What Is SPM Buoy Inspection?
A Single Point Mooring (SPM) is an offshore terminal that lets a tanker moor at a single connection point and weathervane freely as wind, current and waves shift. It is how crude and product are loaded and discharged at sites where a fixed jetty is impractical or the water is too shallow for a berth. The most widely used configuration is the CALM buoy — Catenary Anchor Leg Mooring — a large steel floating buoy held on station by a spread of catenary anchor chains, with the tanker connected through mooring hawsers and product routed through floating and submarine hoses, a rotating product swivel and a seabed Pipeline End Manifold (PLEM).
SPM buoy inspection is the systematic condition assessment of that entire terminal, both the parts you can see above the waterline and the far larger portion hidden beneath it. Above water sit the buoy deck and structure, navigation aids, fenders, the exposed section of the product swivel and piping, and the floating hose string. Below water lie the submerged buoy body and its compartments, the chain table, the mooring legs and their anchor chains, the PLEM and the submarine hoses. A complete inspection reads all of these as one interconnected system.
What makes SPM inspection distinct from a routine hull or jetty survey is that a single terminal spans two very different working environments. The topside structure is inspected the way any tall marine steelwork is, while the mooring and product-transfer components live on the seabed under load. Covering both properly, in a single mobilisation, is the whole point of a dedicated SPM inspection — and it is where our above-water and underwater capability comes together on one asset.
Why SPM Terminals Need Regular Inspection
An SPM is a continuously-loaded critical asset. Unlike a vessel that returns to a yard on a fixed docking cycle, the buoy stays on station year-round, taking mooring loads every time a tanker connects and enduring constant fatigue from wave action even between callings. In Singapore's warm, high-salinity waters, corrosion, marine growth and chain wear all advance quickly, and the consequences of a missed defect are serious: a parted mooring leg, a failed product swivel, a ruptured submarine hose or a flooded buoy compartment can each cause pollution, unplanned downtime and a genuine safety incident.
Because the terminal handles hydrocarbons at a busy loading point, its integrity is also a regulatory and commercial matter. Periodic inspection underpins the terminal's integrity-management programme and supports the periodic condition assessments expected under OCIMF guidance and classification-society survey regimes. A well-evidenced inspection record is what lets an operator justify continued service, plan interventions during a scheduled window rather than a breakdown, and demonstrate due diligence to class, charterers and the authorities.
Singapore's position as one of the world's largest bunkering and oil-terminal hubs makes this especially relevant. The concentration of loading terminals, storage and tanker traffic in local and nearby waters means SPM assets here work hard, and the value of catching a developing mooring-chain or hose defect early — before it interrupts a loading programme — is high. Regular, thorough inspection is the cheapest insurance against a very expensive failure.
SPM Components We Assess
Our inspection is structured around the specific ways each part of an SPM terminal deteriorates. Every finding is identified, imaged, located to a component reference and logged for the operator's integrity plan.
| Component | What We Check | Why It Matters |
|---|---|---|
| Buoy body & structure | External hull plating, welds, skirt, coating breakdown and watertight compartment boundaries above and below the waterline | Structural loss or a flooded compartment affects buoyancy, freeboard and the safe transfer of mooring loads. |
| Corrosion & coating | Coating condition, pitting and general wastage; anode consumption and cathodic protection status | Corrosion is the dominant deterioration mode; CP and coating condition drive the buoy's remaining life. |
| Chain table & mooring legs | Chain link wear, connecting hardware, catenary profile, seabed touchdown and scour along each mooring chain | The mooring legs hold the terminal on station; link wear and fatigue are the primary structural risk. |
| Submarine & floating hoses | External damage, kinking, chafe, coupling condition and buoyancy loss along the hose string | A hose failure during transfer is a direct pollution and downtime risk; early wear signs guide testing. |
| Product swivel & piping | Leakage, seal weepage, corrosion and fastener condition on the rotating swivel and deck piping | The swivel is the single rotating interface for product flow; a leak there stops the terminal. |
| PLEM & subsea connections | Pipeline End Manifold structure, valves, hose connections and seabed stability | The PLEM ties the buoy to the shore line; damage or exposure threatens the whole transfer path. |
| Navigation aids & fenders | Lights, racons, fender condition and general topside furniture above the waterline | Navigation aids are a safety and compliance requirement; damaged fenders expose the buoy to impact. |
| Mooring hawsers & hardware | Hawser condition, chafe chains, shackles and the pick-up and support gear on deck | The hawser is the tanker's live connection; its condition is a direct mooring-safety item. |
How Combined Above- and Below-Water Inspection Works
An SPM sits across the waterline, so we inspect it with two complementary teams working the same asset in one mobilisation. Above the water, drone and topside close-visual methods cover the buoy deck, the exposed structure and skirt, navigation aids and fenders, the deck piping and the visible section of the product swivel, and the floating hose string as it runs out to the tanker connection. Working from the air keeps inspectors off awkward, moving steelwork and captures the whole topside quickly and safely.
Below the water, ROV and, where the task calls for hands-on work, commercial divers take over. The ROV surveys the submerged buoy body and its coating, follows the chain table and each mooring leg down the catenary to the seabed touchdown, inspects the anchor chains and connecting hardware, and tracks the submarine hoses and the PLEM. Divers are deployed where close contact, cleaning of a specific area or physical measurement is needed that an ROV cannot provide. This mirrors the methods we use for underwater pipeline inspection and general subsea survey.
The decisive advantage is that both halves come from one vendor and land in one report:
- Single mobilisation — the above-water and below-water scopes run together, avoiding two separate contracts, two spreads and two sets of coordination.
- One consolidated report — topside and subsea findings are cross-referenced in a single condition document, so the terminal is assessed as one system rather than in fragments.
- ROV plus diver flexibility — remote survey for broad coverage and depth, divers for close, hands-on tasks, chosen to suit each component.
- Integrity-ready evidence — every finding is imaged, referenced and severity-noted, giving the operator and class surveyor a traceable record for the integrity plan.
After the fieldwork, imagery and video from both environments are compiled into a component-by-component condition report. Anomalies are described, located and flagged for follow-up, so the terminal operator can plan any cleaning, further testing, resealing, hose replacement or chain renewal within a controlled maintenance window.
Standards and Context
SPM inspection sits within a well-established framework of industry guidance rather than a single prescriptive code. The Oil Companies International Marine Forum (OCIMF) publishes the most widely referenced guidance on SPM design, operation and inspection, and its Guide to Manufacturing and Purchasing Hoses for Offshore Moorings (GMPHOM) sets the intent for how floating and submarine hoses are examined and maintained. We structure our hose and terminal survey work around that intent so the data slots into an operator's existing regime.
Classification societies — ABS, DNV, Lloyd's Register and Bureau Veritas among them — set survey and condition-assessment requirements for buoy structures, mooring systems and the associated hardware, and periodic inspection is how an operator demonstrates compliance between formal surveys. For the subsea diving and ROV scopes, the practices promoted by IMCA (the International Marine Contractors Association) inform how the work is planned and executed safely. We cite these frameworks because they define good practice for SPM inspection; we do not claim to hold any specific approval, and any class attendance or certification of the terminal remains a matter for the operator and its appointed surveyor.
What We Inspect on an SPM
Every SPM is configured a little differently, but the inspection breaks down into a consistent set of scopes across the waterline.
Buoy Body & Structure
The floating steel buoy above and below the waterline — plating, welds, skirt, coating and watertight compartment boundaries — checked for corrosion, damage and any sign of compromised buoyancy.
Mooring Legs & Chain Table
The chain table and each catenary mooring leg followed to the seabed, assessing link wear, connecting hardware, marine growth and scour — the core of the terminal's structural integrity.
Submarine & Floating Hoses
The full hose string from the buoy to the tanker and down to the PLEM, inspected for external damage, chafe, coupling condition and buoyancy loss along its length.
Product Swivel & CP
The rotating product swivel and deck piping for leaks and corrosion, alongside anode and cathodic-protection status that governs the buoy's protection against corrosion.
Why Choose SG Drone Inspections
We are a specialist inspection provider covering both the above-water and below-water sides of marine assets in Singapore, which is exactly what an SPM terminal demands.
One Vendor, Air and Water
Topside drone survey and subsea ROV and diver inspection under a single scope and a single report — no stitching together two contractors across the waterline.
ROV and Drone Capability
Remotely operated vehicles and inspection-class drones let us cover depth, reach and awkward topside steelwork efficiently, with divers deployed for close, hands-on tasks.
CP and Hose Checks Included
Cathodic-protection and anode assessment and hose-condition survey are built into the scope, so corrosion protection and product-transfer integrity are covered, not just structure.
Integrity-Ready Reporting
Findings are imaged, component-referenced and severity-noted in a consolidated report your integrity team and class surveyor can act on directly.
Frequently Asked Questions
Get an SPM Buoy Inspection Quote
Tell us your terminal type, location and inspection window. We reply with a scope and quote — covering both the above-water and below-water work — with no obligation.