Marine Breakaway Coupling (MBC)
Also known as: Offshore Breakaway Coupling or Marine Pull-Apart Quick Coupling. This device serves as a critical safety mechanism for fluid transfer operations (involving oil, chemicals, LNG, etc.) between vessels and terminals or offshore platforms. It is typically installed mid-hose or at the terminal end of a loading arm.
I. Core Functions
Automatic Separation upon Over-Tension: In the event of vessel drift, tension caused by wind and waves, or mooring line failure, the coupling automatically separates when the tensile force reaches a preset threshold (e.g., 1–5 tons).
Instantaneous Self-Closure: Internal bi-directional valves close instantly upon separation, ensuring zero leakage to prevent environmental pollution, fire hazards, and explosions.
Equipment Protection: Prevents hoses, loading arms, and pipelines from rupturing or sustaining damage due to excessive tension.
Passive Safety: Requires no external power source; operation is purely mechanically triggered, ensuring high reliability.
II. Working Principle (Three Steps)
Normal Connection: Internal valves are fully open, allowing for smooth fluid flow; the coupling is secured by shear pins or a locking mechanism.
Over-Tension Trigger: Vessel drift generates axial tension; once this force exceeds the preset threshold, the shear pins are severed or the locking mechanism is released.
Separation + Sealing: Spring force drives the valve cores at both ends to close simultaneously, achieving a complete seal; the coupling separates, thereby protecting the entire system.
III. Typical Structure
Body: Constructed from 316 stainless steel, aluminum alloy, or brass to ensure resistance to seawater corrosion.
Valve Core: Features a dual ball valve or dual flap valve design to ensure bi-directional sealing.
Trigger Mechanism: Comprises shear pins (calibrated for the specific trigger tension) and springs (providing the power for self-closure).
Connection Ends: Available with flange or clamp connections to ensure compatibility with standard hoses.
IV. Key Parameters (Common Specifications)
Size: DN25–DN400 (1"–16").
Pressure Rating: PN16–PN40 (16–40 bar).
Material: 316 Stainless Steel (preferred for marine applications), Aluminum Alloy, or Brass.
Trigger Tension: 1–10 tons (customizable based on specific operating conditions).
Temperature Range: -196°C (for LNG applications) to +200°C (for hot oil applications). V. Application Scenarios
Ship-to-Shore: Loading and unloading operations at oil tanker and chemical tanker terminals.
Ship-to-Ship: Offshore bunkering, lightering, and FPSO offloading.
Offshore Platforms: Connection between platforms and shuttle tankers.
LNG Bunkering: Transfer of cryogenic media; prevention of leaks and explosions.
VI. Distinction from Standard Couplings
Standard Quick Couplings: Manual unlocking; no tension-triggered release mechanism; no automatic shut-off.
Marine Emergency Release Couplings: Automatic triggering + Bi-directional automatic shut-off + Resistance to harsh marine environments; offers a high level of safety.
VII. Selection Criteria
Media: Oil, chemicals, LNG (cryogenic).
Pipe Diameter and Pressure: Must match the hose specifications and system operating pressure.
Trigger Tension: Calculated based on wind and wave conditions, vessel type, and hose length.
Material: 316 stainless steel is recommended for seawater environments.
Standards: Compliant with maritime regulations such as OCIMF and ISO 18758.
VIII. Safety Value
Leak Prevention: Prevents marine pollution, fires, and explosions.
Equipment Protection: Minimizes damage to hoses and loading arms, thereby reducing maintenance costs.
Compliance: Satisfies international maritime requirements for pollution prevention.
