JPS6249478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention mainly relates to a shaft sealing device for a rotary pump that handles high-temperature and high-pressure fluid.

[Prior art]

As shown in FIG. 1, a conventional pump of this kind, that is, a boiler feed water pump for a thermal power plant that handles high-temperature and high-pressure fluid, has a casing 1 having a suction portion 1a and a discharge portion 1b, and a rotating shaft 2 passing through the casing 1. and an impeller 3 attached to the rotating shaft 2 and housed within the casing 1. A shaft sealing portion 4 is formed in the portion where the rotating shaft 2 passes through the casing 1.

As shown in FIG.
It consists of a sleeve 5 attached to the outer circumferential surface of the casing 1, and a cylindrical bushing seal 6 (hereinafter referred to as labyrinth) attached to the inner circumferential surface of the casing 1 and opposed to the sleeve 5 with minute gaps 8a to 8d,
The labyrinth 6 is provided with passages 7a, 7c, and 7b that communicate with sealed water supply channels 9a, 9c and sealed water extraction channels 9b provided in the casing 1, respectively.

In the conventional shaft sealing section 4 having the above structure, high pressure water a is supplied from the sealing water supply channels 9a and 7a, and low pressure water C is supplied from the sealing water supply channels 9c and 7c through the minute gaps 8a, 8b and 8c, respectively. 8d, and extracted water b, which is a mixture of the high-pressure water a and low-pressure water c, is extracted from the extraction passages 7a and 9b. The extraction water b extracts the high pressure water a to the outside, thereby reducing the pressure and reducing the amount of high temperature fluid on the pump side A leaking to the outside. However, when the pressure of the high temperature fluid is reduced, this fluid may evaporate and cause seizure of the shaft seal sliding part. For this reason, low pressure sealing water C
By sealing water into the minute gaps 8c, 8d from the sealed water supply channels 9c, 7c on the anti-pump side B, it is possible to prevent the high temperature water a leaking into the minute gap 8c from vaporizing.

Figure 3 shows the water sealing system of the boiler feed water pump, and first we will discuss part of the flow of the boiler feed water. The feed water flowing out from the deaerator A is once pressurized by the booster pump PRO, then boosted to about 200 atm by the low pressure boiler feed water pump C, and then heated to about 400°C by the superheater E. This heated feed water is introduced into a high-pressure boiler pump, and then the pressure is increased to about 400 atmospheres before being sent to a boiler (not shown).

The sealing system of the shaft sealing part of the high-pressure boiler pump 2 is as described above with reference to Fig. 2, so the explanation will be omitted, but the sealing water a is fed to the boosting impeller provided for water sealing in the low-pressure boiler feed water pump h. , the pressure is increased above the absorption pressure of the high-pressure boiler feed water pump 2, and the water is supplied to the shaft sealing portion of the water feed pump 2. Seal water C is low-pressure, low-temperature water supplied from a condensate pump (not shown). Extracted water b is supplied to dehydrator i.

[Problem that the invention seeks to solve]

As mentioned above, in conventional rotary pumps for high-temperature and high-pressure fluids, water is sealed and extracted from the shaft seal.
In addition, since high-pressure water sealing is required, not only the shaft sealing portion becomes significantly long, but also the water sealing system becomes complicated.
Furthermore, if the supply of shaft sealing water is interrupted, the high-temperature, high-pressure water inside the pump may leak to the outside and vaporize, causing the pump to become inoperable.

In view of the above, the present invention aims to shorten the length of the shaft seal, simplify the water sealing system, significantly reduce the cost, and improve reliability during pump operation.

[Means for solving problems]

The first feature of the present invention for achieving the above object is that a mechanical seal and a cylindrical bushing seal are provided on the pump side and anti-pump side of the shaft seal part where the rotating shaft passes through the pump casing, so that the high temperature and high pressure inside the pump can be improved. The pump is configured to extract fluid from the shaft seal sliding part near the mechanical seal to the outside of the pump, and introduce the extracted high-temperature, high-pressure fluid into the shaft seal sliding part near the cylindrical bushing seal through a heat exchanger. Located in the shaft sealing device of a rotary pump for high temperature and high pressure fluids.

The second feature of the present invention is that a cylindrical bushing seal is provided in the shaft sealing part where the rotating shaft passes through the pump casing, and the high temperature and high pressure fluid inside the pump is transferred from the shaft sealing sliding part near the cylindrical bushing seal on the pump side. The high-temperature/high-pressure fluid is extracted to the outside and introduced into the shaft seal sliding part near the cylindrical bushing seal on the anti-pump side through a heat exchanger.
Located in the shaft sealing device of a rotary pump for high-pressure fluid.

In the above description of the present invention, the term "anti-pump side" means, in other words, the atmosphere side.

[Embodiments of the invention]

The present invention will be explained below with reference to the drawings.

In FIG. 4 and FIG. 5, 1 is a suction part 1a.
2 is a rotating shaft passing through the pump casing 1; 5 is a sleeve attached to the rotating shaft 2; 10 is a shaft sealing part through which the rotating shaft 2 passes through the pump casing 1; The sealing part 10 has a mechanical seal 11 on the pump side A,
Cylindrical bushing seal 1 on the anti-pump side (atmospheric side) B
2 (hereinafter referred to as labyrinths) are provided respectively. 13a and 13b are passages provided in the pump casing 1;
3b communicate with the shaft seal portion 10b between the mechanical seal 11 and the labyrinth 12, respectively.
14 is a heat exchanger provided outside the pump casing 1; 15a and 15b are water extraction pipes connecting the heat exchanger 14 and the passages 13a and 13b of the pump casing 1, respectively; and 16 is connected to the heat exchanger 14. It's a cold water pipe.

Next, the operation of this embodiment configured as described above will be explained.

The high-temperature, high-pressure fluid in the pump side A that has entered the shaft seal 10a near the mechanical seal 11 is extracted through the passage 13a of the pump casing 1 and the extraction pipe 15a, flows into the heat exchanger 14, At 14, it is cooled by cooling water flowing through a cooling pipe 16. This cooled extraction water is extracted from extraction pipe 1
5b and the passage 13b of the pump casing 1, after cooling the mechanical seal 11 and each shaft seal sliding part near the labyrinth 12, it is discharged to the atmosphere side B.

In another embodiment shown in FIG. 6, a cylindrical bush seal (labyrinth) 17 is attached to the inner circumferential surface of the pump casing 1 of the shaft seal portion 10 where the rotating shaft 2 fitted with the sleeve 5 passes through the pump casing 1.
The opening 18 provided in the labyrinth 17 is installed so as to face the labyrinth 17 to form a minute gap.
a, 18b to the passages 13a, 1 of the pump casing.
3b, respectively. The passages 13a, 13b are connected to a heat exchanger 14 provided outside the pump casing 1 via extraction pipes 15a, 15b, as in the previous embodiment. Since the second embodiment constructed in this manner operates in the same manner as the first embodiment shown in FIG. 5, a description thereof will be omitted.

High temperature (400°C) to which the above first and second embodiments are applied;
Figure 7 shows the water sealing system of a boiler feed pump for a thermal power plant that handles high-pressure (400 atm) water. Comparing this water sealing system with the conventional water sealing system (Fig. 3), we can see that in this embodiment, high-temperature, high-pressure water is extracted from the pump side, cooled by the heat exchanger 14, and then returned to the atmosphere side. In the case where the water is injected into the labyrinth, not only can the piping for sealing and extracting high-temperature/high-pressure water be simplified, but also the booster impeller for boosting the pressure of the low-pressure boiler feed water pump can be omitted. Furthermore, by shortening the length of the shaft seal portion and shortening the length between the bearings of the pump, reliability during pump operation can be improved.

Furthermore, in another embodiment shown in FIG. 8, the high-temperature, high-pressure water from the pump side A that has entered the inside of the labyrinth 17 is extracted to the outside twice before being discharged to the atmosphere side B, and the heat exchanger 14, and then injected into the labyrinth 17 on the atmosphere side B. That is, the openings 18a to 18b provided in the labyrinth 17 are communicated with passages 13a to 13d provided in the pump casing 1, respectively, and these passages 13a to 13d are connected to the extraction pipe 15, respectively.
It is connected to the heat exchanger 14 via a to 15d. With this configuration, water extraction, cooling, and return operations are performed twice each, which not only greatly increases the pressure reduction effect in the labyrinth 17 compared to the first and second embodiments, but also reduces the temperature of the leaked fluid. It is possible to lower the

〔Effect of the invention〕

As explained above, according to the present invention, it is no longer necessary to separately inject high-pressure seal water into the shaft seal portion of the high-pressure boiler feed water pump as in the past, and the booster booster provided at the final stage of the low-pressure boiler feed water pump Since the impeller can be eliminated, the water sealing system can be simplified and costs can be significantly reduced.

Further, according to the present invention, reliability during operation can be improved by shortening the length between the bearings of the pump. Furthermore, by using a mechanical seal in the shaft seal of the high-pressure boiler pump, the amount of leakage can be significantly reduced, making it possible to operate more safely in the event of a water seal failure.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional boiler feed pump for high temperature and high pressure fluids, Figure 2 is an enlarged detailed view of the shaft seal in Figure 1, and Figure 3 is a water seal of a conventional boiler feed pump for thermal power plants. System diagram, Fig. 4 is a vertical sectional view of a boiler feed water pump to which the shaft sealing device of the present invention is applied, Fig. 5
6 and 8 are sectional views showing respective embodiments of the shaft sealing device of the present invention, and FIG. 7 is a water sealing system diagram of a boiler feed pump for a thermal power plant to which the same embodiment is applied. DESCRIPTION OF SYMBOLS 1... Pump casing, 2... Rotating shaft, 10... Shaft seal part, 11... Mechanical seal, 12, 17... Cylindrical bush seal, 14... Heat exchanger, 15a-1
5d...Water extraction pipe.

Claims (1)

[Claims] 1. A mechanical seal and a cylindrical bushing seal are provided on the pump side and the anti-pump side of a shaft seal portion where the rotating shaft passes through the pump casing, and the high temperature and high pressure fluid inside the pump is transferred to the shaft seal near the mechanical seal. A high-temperature/high-pressure fluid, characterized in that the high-temperature/high-pressure fluid is extracted from the sliding part to the outside of the pump, and the extracted high-temperature/high-pressure fluid is introduced into the shaft seal sliding part near the cylindrical bushing seal through a heat exchanger. Shaft sealing device for rotary pumps. 2. A cylindrical bushing seal is installed in the shaft sealing part where the rotating shaft passes through the pump casing to prevent high temperatures and
High-pressure fluid is extracted from the shaft seal sliding part near the cylindrical bushing seal on the pump side to the outside of the pump, and the extracted high-temperature, high-pressure fluid is introduced into the shaft seal sliding part near the cylindrical bushing seal on the anti-pump side through a heat exchanger. A shaft sealing device for a rotary pump for high-temperature/high-pressure fluid, characterized by being configured as follows.