Centrifugal pump for the delivery of hot liquids

Details Centrifugal pump for the delivery of hot liquids Centrifugal pump for the delivery of hot liquids

1989-04-14

1990-12-25

Garrett, Robert E.

Rotary kinetic fluid motors or pumps

Including means for handling working fluid leakage

415227, 277 67, F04D 2912

Patent

active

049798758

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a centrifugal pump for the delivery of hot liquids with at least one shaft passage through the pump housing to the outside, which passage is provided with a mechanical seal, which is arranged inside a sealing space which contains the delivered liquid, is separated from the pump housing by a spacing zone with close shaft play and comprises means for the generation of a liquid circulation within the sealing space for the flushing of the sliding surface area of the mechanical seal.
Highly stressed mechanical seals are rinsed in order to carry away the heat occurring in the sliding surface area. In the case of the known pump mentioned at the beginning (DE-A-No. 21 40 959), the flushing is effected by liquid circulation within the sealing space. For this, there is provided on a rotating part of the mechanical seal a delivery thread, which interacts with the close sealing housing and generates an axial flow in the sealing space, which is returned through a channel connecting the ends of the sealing space such that it hits the sliding surface area of the mechanical seal. The heat taken up by the flushing stream is given off by the ambient air in the region of the return channel. Heat input by liquid exchange with the delivery stream of the pump is virtually ruled out by the fact that the sealing space is in connection with the pump only via a narrow shaft gap.
This arrangement is suitable for liquids such as thermal oil. In the case of use for hot water, however, difficulties have arisen at the mechanical seal. The invention comprises the realization of the decisive reasons for this. Even if the sealing space is completely filled with hot water at the beginning of operation, gas can gradually separate out from it and accumulate in the sealing space. This process does not end when the quantity of liquid in the sealing space has given off its gas content, because a very slight liquid exchange with the pump takes place all the time and therefore small amounts of gas are also separated out all the time and cannot be flushed out of the sealing space due to the design. On account of the centrifugal effect of the liquid rotating in the sealing space with the mechanical seal, the separated gas tends to accumulate on the mechanical seal and to disturb the flushing effect necessary there. Cooling and lubrication of the sliding surface area is thereby put at risk.
This problem occurs not only in the case of pumps other than of the generic type in which the sealing space is in flushing connection with the delivery stream, because then any separations are carried away out of the sealing space, as are solid foreign particles. For instance, a pump is known (DE-A-34 38 662), in which the sealing space is in connection by a first channel with a region of high pressure and by a second channel with a region of low pressure of the pump. In the case of another known pump (DE-A-31 37 692), a circulation path which serves for the flushing away of foreign substances, such as sand, from the mechanical seal, is formed by constructing a tubular wall within the sealing space. It remains open here in which way the sealing space is connected to the pump space. However, since it is not to be assumed that the seal flushing stream may enrich the foreign substances and return to the mechanical seal, there must be a flushing connection with the pump space.
Finally, it is known (FR-A-2 288 241), to provide the sealing space, separated from the pump space by a narrow shaft gap, with a flushing and cleaning opening arranged at the top, which would be suitable for the removing of gas accumulations when the pump is at a standstill; but there is no corresponding indication as to use.
The invention is therefore based on the object, on the basis of the realization explained above, of making a centrifugal pump of the type mentioned above suitable for the use of gas-containing liquids.
The solution according to the invention consists in the combination of features that include mechanical seal, and
The first functional element of the

REFERENCES:
patent: 1990519 (1935-02-01), Bigelow et al.,
patent: 2203525 (1940-06-01), Dupree, Sr.
patent: 3111904 (1963-11-01), Burns
patent: 3589738 (1971-06-01), Tracy
patent: 3600101 (1971-08-01), Oglesby
patent: 4621975 (1986-11-01), Larson
patent: 4695223 (1987-09-01), Caspar et al.

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