CN111536285A - Spring Direct Loaded Safety Valve - Google Patents

Abstract

The invention relates to the field of safety valves, in particular to a spring direct load type safety valve which comprises a valve seat, a valve body structure, a protection structure, an alarm structure and a sealing structure; through the protection architecture who sets up at fixed outside of tubes portion, can prevent through discharge medium outside to the system that medium pressure from surpassing regulation numerical value in pipeline or the equipment, reach the effect of protective equipment, the cooperation is at the alarm structure of fixed outside of tubes portion dress, can send the warning when equipment pressure surpasss the predetermined value, thereby can avoid dangerous emergence, setting through seal structure, not only can seal up the compensation to the clearance between disk seat and the erection equipment, can also play the fixed more firm effect of messenger's disk seat, can avoid the condition that the disk seat takes place automatic dropout, setting through the valve body structure, can enough realize good leakproofness, again can be according to the safe load of in-service behavior regulating valve, be convenient for be applicable to different operational environment and equipment, thereby the application range of device has been increased.

Description

Spring Direct Loaded Safety Valve

technical field

The invention relates to the field of safety valves, in particular to a spring direct load safety valve.

Background technique

The safety valve is a special valve that is in a normally closed state under the action of external force. When the pressure of the medium in the equipment or pipeline rises beyond the specified value, it discharges the medium to the outside of the system to prevent the medium pressure in the pipeline or equipment from exceeding the specified value. . Safety valves are automatic valves, mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. The safety valve plays a safety protection role in the system. When the system pressure exceeds the specified value, the safety valve is opened, and part of the gas/fluid in the system is discharged into the atmosphere/pipeline, so that the system pressure does not exceed the allowable value, thereby ensuring that the system does not cause an accident due to excessive pressure.

In the process of using the general spring direct load safety valve, although a part of the gas/fluid in the system can be discharged into the atmosphere/pipe when the system pressure exceeds the specified value, it is precisely because of this that if it is not checked manually, it is very difficult to It is difficult to find the overpressure of the equipment, which may cause high pressure damage to the equipment or even cause an accident.

SUMMARY OF THE INVENTION

In view of the problems in the prior art, the present invention provides a spring direct load safety valve.

The technical solution adopted by the present invention to solve the technical problem is: a spring direct load safety valve, including a valve seat, a valve body structure, a protection structure, an alarm structure and a sealing structure, which are used to install the safety valve in the One end of the valve seat of the equipment is installed with the valve body structure for the function of opening and closing, and the valve body structure is installed outside the valve body structure to prevent the medium pressure in the pipeline or equipment from exceeding the specified value by discharging the medium to the outside of the system. The protection structure; the alarm structure is installed on the outside of the valve body structure to play an alarm function, and the alarm structure is installed on the inside of the valve seat to protect the gap between the valve seat and the installation device. Supplemented with the sealing structure.

Specifically, the valve body structure includes a fixing tube, an adjusting screw, a first spring, a spring seat, a valve core, a sealing ring, a groove and a sealing ring, and the fixing tube with an inner hollow and annular structure is fixed to the One end of the valve seat is slidably connected with the spring seat inside the valve seat, the adjusting screw is threadedly connected to one end of the valve seat, and the adjusting screw is clamped between the adjusting screw and the spring seat. For the first spring, the valve core is fixed at the end of the spring seat away from the first spring, and the valve core is slidably connected with the valve seat, and the ring-shaped structure is fixed at one end of the valve seat. the sealing ring, and the cross section of the sealing ring is a trapezoidal structure, the groove in the annular structure is arranged inside the sealing ring, and the annular structure is fixed at the end of the valve core close to the sealing ring. the sealing ring.

Specifically, the protective structure includes a protective sleeve, a rubber column, an air outlet, a communication groove, a second spring and a pressure relief hole, and the protective sleeve with an annular structure and a hollow interior is fixed to the outside of the fixing tube, and is The inside of the protective sleeve is provided with the communication groove, the outside of the fixed tube is provided with a plurality of the air outlet holes in an annular array, and the plurality of the air outlet holes are all communicated with the communication groove. The inside of the sleeve is slidably connected with a plurality of the rubber columns, the second spring is clamped and fixed between the rubber columns and the protective sleeve, and a cross section of the rubber column is provided with a L-shaped structure. The pressure relief hole is in communication with the interior of the communication groove.

Specifically, the alarm structure includes a mounting plate, an alarm, a first contact, a second contact, an electric wire and a battery box. There are two mounting plates, and the two mounting plates are symmetrically fixed on the On the outside of the fixing tube, the alarm device is fixed on one end of one of the mounting plates, the second contact is fixed on the other mounting plate, and the top end of one of the rubber columns is fixed. A first contact, and the first contact is electrically connected to the alarm through the wire, the battery box is fixed on the outer side of the fixing tube, and the battery box is connected to the battery box through the wire The alarm is electrically connected, and the battery box is electrically connected to the second contact through the wire.

Specifically, the sealing structure includes an air storage tank, a piston, a third spring, a top plate, a rubber ring and an air passage, and the air storage tank in an annular structure is provided inside the valve seat. The inside of the piston is slidably connected with the piston in an annular structure, the third spring is clamped and fixed between the piston and the valve seat, and the annular structure is fixed at the end of the piston away from the third spring. The top plate is provided with the rubber ring inside the valve seat, and the rubber ring is an inner hollow annular structure, and the air storage groove is communicated with the rubber ring through the air passage.

Beneficial effects of the present invention:

(1) The spring direct load type safety valve of the present invention can not only achieve good sealing performance through the setting of the valve body structure, but also adjust the safety load of the valve according to the actual use situation, which is convenient to be suitable for different working environments and Working equipment, thereby increasing the use range of the device, that is, because the valve core used for sealing is fixed at one end of the spring seat, and the cross section of the valve core is an inverted "concave" structure, and one end of the valve seat is fixed in a ring shape The sealing ring of the sealing ring has a trapezoidal structure, and the sealing performance of the valve can be greatly improved by the cooperation of the valve core and the sealing ring. One end of the core is fixed with a ring-shaped sealing ring. The sealing ring and the groove are used together to further increase the sealing performance. Because the adjusting screw is threaded at one end of the fixing tube, the parts inside the fixing tube can be easily dismantled. And because the first spring is clamped between the adjusting screw and the spring seat, the elastic force of the first spring can be used to control the pressure value of the valve core, so that the medium in the pipeline or equipment can be prevented by discharging the medium to the outside of the system. When the pressure exceeds the specified value, the function of protection is achieved, and by rotating the adjusting screw, the position of the adjusting screw can be changed to achieve the effect of changing the pressure value.

(2) The spring direct load safety valve of the present invention can prevent the medium pressure in the pipeline or equipment from exceeding the specified value by discharging the medium to the outside of the system through the protection structure arranged outside the fixed pipe, so as to achieve the function of protecting the equipment. In addition, the alarm structure installed outside the fixed pipe can issue an alarm when the equipment pressure exceeds a predetermined value, so as to avoid the occurrence of danger. When the air pressure inside the fixed pipe pushes the valve core to stop blocking the air outlet, the gas inside the fixed pipe will enter the communication groove from the air outlet. When the gas pressure inside the communication groove is greater than the pressure of the second spring, the Push the rubber column to slide upward. When the pressure relief hole on the rubber column is no longer blocked, the pressure relief work inside the fixed pipe can be completed to avoid equipment damage. Since the first contact is fixed at one end of the rubber column, it can be installed after the installation. One end of the board is fixed with the second contact. When the first contact rises with the rubber column, it will interfere with the second contact. When the second contact is in contact with the first contact, the battery box and the alarm will be closed. It will be in an electrical connection state, and the alarm will start to alarm at this time, so that the operator can be informed in time, so as to avoid the occurrence of accidents.

(3) The spring direct load type safety valve of the present invention, through the setting of the sealing structure, can not only seal the compensation for the gap between the valve seat and the installation equipment, but also play a role in fixing the valve seat more firmly, It can prevent the valve seat from falling off automatically, that is, because there is an air storage groove inside the valve seat, a piston is slidably connected to the inside of the air storage groove, and a third spring is clamped and fixed between the piston and the valve seat, and the piston The top plate is fixed at the end away from the third spring. When the valve seat is installed on the equipment, the top plate will first collide with the surface of the equipment, and then the piston will be driven to squeeze the internal gas of the gas storage tank into the inside of the rubber ring through the air passage. At this time, the rubber ring is inflated and expanded, which can supplement the gap between the valve seat and the installation equipment to avoid air leakage, and cooperate with the third spring and the top plate to further fix it.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

FIG. 1 is a schematic structural diagram of the overall structure of a preferred embodiment of a spring direct-loaded safety valve provided by the present invention;

Fig. 2 is the enlarged schematic diagram of A part shown in Fig. 1;

FIG. 3 is a schematic diagram of the connection structure of the valve seat and the valve body structure shown in FIG. 1;

Fig. 4 is the enlarged schematic diagram of B part shown in Fig. 3;

FIG. 5 is an enlarged schematic view of the C part shown in FIG. 3 .

In the figure: 1, valve seat, 2, valve body structure, 21, fixed tube, 22, adjusting screw, 23, first spring, 24, spring seat, 25, valve core, 26, sealing ring, 27, groove, 28, sealing ring, 3, protection structure, 31, protective sleeve, 32, rubber column, 33, air outlet, 34, communication groove, 35, second spring, 36, pressure relief hole, 4, alarm structure, 41, installation plate, 42, alarm, 43, first contact, 44, second contact, 45, wire, 46, battery box, 5, sealing structure, 51, gas reservoir, 52, piston, 53, third spring , 54, top plate, 55, rubber ring, 56, airway.

Detailed ways

In order to make it easy to understand the technical means, creation features, achieved goals and effects of the present invention, the present invention will be further described below with reference to the specific embodiments.

As shown in Figures 1 to 5, the spring direct load safety valve of the present invention includes a valve seat 1, a valve body structure 2, a protection structure 3, an alarm structure 4 and a sealing structure 5, which are used to use external threads The safety valve is installed on one end of the valve seat 1 of the required equipment, and the valve body structure 2 for opening and closing function is installed, and the valve body structure 2 is installed on the outside of the valve body structure 2 to prevent the pipeline by discharging the medium to the outside of the system. Or the protection structure 3 in which the medium pressure in the equipment exceeds a specified value; the alarm structure 4 is installed outside the valve body structure 2 to play an alarm function, and the inside of the valve seat 1 is installed to play an alarm function. To the sealing structure 5 which supplements the gap between the valve seat 1 and the installation device.

Specifically, the valve body structure 2 includes a fixed tube 21 , an adjusting screw 22 , a first spring 23 , a spring seat 24 , a valve core 25 , a sealing ring 26 , a groove 27 and a sealing ring 28 , the interior is hollow and has a ring structure The fixed pipe 21 is fixed to one end of the valve seat 1, the spring seat 24 is slidably connected to the inside of the valve seat 1, and the adjusting screw 22 is threadedly connected to one end of the valve seat 1. The first spring 23 is clamped between the adjusting screw 22 and the spring seat 24 , the valve core 25 is fixed at the end of the spring seat 24 away from the first spring 23 , and the valve core 25 is slidably connected with the valve seat 1, and the sealing ring 26 in an annular structure is fixed at one end of the valve seat 1, and the cross-section of the sealing ring 26 is in a trapezoidal structure. There is the groove 27 in an annular structure, and the sealing ring 28 in an annular structure is fixed at one end of the valve core 25 close to the sealing ring 26, because it is fixed at one end of the spring seat 24 for the purpose of functioning. The valve core 25 for sealing function, and the cross section of the valve core 25 is an inverted "concave" structure, the sealing ring 26 in an annular structure is fixed at one end of the valve seat 1, and the sealing ring 26 The cross section of the valve has a trapezoidal structure, and the valve core 25 and the sealing ring 26 can be used together to greatly improve the sealing performance of the valve. 27. The sealing ring 28 in the annular structure is fixed at one end of the valve core 25, and the sealing ring 28 and the groove 27 are used together to further increase the sealing performance. One end of the adjusting screw 22 is threadedly connected to the adjusting screw 22, so that the parts inside the fixing tube 21 can be easily disassembled and assembled, and the first spring is clamped between the adjusting screw 22 and the spring seat 24. 23. The elastic force of the first spring 23 can be used to control the pressure value of the valve core 25, so that the medium pressure in the pipeline or equipment can be prevented from exceeding the specified value by discharging the medium to the outside of the system, so as to achieve the function of protection. And by rotating the adjusting screw 22, the position of the adjusting screw 22 can be changed to achieve the effect of changing the pressure value.

Specifically, the protective structure 3 includes a protective sleeve 31 , a rubber column 32 , an air outlet 33 , a communication groove 34 , a second spring 35 and a pressure relief hole 36 , and the protective sleeve 31 having an annular structure and a hollow interior is fixed to the On the outside of the fixing tube 21, the communication groove 34 is arranged inside the protective sleeve 31, and a plurality of the air outlet holes 33 are arranged in an annular array outside the fixing tube 21, and a plurality of the outlet holes 33 are provided. The air holes 33 are all communicated with the communication groove 34 , a plurality of the rubber columns 32 are slidably connected inside the protective sleeve 31 , and the first rubber column 32 is clamped and fixed between the rubber columns 32 and the protective sleeve 31 . Two springs 35, the inside of the rubber column 32 is provided with the pressure relief hole 36 with an L-shaped cross-section, and the pressure relief hole 36 communicates with the inside of the communication groove 34, because the fixed pipe 21 The inside of the valve core 25 communicates with the communication grooves 34 inside the protective sleeve 31 through a plurality of the air outlet holes 33. When the air pressure inside the fixing tube 21 pushes the valve core 25 to stop blocking the air outlet holes 33, At this time, the gas inside the fixed pipe 21 will enter the inside of the communication groove 34 from the air outlet 33 . When the gas pressure inside the communication groove 34 is greater than the pressure of the second spring 35 , the Push the rubber column 32 to slide upward, and when the pressure relief hole 36 on the rubber column 32 is no longer blocked, the pressure relief work inside the fixed pipe 21 can be completed, and equipment damage can be avoided.

Specifically, the alarm structure 4 includes a mounting plate 41, an alarm 42, a first contact 43, a second contact 44, an electric wire 45 and a battery box 46. The mounting plate 41 is provided with two, and the two said The mounting plates 41 are respectively fixed to the outside of the fixing tube 21 in a symmetrical relationship, the alarm 42 is fixed on one end of one of the mounting plates 41 , and the second contact is fixed on the other mounting plate 41 . 44, the first contact 43 is fixed on the top of one of the rubber columns 32, and the first contact 43 is electrically connected to the alarm 42 through the wire 45, and the fixed pipe 21 The outer side of the battery box 46 is fixed, and the battery box 46 is electrically connected to the alarm 42 through the wire 45, and the battery box 46 is connected to the second contact through the wire 45. 44 is electrically connected, because the first contact 43 is fixed at one end of the rubber column 32, and the second contact 44 is fixed at one end of the mounting plate 41. When the first contact 43 follows the When the rubber column 32 rises, it will interfere with the second contact 44. When the second contact 44 is in contact with the first contact 43, the battery box 46 and the alarm 42 will be in an electrical connection state, and the alarm device 42 will start to alarm at this time, so that the operator can be informed in time, so as to avoid the occurrence of accidents.

Specifically, the sealing structure 5 includes an air storage groove 51 , a piston 52 , a third spring 53 , a top plate 54 , a rubber ring 55 and an air passage 56 , and an annular structure of the air storage is arranged inside the valve seat 1 . The groove 51, the piston 52 in the annular structure is slidably connected inside the air storage groove 51, the third spring 53 is clamped and fixed between the piston 52 and the valve seat 1, and the third spring 53 is clamped and fixed between the piston 52 and the valve seat 1. One end of the piston 52 facing away from the third spring 53 is fixed to the top plate 54 having an annular structure. The rubber ring 55 is provided inside the valve seat 1 , and the rubber ring 55 is an annular structure with a hollow inside. The air storage groove 51 communicates with the rubber ring 55 through the air passage 56 . Since the air storage groove 51 is provided inside the valve seat 1 , a sliding connection is made inside the air storage groove 51 . For the piston 52 , the third spring 53 is clamped and fixed between the piston 52 and the valve seat 1 , and the top plate 54 is fixed at the end of the piston 52 away from the third spring 53 . When the valve seat 1 is installed on the equipment, the top plate 54 will first collide with the surface of the equipment, and then the piston 52 will be driven to squeeze the internal gas of the gas storage tank 51 into the gas channel 56 . Inside the rubber ring 55, when the rubber ring 55 is inflated and expanded, the gap between the valve seat 1 and the installation equipment can be supplemented, so as to avoid air leakage, and cooperate with the third spring The function of the top plate 53 and the top plate 54 can further fix the function.

When the present invention is in use, the outer wall of the valve seat 1 is provided with an external thread, and the safety valve is installed at the desired position by using the external thread. The piston 52 is slidably connected inside the air storage groove 51 , the third spring 53 is clamped and fixed between the piston 52 and the valve seat 1 , and the piston 52 faces away from the third spring 53 . One end of the spring 53 fixes the top plate 54 , when the valve seat 1 is installed on the equipment, the top plate 54 will first collide with the surface of the equipment, and then the piston 52 will be driven to move the gas storage tank 51 The internal gas is squeezed into the inside of the rubber ring 55 through the air passage 56. At this time, the rubber ring 55 is inflated and expanded, and the gap between the valve seat 1 and the installation device can be supplemented to avoid occurrence of In the case of air leakage, and with the function of the third spring 53 and the top plate 54, it can play a further fixing role. When the pressure of the gas entering the valve seat 1 is lower than the pressure of the first spring 23, The valve core 25 is pressed on the sealing ring 26 to form a seal, and the safety valve is closed. The cross-section of the core 25 is an inverted "concave" structure, and the sealing ring 26 in an annular structure is fixed at one end of the valve seat 1, and the cross-section of the sealing ring 26 is a trapezoidal structure. The combined use of the sealing ring 26 can greatly improve the sealing performance of the valve, and because the groove 27 in the annular structure is provided at one end of the sealing ring 26, and the valve core 25 is fixed at one end of the valve core 25 in an annular shape. The sealing ring 28 of the structure is used with the sealing ring 28 and the groove 27 to further increase the sealing performance. Because the adjusting screw 22 is threadedly connected to one end of the fixing pipe 21, it can be It is convenient to disassemble and assemble the parts inside the fixing tube 21, and because the first spring 23 is clamped between the adjusting screw 22 and the spring seat 24, the elastic force of the first spring 23 can be used. , control the pressure value of the valve core 25, so that the medium pressure in the pipeline or equipment can be prevented from exceeding the specified value by discharging the medium to the outside of the system, so as to achieve the protective effect. Adjust the position of the screw 22 to achieve the effect of changing the pressure value; since the inside of the fixed tube 21 communicates with the communication groove 34 inside the protective sleeve 31 through a plurality of the air outlet holes 33, when the fixed tube When the air pressure inside 21 pushes the valve core 25 to stop blocking the air outlet 33, the air inside the fixed pipe 21 will enter the communication groove 34 from the air outlet 33. When the gas pressure inside the communication groove 34 is greater than the pressure of the second spring 35, the rubber column 32 can be pushed to slide upward, and when the pressure relief hole 36 on the rubber column 32 is no longer blocked, it can be Complete the pressure relief work inside the fixed pipe 21 to avoid equipment damage. One end of the first contact 43 is fixed, and one end of the mounting plate 41 is fixed to the second contact 44. When the first contact 43 rises with the rubber column 32, it will interfere with the The second contact 44, when the second contact 44 collides with the first contact 43, the battery box 46 and the alarm 42 will be in an electrical connection state, and the The alarm device 42 will start to alarm, so that the operator can be informed in time, so that accidents can be avoided.

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and scope of the equivalents of , are included in the present invention. Any reference signs in the claims shall not be construed as limiting the involved claim.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (5)

1. A spring direct-loaded safety valve, characterized in that it includes a valve seat (1), a valve body structure (2), a protection structure (3), an alarm structure (4) and a sealing structure (5), which are used for use The external thread is used to install the safety valve on one end of the valve seat (1) of the required equipment. The protection structure (3) for discharging the medium to the outside of the system to prevent the medium pressure in the pipeline or equipment from exceeding a specified value; the alarm structure (4) for alarming is installed outside the valve body structure (2). ), the sealing structure (5) for complementing the gap between the valve seat (1) and the installation device is installed inside the valve seat (1). 2. The spring direct-loaded safety valve according to claim 1, wherein the valve body structure (2) comprises a fixed pipe (21), an adjusting screw (22), a first spring (23), a spring seat (24), valve core (25), sealing ring (26), groove (27) and sealing ring (28), the fixing tube (21) which is hollow inside and has an annular structure is fixed on the valve seat ( 1), the spring seat (24) is slidably connected to the inside of the valve seat (1), the adjusting screw (22) is threadedly connected to one end of the valve seat (1), and The first spring (23) is clamped between the adjusting screw (22) and the spring seat (24), and the valve core is fixed at the end of the spring seat (24) facing away from the first spring (23) (25), and the valve core (25) is slidably connected with the valve seat (1), the sealing ring (26) in the annular structure is fixed at one end of the valve seat (1), and the sealing The cross section of the ring (26) is in a trapezoidal structure, the groove (27) in an annular structure is arranged inside the sealing ring (26), and the valve core (25) is close to the sealing ring (26) One end of the ring-shaped sealing ring (28) is fixed. 3. The spring direct-loaded safety valve according to claim 2, wherein the protective structure (3) comprises a protective sleeve (31), a rubber column (32), an air outlet (33), a communication groove (34) ), a second spring (35) and a pressure relief hole (36), the protective sleeve (31) with an annular structure and a hollow interior is fixed to the outside of the fixing tube (21), inside the protective sleeve (31) The communication groove (34) is arranged inside the fixing pipe (21), and a plurality of the air outlet holes (33) are arranged in an annular array on the outside of the fixing pipe (21), and the plurality of air outlet holes (33) are all connected with the The communication grooves (34) communicate with each other, and a plurality of the rubber columns (32) are slidably connected inside the protective sleeve (31), and are sandwiched between the rubber columns (32) and the protective sleeve (31). Holding and fixing the second spring (35), the pressure relief hole (36) with an L-shaped cross-section is arranged inside the rubber column (32), and the pressure relief hole (36) is connected to the pressure relief hole (36). The interior of the communication groove (34) is communicated. 4. The spring direct-loaded safety valve according to claim 3, characterized in that: the alarm structure (4) comprises a mounting plate (41), an alarm (42), a first contact (43), a second Contacts (44), wires (45) and battery boxes (46), two mounting plates (41) are provided, and the two mounting plates (41) are respectively fixed to the fixing tube (21) in a symmetrical relationship ), the alarm device (42) is fixed on one end of one of the mounting plates (41), the second contact (44) is fixed on the other mounting plate (41), and the second contact (44) is fixed on one of the mounting plates (41). The top end of the rubber column (32) fixes the first contact (43), and the first contact (43) is electrically connected to the alarm (42) through the wire (45), The battery box (46) is fixed on the outer side of the fixing tube (21), and the battery box (46) is electrically connected with the alarm (42) through the wire (45), and the The battery box (46) is electrically connected to the second contact (44) through the wire (45). 5. The spring direct-load safety valve according to claim 1, characterized in that: the sealing structure (5) comprises a gas storage tank (51), a piston (52), a third spring (53), a top plate (54) ), a rubber ring (55) and an air passage (56), the air storage groove (51) in an annular structure is arranged inside the valve seat (1), and slides inside the air storage groove (51). The piston (52) in an annular structure is connected, the third spring (53) is clamped and fixed between the piston (52) and the valve seat (1), and the piston (52) faces away from the valve seat (1). One end of the third spring (53) is fixed to the top plate (54) in an annular structure, the rubber ring (55) is arranged inside the valve seat (1), and the rubber ring (55) It is an inner hollow annular structure, and the air storage tank (51) communicates with the rubber ring (55) through the air passage (56).

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