FI76187C - ANORDNING FOER TAETNING AV SPRINGAN MELLAN EN CENTRIFUGALPUMPS AXELTAETNINGSHYLSA OCH AXEL. - Google Patents

Description

761 87

DEVICE FOR SEALING THE GAP BETWEEN THE CENTRAL EXHAUST PUMP SHAFT SEAL AND THE SHAFT

This invention relates to a device for sealing a gap between a shaft sealing sleeve and a shaft of centrifugal pumps used for conveying fluids and suspensions, preferably by attaching a metal bellows to the shaft sealing sleeve and using this as part of the pump power transmission, especially when the pump is started and running.

When using a hydrodynamic seal in a centrifugal pump, the seal is usually performed by means of a separate sleeve structure 15. In this case, a gap is formed between the shaft and the sleeve structure, which is used as a sliding surface of the sleeve along the shaft. Sealing of this gap is generally accomplished using conventional gap seals, such as rubber O-rings or lip seals, which, however, are insecure in use and easily allow pumped liquid to enter the sliding surface. In addition, the gap seals used are poor in withstanding the power transfer due to the sliding surface property of the gap. Therefore, a power take-off made of a wear-resistant material, such as a metal wedge, must be placed in connection with the slot seals in order to be able to provide a seal that reaches even the most profitable service life. However, the structure becomes complex and thus easily malfunctioning.

It is an object of the present invention to obviate the drawbacks of the prior art 30 and to provide an improved device for sealing a gap between a centrifugal pump shaft seal and a shaft while transferring power by means of this gap seal to enable hydrodynamic sealing. The essential features of the invention appear from the appended claim 1.

761 87 2

According to the invention, the sealing of the gap between the shaft sealing sleeve of the centrifugal pump and the shaft is performed by connecting a bellows, preferably of metal, to the shaft sealing sleeve. By selecting a metal, such as steel, as the bellows material, the bellows can be used as a power transmission at the same time. By means of the power transfer, the shaft sealing sleeve is slid along the shaft without a special structure, such as a wedge, to form a hydrodynamic seal which is advantageous for centrifugal pumps.

By using the bellows construction according to the invention as a power transmitter for the shaft sealing sleeve of a centrifugal pump and for sealing the shaft gap, the sealing structure can be assembled outside the pump itself, whereby during installation or repair the seal installation time is shortened and the pump efficiency can be increased.

The bellows seal according to the invention is a simple and thus also inexpensive solution. At the same time, the reliability of the seal is greatly improved.

The invention will be described in more detail below with reference to the accompanying drawing, in which Figure 1 shows a preferred embodiment 25 of the invention in a partially sectioned side view with the centrifugal pump in operation.

According to Figure 1, there is a sealing sleeve 2 around the shaft 1 of the centrifugal pump, at both ends of which a bellows 3 according to the invention is mounted. The bellows 3 is located between the impeller 4 and the auxiliary impeller 5 connected to the sleeve 2 and the sleeve 2 and the sleeve 2 1 between the flange or, as shown in the figure, the flange 8 of the shaft sleeve.

When the pump is stopped, the force member 7 seals the sealing surfaces 10 and 11 together to provide a mechanical seal 3 761 87, the bellows 3 in the intermediate 8 being at its widest, while the bellows 3 in the intermediate 6 being the smallest.

When the pump starts, the impeller 4 raises the pressure of the gap 6 to the working pressure of the pump. At the same time, the auxiliary vane 5 provides a pressure balance in the space 15 between the auxiliary vane 5 and the pump housing 13 wall 14, which causes a liquid ring 16 to form in the space 18 perpendicular to the auxiliary vane 5 and the wall 1 of the pump housing 13 perpendicular to the shaft 1. the resultant cancels the mechanical force caused by the force member 7. In this case, the sealing sleeve 2 starts to slide axially 1 away from the impeller 4 in order to maintain a balance of hydrodynamic and mechanical forces. At the same time, the bellows 3 according to the invention in space 8 shrinks, while the bellows in space 6 increases. Since the bellows 3 is attached to the shaft 1 at one end in both gaps 6 and 8, the liquid to be pumped cannot flow out of the pump 20 through the gap 9.

When the pump is running, the bellows 3 still acts as a power transmitter to maintain a favorable position for the power balance of the sleeve 2 and to compensate for pressure fluctuations in the pipelines.

When the pump stops, the compressive forces caused by the liquid to be pumped are reduced and the sealing sleeve 2 moves back towards the impeller 4 under the control of the bellows 3.

30

Claims (4)

761 87 An apparatus for sealing a gap between a shaft sealing sleeve of a centrifugal pump and a shaft in connection with a hydrodynamic shaft seal, to which an auxiliary impeller forming a hydrodynamic seal or the like is attached and one of the surfaces forming a mechanical seal 10 is arranged, the gap between the shaft sealing sleeve and the shaft ), a bellows (3) is connected to both ends of the sealing sleeve (2) as part of the power transmission between the sealing sleeve (2) and the shaft (1). 15 Device according to Claim 1, characterized in that the bellows (3) is arranged both between the impeller (4) and the sleeve (2) and between the sleeve (2) and the flange on the shaft (1). 20 Device according to Claim 1 or 2, characterized in that each bellows (3) is connected at one end to the pump shaft (1). Device according to one of the preceding claims, characterized in that the bellows (3) is made of metal.