DE19726889A1 - Pump housing for single-stage centrifugal pump - Google Patents

Abstract

The pump housing has an inner and outer shell of different materials. The outer contour of the inner shell (1) and the inner contour of the outer shell (2) are the same so that the inner shell fits exactly in the outer shell and the contact between the two shells is solely through flat or rotationally symmetrical surfaces. The inner shell is made from several matching parts (4-6) contacting each other through flat or rotationally symmetrical faces. The conveyor medium can pass through gaps remaining between the fitted parts of the inner shell.

Description

The invention relates to a pump housing of a single-stage centrifugal pump, which consists of an inner and an outer shell, the inner and the Outer shell are made of different materials.

In process engineering, there are more and more applications in which through Centrifugal media that are conveyed under high temperatures, often too are under high pressures, but above all a high proportion Include abrasives.

The high pressures require ductile, the high temperatures ductile and temperature-resistant materials. However, these materials show due to their Structure only conditional wear resistance in the presence of Abrasives. Wear-resistant materials such as ceramics or carbide Steels, however, are brittle, so they are not suitable for the existing risk of breakage pressure-bearing pump components can be used.

To solve the contradiction shown, double-shell housings used in which the inner shell is made of a brittle, wear-resistant Material and the outer shell from a ductile or a temperature-resistant and ductile material is produced. This ensures that if the brittle shell breaks, at most a small amount of pumped medium in the environment can leak. The largest compression part of a single stage Centrifugal pump is the pump housing. Because this is an irregular shape  shows, a division into two shells is not so easy developed, two were implemented to achieve the two-shell construction different approaches:

In the first solution, the inner shell is supported only at a few points on the outer shell. This can become severe under extreme operating conditions Lead loads on the inner shell. So z. B. Blows one Destruction of the inner shell.

In the second solution, the remaining spaces between the inner and the outer shell by a flowable and then hardening during assembly Mass filled out. The masses used for this purpose are mostly organic substances with a relatively low temperature resistance, so that high temperatures cannot be controlled. Another disadvantage of this The solution is that when the inner shell leaks at different Pumped media a reaction between the filling mass and the pumped medium can take place.

The invention has for its object a consisting of two shells To design centrifugal pump housing so that the disadvantages of Known solutions can be avoided that especially the risk of breakage for the Inner housing significantly reduced and by a nonetheless occurring Breakage hazards are minimized.

Starting from a pump housing of the type mentioned, the object is achieved in that

• a) the outer contour of the inner shell and the inner contour of the outer shell are equal to each other,
• b) the inner shell is inserted into the outer shell with a precise fit,
• c) the contact between the inner shell and the outer shell exclusively over flat and / or rotationally symmetrical surfaces he follows.

Because the outer shape of the inner shell and the inner shape of the outer shell match each other same and because only simple shapes such as cylinders and planes are used the surfaces of the two shells that are in contact with one another can be manufactured easily and with great precision. This enables one form-fitting fitting of the inner shell into the outer shell without one Intermediate layer is required.

The inner and outer shell can be made in several parts, whereby it It is recommended to make contact between the individual parts of the inner shell to be carried out over flat and / or rotationally symmetrical surfaces.

Since the inner shell is supported by the outer shell, it becomes one breakable material existing housing part only under pressure claimed. Such materials, in particular those, are opposed to compressive forces Ceramics, very resistant.

Now the existing between the inner shell and the outer shell can minimal gap when operating over a larger temperature range by a higher thermal expansion of the outer shell can be expanded so that the Support of the inner by the outer shell is loosened somewhat. For such cases provides an expedient embodiment of the invention that on the inner shell a connection between the Interior of the centrifugal pump and the area surrounding the inner shell consists. This creates a pressure equalization between the inside and the outside the inner shell. The danger of a load leading to breakage will canceled.

With an inner shell assembled from several parts, the between the individual parts remaining column than the passage of Connection allowing fluid to be used.

The design according to the invention provides a high level of security against breakage the inner shell. Even after a break that cannot be completely excluded remains one equipped with the pump housing according to the invention  Centrifugal pump is still fully operational in most cases. One at a break adjusting crack in the inner shell leads through the Outer shell does not cause the inner shell to fall apart; the crack filled only the desired function of the passage of the medium external connection.

The invention is explained in more detail using an exemplary embodiment. The Drawing shows in

Fig. 1 is an axial section through one half of the invention designed according to the pump housing;

FIG. 2 shows a radial section through a pump housing corresponding to FIG. 1.

The pump housing of FIGS. 1 and 2 consists essentially of an inner shell 1 made of ceramic and an outer shell 2 made of metal. Both the inner shell 1 and the outer shell 2 are made in several parts.

Parts 4 and 5 enclosing a pump chamber 3 and part 6 forming the outlet from the pump housing belong to the inner shell. The outer shell 2 is formed by a suction-side housing cover 7 , a pressure-side housing cover 8 and a middle housing part 9 arranged between them.

All parts 4 to 9 , where they rest on one of the other parts 4 to 9 , have a geometrically simple surface that is rotationally symmetrical and / or flat. Since surfaces of this type can be produced simply and with high precision, an exact positive fit of the inner shell 1 into the outer shell 2 and the parts 4 to 6 of the inner shell 2 is made possible.

The necessary sealing of the pump housing takes place by means of seals 10 , which are arranged between the suction-side housing cover 7 and the housing middle part 9 and between the pressure-side housing cover 8 and the housing middle part 9 . This sealing made in the area of the outer shell 2 allows liquid from the pump chamber 3 to pass into the gap between the inner shell 1 and the outer shell 2 through specially provided openings and / or through gaps between parts 4 and 5 of the inner shell 1 , without pumping liquid getting to the outside of the pump housing.

The gap between the inner shell 1 and the outer shell 2 , which is initially very small, can widen if the outer shell 2 has a greater thermal expansion than the inner shell 1 during operation over a larger temperature range. The pumping medium coming out of the pump chamber 3 via openings and / or gaps fills this gap, as a result of which the pressures acting on the inside and the outside of the inner shell 1 are kept in balance. The inner shell 1 is thus constantly kept in a state of pressure equilibrium over the entire operating range between starting at a relatively low temperature and continuous operation at a high temperature.

The supporting function of the outer shell 2 also ensures that a crack present in the inner shell 1 does not lead to the breakup. Rather, smooth operation can also be maintained in this case.

Of course, the adaptation to changing temperatures and the constant support of the inner shell 1 by the outer shell 2 can also be achieved in that the expansion coefficients of the outer shell 2 and the inner shell 1 are adapted to one another. So the inner shell 1 and the outer shell 2 would expand and contract to the same extent, the gap between them remaining minimal.

Claims (4)

1. Pump housing of a single-stage centrifugal pump, which consists of an inner and an outer shell, the inner and outer shell are made of different materials, characterized in that

• a) the outer contour of the inner shell ( 1 ) and the inner contour of the outer shell ( 2 ) are identical to one another,
• b) the inner shell ( 1 ) is inserted with a precise fit in the outer shell ( 2 ),
• c) the contact between the inner shell ( 1 ) and the outer shell ( 2 ) takes place exclusively over flat and / or rotationally symmetrical surfaces.

2. Pump housing according to claim 1, characterized in that the inner shell ( 1 ) consists of several precisely fitted parts ( 4 to 6 ), the contact between the individual parts ( 4 to 6 ) via flat and / or rotationally symmetrical surfaces. 3. Pump housing according to claim 1 or 2, characterized in that via the inner shell ( 1 ) there is a passage of the conveying medium connection between the interior ( 3 ) of the centrifugal pump and the area surrounding the inner shell ( 1 ). 4. Pump housing according to claims 2 and 3, characterized in that the connection permitting the passage of the conveying medium takes place via the gap remaining between the joined parts ( 4 to 6 ) of the inner shell ( 1 ).