WO1998031939A1

WO1998031939A1 - Vertical fan

Info

Publication number: WO1998031939A1
Application number: PCT/FI1998/000036
Authority: WO
Inventors: Rauli Tapani Hulkkonen; Jyri-Markku Vuorenmaa
Original assignee: ABB Fläkt Oy
Priority date: 1997-01-17
Filing date: 1998-01-16
Publication date: 1998-07-23
Also published as: FI101566B1; FI970213A0; AU5665598A; EP0953116A1; FI101566B

Abstract

The invention relates to a vertical fan comprising a blade wheel (1) and a vertical electric motor (2) to operate the blade wheel, the blade wheel being mounted below the electric motor directly on its shaft (3) to rotate around a substantially vertical shaft, there being means (4) arranged to the upper part of the electric motor (2) to damp down the vibration caused by the fan.

Description

VERTICAL FAN

The invention relates to a vertical fan comprising a blade wheel and a vertical electric motor to operate the blade wheel, the blade wheel being mounted below the electric motor directly on its shaft to rotate around a substantially vertical shaft.

In some process plants it is advantageous to use an integrated vertical fan. The fan is placed, for example, on the heat exchange unit of an evaporating plant without using any proper bed arrangement or canalization. Thus it is possible to build compact plants and save in the production costs.

The motor-driven vertical fan is implemented by mounting a blade wheel directly on the shaft of a vertical flanged electric motor. The fan differs from a normal motor-driven fan only with respect to its position, and as a consequence, the rotor system behaves differently than that of a horizontal fan. Because the static load focusing on the motor is only axial, no static force focuses on the bearings in the radial direction. Therefore, the position of the shaft in the bearing is very changeable when the fan is on, and even a slight change in the force balance of the system alters the position of the shaft. Even a very slight unbalance in the blade wheel makes the shaft rotate unevenly in the bearing when the fan is on, which is seen as vibration in the measurements. If the vibration continues for a long time, the bearings will be damaged.

Vertical fans are usually used in processes in which the blade wheel is prone to wear and dirty. This unbalances the blade wheel, and thus causes vibrations in the shaft/bearing system. To ensure undisturbed operation these fans should be post-balanced frequently enough and vibrations in the bearings should be monitored with constant measurements. This increases the operating and service costs of the plants designed to be unattended.

An object of the present invention is to eliminate the drawbacks described above. This is achieved with a vertical fan of the invention, characterized in that there are means arranged to the upper part of an electric motor to damp down vibrations.

The means for damping down vibration preferably comprise a bed mounted on the upper par of the electric motor, flexible material fitted on the bed, and damping mass arranged onto the flexible material. The solution of the invention allows to reduce the sensitivity of the fan to vibrations and damage. Furthermore, it is neither necessary to post- balance the fan nor to wash and service the blade wheel as often as earlier.

In the following, the invention will be described in greater detail by means of a preferred embodiment with reference to the accompanying drawings, in which

Figure 1 shows a fan of the invention,

Figure 2 shows a partially sectional side view of the damping bed illustrated in Figure 1 , Figure 3 shows a top view of the damping bed illustrated in Figure

2,

Figure 4 shows a partially sectional side view of the damping mass illustrated in Figure 1 ,

Figure 5 shows a bottom view of the damping mass illustrated in Figure 4, and

Figure 6 shows a partially sectional side view of the damping bed, damping mass and intermediate flexible material of the previous figures, illustrating their co-operation.

The vertical fan shown in Figure 1 comprises a blade wheel 1 , a vertical electric motor 2 to operate the blade wheel 1 , the blade wheel being mounted below the electric motor directly on its shaft to rotate around a substantially vertical shaft, and a construction 4 arranged to the upper part of the electric motor 2 to damp down the vibrations of the fan. The fan is fastened on top of the heat exchange unit 12 with flange joints without using a proper bed arrangement or canalization.

The construction 4 damping down vibrations, illustrated in Figures 1 to 6, comprises a bed 5 fastened to the upper part of the electric motor 2, flexible material 6 fitted on the bed 5, and damping mass 7 arranged onto the flexible material, the damping mass resting on the flexible material 6. The bed 5 is a cylinder-like rack, which has an opening 8 in the middle so that the rack can be mounted at the desired height around the casing of the electric motor 1 , and an annular flange 9 for the ring-shaped flexible material 6 and ring-shaped damping mass 7 to be fitted on the flexible material. In this example, the bed 5 is fastened with screws to the upper part of the casing of the electric motor. In the flange 9 and on the lower surface of the damping mass 7 there are respective grooves 10 and 11 for the flexible material 6 so that the damping mass 7 would rest immovably on the flexible material 6.

The flexible material 6 is preferably rubber, and its width is such that the damping mass 7 never touches the bed 5.

The damping mass 7 consists of basic mass 7a and possible additional damping masses 7b, i.e. additional damping mass/masses 7b can be fastened on top of the ground mass 7a e.g. with screws.

The above construction 4 allows to substantially reduce the sensitivity of the fan 4 to the vibrations caused by the unbalance of the blade wheel 1. This is realized by tuning the construction 4 to the same resonance frequency as the fan by altering the flexibility of the flexible material 6 and by adjusting the weight of the damping mass 7 e.g. by means of additional damping masses 7b. When unbalanced mass makes the fan vibrate, the damping mass 7 resonates with the fan at a reverse stage. The use of suitable masses at the reverse stage damps down the vibration since the opposite forces cancel each other out. A system implemented in this way is considerably less sensitive to vibrations.

The invention has been described above only by means of one preferred embodiment of it. One skilled in the art can, however, implement the fan of the invention and its details in several alternative ways within the scope of the appended claims.

Claims

1. A vertical fan comprising a blade wheel (1) and a vertical electric motor (2) to operate the blade wheel, which is mounted below the electric motor directly on its shaft (3) to rotate around a substantially vertical shaft, characterized in that there are means (4) arranged to the upper part of the electric motor to damp down the vibration of the fan.

2. A fan as claimed in claim 1, characterized in that the means (4) for damping down vibration comprise a bed (5) fastened to the upper part of the electric motor (2), flexible material (6) fitted on the bed and damping mass (7) arranged onto the flexible material.

3. A fan as claimed in claim 2, characterized in that the bed (5) is a cylinder-like rack which has an opening (8) in the middle so that it can be arranged at the desired height around the casing of the electric motor (2), and an annular flange (9) for the ring-shaped flexible material (6) and ring- shaped damping mass (7) to be fitted on the flexible material.

4. A fan as claimed in claim 3, characterized in that said flange (9) and damping mass (7) comprise respective grooves (10, 11) for the flexible material (6).

5. A fan as claimed in any one of claims 2 to 5, characterized in that the damping mass (7) consists of basic mass (7a) and possible additional damping masses (7b).