JP3500355B2 - Centrifugal compressor shaft seal system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type shaft sealing system (dry gas sealing system) used in a centrifugal compressor, and particularly to a case where a seal surface comes into contact with the compressor while the compressor is in operation and is damaged. The present invention relates to a technique for preventing such a problem.

[0002]

2. Description of the Related Art A non-contact type shaft sealing device (dry gas seal) for a centrifugal compressor is an API 614 FOURTH EDITI.
ON, APRIL 1999 CHAPTER4 FIG.
Known as described in 4A-1 to 9C. In these devices, as described in the same API 614 TABLE1,
As a function for detecting damage to the seal, a method of detecting damage to the seal by measuring gas leakage (leakage) due to an increase in the gap between the seal surfaces, that is, an increase in pressure or flow rate of the leak gas is used.

[0003]

As described above, in the prior art, the damage of the seal is detected by measuring the increase of the leak gas pressure or the flow rate. However, the increase of the leak gas pressure or the flow rate is measured. However, since the increase in leak pressure or flow rate is a secondary phenomenon after the seal is damaged, the damage to the seal cannot be prevented.

The dry gas seal is API617 6T
H EDITION (FEBRUARY 1995) F
As described in IG.7, the rotating ring (ROTATING R
ING) and a stationary ring (STATIONARY RING)
By maintaining the minute gaps formed by the flow of gas, the leakage of the gas handled by the compressor is minimized.

Since a brittle material such as silicon carbide (SiC) is generally used as the material of the rotary ring, dust, oil, water, etc., may enter the gap due to some abnormality, and the rotary ring and the stationary ring may be separated. If the sealing surfaces of No. 3 directly contact each other, the temperature rises rapidly, and the rotating ring collapses and breaks in a short time, leading to damage. It is difficult to get an indication of damage from measuring leak pressure or flow rate. If the rotary ring is damaged, the fragments will damage not only the sealing surface but also the compressor casing.Therefore, not only must the seal be replaced, but the compressor casing must be repaired or replaced. And it will be expensive.

It is an object of the present invention to provide a shaft compressor system for a centrifugal compressor, which detects an abnormality before breakage, rather than detecting the result of breakage of the dry gas seal.

[0007]

In order to achieve the above object, the shaft sealing system for a centrifugal compressor according to the present invention is characterized by a leak gas temperature measuring device provided in a leak gas flow path. The controller measures the temperature of the leak gas discharged from the control unit, and the control device stops the centrifugal compressor when the measured leak gas temperature exceeds a preset set value.

Specifically, the present invention provides the following shaft sealing system.

According to the present invention, a shaft sealing device incorporated between a compressor rotor and a casing of a centrifugal compressor, and a buffer gas flow passage for supplying a buffer gas to the shaft sealing device are blown into the shaft sealing device. A buffer gas temperature measuring device for measuring the temperature of the buffer gas, and a leak gas temperature measuring device for measuring the temperature of the leak gas provided in a leak gas flow path for discharging the buffer gas passing through the shaft sealing device as leak gas to the outside. A shaft seal system for a centrifugal compressor, comprising: a container; and a controller that stops the centrifugal compressor when the measured leak gas temperature exceeds a preset value.

Preferably, the control device stops the compressor when the measured temperature difference between the leak gas temperature and the buffer gas temperature exceeds a preset value.

Preferably, a rotation speed measuring device for measuring the rotation speed of the compressor rotor is provided, and the control device has means for changing the set value according to the measured rotation speed.

Preferably, a buffer gas molecular weight measuring device for measuring the molecular weight of the buffer gas is provided in the buffer gas passage, and the control device has means for changing the set value according to the measured molecular weight.

Preferably, a buffer gas pressure measuring device for measuring the pressure of the buffer gas is provided in the buffer gas passage, and the control device has means for changing the set value according to the measured pressure.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A shaft seal system for a centrifugal compressor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall construction of a shaft seal system for a centrifugal compressor according to an embodiment of the present invention.

The present shaft sealing system includes a shaft sealing device 200 installed inside bearings of a casing 2 for supporting both ends of a compressor rotor 1 and a buffer gas flow path 6a for sending a buffer gas 6 to the shaft sealing device 200. A buffer gas pressure measuring device 8 for measuring the pressure of the buffer gas 6 provided in the shaft sealing device 200, a buffer gas temperature measuring device 9 for measuring the temperature of the buffer gas 6, and a molecular weight of the buffer gas 6 are also measured. Buffer gas molecular weight measuring instrument 10
And the leak gas temperature measuring device 11 for measuring the temperature of the leak gas 7 provided in the leak gas passage 7a for discharging the buffer gas 6 passing through the shaft sealing device 200 as the leak gas 7 to the outside of the centrifugal compressor 100, and A leak gas pressure measuring device 12 for measuring the pressure, a rotation speed measuring device 13 for measuring the rotation speed of the compressor rotor 1, and a control device 300 for controlling the centrifugal compressor 100 based on the measurement values measured by the respective measurement devices. It is composed of.

The buffer gas flow path 6a is provided with a pressure control valve 14 and a filter 15. The buffer gas 6 is reduced to an appropriate pressure by the pressure control valve 14 and then contained in the buffer gas 6 by the filter 15. The dust and liquid components are removed and blown into the shaft sealing device 200.

FIG. 2 shows a cross section of a shaft sealing device 200 used in the shaft sealing system of FIG. The shaft sealing device 200 includes a shaft sleeve 3, a primary seal 4 including a rotating ring 4a and a stationary ring 4b, a rotating ring 5a and a stationary ring 5.
and a secondary seal 5 composed of b.

The rotating ring 4a and the rotating ring 5a are attached to the compressor rotor 1 side, and the stationary ring 4b and the stationary ring 5b are
It is attached to the casing 2 side.

When the rotary ring 4a and the rotary ring 4b are rotated by the rotation of the compressor rotor 1 through the shaft sleeve 3 fitted in the compressor rotor 1, the buffer gas blown into the upstream side of the primary seal 4 is rotated. Due to 6, a minute gap 20, that is, a seal is formed between the rotating ring 4a and the stationary ring 4b and between the rotating ring 5a and the stationary ring 5b. As a result, it is possible to operate the centrifugal compressor 100 without contacting the compressor rotor 1 and the casing 2 and keeping gas leakage from the inside of the centrifugal compressor 100 to a minimum.

However, since the gap 20 between the rotary ring 4a and the stationary ring 4b and between the rotary ring 5a and the stationary ring 5b is very small, if dust or the like enters the gap 20, the sealing surface in the gap 20 is damaged and the seal is damaged. May invite you. Therefore, during operation of the centrifugal compressor 100, a clean buffer gas 6 containing no dust, dust, or liquid is provided on the upstream side of the primary seal 4.
Is always infused. And the primary seal 4
Also, the buffer gas 6 that has passed through the minute gap 20 of the secondary seal 5 serves as a leak gas 7 and is used as the centrifugal compressor 100.
It is discharged to the outside.

However, clean buffer gas 6
Although it always blows in dust, it does not mean that there is no ingress of dust, etc.
The seal is broken, and the sealing surface of the rotating ring 4a and the stationary ring 4b
The surface of the seal comes into direct contact with the seal surface, and friction causes abnormal heat generation in the seal.

Generally, brittle materials such as silicon carbide are often used as the material of the rotating ring 4a and the stationary ring 4b. Therefore, when the sealing surfaces come into contact with each other, the sealing surfaces mesh with each other to cause a rapid temperature rise. In many cases, the sealing surface is damaged.

In this embodiment, the temperature of the leaked gas 7 discharged is constantly measured by the leaked gas temperature detector 11, and the measured value is output to the controller 300.

The control device 300 compares the input measured temperature value of the leak gas 7 with a preset set value, and if the measured temperature value of the leak gas 7 exceeds the set value, the sealing surface is caused for some reason. And the seal abnormally heats up, and it is determined that the temperature of the leak gas 7 has risen. Therefore, a signal is sent to the drive unit 101 of the centrifugal compressor 100 to stop the centrifugal compressor 100.

Thus, the centrifugal compressor 100 can be stopped before the seal is broken, and appropriate measures such as seal replacement can be taken.

The temperature of the leak gas 7 is the temperature of the buffer gas 6, the molecular weight, the blowing pressure, and the centrifugal compressor 10.
It also changes depending on operating conditions such as 0 rpm. For example,
When the temperature of the buffer gas 6 rises, the temperature of the leak gas 7 naturally rises. As the molecular weight of the buffer gas 6 and the blowing pressure increase, the specific gravity of the gas increases, so that heat generated by stirring by the seal increases and the temperature of the leak gas 7 rises.
Further, as the number of revolutions of the compressor rotor 1 rises, the heat generated by stirring also increases and the temperature of the leak gas 7 rises.

As described above, it may be difficult to detect the presence or absence of abnormality of the seal only from the temperature of the leak gas 7. Therefore, in the present embodiment, the blowing temperature is measured by the buffer gas temperature measuring device 9 and the buffer temperature is measured. Gas molecular weight measuring instrument 10
To measure the molecular weight of the buffer gas 6, the buffer gas pressure measuring device 8 to measure the blowing pressure, the rotation speed measuring device 13 to measure the rotation speed of the compressor rotor 1, and the leak gas pressure measuring device 12 to measure the pressure of the leak gas 7. Is measured, and each measuring device outputs the measured value to the control device 300.

The control device 300 calculates the temperature difference between the input temperature measurement value of the leak gas 7 and the input temperature measurement value of the buffer gas 6, and when the calculated temperature difference exceeds a preset set value, some kind is detected. Due to the cause, the seal surfaces contact each other and the seal abnormally heats up, and it is determined that the temperature of the leak gas 7 has risen, and the drive unit 10 of the centrifugal compressor 100 is determined.
1 to stop the centrifugal compressor 100.

Further, the control device 300 has means for changing the above-mentioned set value according to the input molecular weight of the buffer gas 6, the blowing pressure, the rotational speed of the compressor rotor 1 and the pressure of the leak gas 7. Thereby, the state of the sealing surface can be grasped more quickly and more accurately.

[0031]

According to the present invention, since it is possible to detect an abnormality before the dry gas seal is damaged, it is possible to prevent the seal from being damaged.

As a result, the time and cost required for disassembling the centrifugal compressor due to damage to the seal and taking measures to replace the seal can be greatly reduced, which in turn shortens the plant operation suspension period due to the shutdown of the centrifugal compressor and results in loss. Can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a shaft sealing system for a centrifugal compressor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a shaft sealing device used in the shaft sealing system of FIG.

[Explanation of symbols]

1 ... Compressor rotor, 2 ... Casing, 3 ... Shaft sleeve, 4 ... Primary seal, 4a ... Rotating ring, 4b ...
Stationary ring, 5 ... Secondary seal, 5a ... Rotating ring, 5b
... stationary ring, 6 ... buffer gas, 6a ... buffer gas flow path, 7 ... leak gas, 7a ... leak gas flow path, 8 ... buffer gas pressure measuring device, 9 ... buffer gas temperature measuring device, 1
0 ... Buffer gas molecular weight measuring device, 11 ... Leak gas temperature measuring device, 12 ... Leak gas pressure measuring device, 13 ... Rotation speed measuring device, 14 ... Pressure control valve, 15 ... Filter, 2
0 ... gap, 100 ... centrifugal compressor, 101 ... drive unit, 20
0 ... Shaft sealing device, 300 ... Control device

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F04D 27/00 F04B 49/10

Claims (5)

(57) [Claims] 1. A shaft seal device incorporated between a compressor rotor and a casing of a centrifugal compressor, and a buffer gas flow path for supplying a buffer gas to the shaft seal device, wherein the shaft seal device is blown into the shaft seal device. A buffer gas temperature measuring device for measuring the temperature of the buffer gas, and a leak gas temperature measuring device for measuring the temperature of the leak gas provided in a leak gas flow path for discharging the buffer gas passing through the shaft sealing device to the outside as a leak gas, and A shaft seal system for a centrifugal compressor, comprising: a controller that stops the centrifugal compressor when the measured leak gas temperature exceeds a preset value. 2. The control device according to claim 1, wherein the controller stops the compressor when the temperature difference between the measured leak gas temperature and the buffer gas temperature exceeds a preset set value. A shaft seal system for a centrifugal compressor. 3. The rotation speed measuring device for measuring the rotation speed of the compressor rotor according to claim 1 or 2, wherein the controller changes the set value according to the measured rotation speed. A shaft-sealing system for a centrifugal compressor, comprising: 4. A buffer gas molecular weight measuring device for measuring the molecular weight of the buffer gas is provided in the buffer gas flow path according to claim 1 or 2, and the controller sets the setting according to the measured molecular weight. A shaft seal system for a centrifugal compressor, characterized by having means for changing a value. 5. The buffer gas pressure measuring device according to claim 1 or 2, wherein a buffer gas pressure measuring device for measuring the pressure of the buffer gas is provided in the buffer gas passage, and the control device sets the setting according to the measured pressure. A shaft seal system for a centrifugal compressor, characterized by having means for changing a value.