Port Agents for STS Operations

Two Aframax tankers approaching a designated STS transfer area for a 80,000 tonne crude oil transfer between them need coordinated positioning, fender deployment, mooring master supervision, and a hose connection that survives the sea state for 12 to 18 hours of pumping. A failure at any step - fender misplacement causing hull damage, mooring line parted under swell, hose burst mid-transfer with cargo release into the water - turns a routine operation into a Marine Pollution Casualty with regulatory and reputational consequences. STS operations port agents coordinate the operational chain that makes ship-to-ship transfer routine: mooring master booking, fender and hose deployment, POAC (Person in Overall Advisory Control) supervision, and Environmental Compliance under MARPOL Annex I Regulation 40 to 42. STS operations port agents also secure the coastal state permit and manage the go/no-go decisions against real-time weather monitoring.

The scope is offshore transfer coordination distinct from routine port-side cargo work. STS operations happen at anchor or in a designated STS zone under specific coastal state authorisation, with weather windows, tide, and swell conditions that constrain when transfer can safely proceed. The agent's role covers permit coordination with the coastal state, POAC and mooring master engagement, equipment provider selection, and continuous monitoring through the transfer window.

What STS Operations Cover

The scope across a port agent handling STS operations includes:

• Coastal state permit coordination - obtaining STS operation authorisation from the coastal state under MARPOL Regulation 41 pre-notification requirements at least 48 hours ahead of the transfer.
• POAC engagement - contracting Person in Overall Advisory Control with the qualifications and experience matching the vessel type, cargo, and transfer configuration.
• Mooring master and equipment provider selection - booking OCIMF/ISGOTT-compliant service provider with Yokohama fenders, primary and secondary hose configuration, and mooring line arrangement.
• ISGOTT compliance verification - reviewing the STS Operations Plan against current ISGOTT edition (7th, 2020) and the OCIMF/ICS Ship-to-Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases.
• Weather window monitoring - continuous forecast tracking against the operation's specific limiting conditions (wave height, wind speed, current) and go/no-go decision support.
• Cargo compatibility verification - checking cargo grade compatibility, tank readiness, and any specific segregation or heating requirements before commencement.
• Emergency response coordination - liaison with coastal state emergency services, oil spill response contractors, and the vessels' P&I clubs on incident response arrangement.
• Post-transfer documentation - completing the Statement of Facts, cargo transfer certificate, and any environmental notification the coastal state requires after operation completion.

MARPOL Regulation 40-42 and ISGOTT Compliance

MARPOL Annex I Regulations 40 to 42 set the international framework for STS operations. Regulation 40 defines the scope covering oil transfers between oil tankers at sea. Regulation 41 requires vessels to maintain an STS Operations Plan approved by the flag administration and to notify the coastal state at least 48 hours before commencement. Regulation 42 restricts STS operations to areas the coastal state has not designated as no-STS zones. ISGOTT 7th Edition (2020, jointly published by OCIMF, ICS, and IAPH) is the operational standard for tanker cargo handling and STS operations, covering hose specifications, fender arrangement, mooring configuration, pre-transfer safety meeting, cargo compatibility check, and post-transfer verification. The OCIMF/ICS Ship-to-Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases (5th Edition) provides the specialised guidance for the offshore transfer scope. Port agents coordinating STS operations verify that all these procedural layers are executed and documented before transfer starts. For broader cargo operation supervision on conventional port-side loading and discharge scope, cargo handling and supervision covers that distinct operational scope alongside the offshore STS specialty.

POAC, Mooring Master, and Service Provider Selection

The Person in Overall Advisory Control is the STS specialist directing the transfer sequence from arrival through separation. POAC qualifications include senior tanker command experience, ISGOTT familiarity, and specific STS experience against the vessel type and cargo (crude oil, refined products, LNG, LPG, or chemicals). The POAC provides advisory control - the Master of each vessel retains legal command - and coordinates approach, mooring, cargo compatibility check, transfer supervision, and departure. Mooring master (sometimes the same person as POAC on smaller operations) directs the physical mooring approach and line handling. STS service providers supply the operational equipment (Yokohama pneumatic fenders sized to vessel displacement, cargo hoses with the correct diameter and material for the specific product, mooring lines with the required MBL), the workboats and pilots, and the transfer crew. OCIMF member service providers offer standardised OCIMF-audited service quality; independent providers vary in capability and equipment condition. Port agents selecting the service provider verify equipment certification, insurance coverage, and prior operation record.

Cargo Grade, Compatibility, and Tank Readiness

Cargo compatibility check is one of the pre-transfer safety-critical items. The STS operation typically transfers a homogeneous product from the discharging ship (VLCC or Suezmax) to the receiving ship (smaller Aframax or Panamax for further distribution). Cargo grade has to match between the two ships - even minor grade differences require specific tank preparation on the receiver. Tank readiness on the receiving vessel means the tanks have been cleaned, gas-freed if necessary, and inspected for the intended cargo. Heating requirements on high-viscosity products (heavy crude, fuel oil) have to be coordinated between the two ships to maintain cargo temperature during transfer. IGS (Inert Gas System) status on the discharging ship, ODME (Oil Discharge Monitoring Equipment) calibration, and cargo pump condition all appear on the pre-transfer checklist that POAC verifies. Any discrepancy blocks commencement until resolved. For related stevedoring booking and terminal-side operational coordination on standard cargo operations, stevedoring arrangements support that adjacent scope alongside offshore STS transfer.

Weather Window and Sea-State Monitoring

STS operations depend on acceptable sea conditions for the entire transfer window - typically 12 to 24 hours end-to-end depending on cargo volume, pump rate, and vessel size difference. Limiting conditions vary by service provider and specific fender arrangement but typically fall in the range of significant wave height 1.5 to 2.5 metres, wind speed 20 to 25 knots, and no adverse current. Coastal state STS zones sometimes publish more restrictive limits. Port agents monitor forecast against these limits ahead of and during transfer, coordinating go/no-go decisions with the POAC and both Masters. Deteriorating conditions during transfer trigger emergency separation procedures under ISGOTT - both ships have to be capable of clean separation with cargo lines drained and pigged, mooring lines slipped in sequence, and fenders retrieved. Weather-related aborts add cost through re-mobilisation but avoid the higher exposure of an emergency separation under marginal conditions.

What to Verify Before Booking an STS Operations Port Agent

Practical criteria that distinguish a competent STS operations port agent from a generic ship agency:

• Coastal state permit relationships - documented working history with the coastal state's environmental and maritime authorities on STS pre-notification and approval workflow.
• POAC and service provider network - established connections with OCIMF-audited STS service providers, qualified POACs, and specialised equipment suppliers.
• ISGOTT familiarity - practical knowledge of ISGOTT 7th Edition procedures, OCIMF/ICS STS Guide requirements, and current industry best practice on transfer arrangements.
• Weather monitoring capability - forecast service integration, real-time sea state monitoring during transfer, and clear go/no-go decision protocol.
• Emergency response coordination - working relationships with local oil spill response contractors, coastal state emergency services, and the vessels' P&I clubs.
• Documentation discipline - practical experience preparing Statement of Facts, cargo transfer certificates, and post-transfer environmental notifications for STS operations.

For offshore ship-to-ship transfer coordination and STS zone operational support, browse the STS operations port agents shown below and apply the country filter to narrow to agencies positioned near the transfer areas your operations use.