G4-68 and Y4-68 type boiler ventilators

The G/Y4-68 boiler centrifugal induced-draft fans are a series jointly designed by the fan industry in 1982. They are primarily suitable for the forced-draft and induced-draft systems of steam boilers with an evaporation capacity of 230 t/h or less in thermal power plants. When performance is comparable and no special requirements exist, the G4-68 can also be used for mine ventilation and general ventilation applications. Both fan models boast advantages such as high efficiency, low noise, and high strength.

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Usage

The G and Y4-68 type boiler centrifugal induced-draft fans are a series jointly designed by the fan industry in 1982. They are primarily suitable for the forced-draft and induced-draft systems of steam boilers with an evaporation capacity of 230 t/h or less in thermal power plants. When performance is comparable and no special requirements exist, the G4-68 can also be used for mine ventilation and general ventilation applications. Both types of fans boast advantages such as high efficiency, low noise, and high strength.

The medium conveyed by the ventilator is air, and its maximum temperature must not exceed 80℃. The medium conveyed by the induced draft fan is flue gas, and its maximum temperature must not exceed 250℃.

Before the induced draft fan, a dust removal device with a dust removal efficiency of at least 85% must be installed to reduce the dust content in the flue gas entering the fan and thereby extend the fan's service life.

Form

1. Both the ventilator and the induced-draft fan are designed with single-inlet impellers, each available in 7 models ranging from No. 8 to No. 16.

2. Each type of fan can be manufactured in either a right-rotating or left-rotating configuration. When viewed from the motor end, if the impeller rotates clockwise, the fan is referred to as a right-rotating fan and denoted by “right”; if the impeller rotates counterclockwise, the fan is referred to as a left-rotating fan and denoted by “left”.

3. The outlet position of the fan is indicated by the angle of the air outlet on the fan casing. Both “right” and “left” fans can be manufactured in six different angles: 0°, 45°, 90°, 135°, 180°, and 225°.

4. The fan is driven in D-type configuration, and the motor is directly connected to the fan via an elastic coupling.

5. Here are some examples of full product names: “G/Y4-68No.8D Right 90,” where G and Y respectively stand for boiler ventilator and boiler induced draft fan.

Structural features

① The impeller—consisting of 12 backward-curved, airfoil-shaped blades welded between an arc-conical shroud and a flat disc—is typically made of 16Mn for induced-draft fans. At the junction between the blades and the shroud, wear-resistant protective plates are installed. The blade tips are solid structures, and wear-resistant materials are built up by surfacing welding at areas prone to abrasion, thereby significantly extending the blade’s service life. Ventilation fans, however, differ in this respect. All impellers undergo static and dynamic balancing corrections as well as overspeed operation tests, ensuring smooth and reliable operation.

② Casing—A volute-shaped structure welded from ordinary steel plates. The casings of single-inlet fans are available in two different designs: for sizes №8 through №12.5, the casing is constructed as a monolithic unit; for sizes №14 and №16, one-quarter of the casing can be removed. For induced-draft fans, the volute plate is equipped with an ash-removal door and is appropriately thickened to prevent wear caused by flue dust.

③ Air inlet—A streamlined, converging integral structure fixed to the casing inlet side with bolts.

④ Used to adjust the airflow rate of the fan. Nos. 8 and 12.5 are equipped with 11 vane-type blades, while Nos. 14 and 16 have 13 vane-type blades. All blades are axially mounted upstream of the air inlet. Thanks to the external transmission mechanism, these blades rotate smoothly and conveniently, with an adjustment range from 90° (fully closed) to 0° (fully open). When adjusting the position of the damper lever, viewed from the direction of the air inlet, the lever is located on the right side. For right-handed fans, pushing the lever downward—from bottom to top—corresponds to the transition from fully closed to fully open; for left-handed fans, pulling the lever upward—from top to bottom—achieves the same transition from fully closed to fully open. To ensure proper operation of all parts of the damper, lubrication must be carefully maintained. For dampers on ventilation fans, calcium-sodium-based grease should be used for lubrication; for induced draft fans, given the higher gas temperatures, molybdenum disulfide high-temperature grease (up to 260℃) is required.

⑤ Drive Assembly—All drive methods are of Type D. The assembly consists of a main shaft, bearing housing, coupling, and other components. The main shaft is made of high-quality steel. The bearing housing, which features integral water cooling with rolling bearings, requires the installation of a water supply pipe. Water consumption varies depending on ambient temperature but is typically estimated at 0.5 to 1 m³/h. The bearing housing is equipped with a thermometer and an oil-level indicator. The lubricating oil used is L-AN46, a fully synthetic oil for total-loss systems; the oil level should be maintained according to the markings on the oil-level gauge.

Run operation

If the operation is running smoothly, proceed to full-load operation (with specified total pressure and flow rate).

① Operate under full load for no less than 2 hours for newly installed fans and no less than half an hour for repaired fans.

② After the fan is started, gradually open the regulating damper until it reaches normal operating conditions. During operation, the temperature rise of the bearings shall not exceed 40℃ above the ambient temperature. The root-mean-square value of vibration velocity at the bearing location shall not exceed 6.3 mm/s.

Keywords:

G4-68 and Y4-68 type boiler ventilators

Category:

Industrial centrifugal fan