment of operating parameters, or changes to safety-related control functions.

The more profound the impact of a change on existing processes or safety functions, the more important it becomes to consider how it affects the safety of the entire plant. 

There is no one-size-fits-all answer as to which measures are necessary. Rather, a project-specific assessment is required that takes into account both the technical changes and the applicable regulatory framework.

Does that mean a full HAZOP must always be conducted? The short answer is: No.

Not every change requires a complete reassessment of the entire system.

It is often sufficient to conduct a targeted analysis of the affected area of the plant and to assess the impact on adjacent systems. A partial HAZOP, for example, may be an appropriate approach when changes are limited to clearly defined areas.

The situation may be different if numerous modifications have accumulated over many years or if there is no comprehensive safety assessment of the entire facility. In such cases, a more comprehensive analysis may be advisable in order to evaluate the facility’s current condition in a structured manner. The decisive factor here is not the scale of an individual change, but rather its impact on the facility’s safety concept.

The biggest challenge

In our experience, the real challenge with existing facilities often lies not in conducting the HAZOP itself, but rather in the preparation phase.

• Are the existing R&I flow diagrams up to date?
• What changes have been implemented in recent years?
• Which safety features have been modified?
• What documentation is actually still available?

Particularly in the case of systems that have been optimized and adapted over decades, information is often scattered across various documents or exists only in the tacit knowledge of employees.

For this reason, a HAZOP for existing facilities often begins with a joint assessment of the current status. The goal is to document the actual condition of the facility, as well as the availability and currency of the associated documentation, as completely as possible, and to use this information to determine an appropriate scope for the analysis.

A HAZOP relies on people’s knowledge

No documentation can replace the knowledge of those who operate a facility on a daily basis.

That is why successful HAZOP workshops bring together different perspectives: operations, maintenance, process engineering, instrumentation and control, and project planning. Only through joint discussion can a complete picture of the plant emerge.

Particularly with existing facilities, it is often the case that many years of operational experience provide valuable insights that would not be apparent from the plans alone.

Our Approach at CONENGA

Every existing plant has its own history. That’s why there is no simple, one-size-fits-all solution—but there is a clearly structured approach based on experience.

Our initial goal is to work with the operator to understand what the actual task entails:

• What changes were made?
• What documentation is already available?
• What question should be answered?
• What scope of examination is reasonable and appropriate?

Based on this, we work with our clients to design the process—from preparation and facilitation of the HAZOP analysis through to implementation and transparent documentation of the results. We tailor the roles to the client’s existing capabilities, thereby ensuring that resources are used as efficiently as possible.

We place particular emphasis on a pragmatic approach. Our focus is not on conducting the most extensive investigation possible, but rather on a structured and transparent assessment that is tailored to the specific facility and project and makes the best possible use of our existing expertise.