Tugboat Bollard Pull Full Test Content
1. Purpose of the Bollard Pull Test
The test verifies the maximum continuous bollard pull and short‑term maximum bollard pull of the tugboat. It checks the matching between the propulsion system and main engine load, provides evidence of operational capacity for owners and port operators, and meets requirements of IMO, ISO and classification societies including BV, DNV and CCS. The main reference standard is ISO 7365 for shipbuilding bollard pull testing.
2. Pre‑Test Preparations
Environmental ConditionsWater depth must be at least 2.5 times the vessel’s draft to avoid propeller cavitation. Wind speed should be less than 5 m/s, current speed below 0.5 knot, with calm waves and no interference from other ship wakes. Mooring ArrangementThe tug is connected to a fixed shore bollard or a secured large barge using steel wire rope. The towline must align with the ship’s centerline, remain nearly horizontal, and avoid contact with the water surface. Measuring EquipmentRequired devices include a load cell with error within ±1%, data acquisition system, and GPS to confirm near‑zero speed. An anemometer is recommended. All equipment must be calibrated and valid. 3. Standard Test Procedures
First, confirm the vessel condition by recording draft, displacement, fuel and fresh water quantity, and loading status, usually set to 50%–75% fuel to simulate design working condition.
Next, tension the towline slowly at low engine speed to eliminate slack and ensure correct alignment without sudden loading.
Then apply load step by step, increasing engine load gradually. Hold each load level steadily for 1 to 2 minutes and record towing force, engine rpm, torque, fuel consumption and exhaust temperature.
At 100% MCR, maintain the condition to measure maximum continuous bollard pull for 10 minutes and short‑term maximum bollard pull for about 1 minute. The continuous pull is the 10‑minute average value and the maximum pull is the peak value.
If required, conduct astern bollard pull test to measure reverse thrust. Finally, reduce engine speed gradually, slacken the towline, stop the engine and dismantle the equipment.
4. Data Processing
Calculate the bollard pull as the average force in the stable period, using the conversion 1 ton ≈ 9.81 kN. Corrections for wind, current and water depth may be applied if needed; they are often neglected when environmental conditions meet standard requirements.
5. Key Precautions
Ensure sufficient water depth to prevent propeller cavitation, thrust loss and excessive vibration. Keep the towline horizontal to avoid vertical force components that cause inaccurate readings. Do not overload the main engine; monitor exhaust temperature, turbo pressure and torque continuously. Maintain a distance from the bank greater than four times the ship’s length to avoid thrust reflection. Install the load cell in‑line without bending. Keep personnel clear of the towline path due to high risk of rope breakage.
6. Common Errors and Impacts
Insufficient water depth leads to low measured pull. Being too close to the bank results in high readings. Inclined towline, unsteady data recording, strong wind or current, and incomplete engine load all cause inaccurate or deviated test results.
7. Typical Test Report Content
A complete test report includes vessel basic information, main engine parameters, propulsion type, test area, environmental conditions, measuring equipment, pull‑versus‑rpm curves, maximum and continuous bollard pull values, and the signature of the classification society surveyor.
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