G4-73 and Y4-73 type boiler ventilators

The G4-73 and Y4-73 boiler induced-draft and forced-draft fans are primarily designed for use in steam boiler systems ranging from 2 to 670 tons per hour in thermal power plants. Under conditions where no other special requirements exist, the G4-73 can also be used for mine ventilation and general ventilation applications. The medium conveyed by these fans is air, with a maximum temperature not exceeding 80℃; the medium conveyed by the induced-draft fan is flue gas, with a maximum temperature not exceeding 250℃. Before the induced-draft fan, a dust removal device must be installed to minimize the dust content of the flue gas entering the fan as much as possible. According to typical operating conditions in power plants, the efficiency of the dust collector equipped should be no less than 85%.

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Usage

The G4-73 and Y4-73 boiler induced-draft and forced-draft fans are primarily designed for use in steam boiler systems ranging from 2 to 670 tons per hour in thermal power plants. When no other special requirements exist, the G4-73 fan can also be used for mine ventilation and general ventilation applications. The medium conveyed by these fans is air, with a maximum temperature not exceeding 80℃; the medium conveyed by the induced-draft fan is flue gas, with a maximum temperature not exceeding 250℃. Before the induced-draft fan, a dust removal device must be installed to minimize the dust content of the flue gas entering the fan as much as possible. According to typical usage conditions in power plants, the efficiency of the dust remover equipped should be no less than 85%.

Form

1. Both the ventilator and the induced-draft fan are designed with single-inlet configurations, each available in 13 model sizes ranging from №8 to №29.5.

2. When viewed from the end of the motor, if the impeller rotates clockwise, the fan is referred to as a right-hand rotating fan and is denoted by “right”; conversely, if it rotates counterclockwise, the fan is a left-hand rotating fan and is denoted by “left.”

3. The position of the fan’s air outlet is indicated by the angle of the casing’s air outlet.

4. The fan’s transmission method is Type D, and all connections are made using flexible couplings.

Structural features

① Impeller—12 backward-curved, wing-shaped blades with beveled edges are welded between a conical arc-shaped front disc and a flat rear disc.

Thanks to the use of airfoil-shaped blades, the fan boasts high efficiency, low noise, and high strength. The impeller has undergone static and dynamic balancing corrections as well as overspeed operation tests, ensuring smooth and reliable operation. Impellers for both supply and induced draft fans of the same model number share the same structural design but differ in material; generally, A3 steel is selected for supply fans, while 16Mn steel is chosen for induced draft fans.

② Casing — The casing is welded from ordinary steel plates into a volute shape. For single-inlet fans, the casings are available in three different designs: (Casing sizes №8 to №12 are designed as integral structures and cannot be disassembled; casing sizes №14 to №16 are designed with a two-part split structure; casing sizes №18 to №29.5 are designed with a three-part split structure). For induced-draft fans, the volute plates have been appropriately thickened to prevent wear.

③ Air inlet—The converging, streamlined air inlet is designed as an integral structure and secured to the fan inlet side using bolts.

④ A device used to regulate airflow, installed axially upstream of the air inlet. The adjustment range spans from 0° (fully open) to 90° (fully closed). Regarding the position of the lever on the damper: when viewed from the direction of the air inlet, for right-hand rotation fans, pushing the lever upward from bottom to top corresponds to a transition from fully closed to fully open; for left-hand rotation fans, pulling the lever downward from top to bottom corresponds to a transition from fully closed to fully open.

⑤ Drive Assembly—The main shaft of the drive section is made of high-quality steel, and all fans in this series are equipped with rolling bearings. There are two types of bearing housings: for sizes №8 to №16, a monolithic cylindrical bearing housing is used; for sizes №18 to №29.5, two separate pillow-block bearing housings are employed. The bearing housings are fitted with thermometers and oil-level indicators (for induced-draft fans only). The lubricating oil used is No. 30 mechanical oil, and the oil level must be maintained according to the markings on the oil-level indicator. For sizes №8 to №16, if a dry-lubrication system is adopted in the monolithic cylindrical bearing housing, an oil-deflector plate should be installed on the ball-bearing side inside the housing; the mounting slots for this plate are pre-machined. The induced-draft fans are equipped with a water-cooling system; therefore, a water supply pipe must be installed. The water consumption varies depending on the ambient temperature but typically ranges from 0.5 to 1 m³/h.

Run operation

G、Y4—73No20F ～ 31.5F are induced draft fans designed to match 100,000- and 200,000-kilowatt thermal power generating units.

It is a new-type product redesigned based on the G, Y4—73Nn20 D~29.5 D model, taking into account issues that have arisen over more than 20 years of production and use. Compared to the original series of fans, it features the following significant improvements:

① The original fan’s cantilever support (D-type) transmission method has been changed to an intermediate support (F-type) transmission method, thereby enhancing the stability of fan operation.

② Based on model tests (impeller outer diameter D = 1000 mm), the intake chamber adapted to this type of fan was added, and the original inlet shape was modified to an eccentric inlet.

③ An adjustable vane damper with airfoil-shaped blades is installed at the inlet of the intake chamber to regulate the fan’s performance and enhance its adjustment efficiency. The support points of the adjustable blades are equipped with rolling bearings, ensuring smooth rotation and reliable operation.

④ Since most blowers operate in environments with relatively high temperatures, their bearings tend to heat up easily. Therefore, the bearing housings of the new series of blowers, like those of induced draft fans, also adopt a water-cooling system.

⑦ The fresh-air fan’s design enhances the rigidity of both the casing and the intake chamber. Appropriate-height grid-shaped stiffening ribs are welded to the exterior of the casing and intake chamber, while hollow tubes are welded inside for support. As a result, vibrations caused by insufficient casing rigidity are eliminated.

Ⓑ Considering the dust particle wear issue on the induced-draft fan impeller, we have increased the solid portion at the leading edge of the airfoil blades and added wear-resistant plates near the trailing edge of the blades. Additionally, we have applied wear-resistant weld overlays using wear-resistant electrodes to areas prone to severe wear, achieving a hardness of HRC48 or higher. This has significantly extended the service life of the impeller and met the operational and maintenance requirements of power plants.

Keywords:

G4-73 and Y4-73 type boiler ventilators

Category:

Industrial centrifugal fan