During decommissioning, navigation risks don’t disappear just because an asset is nearing the end of its life. In many cases, they increase.

As permanent power is reduced, structures are modified, and site activity changes, offshore operators must continue to ensure assets remain clearly marked and identifiable to mariners. Choosing the right Aids to Navigation (AtoN) during decommissioning is critical – particularly when deciding between audible signals like foghorns and electronic aids such as racons.

This guide explains when a foghorn is typically required, when a racon is more appropriate, and how offshore operators often combine both during decommissioning projects, where reliability, reduced maintenance, and compliance remain essential.

Why Navigation Aids Matter During Decommissioning

Decommissioning is rarely a single, clean event. Assets often remain partially in place for extended periods, with changing profiles, temporary hazards and reduced onboard systems.

Structures may be cut down, modified, or left in transitional states for months, sometimes years, while work progresses. During this time, AtoN must continue to:

  • Warn mariners of structures and hazards
  • Clearly identify asset location and type
  • Perform reliably with minimal intervention
  • Remain compliant with applicable authority requirements

Crucially, decommissioning often takes place when permanent power has been scaled back or removed, access windows are limited, and offshore intervention is costly. This places far greater emphasis on robust, low-maintenance navigation aids that can operate unattended for long periods.

The Role of Foghorns in Decommissioning

Foghorns (or audible fog signals) provide sound-based warnings to vessels when visual identification alone may not be sufficient.

Where Foghorns Are Most Effective

Foghorns are typically specified where:

  • Visibility is frequently reduced due to fog, rain or snow
  • Assets sit in congested or high-risk navigation areas
  • Authority guidance requires an audible warning
  • Visual AtoN may be obscured by weather or background lighting

During decommissioning, foghorns can be particularly useful where temporary hazards remain present or where a structure’s visual profile has changed and may be less immediately recognisable to mariners.

Limitations to Consider

Foghorns also come with practical constraints, especially in late-life operations:

  • Sound propagation can be affected by wind and sea conditions
  • Power requirements are often higher than electronic aids
  • Maintenance and inspection access can be challenging

For these reasons, foghorns are rarely relied on in isolation during decommissioning and are more commonly used as part of a layered AtoN strategy.

The Role of Racons in Decommissioning

Racons (radar beacons) are electronic navigation aids that respond to a vessel’s radar signal, displaying a coded identifier on the radar screen.

Why Racons Are Well-Suited to Decommissioning

Racons are widely used during decommissioning because they:

  • Provide positive radar identification of an asset
  • Remain effective regardless of visibility or lighting conditions
  • Support mariner decision-making during complex operations
  • Perform reliably on reduced or alternative power systems

For assets undergoing change, such as partial removal, height reduction or reclassification, racons help ensure mariners can clearly identify what remains and where it is located.

Practical Benefits Offshore

From an operational perspective, racons are particularly well-suited to late-life projects because they offer:

  • Low ongoing maintenance requirements
  • Compatibility with solar and long-life power solutions
  • Strong alignment with remote monitoring systems
  • Clear audit trails for availability and performance

These characteristics make racons a common choice where long unattended operation and demonstrable compliance are required.

Foghorn vs Racon: Understanding the Difference

Foghorns and racons are not direct substitutes. They mitigate different navigation risks and support mariners in different ways.

Foghorns provide an audible warning that alerts mariners to the presence of a nearby hazard, particularly in poor visibility or high-traffic areas.

Racons provide electronic identification on radar, helping mariners confirm the nature and position of an asset.

In many decommissioning projects, the most effective approach is not choosing one over the other, but understanding which risk each aid is addressing.

Making the Right Choice: A Practical Decision Framework

When specifying AtoN for decommissioning, offshore operators typically assess risk rather than selecting equipment in isolation.

A foghorn is commonly specified where:

  • The asset is located in congested or high-risk waters
  • Persistent low visibility is expected
  • An audible warning is required by the local authority
  • Short-term or temporary hazards need immediate attention

A racon is commonly specified where:

  • A long unattended operation is required
  • Permanent power has been removed or reduced
  • Positive radar identification is essential
  • Monitoring and reporting are expected
  • Maintenance access is limited

In many cases, a combination of both is used to provide layered protection during different operating and visibility conditions.

Authority Expectations During Decommissioning

Most AtoN requirements during decommissioning are guided by international recommendations from the International Association of Marine Aids to Navigation and Lighthouse Authorities, supported by regional and national authorities.

During decommissioning phases, authorities typically place emphasis on:

  • Continued availability of navigation aids
  • Clear identification of remaining hazards
  • Reliability with reduced infrastructure
  • Demonstrable monitoring and reporting

In the UK, bodies such as the Northern Lighthouse Board and Trinity House often expect solutions that are appropriate for late-life conditions, where permanent power is unavailable, and intervention should be minimised. This frequently drives the use of racons, monitored lighting and long-life power systems, with fog signals specified where audible warning is still required following risk assessment.

How Wellhead Electrical Supplies Supports Decommissioning AtoN Projects

WES supports offshore decommissioning projects with a practical, compliance-led approach to Aids to Navigation.

We supply:

Our focus is on equipment that performs reliably in real offshore conditions – even as infrastructure is scaled back.

Planning Ahead for Decommissioning Navigation Safety

Decommissioning does not reduce responsibility for navigation safety – it changes how that responsibility must be managed.

The right AtoN approach during decommissioning is rarely about a single device. It’s about matching risk, authority expectations and late-life operating conditions with solutions that can perform reliably with minimal intervention.

By reviewing hazards, assessing visibility and access constraints, and specifying appropriate combinations of navigation aids, offshore operators can maintain compliance and reduce operational risk throughout the decommissioning lifecycle.

If you’re reviewing AtoN requirements for an upcoming decommissioning project, we can help assess options and identify fit-for-purpose solutions for late-life conditions. Contact us to find more.

 

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