How to Calculate Mooring Bollards: A Guide to Safe and Efficient Mooring

ESC 100 Tons T-head bollard, a simple with high strength bollard system that fulfills tough mooring requirements

Mooring bollards are critical fixtures at docks and quays that secure vessels against movement. Made from durable cast iron or steel, these structures withstand substantial forces from vessel weight, wind, and waves. The standard "T" shape design features a vertical post with a horizontal crossbar that allows deck crews to easily secure mooring lines.

We position bollards at calculated intervals along docks, enabling multiple vessels to moor simultaneously while ensuring crew members can quickly attach or release lines during operations. This strategic placement is essential for port efficiency. Though simple in design, these robust fixtures are fundamental to maritime safety - without them, vessels couldn't remain securely positioned, risking damage to both ships and infrastructure during changing tide and weather conditions.

Anchoring Confidence: Mooring bollards designed to withstand environmental forces and vessel movement

Importance in Maritime Industry

Mooring bollards secure vessels to docks by handling the high tension forces in mooring lines, preventing accidents and damage. They're strategically placed to maximize dock space efficiency and allow multiple vessels to moor simultaneously. These fixtures speed up loading operations by providing easy access points for quick line attachment and detachment. Made from corrosion-resistant materials like cast iron or steel, bollards withstand harsh marine environments for decades of service. Their reliable performance is critical for both vessel safety and efficient port operations.

Design Considerations

Each bollard's load capacity must match the largest vessels it will secure, accounting for vessel weight, weather conditions, and line strength. Placement requires careful planning to ensure accessibility for crew while maximizing available mooring space. We select materials like cast iron or steel specifically for their durability against saltwater corrosion and constant use. The design must balance functionality with practical concerns like maintenance access and dock integration. Both traditional T-shaped and custom designs serve different operational needs depending on the port's requirements.

Installation Process

Before installation, we carefully prepare the site by clearing debris and creating a level, stable foundation. The concrete foundation must be engineered to support the bollard's rated load capacity plus a safety margin. We secure bollards to foundations using specialized bolts or anchor rods designed for marine environments. After installation, each bollard undergoes load testing to verify it can safely handle its rated capacity. Proper installation documentation helps establish maintenance schedules and expected service life.

Safety Considerations

Safety is ESC’s primary concern since improperly used bollards can cause serious accidents affecting crew, vessels, and port infrastructure. Modern bollards feature high visibility paints and sometimes reflective markings to remain visible in all conditions. Crew training is essential, covering proper line attachment techniques and understanding load limitations. Regular inspections check for cracks, corrosion, or foundation issues that could compromise safety. Always use appropriate mooring lines that match both the vessel and bollard load ratings to prevent failures.

Understanding Mooring Bollard Load Calculation

Heavy-duty mooring bollards rated at 25 tons, precision-engineered for global marine applications

When designing wharf bollards and fenders, we calculate the forces that will transfer through to the supporting piles. Our wharf uses steel mono-piles with platforms that can handle barges and tugs of different sizes mooring on both sides. At ESC we install either cone-type or tire fenders on the piles to absorb impact when vessels dock and protect both the ship and our structure. The mooring system uses braided nylon ropes with mooring bits (small bollards), all designed to withstand the worst environmental conditions expected every 10 years at this location.

We specify maximum approach speeds and angles that ships must follow when docking to ensure our wharf structure can safely handle the berthing forces:

• Vessel Displacement (Mv) – The total weight of the ship, measured in tonnes.

• Wind and Current Forces – Environmental conditions affecting the vessel’s stability.

• Mooring Line Angle – The direction and tension of mooring lines.

• Berthing Energy (E) – The kinetic energy absorbed by the mooring system during docking.

Formula for Mooring Load Calculation

Twin-post mooring bollard installed for secure vessel docking—engineered for durability in marine environments.

The total force exerted on a mooring bollard can be estimated using:

Where:

• Berthing Velocity (Vb)

  • This is the speed at which the ship moves toward the berth.

  • It depends on ship size, type, how often ships arrive, space to move near the berth, and weather like waves, wind, and current.

  • Berthing speed is the most important factor for calculating the energy the fender system must absorb.

  • Different conditions affect speed:

    1. Easy berthing, sheltered area

    2. Hard berthing, sheltered area

    3. Easy berthing, exposed to waves/currents

    4. Hard berthing, exposed to waves/currents

    5. Very bad berthing, exposed to waves/currents

• Hydrodynamic Mass Coefficient (CM)

  • Accounts for water moving around the ship, adding to the ship’s effective mass.

  • Formula: CM = 1 + 2T/B (usually about 1.5)

  • T = ship draft (how deep it sits in water)

  • B = ship beam (width)

• Eccentricity Coefficient (CE)

  • Ships usually hit the berth at an angle and turn while berthing.

  • Some kinetic energy turns the ship; the rest hits the berth.

  • CE shows how much energy actually hits the berth after turning.

  • Calculated using ship’s radius of gyration (K), block coefficient (Cb), contact point distance (R), and angle (γ).

  • K depends on ship length and block coefficient.

  • Cb = ship displacement divided by hull volume.

• Softness Coefficient (CS)

  • Represents energy absorbed by the ship’s hull during impact.

  • Usually between 0.9 and 1.0.

  • For ships with rubber fenders, use 0.9. Otherwise, use 1.0.

• Berth Configuration Coefficient / Water Cushion Effect (CC)

  • Accounts for energy absorbed by water trapped between ship and berth.

  • Depends on berth type, distance from ship, berthing angle, hull shape, and water depth under keel.

  • Use 1.0 for open pile wharves.

  • Use 0.8 to 1.0 for solid wharves.

This formula helps determine the Bollard strength required to safely secure a vessel.

Considering Different Ship Sizes

Cargo vessel moored securely with bollard and buoy system—ensuring safe docking in dynamic coastal conditions

The size and type of vessel significantly impact mooring bollard calculations:

Small Vessels (like fishing boats and tugboats)

• They don’t need very strong bollards because they are light and have less weight.

• The main forces on their mooring lines come from wind and water currents, not from the ship hitting the berth.

Medium-Sized Ships (cargo ships, ferries)

• Require medium-strength bollards to handle normal port movements.

• Mooring lines should be arranged carefully to spread the forces evenly across the bollards.

Large Ships (oil tankers, cruise ships, big container ships)

• Need very strong bollards because they are heavy and have a lot of momentum.

• Several bollards and stronger mooring setups to keep the ship stable when docked.

Final Thoughts

Durable mooring cleat with synthetic rope—ensuring secure vessel tie-down at busy docks.

Mooring bollards are essential for keeping vessels safely secured to docks, with their design and strength carefully matched to the size and type of ship, environmental conditions, and docking forces. From small boats to massive tankers, each requires the right bollard capacity and arrangement to handle the unique stresses they face.

Accurate calculations considering ship speed, hull impact, and water effects ensure the bollards can absorb the forces during berthing. Proper installation, maintenance, and crew training are vital to maintain safety and efficiency in port operations. Ultimately, well-designed mooring systems protect both ships and infrastructure, enabling smooth and secure docking under all conditions.

Ready to elevate your marine infrastructure? 

ESC Marine Systems stands at the forefront of innovation, offering high-performance mooring bollards, marine fender systems, and cathodic protection solutions tailored to global standards. With strategic partnerships and over 20 years of expertise, ESC delivers end-to-end marine systems across continents—from North America to Southeast Asia, the Middle East to Europe.

Explore the full range of products and solutions at ESC Marine Systems and connect with their expert team via the Contact Us Page for prompt, personalized support.  For localized services and insights, you may also visit ESC’s affiliated regional websites—ensuring global expertise with local understanding.