Ordinary local ventilation fan: consists of a collector, a primary host, a secondary host, an outlet silencer, etc. (as shown in Figure 1)

Figure 1: Ordinary local ventilation fan

FBD Series Product Introduction

1. Overview

The FBD series of explosion-proof, pressure-inlet, contra-rotating axial flow local ventilation fans (hereinafter referred to as ventilation fans) comply with the standards MT222-2007 "Technical Conditions for Contra-rotating Local Ventilation Fans" and Q/YAF001-2011 "FBD Series Mine Explosion-proof Pressure-inlet Contra-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. Details are as follows:

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

(2) The ventilation 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 the different needs of users, 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 airflow direction of the inlet without affecting the air intake, refracts the noise, and cooperates with the inlet and outlet silencers to significantly reduce the 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 ventilation 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 ventilation fans used underground, the roadway air supply volume should be greater than the maximum operating air volume of the ventilation fan.

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

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

(6) Service Life

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 ventilation 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 ventilation fan shell structural parts are all welded from steel plates, the inner cylinder is welded from perforated steel plates, lined with sound-absorbing material, and the motor is connected to the air duct by flange joints with bolts. The motor shell and perforated steel plate serve as the inner air duct, and the two impellers rotate contra-rotating at the same speed.

(2) Working Principle

The ventilation fan is driven by two explosion-proof motors of the same capacity and model, respectively driving the first and second impellers. The rotation directions of the two impellers are contra-rotating. Air enters the first impeller, obtains energy, and is discharged through the second impeller. The second 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) Technical parameters of the ventilation fan are shown in Figures 1-3

Figure 1 Ventilation fan structural diagram (with ordinary silencer)

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

Figure 2 Ventilation fan structure diagram (with inlet and outlet silencers)

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

Figure 3 Ventilation fan structure diagram (with side-entry combined silencer)

1. Side-entry device, 2. Current collector, 3. Inlet silencer, 4. Motor, 5. Primary main unit, 6. Primary impeller, 7. Secondary impeller, 8. Secondary main unit, 9. Outlet silencer

3. Installation and Debugging

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

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

(3) The ventilation fan must be managed and operated by dedicated personnel.

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

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

Figure 2  Motor Wiring Diagram (Note: Motor voltage levels are 380V/660V and 660V/1140V respectively)

4. Use and Operation

(1) Preparation and Inspection Before Use

a) The cold insulation resistance between the motor stator winding and the casing should be measured and must be higher than 50MΩ; if it does not meet the requirements, drying treatment should be performed.

b) Whether there are safety signs and explosion-proof certificate numbers.

c) All flameproof surface parts are free of cracks and defects affecting flameproof performance (new motors that have not been disassembled do not need to be checked).

d) The introduced cable cores must be pressed and fixed with wiring clamps or bowed washers to prevent cable movement.

e) Check whether all fasteners and fittings of the ventilation fan are complete and secure, whether connections are reliable, whether trial operation is flexible, whether there is noise, abnormal sound, or impact sound, whether the impeller rotation direction is correct, and whether the grounding wire is properly connected.

(2) Instructions During Use

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

b) When starting, turn on the first-stage ventilation fan in sequence, and after 5 seconds of operation, start the second-stage ventilation fan.

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

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

e) The motor bearings should be inspected 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. ZL-3 lithium-based grease (Sy142-75) should be used, with the filling amount being 1/2 of the net empty volume of the bearing chamber. (For 180000 series sealed bearings, grease does not need to be replaced during their service life)

f) The bearing clearance during use should be within the allowable range, the bearing temperature during operation should not exceed the allowable value, and the sound should be normal. If bearings are worn or damaged, new bearings should be replaced.

g) If the motor becomes 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 the ventilation is stopped due to power failure for maintenance, personnel must be evacuated and the power must be cut off.

(2) Before resuming ventilation, gas must be checked. Only when the gas concentration in the airflow 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, gas must be checked first. Only when the highest 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 startup is not permitted.