Natural gas pressure energy screw expander mechanical sealing system

Abstract

The utility model discloses a natural gas pressure energy screw expander mechanical sealing system which comprises a mechanical sealing structure, a magnetic sealing structure, a mechanical sealing cooling and lubricating system and an emptying structure, and the mechanical sealing structure and the magnetic sealing structure are installed in a sealing cavity composed of a rotating shaft, an outer shell and a sealing shell. A cavity among the main sealing pair, the auxiliary sealing pair and the sealing shell is an exhaust cavity, an isolation cavity is formed between the mechanical sealing structure and the magnetic sealing structure and discharges internal gas into the air through an emptying structure, and the exhaust cavity is connected with a pressure-bearing oil tank of the mechanical sealing cooling and lubricating system through an exhaust pipe. Multiple sealing is carried out through the mechanical sealing structure and the magnetic sealing structure, leakage of natural gas is effectively reduced, meanwhile, leaked natural gas is collected and treated through the cooling and lubricating system, and trace leakage at the tail end is directly discharged at high altitude on the premise that the emission standard is met, so that safety of a running workshop is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of screw expander sealing structures, and particularly relates to a mechanical seal system for a screw expander of natural gas pressure energy. Background Art

[0002] At present, there are mainly three existing sealing methods for screw expanders, namely mechanical seal, carbon ring seal and dry gas seal. The carbon ring seal is the cheapest and the simplest in device, but it also has the largest leakage amount. Generally, the medium for sealing is water vapor and non-flammable and explosive gases, and it is not suitable for working conditions where the medium is natural gas and other flammable and explosive gases. The price of the dry gas seal is the most expensive among these three sealing methods. The domestic dry gas seals used for screw expanders are all above 400,000 yuan, and the import price is generally 3-4 times that of the domestic price. The device is also the most complex. For sealing of flammable and explosive gases such as natural gas, process nitrogen must be available on site to ensure the safe operation of the sealing device. Generally, natural gas gate stations are relatively remote and rarely can provide the condition of process nitrogen. The price of the mechanical seal is about 1 / 3 to 1 / 2 of that of the dry gas seal. It can operate without process nitrogen, and the system device is relatively simple. A magnetic seal can be added behind the mechanical seal to further improve the safety and stability of the sealing system. Provide a new, reliable and stable sealing system for flammable and explosive gases such as natural gas. Content of the Utility Model

[0003] The purpose of the utility model is to provide a mechanical seal system for a screw expander of natural gas pressure energy.

[0004] The above technical purpose of the utility model is achieved through the following technical solutions:

[0005] A mechanical seal system for a screw expander using natural gas pressure energy, comprising a mechanical seal structure, a magnetic seal structure, a mechanical seal cooling and lubrication system, and a venting structure. The mechanical seal structure and the magnetic seal structure are installed in a sealed cavity composed of a rotating shaft, a housing, and a seal housing. The magnetic seal structure is installed at the rear end of the mechanical seal structure. The mechanical seal structure includes a main seal pair and an auxiliary seal pair. The cavity between the main seal pair, the auxiliary seal pair, and the seal housing is an exhaust cavity. An isolation cavity is formed between the mechanical seal structure and the magnetic seal structure. The internal gas in the isolation cavity is discharged into the air through the venting structure. The exhaust cavity is connected to the pressure-bearing oil tank of the mechanical seal cooling and lubrication system through an exhaust pipe. A pressure relief pipe, a pressure transmitter I, and a magnetic flap level gauge are installed on the pressure-bearing oil tank. A pressure relief valve and a check valve are installed on the pressure relief pipe, and the end of the pressure relief pipe is connected to a flare. The pressure transmitter I and the pressure relief valve are set to be interlocked. The bottom of the pressure-bearing oil tank is connected to the mechanical seal structure through an oil outlet pipe. An oil pump, a cooler, and a filter are sequentially installed on the oil outlet pipe. The oil outlet pipe between the oil pump and the cooler is connected back to the pressure-bearing oil tank through a return pipe, and a ball valve is installed on the return pipe. A differential pressure transmitter is connected in parallel at both ends of the filter.

[0006] Further, the main seal pair includes a stationary ring I, a sealing ring I, and a rotating ring I. The stationary ring I is positioned and installed at the left end of the inner cavity of the seal housing through a positioning pin and fixed by a baffle and baffle bolts. The right end of the rotating ring I is connected to the shaft sleeve through a spring I and an anti-rotation pin I. The sealing ring I is installed between the stationary ring I and the rotating ring I. The spring I pushes the rotating ring I and the sealing ring I to tightly seal against the stationary ring I. The rotating ring I is connected to the shaft sleeve through an anti-rotation pin I. The auxiliary seal pair includes a rotating ring II, a sealing ring II, a spring II, and a stationary ring II. The rotating ring II is connected to the shaft sleeve through a transmission pin. The stationary ring II is connected to the gland through a spring II and an anti-rotation pin II. The gland is fixedly connected to the seal housing through gland bolts. The sealing ring II is installed between the rotating ring II and the stationary ring II. The spring II pushes the stationary ring II and the sealing ring II to tightly seal against the rotating ring II. O-ring seals are used for sealing at the various sealing joints between the main seal pair, the auxiliary seal pair, the housing, the seal housing, and the shaft sleeve.

[0007] Further, the magnetic seal structure includes a magnetic end cover, a magnetic seal stationary ring, a magnetic seal rotating ring, a snap ring, and magnet blocks. The magnetic end cover and the magnetic seal stationary ring are installed on the shaft sleeve through bearings and fixed in the card slot of the housing by a snap ring. The magnetic seal rotating ring is sleeved on the shaft sleeve. The magnet blocks are fixedly installed at one end of the magnetic seal rotating ring facing the magnetic seal stationary ring. O-ring seals are used for sealing at the various sealing joints of the magnetic seal structure.

[0008] Further, the oil pump includes a main oil pump and a standby oil pump, and the main oil pump and the standby oil pump are installed in parallel on the outlet pipe.

[0009] Further, the evacuation structure includes an evacuation pipe and a check valve installed on the evacuation pipe.

[0010] Further, a ball valve is installed on the exhaust pipe, and a second pressure transmitter is installed on the outlet pipe.

[0011] In summary, the present utility model has the following beneficial effects:

[0012] 1. The mechanical seal system of the present utility model adopts a cartridge type mechanism, which is convenient for installation and maintenance. The mechanical seal adopts a series structure, which is composed of a main seal pair and an auxiliary seal pair. When the main seal pair fails, the auxiliary seal pair can effectively seal, which can effectively improve the stability and safety of the mechanical seal.

[0013] 2. The present utility model is provided with a magnetic seal structure and an evacuation structure, and discharges the trace natural gas leaked at the rear end into the high altitude under the condition of meeting the emission standards, ensuring the safety of the equipment operation workshop.

[0014] 3. The mechanical seal cooling and lubrication system of the present utility model provides cooling and lubrication for the mechanical seal of the expander. At the same time, the pressure-bearing oil tank can collect the leaked natural gas. When a certain amount is collected, it is discharged to the flare through the pressure relief pipe for combustion treatment, effectively protecting the environment from being polluted. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the overall structural schematic diagram of the seal system of the present utility model;

[0016] Figure 2 is the structural schematic diagram of the mechanical seal part Figure 1 ;

[0017] Figure 3 is the structural schematic diagram of the mechanical seal part Figure 2 ;

[0018] Figure 4 is the structural schematic diagram of the magnetic seal part.

[0019] In the figure, 1. rotating shaft; 2. outer shell; 3. mechanical seal structure; 4. magnetic seal structure; 5. exhaust pipe; 6. pressure-bearing oil tank; 7. drain pipe; 8. pressure relief pipe; 9. pressure relief valve; 10. oil outlet pipe; 11. main oil pump; 12. standby oil pump; 13. return pipe; 14. pressure transmitter I; 15. cooler; 16. filter; 17. sealing shell; 18. stationary ring I; 19. baffle; 20. sealing ring I; 21. rotating ring I; 22. spring I; 23. rotating ring II; 24. sealing ring II; 25. spring II; 26. gland; 27. stationary ring II; 28. shaft sleeve; 29. positioning pin; 30. baffle bolt; 31. anti-rotation pin I; 32. drive pin; 33. anti-rotation pin II; 34. gland bolt; 35. magnetic end cover; 36. magnetic seal stationary ring; 37. magnetic seal rotating ring; 38. circlip; 39. magnetic flap level gauge; 40. differential pressure transmitter; 41. pressure transmitter II; 42. magnet block. Detailed implementation mode

[0020] The following further elaborates on the present utility model in conjunction with the attached drawings. The technical solutions in the embodiments of the present utility model are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts belong to the scope of protection of the present utility model.

[0021] As Figure 1As shown in the figure, a mechanical seal system for a screw expander using natural gas pressure energy includes a mechanical seal structure 3, a magnetic seal structure 4, a mechanical seal cooling and lubrication system, and a venting structure. The mechanical seal structure 3 and the magnetic seal structure 4 are installed in a sealed cavity composed of a rotating shaft 1, a housing 2, and a sealing shell 17. The magnetic seal structure 4 is installed at the rear end of the mechanical seal structure 3. The mechanical seal structure 3 includes a main seal pair and an auxiliary seal pair. The cavity between the main seal pair, the auxiliary seal pair, and the sealing shell 17 is an exhaust cavity. An isolation cavity is formed between the mechanical seal structure 3 and the magnetic seal structure 4. The internal gas in the isolation cavity is discharged into the air through the venting structure. The exhaust cavity is connected to a pressure-bearing oil tank 6 of the mechanical seal cooling and lubrication system through an exhaust pipe 5. A pressure relief pipe 8, a first pressure transmitter 14, and a magnetic flap level gauge 39 are installed on the pressure-bearing oil tank 6. A pressure relief valve 9 and a check valve are installed on the pressure relief pipe 8. The end of the pressure relief pipe 8 is connected to a flare. The first pressure transmitter 14 and the pressure relief valve 9 are linked. The bottom of the pressure-bearing oil tank 6 is connected to the mechanical seal structure through an oil outlet pipe 10. An oil pump, a cooler 15, and a filter 16 are successively installed on the oil outlet pipe 10. The oil outlet pipe 10 between the oil pump and the cooler 15 is connected back to the pressure-bearing oil tank 6 through a return pipe 13. A ball valve is installed on the return pipe 13. A differential pressure transmitter 40 is connected in parallel at both ends of the filter 16.

[0022] Further, as Figure 2 and Figure 3 shown in the figure, the main seal pair includes a stationary ring I 18, a sealing ring I 20, and a rotating ring I 21. The stationary ring I 18 is positioned and installed at the left end of the inner cavity of the sealing shell 17 through a positioning pin 29 and fixed by a baffle 19 and baffle bolts 30. The right end of the rotating ring I 21 is connected to a shaft sleeve 28 through a spring I 22 and an anti-rotation pin I 31. The sealing ring I 20 is installed between the stationary ring I 18 and the rotating ring I 21. The spring I 22 pushes the rotating ring I 21 and the sealing ring I 20 to tightly seal against the stationary ring I 18. The rotating ring I 21 is connected to the shaft sleeve 28 through the anti-rotation pin I 31. The auxiliary seal pair includes a rotating ring II 23, a sealing ring II 24, a spring II 25, and a stationary ring II 27. The rotating ring II 23 is connected to the shaft sleeve 28 through a transmission pin 32. The stationary ring II 27 is connected to a gland 26 through a spring II 25 and an anti-rotation pin II 33. The gland 26 is fixedly connected to the sealing shell 17 through gland bolts 34. The sealing ring II 24 is installed between the rotating ring II 23 and the stationary ring II 27. The spring II 25 pushes the stationary ring II 27 and the sealing ring II 24 to tightly seal against the rotating ring II 23. O-ring seals are used for sealing at each sealing joint between the main seal pair, the auxiliary seal pair, the housing 2, the sealing shell 17, and the shaft sleeve 28. When the main seal pair fails, the auxiliary seal pair can effectively seal, effectively providing the stability and safety of the mechanical seal.

[0023] Further, as Figure 4 shown, the magnetic seal structure 4 includes a magnetic end cover 35, a magnetic seal static ring 36, a magnetic seal dynamic ring 37, a snap ring 38, and a magnet block 42. The magnetic end cover 35 and the magnetic seal static ring 36 are mounted on the shaft sleeve 28 through bearings and fixed in the card slot of the housing 2 by the snap ring 38. The magnetic seal dynamic ring 37 is sleeved on the shaft sleeve 28, and the magnet block 42 is fixedly installed at one end of the magnetic seal dynamic ring 37 facing the magnetic seal static ring 36. O-ring seals are used to seal the respective sealing gaps of the magnetic seal structure 4.

[0024] Further, the oil pump includes a main oil pump 11 and a standby oil pump 12. The main oil pump 11 and the standby oil pump 12 are installed side by side on the oil outlet pipe 10. The provision of two oil pumps can ensure that when one oil pump fails, the other can continue to operate. At the same time, by the coordinated operation of the two oil pumps, the delivery volume of the cooling lubricating oil can be adjusted.

[0025] Further, the evacuation structure includes an evacuation pipe 7 and a check valve installed on the evacuation pipe 7. The evacuation pipe 7 evacuates the trace amount of natural gas in the isolation chamber through the check valve. The purpose of the check valve is to prevent gas from flowing back, ensuring that the natural gas in the isolation chamber does not leak into the equipment device, providing an additional layer of protection.

[0026] Further, a ball valve is installed on the exhaust pipe 5, and a second pressure transmitter 41 is installed on the oil outlet pipe 10. The second pressure transmitter 41 is used to monitor the pressure on the oil outlet pipe 10.

[0027] Working principle: A mechanical seal structure and a magnetic seal structure composed of a main seal pair and an auxiliary seal pair are provided at the end of the rotating shaft to form a triple seal structure, effectively reducing the leakage of natural gas. The mechanical seal cooling and lubrication system provides cooling and lubrication for the mechanical seal of the expander. At the same time, its pressure-bearing oil tank can collect the leaked natural gas, and the first pressure transmitter on the pressure-bearing oil tank can timely feedback the usage condition of the mechanical seal. When the pressure reaches the design value, the pressure transmitter provides a signal to the PLC to control the opening of the pressure relief valve, and the natural gas is discharged to the flare for combustion treatment through the check valve. The purpose of the check valve is to prevent gas from flowing back.

[0028] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A mechanical seal system for a screw expander using natural gas pressure energy, characterized in that: It includes a mechanical seal structure (3), a magnetic seal structure (4), a mechanical seal cooling and lubricating system, and a drainage structure. The mechanical seal structure (3) and the magnetic seal structure (4) are installed in a sealed cavity composed of a rotating shaft (1), a housing (2), and a sealing shell (17). The magnetic seal structure (4) is installed at the rear end of the mechanical seal structure (3). The mechanical seal structure (3) includes a main seal pair and an auxiliary seal pair. The cavity between the main seal pair, the auxiliary seal pair, and the sealing shell (17) is an exhaust cavity. An isolation cavity is formed between the mechanical seal structure (3) and the magnetic seal structure (4). The internal gas in the isolation cavity is discharged into the air through the drainage structure. The exhaust cavity is connected to a pressure-bearing oil tank (6) of the mechanical seal cooling and lubricating system through an exhaust pipe (5). A pressure relief pipe (8), a first pressure transmitter (14), and a magnetic flap level gauge (39) are installed on the pressure-bearing oil tank (6). A pressure relief valve (9) and a check valve are installed on the pressure relief pipe (8). The end of the pressure relief pipe (8) is connected to a flare. A linkage is provided between the first pressure transmitter (14) and the pressure relief valve (9). The bottom of the pressure-bearing oil tank (6) is connected to the mechanical seal structure through an oil outlet pipe (10). An oil pump, a cooler (15), and a filter (16) are successively installed on the oil outlet pipe (10). The oil outlet pipe (10) between the oil pump and the cooler (15) is connected back to the pressure-bearing oil tank (6) through a return pipe (13). A ball valve is installed on the return pipe (13). A differential pressure transmitter (40) is connected in parallel at both ends of the filter (16).

2. The mechanical seal system of a screw expander for natural gas pressure energy according to claim 1, characterized in that: The main seal pair includes a stationary ring I (18), a sealing ring I (20), and a rotating ring I (21). The stationary ring I (18) is positioned and installed at the left end of the inner cavity of the seal housing (17) through a positioning pin (29), and is fixed by a baffle plate (19) and baffle bolts (30). The right end of the rotating ring I (21) is connected to the shaft sleeve (28) through a spring I (22) and an anti-rotation pin I (31). The sealing ring I (20) is installed between the stationary ring I (18) and the rotating ring I (21). The spring I (22) pushes the rotating ring I (21) and the sealing ring I (20) to closely contact the stationary ring I (18) for sealing. The rotating ring I (21) is connected to the shaft sleeve (28) through the anti-rotation pin I (31). The auxiliary seal pair includes a rotating ring II (23), a sealing ring II (24), a spring II (25), and a stationary ring II (27). The rotating ring II (23) is connected to the shaft sleeve (28) through a transmission pin (32). The stationary ring II (27) is connected to the gland (26) through the spring II (25) and an anti-rotation pin II (33). The gland (26) is fixedly connected to the seal housing (17) through gland bolts (34). The sealing ring II (24) is installed between the rotating ring II (23) and the stationary ring II (27). The spring II (25) pushes the stationary ring II (27) and the sealing ring II (24) to closely contact the rotating ring II (23) for sealing. O-ring seals are used for sealing the various sealing joints between the main seal pair, the auxiliary seal pair, the outer shell (2), the seal housing (17), and the shaft sleeve (28).

3. A mechanical seal system for a screw expander using natural gas pressure energy according to claim 1, characterized in that: The magnetic seal structure (4) includes a magnetic end cover (35), a magnetic seal stationary ring (36), a magnetic seal rotating ring (37), a snap ring (38), and a magnet block (42). The magnetic end cover (35) and the magnetic seal stationary ring (36) are installed on the shaft sleeve (28) through bearings, and are fixed by being clamped in the card slot of the outer shell (2) through the snap ring (38). The magnetic seal rotating ring (37) is sleeved on the shaft sleeve (28). The magnet block (42) is fixedly installed at one end of the magnetic seal rotating ring (37) facing the magnetic seal stationary ring (36). O-ring seals are used for sealing the various sealing joints of the magnetic seal structure (4).

4. A mechanical seal system for a natural gas pressure energy screw expander according to claim 1, characterized in that: The oil pump includes a main oil pump (11) and a standby oil pump (12). The main oil pump (11) and the standby oil pump (12) are installed side by side on the outlet pipe (10).

5. The mechanical seal system of a natural gas pressure energy screw expander according to claim 1, characterized in that: The evacuation structure includes an evacuation pipe (7) and a check valve installed on the evacuation pipe (7).

6. The mechanical seal system of a screw expander for natural gas pressure energy according to claim 1, wherein: A ball valve is installed on the exhaust pipe (5), and a second pressure transmitter (41) is installed on the outlet pipe (10).

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