Double-silenced local ventilation fan: This fan adds an inlet silencer (as shown in Figure 2) to a standard three-section fan, reducing noise by 5-10 decibels.

FBD Series Product Introduction

1. Overview

The FBD series of explosion-proof, pressure-inlet, counter-rotating axial flow local ventilation fans (hereinafter referred to as fans) comply with the standards MT222-2007 "Technical Conditions for Counter-Rotating Local Ventilation Fans" and Q/YAF001-2011 "FBD Series Explosion-proof, Pressure-inlet, Counter-rotating Axial Flow Local Ventilation Fans". They are suitable for local ventilation in underground coal mines containing methane gas or coal dust and other explosive hazardous environments, and are used with positive pressure ventilation ducts. They can also be used as ventilation equipment for tunnel construction. Specific details are as follows:

(1) The fan uses computational fluid dynamics for multi-objective overall optimization design. The blades use aviation engine FMIA airfoils, resulting in a large area of high-efficiency operating conditions. The fan features a compact structure, large air volume, high air pressure, long air delivery distance, high efficiency, energy saving, and low noise.

(2) The fan is directly driven by two YBF2 series explosion-proof motors for fan use. To extend the service life of the fan, SKF series bearings from Sweden are used for the motor bearings. (Add bearing photo)

(3) According to different user needs, there are 3 types of silencers to choose from;

　　a) Ordinary outlet silencer; (Add photo)

　　b) Inlet and outlet combined silencer; (Add photo)

　　c) Side inlet, inlet and outlet combined silencer. (Add photo)

The third type (c) of combined silencer adds a side inlet component, which changes the inlet airflow direction without affecting the air intake, refracting the noise. Combined with inlet and outlet silencers, this significantly reduces noise. Testing by the National Mine Equipment Testing Center shows that the noise level is 20-30 decibels lower than that of ordinary ventilation fans.

(4) The explosion-proof type of the fan and motor is: explosion-proof, and the explosion-proof mark is: ExdbI.

(5) The operating voltage is 380V/660V, 660V/1140V, and does not exceed ±5% of the rated value, and the voltage frequency is 50HZ.

For underground ventilation fans, the roadway air supply should be greater than the maximum operating air volume of the fan.

The foundation for installing the fan should be firm and free from water splashing. The height of the edge of the fan inlet from the ground or ceiling should be no less than 0.3m.

The ventilation duct used should be able to withstand the highest pressure of the fan, and the diameter of the ventilation duct should not be less than the diameter of the impeller.

(6) Service Life

The service life is no less than 5 years, and the safe operating time before the first overhaul is no less than 13000 hours.

2. Structural Features, Working Principle and Technical Parameters

(1) The fan consists of a collector, motor, primary fan, secondary fan, motor, silencer, etc. (Figure 1 with ordinary silencer; Figure 2 with inlet and outlet silencers; Figure 3 with side inlet combined silencer). The fan housing structural parts are all welded from steel plates, and the inner cylinder is welded from perforated steel plates, lined with sound-absorbing material. The motor is connected to the air duct by bolts using a flange joint. The motor housing and perforated steel plate serve as the inner air duct, and the two impellers rotate counter-rotationally at the same speed.

(2) Working Principle

The fan is driven by two explosion-proof motors of the same capacity and model, with the two impellers rotating in opposite directions. Air enters the primary impeller, obtains energy, and is then discharged through the secondary impeller. The secondary impeller also has the function of the stationary blades in an ordinary axial flow fan. While obtaining the straightened circumferential velocity component, it also adds energy to the airflow, thus achieving the high efficiency and high air pressure that ordinary axial flow fans cannot achieve.

(3) Fan technical parameters are shown in Figures 1-3

Figure 1 Fan structural diagram (with ordinary silencer)

1. Collector, 2. Motor, 3. Primary unit, 4. Primary impeller, 5. Secondary impeller, 6. Secondary unit, 7. Outlet silencer

Figure 2: Ventilation System Diagram (with inlet and outlet silencers)

1. Collector, 2. Inlet silencer, 3. Motor, 4. Primary unit, 5. Primary impeller, 6. Secondary impeller, 7. Secondary unit, 8. Outlet silencer

Figure 3: Ventilation System Diagram (with side inlet combination silencer)

1. Side inlet device, 2. Collector, 3. Inlet silencer, 4. Motor, 5. Primary unit, 6. Primary impeller, 7. Secondary impeller, 8. Secondary unit, 9. Outlet silencer

3. Installation and commissioning

(1) Before assembly, the radial clearance between the top of the blade and the inner cylinder of the casing must be checked. The radial clearance should be between 1.5‰ and 3.5‰ of the impeller diameter, and not less than 1 mm; no axial clearance is allowed after assembly of each casing.

(2) The impeller rotation direction must conform to the direction indicated by the casing marking.

(3) The ventilator must be managed and operated by a designated person.

(4) The installation and use of the ventilator must comply with the relevant provisions of the "Coal Mine Safety Regulations", and the internal and external grounding wires must be securely connected before operation.

(5) The stripped connection of the motor lead-in wire should not exceed 1.5 mm, and the motor should be installed according to the requirements of the motor instruction manual. Six terminals in the motor junction box can be used for two different voltages when changing the connection method (see Figure 2). The phase sequence U, V, W of the motor must correspond to the phase sequence A, B, C of the incoming external power supply. The motor rotation direction should be clockwise when viewed from the shaft extension end; otherwise, the motor will reverse.

Figure 2: Motor wiring diagram (Note: Motor voltage levels are 380V/660V, 660V/1140V)

4. Use and operation

(1) Preparation and inspection before use

a) The cold-state insulation resistance between the stator winding and the frame of the motor should be measured and must be higher than 50MΩ; if it does not meet the requirements, drying treatment should be carried out.

b) Whether there are safety marks and explosion-proof certification numbers.

c) All explosion-proof surface parts have no cracks or defects that affect the explosion-proof performance (new motors that have not been disassembled can be omitted).

d) The incoming cable cores must be tightly fixed with wiring plates or U-shaped washers to prevent cable movement.

e) Check whether all fasteners of the ventilator are complete and firm, whether the connections are reliable, whether the trial operation is flexible, whether there are any abnormal noises or sounds, impact sounds, whether the impeller rotation direction is correct, and whether the grounding wire is connected well.

(2) Instructions during use

a) To ensure the long-term safe operation of the ventilator, attention should be paid to correct use and regular maintenance.

b) When starting, turn on the first-stage ventilator first, and after running for 5 seconds, start the second-stage ventilator.

c) During operation, frequently check whether the sound is normal and whether there is any loosening at the joints.

d) Motor maintenance should be carried out according to the provisions in the motor instruction manual.

e) The motor bearings should be checked at least once every 6 months of operation. If the bearing grease is found to be deteriorated or leaking, it must be replaced in time. Before replacement, the bearings must be cleaned with gasoline. The grease used is ZL-3 lithium-based grease (Sy142-75), and the amount added is 1/2 of the net volume of the bearing chamber. (For the 180000 series sealed bearings, the grease does not need to be replaced during the service life).

f) The bearing clearance during use should be within the allowable range, the operating temperature of the bearing should not exceed the allowable value, and the sound should be normal. When the bearing is worn or damaged, a new bearing should be replaced.

g) If the motor is damp, it must be dried.

h) After a period of use, the silencing holes may become blocked by coal dust, necessitating cleaning with high-pressure airflow to prevent increased fan noise.

i) Inspect the ventilation fan monthly, checking all components.

j) When not in use, the ventilation fan should be stored in a well-ventilated, dry location to prevent moisture damage and other losses.

5. Fault Analysis and Troubleshooting

Table 1 Main Faults and Troubleshooting Methods

6. Precautions for Ventilation Fan Use

When using a ventilation fan underground in a coal mine, strictly adhere to the relevant regulations in the "Coal Mine Safety Regulations":

(1) The mining face using the ventilation fan must not be stopped. If ventilation is stopped due to maintenance power outages, personnel must be evacuated, and the power must be cut off.

(2) Before resuming ventilation, methane gas must be checked. Only when the methane gas concentration within 10 meters of the ventilation fan and its switch does not exceed 0.5% can the local ventilation fan be manually started.

(3) If the ventilation fan stops running for any reason, before resuming ventilation, methane gas must be checked first. Only when the highest methane gas concentration in the stopped ventilation area does not exceed 1.0% and the highest carbon dioxide concentration does not exceed 1.5%, and the conditions in point 2 are met, can the ventilation fan be manually started to resume normal ventilation.

(4) When using a counter-rotating axial flow fan, both sets of impellers must be started simultaneously. If one motor is damaged, the entire unit must be stopped for maintenance, and single-stage start-up is not permitted.