JPH06129392A - Overhung centrifugal compressor - Google Patents

Abstract

PURPOSE:To reduce the thrust load of a thrust bearing generated by the pressure on the process side while an overhung type centrifugal compressor is at a standstill. CONSTITUTION:A main shaft 2 whose inside is hollow, is secured to a suction casing 4 with guide vane 5 interposed and supports an impeller 1, and the inside of a boss 3 covering the tip of this main shaft 2 is leading to outside the suction casing 4 through a hole bored in the guide vane 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhang type centrifugal compressor applied to the compression and feeding of various gases.
In addition, the centrifugal compressor in this specification includes a centrifugal blower.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of a conventional overhang type centrifugal compressor used for compressing and feeding various gases. In the figure, the rotor of this overhang type centrifugal compressor has an impeller 1 attached to the tip of a main shaft 2 and is of an overhang type. Even when the overhang type centrifugal compressor is stopped, a settling pressure of 20 to 30 atm of process gas is applied from the process side to the rotor in the direction indicated by the arrow, and the process side pressure and the back side pressure of the impeller 1 are applied. However, the pressure applied to the boss 3 of the impeller 1 is not offset, and a large thrust load is applied to the thrust bearing 9. After the start, the pressure at the outlet of the impeller 1 rises and pressure also acts on the back surface of the impeller 1, and thrust load acts in the direction opposite to that at the time of stop, and the thrust bearing 9 is maintained in a properly balanced state. It In the figure, reference numeral 4 is a suction casing, reference numeral 14 is a seal, and reference numeral 15 is a journal bearing.

[0003]

In the conventional overhang type centrifugal compressor as described above, when the thrust bearing 9 is started under a large thrust load, the lubricating oil is supplied before starting. Nevertheless, due to the large thrust load, the thrust bearing 9 starts to rotate without lubrication. For this reason, the thrust bearing 9 having a large size and a large load capacity is used in the overhang type centrifugal compressor, and the bearing portion becomes large and the cost increases.

[0004]

SUMMARY OF THE INVENTION An overhang type centrifugal compressor according to the present invention is intended to solve the above-mentioned problems, and is fixed to a suction casing through guide vanes to form a hollow interior for supporting an impeller. Is provided with a boss that covers the tip of the main shaft, and a hole that is formed in the guide vane and that connects the inside of the boss to the outside of the suction casing.

Further, in the overhang type centrifugal compressor according to the present invention, the boss fixed to the suction casing via the guide vanes and having a hollow interior for covering the tip of the main shaft supporting the impeller, and the guide vanes. A hole that is bored in the boss and that connects the inside of the boss to the outside of the suction casing, and a hole that is provided in communication with the hole that is formed in the guide impeller. And a pressure control valve for controlling.

[0006]

That is, in the overhang type centrifugal compressor according to the present invention, the inside of the boss which is fixed to the suction casing through the guide vanes and which has a hollow inside and which covers the tip of the main shaft supporting the impeller is the guide vanes. A hole drilled in the suction casing leads to the outside of the suction casing, and the inside of the boss is decompressed below the internal pressure of the suction casing. The thrust load of the thrust bearing that supports the shaft is reduced.

Further, in the overhang type centrifugal compressor according to the present invention, the inside of the boss which is fixed to the suction casing through the guide vanes and which has a hollow interior and which covers the tip of the main shaft for supporting the impeller is the guide vanes. A pressure control valve, which is connected to the outside of the suction casing by a hole formed in the suction casing and communicates with the hole formed in the guide blade, controls the gas flow rate of the hole according to the thrust load of the main shaft. By reducing the internal pressure of the boss below the internal pressure of the suction casing, the thrust load of the thrust bearing that supports the main shaft due to the pressure on the process side while the overhang type centrifugal compressor is stopped is reduced. In addition, the gas flow rate in the holes drilled in the guide vanes is controlled according to the thrust load of the main shaft, and before and after the start, the gas is discharged from the inside of the boss to the outside of the suction casing. The amount of gas released into can be minimized.

[0008]

1 and 2 are explanatory views of an overhang type centrifugal compressor according to an embodiment of the present invention. In the figure,
The overhang type centrifugal compressor according to the present embodiment is used for compressing and feeding various gases. The rotor of this overhang type centrifugal compressor has an impeller 1 attached to the tip of a main shaft 2 to prevent overhang. Shaped. Even when the overhang type centrifugal compressor is stopped, a settling pressure of 20 to 30 atmospheres of process gas is applied to the rotor in the direction indicated by the arrow from the process side, and a large thrust load is applied to the thrust bearing 9. Has become. After the start, the pressure at the outlet of the impeller 1 rises and pressure also acts on the back surface of the impeller 1, and thrust load acts in the direction opposite to that at the time of stop, and the thrust bearing 9 is maintained in a properly balanced state. It Reference numeral 14 in the drawing is a seal, reference numeral 15
Is a journal bearing.

In this overhang type centrifugal compressor, in order to prevent a large thrust load from acting on the thrust bearing 9 while the overhang type centrifugal compressor is stopped, as shown in FIG. 1, the tip of the rotor main shaft 2 is covered. As described above, the boss 3 having a hollow inside is attached by being supported by the plurality of guide blades 5 of the suction casing 4. Spindle 2 inside the boss 3
A labyrinth 6 is attached to the portion covering the tip portion. The inside of the boss 3 is communicated with the outside of the suction casing 4 by a hole H formed in one of the guide blades 5 of the suction casing 4. As shown in FIG. 2, a pipe 7 is provided in a hole H that connects the inside of the boss 3 attached to the suction casing 4 and the outside of the suction casing 4, and the pipe 7 is provided with a pressure control valve 8. The pipe 7 can be opened to the atmosphere via the pressure control valve 8. A load cell (strain gauge) 10 for measuring a thrust load is attached to the metal back surface of the thrust bearing 9.
Is provided with a circuit 11 for extracting the distortion as an electrical output. Further, a thrust load controller 12 is provided in the circuit 11, and an electropneumatic converter 13 is installed downstream of the controller 12 to convert the electrical output of the load cell 10 into a gas pressure for pressure adjustment. The valve 8 is controlled according to the thrust load of the thrust bearing 9.

If the overhang type centrifugal compressor is started in a state where a large thrust load is applied to the thrust bearing 9, the thrust bearing 9 will not be present due to the large thrust load even though the lubricating oil is supplied before the start. Although it starts to rotate in a lubricated state, in the present overhang type centrifugal compressor, the inside of the boss 3 of the impeller 1 which causes a large thrust load on the rotor is attached as a hollow structure so as to cover the tip of the main shaft 2 as described above. 3 is opened to the atmosphere outside the suction casing 4 in accordance with the thrust load acting on the thrust bearing 9, whereby the internal pressure of the boss 3 in the suction casing 4 depends on the thrust load acting on the thrust bearing 9. The pressure applied to the tip of the main shaft 2 is reduced because the pressure is greatly reduced compared to the settling pressure of the process gas. A first process side pressure and backside pressure are canceled each other, the thrust load acting on the thrust bearing 9 is reduced. In addition, the pressure control valve 8 controls the flow rate of the process gas in the hole H by the thrust load controller 12.
Since the thrust load acting on the thrust bearing 9 is controlled so as not to exceed the load capacity of the thrust bearing 9, the amount of process gas released from the inside of the boss 3 into the atmosphere before and after starting is minimized. In this way, in the present overhang type centrifugal compressor, the thrust load of the thrust bearing 9 generated by the settling pressure of the process gas is reduced even when the present overhang type centrifugal compressor is stopped, so that the thrust bearing 9 is lubricated before and after starting. It is not necessary to equip the thrust bearing 9 having a large size and a large load capacity in this state, the bearing part can be downsized and the cost can be reduced, and the economical efficiency at the time of starting can be maintained.

[0011]

The overhang type centrifugal compressor according to the present invention is constructed as described above, and the thrust load of the thrust bearing generated by the pressure on the process side while the overhang type centrifugal compressor is stopped is reduced. Even before and after starting, the thrust bearing is in a lubricated state, and it is not necessary to use a thrust bearing having a large size and a large load capacity, so that the bearing portion can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an overhang type centrifugal compressor according to an embodiment of the present invention.

FIG. 2 is an internal pressure control system diagram of the boss.

FIG. 3 is a sectional view of a conventional overhang type centrifugal compressor.

[Explanation of symbols]

 1 Impeller 2 Spindle 3 Boss 4 Suction Casing 5 Guide Blade 6 Labyrinth 7 Piping 8 Pressure Control Valve 9 Thrust Bearing 10 Load Cell 11 Circuit 12 Thrust Load Controller 13 Electro-Pneumatic Converter

Claims (2)

[Claims] 1. A boss fixed to a suction casing via guide vanes to cover the tip of a main shaft having a hollow interior for supporting an impeller; and a boss formed in the guide vanes and having the boss inside the suction casing. An overhang-type centrifugal compressor characterized by having a hole that conducts to the outside of the. 2. A pressure control valve, which is provided in communication with a hole formed in the guide impeller and controls the gas flow rate of the hole in accordance with the thrust load of the spindle. The overhang type centrifugal compressor described in 1.