Lesson Learned: Software Updates Are Crucial for PRS Reliability

By
Mfame Editor
-
12

  • A PSV lost all position reference systems (PRS) during a cargo operation, causing minor contact with an offshore installation.
  • Root causes included degraded PRS signals, software errors, and operational oversights.
  • Improved PRS setup, adherence to guidelines, and enhanced training are essential to prevent future incidents.

During a routine cargo operation at a North Sea offshore installation, a Platform Supply Vessel (PSV) lost Dynamic Positioning (DP) references, resulting in minor vessel and installation damage. There were no injuries or environmental harm, but the incident underscores critical gaps in system reliability and operational compliance, reports MSF.

Incident Overview

The PSV operated under DP Class 2 with CyScan unavailable and functioning under an Operational Risk Assessment (ORA) and amended Activity Specific Operating Guideline (ASOG).

  1. Initially, DGNSS signals were unstable.
  2. A RadaScan responder was deployed but malfunctioned in “multi-target mode.”
  3. The Dynamic Positioning System (DPS) entered Dead Reckoning (DR) mode, inaccurately estimating the vessel’s position and propelling it toward the installation.
  4. Despite the DPO’s intervention, the vessel made contact with a jacket leg due to momentum, swell, and reduced thrust.

Why It Happened

PRS Degradation:

  1. DGNSS signals degraded due to satellite signal blockage by the platform.
  2. Both DGNSS relied on corrections from the same satellite.
  3. RadaScan malfunctioned in multi-target mode due to software errors.

Operational Oversights:

  1. CyScan had been unavailable for five months without resolution.
  2. The Master was not informed of PRS issues per ASOG guidelines.

System and Training Gaps:

  1. DPS entered DR mode, with time-limited accuracy.
  2. Inadequate DP training and risk assessments exacerbated the situation.

Consequences

Damage: Minor damage to the vessel and installation.

Operational Disruption: The vessel had to exit the installation’s 500m zone for assessment.

Safety Risks: Increased collision risk highlights the need for robust PRS management.

Precautions

Ensure three independent PRS systems for DP Class 2/3, with varied measuring principles.

Regularly upgrade RadaScan and other PRS software to address known issues.

Use reliable PRS signals (e.g., DGNSS quality >20%) for critical operations.

Recommendations

Training & Drills: Regular DP emergency and failure response drills.

ASOG Compliance: Ensure the Master is informed of PRS issues and status changes.

Positioning Best Practices: Prefer drift-off positioning where feasible and conduct risk assessments for drift-on operations.

Equipment Redundancy: Maintain and promptly resolve PRS equipment failures.

Did you subscribe to our daily Newsletter?

It’s Free Click here to Subscribe!

Source: MSF