Technical Specification for Marine Fan Installation

   Correct installation of a marine fan is the foundation of long-term, stable operation, and strict engineering practice must be followed. The installation process can be divided into six stages: preparation, foundation work, positioning of the equipment, duct connection, electrical wiring and system commissioning.
   In the preparation stage, the most important point is to verify that the equipment parameters agree with the design drawings; we have encountered a case in which an impeller diameter that did not match the drawing forced the entire system to be reworked.
   Foundation work must take account of the ship's vibration characteristics. We normally adopt a resilient foundation using SD-type rubber isolators or spring isolators, with the natural frequency kept within the 5–8 Hz range. One high-speed passenger vessel project overlooked this point, and fan vibration was transmitted to the passenger cabins, with noise exceeding the limit by 15 dB.
   When positioning the equipment, alignment accuracy requires particular care; we use a laser alignment instrument to keep the coaxiality deviation between motor and fan below 0.05 mm.
   For duct connections, marine ducts are usually made of rectangular galvanised steel plate, and the joints must be sealed with a dedicated sealant (such as polysulphide sealant) to ensure airtightness. We have developed a modular duct system that improves installation efficiency by 40%, as demonstrated on a container ship project.
   Electrical wiring must comply with the classification society's cable installation rules, and explosion-proof areas require dedicated cable glands (such as Ex e).
   System commissioning is the most important stage. We have established a complete commissioning procedure: first a single-machine trial run (2 hours) checking current, vibration and noise parameters; then a system interlock test to verify air balance and control system functions; and finally a 72-hour continuous running test.
   During commissioning, particular attention must be paid to preventing surge. By installing anti-surge valves and optimising the control system, we successfully avoided this hazardous condition on an oil tanker project. Explosion-proof fans have additional requirements: flameproof surfaces must not be painted, bolts must be tightened with a torque wrench (usually 120–150 N·m), and cable entries must be classification-society-approved products. The "three checks" principle we have developed (check the drawings, check the equipment, check the environment) effectively prevents installation errors. On completion, a complete test report must be submitted, including vibration data (velocity RMS normally required to be ≤ 4.5 mm/s), noise data (≤ 85 dB at 1 m from the equipment) and performance data (air flow deviation within ±5% of the design value). These documents are an important basis for classification society inspection. With the adoption of BIM technology we are also moving towards digital installation management: guiding construction with 3D models allows more than 90% of installation clashes to be identified and resolved in advance. Sound installation not only guarantees good equipment operation but is also the key to extending service life.