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Offshore, OVID & DP Safety · MSC.1/Circ.1580 & SOLAS II-1/3-13

Offshore DP Operations (MSC.1/Circ.1580), ASOG / CAMO & Anchor Handling Winch Safety Guide

Whether you operate a DP2 Platform Supply Vessel alongside a North Sea rig, a DP3 subsea construction / walk-to-work vessel, or an Anchor Handling Tug Supply (AHTS) vessel running rig moorings, OCIMF OVID (OVIQ4), IMCA eCMID and Port State Control inspectors scrutinise your FMEA proving trials, ASOG tables, Position Reference Systems and SOLAS II-1/3-13 anchor handling winches. Here is the complete regulatory and operational guide.

Updated · Written by SeaReady in our own words. Not affiliated with OCIMF, RightShip, CDI, any MoU or any administration — always check the current official documents.

1. IMO MSC.1/Circ.1580 & MSC/Circ.645: DP Equipment Classes 1, 2 & 3

Dynamic Positioning (DP) vessels are governed at the IMO level by IMO MSC/Circ.645 (for DP vessels constructed on or after 1 July 1994 and before 9 June 2017) and IMO MSC.1/Circ.1580 (2017 Guidelines for Vessels and Units with Dynamic Positioning (DP) Systems, for vessels constructed on or after 9 June 2017, with operational, training and survey guidance widely applied across the offshore fleet alongside IMCA M 103, M 117, M 182 and M 220).

DP Equipment ClassWorst-Case Single Fault Tolerance (MSC.1/Circ.1580 § 2.2)Power, Thruster, Control & PRS Redundancy
DP Equipment Class 1Loss of position and/or heading may occur in the event of a single fault (MSC.1/Circ.1580 § 2.2).Single DP control computer permitted; no power/thruster redundancy required; at least two independent Position Reference Systems (PRSs) recommended.
DP Equipment Class 2No loss of position and/or heading in the event of a single fault in any active component or system (generators, thrusters, switchboards, remote-controlled valves, computers, PRSs).Redundant power system (divisible into ≥ 2 systems by bus-tie breakers; may operate with closed bus-ties only if FMEA-proven and class-tested not to propagate faults), redundant thrusters after worst-case failure, dual DP control computers, online Consequence Analysis, and ≥ 3 independent PRSs using at least 2 different measurement principles.
DP Equipment Class 3No loss of position and/or heading in the event of any single fault in active OR static components, including complete loss of any single compartment due to fire or flooding.Physical separation by A-60 fire divisions and watertight bulkheads across generators, switchboards, thrusters, cable routing, piping and sensors; ≥ 3 PRSs (at least 1 in a separate A-60 compartment); plus an independent Backup DP Control Station in a separate A-60 compartment.

2. FMEA Proving Trials, CAMO, TAM & Activity-Specific Operating Guidelines (ASOG)

Under IMO MSC.1/Circ.1580 §§ 3.1.4 & 4.1 and OCIMF OVID (OVIQ4 Chapter 5 / Navigation & DP Supplements), inspectors verify that the ship's technical redundancy documented in the Failure Modes and Effects Analysis (FMEA) is translated into clear bridge and engine-room operating limits:

  • Ship-Specific FMEA & Annual DP Trials: Every DP Class 2 and Class 3 vessel must carry an approved, up-to-date FMEA report defining its Worst-Case Failure Design Intent (WCFDI) (for example, loss of one complete HV switchboard section and its connected generators and thrusters). Annual DP trials must physically test the WCFDI and verify that cross-connections, UPS supplies, fuel headers, cooling-water cross-over valves and power management load-shedding behave as designed.
  • CAMO (Critical Activity Mode of Operation) & TAM (Task Appropriate Mode): CAMO defines how the vessel's power plant, HV/LV bus-ties, thrusters, fuel systems, cooling systems and UPS units must be configured to guarantee full single-fault tolerance inside the 500 m safety zone. TAM defines a documented configuration for lower-risk operations where reduced redundancy is acceptable.
  • ASOG (Activity-Specific Operating Guidelines): Posted on the bridge and in the Engine Control Room (ECR) for each offshore field/task, dividing operational status into four colour bands: GREEN (all systems inside CAMO limits; thruster/power load within post-WCFDI capability typically ≤ 40–50% per bus; ≥ 3 PRSs online across ≥ 2 principles), BLUE / ADVISORY (early degradation; inform Master, Chief Engineer and installation), YELLOW (loss of redundancy or Consequence Analysis warning — suspend critical operations immediately and prepare to exit the 500 m zone), and RED (position/heading excursion — execute emergency disconnection and manoeuvre clear along the escape vector).

3. DPO Certification, DP Watches Inside the 500 m Zone & DPVAD Surveys

  • DPO Certification (STCW Section B-V/f & MSC.1/Circ.738/Rev.2): Dynamic Positioning Operators (DPOs) must hold a valid Nautical Institute (NI) or accredited DP Operator Certificate matching the vessel's DP class, backed by an up-to-date DP Logbook and vessel-specific DP familiarisation (OVIQ4 Ch. 2 & Ch. 5).
  • 500-Metre Safety Zone Entry Checklist & Bridge Manning: Before entering the 500 m safety zone around a platform, FPSO, wind turbine or drilling unit, the bridge and engine room must complete the 500 m Zone Pre-Entry Checklist (≥ 500 m standoff trial: testing manual joystick, auto-DP, independent joystick backup, thruster response, communications with installation/rig control, and confirming drift-on vs drift-off vector). Two qualified DPOs should be on the bridge at all times during DP Class 2/3 operations inside the 500 m zone.
  • Online Consequence Analysis & DPVAD Endorsements (MSC.1/Circ.1580 §§ 3.4.2.4 & 5): DP Class 2 and 3 computers must run a continuous software Consequence Analysis simulating whether the vessel will maintain position if the worst-case single failure occurs under current environmental forces, and the vessel's Dynamic Positioning Verification Acceptance Document (DPVAD) must hold valid Initial, Annual (±3 months) and 5-yearly Complete Survey endorsements.

4. Anchor Handling Winches (SOLAS II-1/3-13 & MSC.1/Circ.1662), Shark Jaws & Bollard Pull

From 1 January 2026, SOLAS Regulation II-1/3-13 (IMO Res. MSC.532(107)) and IMO MSC.1/Circ.1662 (Guidelines for Anchor Handling Winches) make statutory testing, examination and maintenance mandatory on all SOLAS ships fitted with anchor handling winches:

Component / OperationRegulatory & Industry StandardCritical Safety & Inspection Checks
Anchor Handling Winch (AHW) Testing & ExaminationSOLAS Reg. II-1/3-13.2.3, .2.5 & .3 + IMO MSC.1/Circ.1662Annual thorough examination and operational testing per MSC.1/Circ.1662; pre-2026 AHWs tested and examined no later than the first renewal survey ≥ 1 Jan 2026; overload alarm and rendering/payout settings calibrated and recorded.
Emergency Quick-Release (EQR) / Free-Wheel SystemIMO MSC.1/Circ.1662 & OCIMF OVIQ4 Ch. 8Must be operable from the bridge and main winch control station under both normal power and dead-ship / emergency power conditions, protected against inadvertent activation, and functionally tested before every anchor-handling job.
Shark Jaws, Towing Pins & Stern RollerOCIMF OVIQ4 Ch. 8 & COSWP Ch. 26Hydraulic/mechanical shark jaws and vertical locking towing pins must be remotely operated from a safe control station clear of the wire sweep zone, with emergency local/hydraulic accumulator release tested before operations.
Stability during Anchor Handling (2008 IS Code Part B)IMO Res. MSC.267(85) (as amended by MSC.415(97))Verify heeling levers from vertical and transverse wire tension at the stern roller/towing pins against the approved Stability Booklet anchor-handling curves; keep watertight deck/engine-room doors closed and freeboard within minimum stern immersion limits.
Continuous Bollard Pull Certificate & Towline Safety FactorIMO MSC/Circ.884 & OCIMF OVIQ4Carry a Class-witnessed Continuous Static Bollard Pull Certificate (BP_cont); size main tow wires, pennants, stretcher/spring lines and shackles to meet minimum Breaking Load safety factors (typically ≥ 2.0–3.0 × BP_cont).

Use the Bollard Pull & Offshore Towline Calculator and the SOLAS 2026 Lifting & Winch Guide to verify your winch proof-load and towline safety factors offline.

Questions seafarers ask

What is the difference between DP Equipment Class 1, Class 2 and Class 3 under IMO MSC.1/Circ.1580?

Under the IMO Guidelines for Vessels and Units with Dynamic Positioning (DP) Systems (MSC.1/Circ.1580, updating MSC/Circ.645 for vessels constructed on or after 9 June 2017): (1) DP Equipment Class 1 has no redundancy, so a loss of position and/or heading may occur in the event of a single fault; (2) DP Equipment Class 2 has redundancy of all active components so that no loss of position and/or heading occurs in the event of a single fault in any active component or system (generators, thrusters, switchboards, remote-controlled valves, computers, Position Reference Systems), though a loss may occur after failure of a static component (cables, pipes, manual valves) where documented by risk analysis; and (3) DP Equipment Class 3 withstands any single fault in active or static components PLUS complete loss of any single compartment due to fire or flooding (protected by A-60 fire divisions and watertight bulkheads, with an independent backup DP control station in a separate A-60 compartment).

What is the difference between CAMO, TAM and ASOG on a Dynamically Positioned vessel?

Under IMO MSC.1/Circ.1580 § 4.1 and IMCA M 220 operational guidance: (1) CAMO (Critical Activity Mode of Operation) is the most fault-tolerant configuration of the vessel's power, propulsion, electrical switchboards (e.g., open vs closed bus-tie when class-approved and FMEA-proven) and thrusters required for critical DP operations; (2) TAM (Task Appropriate Mode) is a risk-based configuration where the vessel may operate with reduced fault tolerance during non-critical tasks where the consequence of a loss of position is acceptable; and (3) ASOG (Activity-Specific Operating Guidelines) is the tabular bridge/engine-room operational matrix for a specific location and task defining Green (normal), Advisory/Blue (inform Master/Chief Engineer, assess), Yellow (degraded redundancy — suspend critical operations and prepare to move off) and Red (emergency — abort operation immediately and move to safe position) limits.

How many Position Reference Systems (PRSs) are required for DP Class 2 and DP Class 3 vessels?

Under IMO MSC.1/Circ.1580 § 3.4.3, for DP Equipment Classes 2 and 3, at least three independent Position Reference Systems (PRSs) must be installed and simultaneously available to the DP control system during operation, and they must not all be based on the same measurement principle (for example, combining two independent DGNSS receivers with a laser CyScan/Fanbeam, radar RadaScan/SpotTrack, taut wire or hydroacoustic HPR/HiPAP system so that ionospheric scintillation or GNSS spoofing cannot disable all three PRSs simultaneously).

What does SOLAS Regulation II-1/3-13 and MSC.1/Circ.1662 require for Anchor Handling Winches from 1 January 2026?

Under SOLAS Regulation II-1/3-13 (adopted by IMO Resolution MSC.532(107), effective 1 January 2026) and the IMO Guidelines for Anchor Handling Winches (MSC.1/Circ.1662), anchor handling winches (AHWs) and associated loose gear (shark jaws, towing pins, stern rollers, pennant wires, carpenter stoppers, swivels and shackles) on all SOLAS ships must be operationally tested, thoroughly examined annually, inspected before use, and maintained per MSC.1/Circ.1662. AHWs installed before 1 January 2026 must be tested and thoroughly examined no later than the first renewal survey on or after 1 January 2026 (Reg. II-1/3-13.2.5), including verification of the emergency quick-release (free-wheel / payout) system under both normal and dead-ship power conditions.

What surveys are required to keep a Flag/Class Dynamic Positioning Verification Acceptance Document (DPVAD) valid?

Under IMO MSC.1/Circ.1580 Section 5, a DP vessel undergoes an Initial Survey (including full FMEA proving trials), Annual Surveys (within 3 months before or after each anniversary date to test essential alarms, redundancy switching and annual DP trial completion), and a Complete (Renewal) Survey every 5 years (which includes full FMEA re-testing of worst-case single failure modes) to endorse or renew the Dynamic Positioning Verification Acceptance Document (DPVAD).

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