JP3611442B2 - Double barrel multistage pump structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an inner casing that defines an internal water flow channel and an outer casing that covers the outside of the inner casing and contains internal water, and supports both ends of the pump shaft with water-lubricated bearings. The present invention relates to a structure of a double-cylinder multistage pump in which a shaft sealing chamber is provided outside each bearing, and a thrust bearing is built in one shaft sealing chamber.
[0002]
[Prior art]
The most common structure of the conventional double cylinder multistage pump is that a bearing is provided outside each shaft sealing chamber provided at both ends of the casing, which requires an external bearing lubrication device. there were. Providing this external bearing lubrication device raises the initial cost, which accounts for a significant proportion of the cost of the pump body, and causes many troubles due to this lubrication device. The maintenance cost was also high.
[0003]
In order to solve this problem, the present applicant has disclosed a technique in which a water-lubricated bearing is disposed inside the shaft seal chamber to eliminate the need for an external lubrication device in Japanese Patent Laid-Open No. 9-303281. Yes.
[0004]
According to this known technique, as shown in FIG. 3, an inner casing 10 that surrounds two impellers 2 and 3 fixed to a pump shaft 1 and defines an internal water flow path is provided. Internal water is sealed by an outer casing body 21 provided outside the inner casing 10 and end plates 22 and 24 provided at both ends. The two end plates 22 and 24 are fitted with water-lubricated bearings 5 and 6, respectively, to support the pump shaft 1. The outer sides of the bearings 5 and 6 respectively have first or second shafts. Sealing chambers 23 and 25 are provided. The first shaft seal chamber 25 includes thrust bearings 7 and 7, and the shaft seal chambers 23 and 25 are communicated with each other via a balance pipe 28A.
[0005]
In addition, the code | symbol 4 shows the balance bush for balancing the pressure of the inner chamber 12 pressure-pressed (Pc) with the impeller 2, and the 1st shaft seal chamber 25, Moreover, the code | symbol 26 shows a suction chamber, Reference numeral 27 denotes a discharge chamber.
[0006]
As described above, this known technique can eliminate the need for an external lubrication device. On the other hand, the two shaft seal chambers 23 and 25 containing the bearings 5 and 6 are communicated with each other by a balance pipe 28A. Therefore, the internal pressure and temperature are the same as the pump suction conditions. Therefore, if the suction temperature of the pump is high, the thrust bearings 7 and 7 built in the first shaft seal chamber 25 are also exposed to a high temperature due to the above reason.
[0007]
And when it becomes high temperature, since the viscosity of water will fall remarkably, the lubrication conditions of the thrust bearing 7 will become very inferior. Further, if the suction pressure is high, the internal pressure of both shaft sealing chambers 23 and 25 becomes high, and the thrust load for pushing the shaft 1 to the right in FIG. 3 becomes very large. At present, it is extremely difficult to obtain a reliable underwater thrust bearing that can be used in response to such severe lubrication conditions and load conditions.
[0008]
[Problems to be solved by the invention]
Therefore, the present invention provides a structure of a double-cylinder multi-stage pump that incorporates a water-lubricated bearing in a shaft seal chamber that can be applied to usage applications under high-temperature and high-pressure suction conditions by reducing the thrust bearing lubrication and load conditions. It is intended to provide.
[0009]
[Means for Solving the Problems]
According to the present invention, an inner casing that defines an internal water flow channel and an outer casing that covers the outside of the inner casing and contains internal water are provided, and both ends of the pump shaft are supported by water-lubricated bearings, In the structure of the double cylinder multistage pump in which the first or second shaft sealing chamber is provided outside each of the bearings, and the first shaft sealing chamber has a thrust bearing built therein, the first bearing having the thrust bearing built therein is provided. A shaft thrust balance mechanism is provided between the one shaft seal chamber and the inner casing, a decompression bush is provided between the shaft thrust balance mechanism and the first shaft seal chamber, and pressure is applied to the first shaft seal chamber. An escape port is provided.
[0010]
A cooling water inlet is provided between the axial thrust balance mechanism and the decompression bush.
[0011]
Or the cooling water flow path which cools the said pressure reduction bush is provided.
[0012]
Therefore, according to the present invention, the pressure in the first shaft seal chamber is reduced by the pressure relief port provided in the first shaft seal chamber with the built-in thrust bearing, and the thrust load is reduced.
[0013]
And low temperature water is inject | poured from the cooling water injection port provided between the axial thrust balance mechanism and the pressure reduction bush, This water is pressure-reduced by a pressure reduction bush, enters a 1st shaft sealing chamber, and discharges | emits from a pressure relief port. Then, the thrust bearing is cooled to improve the lubrication conditions, and the high temperature water on the shaft thrust balance mechanism side is prevented from flowing into the shaft seal chamber, so the temperature in the first shaft seal chamber is lowered and the pressure is reduced. This reduces the thrust load. Alternatively, the pressure reducing bush is cooled by the cooling water flow path for cooling the pressure reducing bush, the water flowing from the shaft thrust balance mechanism side to the first shaft sealing chamber is cooled, and the lubrication conditions are improved in the same manner as described above to reduce the thrust load. Is done. In this configuration, the cooling water does not flow from the balance mechanism side to the suction side, which is suitable when it is desired to avoid mixing the pumped liquid and the cooling water.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same components as those in the pump structure described in FIG.
[0015]
In FIG. 1, one end plate 24 is provided with a first shaft sealing chamber 25 containing thrust bearings 7, 7 at the tip, and a water-lubricated bearing 6 is fitted in the inside thereof. . Further, the pump inner chamber 12 is partitioned by a decompression bush 8 and a balance bush 4. Between the decompression bush 8 and the balance bush 4, a first and a second partition partitioned by a partition 32 into two chambers. Two balance chambers 29 and 29A are provided, and the inner first balance chamber 29 is communicated with a second shaft sealing chamber 23 and a balance pipe 28 to constitute an axial thrust balance mechanism. The outer second balance chamber 29 </ b> A is provided with a cooling water inlet 31 for introducing the cooling water W from the outside, and a pressure relief port 30 is provided at the tip of the first shaft seal chamber 25. Is provided.
[0016]
The first balance chamber 29 is communicated with the second shaft sealing chamber 23 by the balance pipe 28, and the second shaft sealing chamber 23 is communicated with the suction chamber 26, so that the pressure of the first balance chamber 29 is Becomes equal to the pressure Ps of the suction chamber 26. On the other hand, the pump inner chamber 11 has a pressure Pc boosted by the impeller 2, and a pressure difference Pc-Ps is generated between the first balance chamber 29 and the inner chamber 11, and a small amount of high-temperature water is generated. It is limited by the balance bush 4 and is circulated by the path of the pump inner chamber 11 → the first balance chamber 29 → the balance pipe 28 → the second shaft sealing chamber 23 → the suction chamber 26.
[0017]
In addition, water squeezed by the decompression bush 8 from the second balance chamber 29A flows into the first shaft seal chamber 25. The shaft seal chamber 25 is provided with a pressure relief port 30 so that the water in the room is Since it always flows out, the pressure in the first shaft sealing chamber 25 is lower than the pressure in the balance chamber 29A, and the pressure acting on the end surface of the pump shaft 1 is low, so the thrust load is reduced and the load on the thrust bearing 7 is reduced. Is alleviated.
[0018]
On the other hand, when the internal pressure of the first shaft seal chamber 25 reaches the saturated vapor pressure at that temperature due to the reduced pressure, the water is flushed and causes various obstacles, so the amount of reduced pressure is restricted by the saturated vapor pressure. Therefore, when the saturated steam pressure is high and the temperature is high, sufficient pressure reduction cannot be performed, and the load on the thrust bearing 7 cannot be sufficiently reduced.
[0019]
In order to cope with such a case, an inlet 31 for cooling water W is provided in the second balance chamber 29A. Since the second balance chamber 29A is partitioned by the inner first balance chamber 29 and the partition 32, the injection pressure of the cooling water W can be set slightly higher than the pressure Ps of the first balance chamber 29. For example, most of the cooling water W injected into the second balance chamber 29A is depressurized by the decompression bush 8 and enters the first shaft sealing chamber 25, is discharged from the pressure relief port 30, and the inner first The outflow to the balance chamber 29 can be reduced. In this way, the flow of high temperature water into the first shaft seal chamber 25 is blocked, the temperature of the chamber becomes low, and the pressure on the thrust bearing 7 is reduced by sufficiently reducing the pressure. And the viscosity of water becomes high by the fall of temperature, and lubrication conditions are eased.
[0020]
When the injection pressure of the cooling water W into the second balance chamber 29A is substantially equal to the pressure Ps of the first balance chamber 29, some high-temperature water is transferred from the first balance chamber 29 to the second balance chamber. It flows into 29A, mixes with the cooling water W here, depressurizes with the decompression bush 8 and flows into the first shaft seal chamber 25. Even in this case, the temperature of the first shaft seal chamber 25 is lowered. There is no change in doing.
[0021]
Next, in the embodiment shown in FIG. 2, a cooling water flow path 33 is provided on the outer peripheral surface of the decompression bush 8A, and a cooling water inlet 34 and a cooling water outlet 35 communicating with the cooling water flow path 33 are provided on the end plate 24. ing.
[0022]
Accordingly, part of the high-temperature water in the balance chamber 29 is decompressed by the decompression bush 8 and enters the first shaft seal chamber 25 and flows out from the pressure relief port 30. At that time, the high-temperature water is cooled by exchanging heat with the cooling water W in the cooling water flow path 33 through the reduced pressure bush 8A in the process of passing through the reduced pressure bush 8A.
[0023]
In the embodiment shown in FIG. 1, mixing of the cooling water and the pumped liquid occurs, whereas in this embodiment, such mixing does not occur. Therefore, this method is suitable for the case where mixing of pumping liquid and cooling water is desired to be avoided.
[0024]
The cooling water channel 33 may be formed in various shapes so that heat exchange can be easily performed in addition to the simple one formed on the outer peripheral surface of the decompression bush 8A as shown in the figure. Absent.
[0025]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
(1) The shaft seal chamber is decompressed by the pressure relief port provided in the first shaft seal chamber incorporating the thrust bearing, and the thrust load can be reduced.
(2) Then, low-temperature water is injected from a cooling water inlet provided between the shaft thrust balance mechanism and the pressure-reducing bush, depressurized by the pressure-reducing bush, enters the first shaft seal chamber, and is discharged from the pressure relief port. As a result, the thrust bearing is cooled to improve the lubrication conditions and the high temperature water on the shaft thrust balance mechanism side is prevented from flowing into the shaft seal chamber, the temperature in the shaft seal chamber is lowered and the pressure is reduced. Is reduced.
(3) The reduced pressure bush is cooled by the cooling water flow path for cooling the reduced pressure bush, the water flowing into the first shaft sealing chamber from the axial thrust balance mechanism side is cooled, the lubrication conditions are improved, and the thrust load is reduced. . In this configuration, the cooling water does not flow from the balance mechanism side to the suction side, which is suitable when it is desired to avoid mixing the pumped liquid and the cooling water.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing the structure of a conventional double cylinder multi-stage pump.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pump shaft 2, 3 ... Impeller 4 ... Balance bush 5, 6 ... Water lubrication bearing 7 ... Thrust bearing 8, 8A ... Decompression bush 10 ... Inner casing 21 ... Outer casing main body 23 ... second shaft sealing chamber 25 ... first shaft sealing chamber 28, 28A ... balance piping 29 ... first balance chamber 29A ... second Balance chamber 30 ... Pressure relief port 31 ... Cooling water inlet 33 ... Cooling water channel 34 ... Cooling water inlet 35 ... Cooling water outlet

Claims (3)

An inner casing that defines the internal water flow channel and an outer casing that covers the outside of the inner casing and contains the inner water are provided, and both ends of the pump shaft are supported by water-lubricated bearings. In the structure of the double cylinder multistage pump in which the first or second shaft sealing chamber is provided in each of the first shaft sealing chamber and the thrust bearing is built in one of the first shaft sealing chambers, A shaft thrust balance mechanism is provided between the casing, a pressure reducing bush is provided between the shaft thrust balance mechanism and the first shaft seal chamber, and a pressure relief port is provided in the first shaft seal chamber. The structure of the double-cylinder multistage pump characterized by the above. The structure of the double cylinder multistage pump of Claim 1 which provided the cooling water injection port between the said axial thrust balance mechanism and pressure reduction bushing. The structure of the double cylinder multistage pump of Claim 1 which provided the cooling water flow path which cools the said pressure-reduction bush.

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