Trencher angle inadvertently altered
- Safety Flash
- Published on 17 March 2020
- Generated on 26 December 2024
- IMCA SF 10/20
- 3 minute read
What happened?
During offshore trenching operations, the ROV pilot unknowingly made contact with the control joystick, inadvertently raising the cutting wheel and thereby decreasing the cutting depth.
During offshore trenching operations, the ROV pilot unknowingly made contact with the control joystick, inadvertently raising the cutting wheel and thereby decreasing the cutting depth. No equipment or permanent material damage occurred.
The pilot inadvertently operated the tool tilt function by making accidental contact with the joystick control.
The subsea trenching tool was lifted to 4 degrees, which raised the tool depth from 1.17 metres to 1.06 metres, resulting in the depressor depth being reduced.
This went unnoticed for approximately 7 minutes while the shift handover was taking place and equated to 27 metres of travel along the product.
What went wrong?
- The pilot inadvertently made contact with the trencher control joystick.
- The joystick and software design did not include controls to reduce the possibility of accidental joystick activation (e.g. joystick lock, dead-man switch).
- The tooling alarm tolerance range was set too broad (-0.2° to +0.5°).
- Trenching operations were not stopped to complete the shift handover.
- The pilot/s did not notice the change to the trencher angle as they were distracted by both the shift handover and the reboot of a crashed control computer which was underway at the time.
Actions
Immediate preventative actions were put in place, which included change in the alarm tolerance with trenching operations ceased during shift handovers and the operating panels being set to maintenance mode, so the joysticks are deactivated.
- Although this alert focused on a trencher the findings are transferable to a wide range of equipment; therefore a review of equipment controls (such as joysticks) that could be inadvertently operated, or activated unknowingly, without an audible and/or visual alarm or joystick lock capability should be carried out.
- Consider carefully your method of handovers during live operations and the implications of reduced focus on the activity during this time.
- Ensure that personnel involved in operations have access to procedures, manuals and have demonstratable awareness training of associated equipment and processes.
- Consider change of controls, processes, procedures and physical layout of control systems that would prevent a similar incident.
Members may wish to refer to:
- Case study – Switching from auto DP to IJS (independent joy stick) mode caused loss of control
- Dropped object fell from crane – Poor communication/lack of awareness/control of work
- Accidental activation of emergency stop during saturation diving operations
- Near miss: emergency stop pressed accidentally
IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of the entire offshore industry.
The effectiveness of the IMCA Safety Flash system depends on the industry sharing information and so avoiding repeat incidents. Incidents are classified according to IOGP's Life Saving Rules.
All information is anonymised or sanitised, as appropriate, and warnings for graphic content included where possible.
IMCA makes every effort to ensure both the accuracy and reliability of the information shared, but is not be liable for any guidance and/or recommendation and/or statement herein contained.
The information contained in this document does not fulfil or replace any individual's or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.
Share your safety incidents with IMCA online. Sign-up to receive Safety Flashes straight to your email.