JPH0769022B2 - Shaft seal device for oil-free compressor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft seal device for an oilless compressor, which is suitable when the compressed gas is harmful such as toxic.

[0002]

2. Description of the Related Art Conventionally, a carbon ring seal has been generally used as a shaft sealing device for an oilless compressor. This is a floating seal, and if the gap between the shaft and the shaft is too small, it will come into contact with the shaft, and thus a large gap is required. Therefore, in order to prevent the compressed gas from leaking out of the machine from the shaft seal part, a large amount of seal gas (eg, an inert gas such as N ₂ ) is supplied to the shaft seal part, and the consumption amount is It has the drawback of becoming large. On the other hand, it is possible to reduce the amount of seal gas consumption by reducing the gap between the seal surfaces, and because no lubricating oil is used unlike mechanical seals, there is no mixing of oil in the compressed gas and there is no lubrication. A non-contact seal (structure will be described later) composed of a fixed ring and a rotary ring is excellent in that the characteristics of the compressor are not impaired.

[0003]

In the case of the non-contact seal, the gap between the seal surfaces of the fixed ring and the rotary ring is small,
Although the consumption of the sealing gas can be reduced, the sealing gas flow path is also small, so that there is a problem that clogging easily occurs and the sealing surface is easily damaged due to contact friction to cause gas leakage. The present invention has been made to solve the above conventional problems, and reduces the amount of seal gas,
An object of the present invention is to provide a shaft seal device for an oil-free compressor capable of preventing seizure of a seal surface due to leakage of compressed gas and lack of seal gas.

[0004]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a non-contact seal which is located between a rotor chamber and a bearing portion and which includes a fixed ring and a rotary ring, and a seal gas supply. A first flow path from a source to a first gas hole which is a seal gas flow passage on the fixed ring side through a pressure control valve and a flow meter; and a second gas hole which is a seal gas flow passage on the rotary ring side. A second flow path reaching a return flow path through a flow path opening / closing means that opens a flow path by a signal from the flow meter only when a value detected by the flow meter is preset and within a range of a lower limit value, A case in which the second flow path is communicated with the second flow path through a flow path opening / closing means that opens a flow path by a signal from the flow meter only when the detected value by the flow meter is out of the upper and lower limit ranges Based on the pressure difference between the third flow path branched from one flow path and the first flow path and the second flow path Te formed from the opening adjustment means for adjusting the degree of opening of the pressure regulating valve.

In the second invention, the first flow path is formed so as to communicate with the accumulator.

Further, in the third aspect of the invention, the non-contact seal, which is located between the rotor chamber and the bearing portion and comprises a fixed ring and a rotary ring, and a seal gas supply source, a pressure control valve and a flow meter, are used to fix the above. In the case where gas is normally supplied from the first flow path to the first gas hole which is the seal gas flow path on the ring side and the seal gas flow path, the seal gas flow path on the rotary ring side is used. From a certain second gas hole, the detection value by the flow meter is preset, and only when the value is within the lower limit, the flow path is opened by the signal from the flow meter to the return flow path through the flow path opening / closing means. Similarly to the second flow path leading up to the second flow path, the flow path is generated by the signal from the flow meter only when there is an abnormality in which the detected value by the flow meter is outside the upper and lower limit values. Communicating with the second flow path through flow path opening / closing means for opening An opening for adjusting the opening degree of the pressure control valve based on the differential pressure between the third flow path branched from the flow path and the third flow path and the above-described first flow path and the second flow path when the normal operation is performed. And a return flow passage and a second flow, provided in the seal gas flow passage so that pressure can be detected and the detected pressure is lower than a preset value. And a pressure switch for forcibly switching the flow path of the flow path opening / closing means so as to communicate with the path, and for switching to the normal operation in other cases.

[0007]

According to the first aspect of the invention, the rotation of the non-contact seal can be detected even when there is an abnormality such as clogging of the seal gas passage or damage to the seal surface. The seal gas is supplied to the second gas hole on the ring side, and the compressed gas does not leak out of the machine. Also, the second
With the configuration of the invention, in addition to the function of the first invention, it is possible to supply sufficient seal gas from the accumulator even when the capacity of the seal gas supply source that supplies the seal gas at the time of the above abnormality is not sufficiently large. Become.
Further, by configuring as in the third aspect of the invention, in addition to the function of the first aspect of the invention, even when the pressure detected by the flow meter at the start of introduction of the seal gas at the time of starting the apparatus is less than or equal to a predetermined set value, From the first channel through the non-contact seal to the second channel
The seal gas is caused to flow into the flow path to increase the pressure detected by the flow meter to smoothly shift to normal operation.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show an oil-free screw compressor to which the shaft sealing device 1 according to the first invention is applied, and a casing 2
A pair of male and female screw rotors 3 that mesh with each other are rotatably supported by bearings 4. Further, a seal 5 such as a carbon ring and a non-contact seal 6 which is a part of the shaft sealing device 1 are provided between the screw rotor 3 and the bearing 4, and a non-contact seal 6 from the rotor chamber 7 accommodating the screw rotor 3 is provided. It is formed to prevent leakage of compressed gas to the outside. The non-contact seal 6 is composed of a fixed ring 10 and a rotating ring 11 that are in contact with each other at sealing surfaces 8 and 9, the fixed ring 10 is slidable in the rotor shaft longitudinal direction, and a sealing surface of the rotating ring 11 is provided by a spring 12. 8 is supported by the casing 2 via the intermediate member 13 while being biased toward 8, while the rotary ring 11 is provided so as to be rotatable integrally with the rotor shaft 14. Further, the casing 2 and the intermediate member 13 are provided with a first gas hole 15 which is a seal gas flow hole on the fixed ring 10 side, and the casing 2 is provided with a rotary ring 1.
A second gas hole 16 which is a seal gas flow hole on the first side is formed, and the first gas hole 15 is formed in the seal surface 8 of the rotary ring 11.
A through hole 17 communicating with the fixed ring 10 is formed in the fixed ring 10.

On the other hand, a return flow from a seal gas supply source (not shown) to the first gas hole 15 via the pressure control valve 21 and the flowmeter 22, and a return flow from the second gas hole 16 to the three-way switching valve 24. A second flow path 26 reaching the path 25 and a third flow path 27 that connects the second flow path 26 to the first flow path 23 via the three-way switching valve 24 are provided. Here, the flow meter 22 detects the seal gas flow rate in the first flow path 23, and
When the detected flow rate is within the range of the upper and lower limit values of the preset seal gas flow rate, the ports a and b of the three-way switching valve 24 are made to communicate with each other so that the seal gas flows from the first flow path 23 to the second flow path 2
6 is led to the return flow passage 25, and when the detected flow rate is out of the above range at the time of abnormality, the ports a and c of the three-way switching valve 24 are made to communicate with each other, and the second flow passage 26 is returned to the return flow passage 25. Is shut off, communicated with the first flow path 23, and the seal gas is also supplied to the second gas hole 16. Further, in this embodiment, in the case of this abnormality, an alarm is issued based on the signal indicated by * in FIG. 1 and the compressor is stopped.

Further, in the first flow path 23 and the second flow path 26, the pressure difference between the two flow paths is detected, and the opening of the pressure control valve 21 is changed based on this pressure difference, and the non-contact seal 6 There is provided an opening degree adjusting means 28 for adjusting the flow rate of the seal gas supplied to the.
As described above, the non-contact seal 6, the first flow path 23, the second flow path 26,
The shaft seal device 1 is composed of the third flow path 27 and the opening degree adjusting means 28. Next, the operation of the shaft sealing device 1 having the above configuration will be described. When the non-contact seal 6 is in a normal state without breakage or clogging, the detected value of the seal gas flow rate by the flow meter 22 is within the upper and lower limit ranges,
A signal from the flow meter 22 causes the three-way switching valve 24 to be in a state where the ports a and b are in communication. Therefore, the seal gas supplied from the first flow path 23 through the first gas hole 15 passes through the through hole 17 and passes between the seal surfaces 8 and 9 toward the rotor chamber 7 side as shown by the arrow in FIG. Flow through the second gas hole 16 and the second flow path 26, and are sent to the return flow path 25. The flow of the seal gas keeps the seal surfaces 8 and 9 in a non-contact state with a minute gap, and prevents the compressed gas from leaking from the rotor chamber 7 to the outside of the machine (right side in the figure). Has been done. Further, the opening degree of the pressure adjusting valve 21 is changed by the opening degree adjusting means 28 in response to the fluctuation of the seal gas flow rate during the operation of the compressor, and the flow rate is adjusted.

On the other hand, for example, when the seal gas flow path is clogged, the flow rate of the seal gas decreases and the flow meter 22
The detected value by is below the above lower limit. Further, for example, when the seal surfaces 8 and 9 are damaged, the flow rate of the seal gas increases, and the detected value exceeds the upper limit value. As described above, when the detected value is out of the upper and lower limit ranges, the signal from the flow meter 22 shuts off the ports a and b of the three-way switching valve 24, and the ports a and c are communicated with each other. The seal gas is supplied from the second gas hole 16 through the third flow path 27 and the second flow path 26 to prevent the compressed gas from leaking out of the machine from the rotor chamber 7. Further, in this case, as described above, the flow meter 22 issues an alarm by the signal indicated by *, and the compressor is stopped to thoroughly prevent the compressed gas from leaking.

FIG. 3 shows an oil-free screw compressor to which the shaft sealing device 1a according to the second aspect of the invention is applied, and is different from the device shown in FIGS. 1 and 2 except that an accumulator 29 is newly provided. The other parts are substantially the same, and the parts corresponding to each other are designated by the same reference numerals and the description thereof will be omitted. The accumulator 29 is provided so as to communicate with the first flow path 23, whereby the capacity of the seal gas supply source to the first flow path 23 when the seal gas is also supplied to the second gas hole 16 at the time of the above abnormality. Even if is not sufficiently large, the required amount can be secured by the seal gas in the accumulator 29. In the first and second inventions, the rotary ring 11 is preferably made of a self-lubricating material, such as molybdenum disulfide, or polytetrafluoroethylene (PTF).
E) It is preferable to apply a coating.

By using such a material having self-lubricating property, it becomes possible to adjust the operation by rotating the rotor even when the apparatus is installed in which the supply of the sealing gas is not always possible, and the actual operation is possible. In particular, when the supply of the seal gas is stopped, it is possible to prevent the seal surface from seizing before the rotation of the rotor is stopped. Further, the drive unit of the pressure control valve 21 may be an electric type or a self-powered type in addition to the pneumatic type using air of an instrumentation line (not shown), and its type is not limited. Further, instead of the three-way switching valve 24, two two-way valves may be provided between the second flow passage 26 and the return flow passage 25 and between the second flow passage 26 and the third flow passage 27. In addition, the third channel 2
The merging point of 7 into the first flow path 23 may be the inlet side of the pressure control valve 21.

FIG. 4 shows an oil-free screw compressor to which the shaft sealing device 1b according to the third invention is applied, and is different from the device shown in FIGS. 1 and 2 except that a pressure switch 30 is newly provided. , And others are substantially the same, and the portions corresponding to each other are denoted by the same reference numerals and the description thereof will be omitted. This pressure switch 3
0 is provided in the first flow path 23 so that pressure can be detected, and if the detected pressure is lower than a preset set value, the return flow path 25
And the second flow path 26 are communicated with each other, the flow path of the three-way switching valve 24 is forcibly switched, and in other cases, that is, when the gas is normally supplied from the first flow path 23, The operation is switched to the same operation as the first invention. Then, even when the pressure detected by the flow meter 22 is equal to or less than the above-mentioned set value at the start of introduction of the seal gas at the time of starting the apparatus, the first
The seal gas is caused to flow from the flow path 23 to the second flow path 26 via the non-contact seal 6 to increase the pressure detected by the flow meter 22 and smoothly shift to normal operation.

More specifically, before starting the apparatus, the seal gas flow in the first flow path 23 is stopped, and the three-way switching valve 2
In No. 4, the a and c ports are in communication with each other. When the seal gas is introduced in this state, the seal gas flows through the third flow path 27 before flowing through the first flow path 23, and the amount of the seal gas flowing through the first flow path 23 decreases. As a result, the pressure detected by the flow meter 22 may not be set within the range of the lower limit value in advance, and the apparatus may not be able to be activated. Thus, the flow rate of the seal gas in the first flow path 23 decreases because the gas pressure flowing from the third flow path 27 to the non-contact seal 6 is the inlet of the seal gas from the first flow path 23. Is higher than the gas pressure in the first gas hole 15 which is
This makes it difficult for the seal gas to flow. In the third aspect of the invention, in order to eliminate such a problem, when the gas pressure in the first flow path 23 is lower than the set value, such as when the apparatus is started, the pressure switch 30 is used to force the three-way switching valve 24 to operate. , B
It is designed to be in port communication. Then, in the normal operation state in which the seal gas without such a defect is flowing, the same operation as that of the first invention is performed. This set value is as small as possible and preferably close to 0. By making the set value small like this, leakage of the compressed gas to the outside of the machine can be prevented until just before the seal gas flow rate is set to 0. Incidentally, also in the third invention, the accumulator 29 may be provided and formed as in the second invention. Further, although the screw type compressor has been described in each of the above embodiments, the present invention is not limited to the screw type compressor.

[0016]

As is apparent from the above description, according to the first aspect of the invention, the non-contact seal, which is located between the rotor chamber and the bearing portion and comprises the fixed ring and the rotary ring, and the seal gas supply source. The first flow path reaching the first gas hole which is the seal gas flow passage on the fixed ring side through the pressure control valve and the flow meter, and the second gas hole which is the seal gas flow passage on the rotary ring side, A second flow path reaching a return flow path through flow path opening / closing means for opening the flow path by a signal from the flow meter only when the value detected by the flow meter is preset and within a range of a lower limit value; A first flow path communicating with the second flow path via a flow path opening / closing means that opens a flow path by a signal from the flow meter only when there is an abnormality in which the detected value by the flow meter is outside the upper and lower limit values Based on the pressure difference between the third flow path branched from the flow path and the first flow path and the second flow path It is formed from the opening adjustment means for adjusting the opening of the serial pressure regulating valve. Therefore, the supply amount of the seal gas is small, and even if the seal gas flow path is clogged, or the seal surface is damaged, it can be detected and the non-contact seal can be detected. It is possible to supply the seal gas to the second gas hole on the rotary ring side and prevent the compressed gas from leaking out of the machine.

According to the second invention, the first flow path is formed so as to communicate with the accumulator. Therefore, in addition to the effects of the first aspect of the present invention, even if the capacity of the seal gas supply source that supplies the seal gas at the time of the above abnormality is not sufficiently large, sufficient seal gas can be supplied from the accumulator, and the compressed gas is discharged outside the machine. It is possible to further improve the reliability of the leakage prevention of

Further, according to the third aspect of the invention, a non-contact seal, which is located between the rotor chamber and the bearing portion and comprises a fixed ring and a rotary ring, a seal gas supply source, a pressure control valve, and a flow meter. When the gas is normally supplied from the first flow path to the first gas hole, which is the seal gas flow passage on the stationary ring side, and the seal gas flow passage, the seal gas flow on the rotary ring side. From the second gas hole, which is a channel, the flow is returned through the flow channel opening / closing means that opens the flow channel by the signal from the flow meter only when the value detected by the flow meter is preset and within the range of the lower limit value. Similarly to the second flow path leading to the passage, if the above-mentioned normal operation is performed, the signal from the flow meter is used only when the detected value by the flow meter is out of the upper and lower limit ranges. The second flow path is connected to the second flow path opening / closing means for opening the flow path. That a third flow path branched from the first flow path, when the same has been made to the normal, the first
An opening adjustment means for adjusting the opening of the pressure control valve based on the differential pressure between the flow passage and the second flow passage, and pressure detection is provided in the seal gas flow passage so that the detected pressure is predetermined. In the case other than the case where the normal operation is performed, which is lower than the set value, the flow path of the flow path opening / closing means is forcibly switched so as to connect the return flow path and the second flow path, and in other cases Is formed of a pressure switch for switching the operation to the normal operation. Therefore, in addition to the effects of the first invention, at the time of starting the apparatus, even if the pressure detected by the flow meter at the start of introduction of the seal gas is equal to or lower than a predetermined set value, the non-contact seal from the first flow path. After that, the seal gas is caused to flow into the second flow path to increase the pressure detected by the flow meter, and the normal operation is smoothly performed.

[Brief description of drawings]

FIG. 1 is a seal gas flow channel and flow channel control system diagram of an oil-free screw compressor to which a shaft sealing device according to a first aspect of the invention is applied.

FIG. 2 is a partial cross-sectional view of the compressor.

FIG. 3 is a seal gas flow path and flow path control system diagram of an oil-free screw compressor to which the shaft sealing device according to the second invention is applied.

FIG. 4 is a seal gas flow channel and flow channel control system diagram of an oil-free screw compressor to which the shaft sealing device according to the second invention is applied.

[Explanation of symbols]

 1, 1a Shaft sealing device 6 Non-contact seal 7 Rotor chamber 10 Fixed ring 11 Rotating ring 15 First gas hole 16 Second gas hole 21 Pressure control valve 22 Flowmeter 23 First flow path 24 Three-way switching valve 25 Return flow path 26 Second flow path 27 Third flow path 28 Opening degree adjusting means 29 Accumulator

Claims (3)

[Claims] 1. A non-contact seal, which is located between a rotor chamber and a bearing portion and comprises a fixed ring and a rotary ring, and a seal gas on the fixed ring side from a seal gas supply source through a pressure control valve and a flow meter. The value detected by the flow meter is preset from the first flow path leading to the first gas hole which is the flow path and the second gas hole which is the seal gas flow path on the rotating ring side, and is within the lower limit range. Only when the signal from the flow meter is used, the second flow path that reaches the return flow path through the flow path opening / closing means that opens the flow path, and the detection value by the flow meter are outside the upper and lower limit ranges. A first flow path opening / closing means for opening a flow path in response to a signal from the flowmeter only when an abnormality occurs
A third flow path branched from the flow path, and an opening degree adjusting means for adjusting the opening degree of the pressure control valve based on the differential pressure between the first flow path and the second flow path. A shaft seal device for an oil-free compressor. 2. The shaft seal device for an oilless compressor according to claim 1, wherein the first flow path is formed so as to communicate with the accumulator. 3. A non-contact seal, which is located between the rotor chamber and the bearing portion and comprises a fixed ring and a rotary ring, and a seal gas on the fixed ring side from a seal gas supply source through a pressure control valve and a flow meter. A first flow path leading to a first gas hole which is a flow path, and a second gas hole which is a seal gas flow path on the rotary ring side when gas is normally supplied from the seal gas flow path. According to the second flow path, the flow path opening / closing means for opening the flow path by the signal from the flow meter reaches the return flow path only when the value detected by the flow meter is preset and within the range of the lower limit value.
In the same way as the flow path, the flow that opens the flow path by the signal from the flow meter only when there is an abnormality in which the detected value by the flow meter is outside the upper and lower limit values when the above normal operation is performed. First communicating with the second flow path via a passage opening / closing means
An opening for adjusting the opening degree of the pressure control valve based on the differential pressure between the third flow path branched from the flow path and the third flow path and the above-described first flow path and the second flow path when the normal operation is performed. And a means for adjusting the degree of pressure, and a pressure detecting means provided in the seal gas flow passage,
When the detected pressure is lower than the preset value and is not normal, the flow passage of the flow passage opening / closing means is forced to communicate the return flow passage and the second flow passage. A shaft seal device for an oil-free compressor, characterized in that it is formed of a pressure switch for switching the operation, and in other cases for switching to the normal operation.