Description of the Host and Some Accessories

1) The complete fan assembly comprises duct connectors, a collector, a primary-stage fan, a secondary-stage fan, a diffuser, and other components. The internal flow passages are uniformly smooth; the collector, flow straightener, and fishbone‑shaped heat‑dissipating tubes are all formed by cold roll‑forming using molds. Meanwhile, the fishbone‑shaped heat‑dissipating tubes and the motor base support plates, while meeting stringent mechanical requirements for strength and stiffness, incorporate features such as arc‑transition designs to reduce flow resistance, ensuring uniform smoothness of the flow path, minimizing pressure loss, and enhancing overall fan performance. All supporting structures adopt a symmetrical design, optimizing the internal flow‑channel configuration. The installation configuration is a horizontal arrangement with two fans mounted side by side. Each fan is equipped with pressure‑measurement rings and other performance‑testing interfaces for measuring negative pressure, airflow rate, and other parameters; these can be connected to pressure sensors to monitor dynamic and static pressures as well as flow rate. Vibration‑monitoring brackets are installed on the outer wall of the duct, with pre‑drilled mounting interfaces for vibration sensors.

2) Machining, anti-corrosion treatment, and rust removal of the fan casing: High-quality Q235 steel is selected as the raw material, with a material certification provided. The entire casing is cut using a CNC laser cutting machine, ensuring high dimensional accuracy and efficiency, thereby better guaranteeing product quality. All welding is performed using CO₂ shielded arc welding to minimize deformation of the fan casing, ensuring that all casings meet design specifications. Following welding, the casing undergoes sandblasting to remove any visible oil, dirt, oxide scale, rust, or paint coatings from the steel surface, enhancing the adhesion of both the primer and topcoat. The primer is applied in two coats; prior to shipment, an additional coat of anti-corrosion polyurethane topcoat is applied. Each primer coat has a film thickness of 30–40 μm, and the final topcoat brings the total coating thickness to 100–140 μm.

3) Noise reduction measures for fans: The primary sources of fan noise include motor operating noise, aerodynamic noise generated by airflow, and other mechanical noises. To address these noise sources, the fan’s flow‑diverting chamber, diffuser, and dedicated silencer are designed not only to optimize fan performance but also to incorporate sound‑absorbing perforated plates and high‑quality, flame‑retardant glass wool within the flow passages. The perforated sound‑absorbing plates are galvanized, while the silencing assembly consists of ultra‑fine glass fiber material with a density of 35 kg/m³ and a thin‑walled, porous acoustic cavity; the sound‑absorbing cotton must be laid evenly, uniformly, and tightly packed. Fastening is achieved using self‑tapping screws. The silencing diffuser includes an internal conical section, which itself is equipped with a resistive silencing device. The diffuser tower adopts a streamlined design, reducing outlet noise and improving efficiency by 2–4%. By implementing measures addressing aerodynamic noise, motor noise, and mechanical noise, the fan’s operating noise has been effectively reduced. The resulting noise levels comply with the requirements of GB/T 8690‑2014 “Industrial Fans — Noise Limits.”

4) Drainage of the fan: A drainage slope is provided at the bottom of the fan housing, and drain ports and drain valves are installed at the lowest points of each component. In addition, heating cables are evenly wrapped around the drainage piping to ensure that the pipelines do not freeze even when the local minimum winter temperatures are reached. The electric heating and insulation systems are explosion-proof devices.

5) Impeller Cylinder Protective Ring: In accordance with GB/T 13813-2001, “Test Methods and Judgment Criteria for Friction Spark Safety of Metallic Materials Used in Coal Mines,” the fan is equipped with an impeller cylinder. This cylinder employs the “explosion‑formed copper/steel composite explosion‑proof copper strip ring” technology, which eliminates the issue of the copper strip protective ring detaching and thereby eliminates potential safety hazards. The impeller cylinder is machined on a high‑precision, large‑scale 4‑meter double‑column CNC drop‑type lathe, effectively ensuring the roundness of the cylinder and the uniformity of the clearance between the blades and the cylinder.

6) Fan braking system: Both the primary and secondary fan units are equipped with reliable braking devices. These brakes employ manual radial braking, ensuring that no axial force is applied to the motor shaft during braking, thereby improving the load conditions on the motor bearings. After shutdown, rapid reverse‑flow operation can be achieved, with a reverse‑flow duration of no more than 10 minutes, as stipulated in the Coal Mine Safety Regulations. The fans utilize direct motor reversal for reverse‑flow, achieving a reverse‑flow rate exceeding 60% of the forward‑flow rate.