A ventilation system is not simply connecting a fan to ducts. If the air volume distribution is unreasonable, some compartments will receive excessive airflow that makes occupants uncomfortable, while others will receive almost no fresh air, and in the engine room, areas with concentrated heat sources will have persistently high temperatures. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. performs air balance commissioning after the ventilation system is installed, ensuring that the air volume at each supply and exhaust terminal reaches the design value.
The first step of air balance commissioning is fan performance testing. Before initial adjustment of the ventilation system, Haizhongzhou uses a hot‑wire anemometer or a pitot tube to measure air volume and pressure at the fan inlet and outlet, verifying that the fan meets the nameplate parameters. If the measured air volume is below ninety percent of the rated value, the fan rotation direction, blade angle or possible duct blockage are checked.
The second step is duct leakage detection. During installation, flange connections and welds in ventilation ducts may have tiny gaps, leading to air leakage. Haizhongzhou uses the smoke method or pressure drop method to detect leaks: smoke is released inside the duct or compressed air is charged, and the smoke escape points are observed or the pressure drop rate is measured. For leak points, sealant or aluminium foil tape is used to seal them. The total leakage rate is required not to exceed five percent of the design air volume.
The third step is air volume distribution adjustment. This is the most critical step. Haizhongzhou installs volume control dampers (typically opposed‑blade multi‑leaf dampers or butterfly dampers) at each supply and exhaust terminal. The commissioning technician measures the air volume at each terminal using a hood or anemometer and compares it with the design value. For terminals with excessive air volume, the damper is closed slightly; for those with insufficient air volume, the damper is opened further. However, adjusting one terminal affects the pressure distribution throughout the duct system, so iterative adjustment is required. Haizhongzhou uses the “proportional balancing method” – coarse adjustment followed by fine adjustment – typically requiring three to five rounds to bring the air volume deviation at all terminals within ten percent of the design value.
For large spaces such as the engine room, merely meeting the air volume at terminals is not sufficient; the airflow pattern must also be verified. Haizhongzhou arranges multiple temperature/humidity sensors and airflow sensors in the engine room, and continuously records data under different operating conditions (e.g., main engine at 50%, 75%, and 100% load). If local hot spots (temperature exceeding 45°C) or dead zones (airflow velocity below 0.5 m/s) are found, the damper positions are adjusted, flow deflectors are added, or local supply branches are installed.
After ventilation system commissioning is completed, Haizhongzhou issues a detailed air balance report, including the initial and final air volume at each terminal, damper opening, and commissioning date. This report is not only part of the delivery documentation but also an important reference for the owner’s future maintenance of the ventilation system. It is this rigorous commissioning procedure that ensures that every compartment on a Haizhongzhou‑built vessel receives the intended ventilation effect.
