Essential services are those necessary for the propulsion and safety of the unit, such as the following:
- Electric propulsion equipment.
- Thruster systems for dynamic positioning.
- Thruster systems for positional mooring.
- Abandonment systems dependent on electric power.
- Ventilation systems for hazardous areas and those maintained at an overpressure to exclude the ingress of dangerous gases.
- Wellhead control and disconnection systems dependent on electric power.
- Electric starting systems for oil engines.
Other items as given in Pt 6, Ch 2,1.6.1 of the Rules for Ships.
Source: Rules and Regulations for the Classification of Mobile Offshore Units, Part 6, Control and Electrical Engineering, June 2013, Lloyd’s Register, Global Standards