Petrochemicals: Process Manufacturing

Closing the Gap Between Documented and Actual Process Safety

A petrochemical producer operating a single processing complex with several interconnected process units.

We revalidated the plant's HAZOP studies and rebuilt its management-of-change process, and no undocumented interlock bypass has been recorded since.

Undocumented interlock bypasses since the program was deployed

Situation

In the United States, OSHA's Process Safety Management standard (29 CFR 1910.119) requires a process hazard analysis to be revalidated at least every five years. It separately requires a management-of-change (MOC) procedure for modifications to process chemicals, technology, equipment and procedures. The two are meant to work together. MOC catches hazard-relevant changes as they happen, and the five-year cycle is the backstop.

At this plant the backstop had become the only control. A new bypass line, an upgraded control system and a revised operating envelope on one reactor train had all gone ahead without a HAZOP revalidation. Then a safety interlock, bypassed temporarily during a modification, was not restored on schedule. That near-miss put the problem in front of leadership.

What we did

We revalidated the HAZOP studies for the three process units most affected by undocumented changes. Operations and process engineering worked with us to reconstruct what had changed on the ground since the original studies were signed off. Then we rebuilt the change process itself.

Element of change control	Before	After
Hazard review on a change	A judgment call, often skipped	Mandatory for any hazard-relevant modification
Scope of the review	Full-facility HAZOP or nothing	Targeted to the affected node or system
Closing a change	Possible without process safety input	Process safety sign-off required
Interlock bypasses	Restoration left to the team doing the work	Trained authorization and restoration procedure

Impact

The documented configuration of all three units now matches what is installed.
The plant has completed its first full cycle in which a change triggered its own hazard review. The review is a scoped process hazard analysis, so it is proportionate enough to be used every time.
Since deployment, the plant has recorded no interlock bypass outside the documented procedure. The case study does not state how long that period is.

What made it work

A gate, not a judgment call

Revalidation alone would have fixed the studies and left the cause in place. Making the hazard review a step the change process cannot skip is what stops studies going stale between five-year cycles.

Scoping mattered too. A review limited to the affected node is small enough that engineers do not look for ways around it.

Results

HAZOP studies brought up to date for all three affected process units

A scoped hazard review now required before a hazard-relevant change can be closed

Operations staff trained on authorizing and restoring interlock bypasses

Engagement facts

Sector: Petrochemicals: Process Manufacturing
Practice area: HSE Advisory
Client profile: Petrochemical producer, single processing complex
Services: HAZOP revalidation, management-of-change redesign, operator training
Key phases: Three process units revalidated; first full change-triggered review cycle completed

This case study is a composite drawn from multiple engagements. Client details have been changed and combined to protect confidentiality, and figures are representative rather than attributable to any single client.