CN116045045B

CN116045045B - Pneumatic spring type safety valve

Info

Publication number: CN116045045B
Application number: CN202310121026.0A
Authority: CN
Inventors: 魏元生
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-02-16
Filing date: 2023-02-16
Publication date: 2023-07-07
Anticipated expiration: 2043-02-16
Also published as: CN116045045A

Abstract

The invention discloses a pneumatic spring type safety valve, which comprises a valve body 1, wherein the valve body 1 comprises an equipment interface 2 and an exhaust port 3, a valve core 7 and an adjusting ring 6 are assembled at a valve seat 4 of a valve cavity in the valve body 1, the valve core 7 is matched and positioned in the adjusting ring 6, a valve cover 5 is assembled on the adjusting ring 6, the bottom surface of the valve cover 5 is a cambered surface, and a closed recoil bin is formed among the valve cover 5, the valve core 7 and the adjusting ring 6; the valve cover 5 is positioned at the lower end of the valve rod 8, namely, the lower end of the valve rod 8 is propped against the conical groove 30 on the surface of the valve cover 5; the upper surface of the valve body 1 is provided with a valve body upper end cover 9, the valve body upper end cover 9 is fixedly provided with a pressure cabin bracket 12, and the pressure cabin bracket 12 is provided with a pressure cabin body 13. According to the invention, the pneumatic element is arranged for pressure transmission, so that the high pressure setting pressure is changed into the low pressure setting pressure, the spring displacement is reduced, the elasticity of the spring is protected, the working condition of the spring is improved, the fatigue problem of the spring is avoided, the service life of the spring is greatly prolonged, and the use cost is reduced.

Description

Pneumatic spring type safety valve

Technical Field

The invention belongs to the technical field of valves, relates to a spring safety valve, and particularly relates to a novel pneumatic spring safety valve.

Background

Safety valves are widely used in the chemical industry, medical and health, tank car transportation, pressure pipeline transportation, boilers, and military and civilian equipment. The aim of normal operation of the equipment in rated parameters is achieved through the automatic pressure relief function of the safety valve under the setting pressure, and the automatic pressure relief device is the last key device for ensuring the safe use of special equipment. Whether the safety valve can act safely and reliably, can respond sensitively, and whether key components formed by the safety valve can be used for a long time under rated parameters or not can be used in severe environments for a long time is critical to safe production. Therefore, research on the existing spring type safety valve used in a large amount is necessary to manufacture a sensitive, reliable and convenient safety valve device which can meet the production and development requirements.

Existing spring type relief valve structure, theory of operation and use the problem that exists:

(1) Spring type safety valve structure: the valve consists of a device interface, a valve body, a valve seat, an adjusting ring, a valve core, a guide sleeve, a valve cover, a valve rod, a spring gland, an adjusting screw, a fixing screw, a handle, a valve cap, an exhaust port and the like.

Working principle: the working action is carried out by means of the balance relation between the elastic force of the spring and the working pressure (or setting pressure) of the equipment.

Spring force: f=kx; wherein: f, spring force, N; k-spring constant, N/mm; x-spring displacement, mm;

operating pressure of the device: f=ps; wherein: f-the force generated by the pressure acting on the valve core, N; p-operating pressure of the apparatus (or setting pressure), N/cm ² The method comprises the steps of carrying out a first treatment on the surface of the S-area of spool cm ² 。

When the working pressure of the closed equipment is greater than the setting pressure of the spring, the valve core leaves the valve seat to drive the valve rod to compress the spring upwards, the spring is acted by the upward pressure, the spring (sleeved on the valve rod of the valve core) is driven by the valve rod to displace upwards, the valve core displacement is maximum, and the valve discharges medium in the equipment. After the pressure relief effect is finished, the pressure in the equipment is reduced and is lower than the setting pressure of the safety valve, under the downward elastic force effect of the spring, the valve rod drives the valve core to seal the valve seat, the equipment is closed, the internal medium is boosted, and the action process of the safety valve is finished. In this way, the operation is continued, ensuring that the device is not used over pressure.

Under the general condition, the setting pressure of the safety valve is higher than the working pressure of equipment and is 1.05-1.1 times of the working pressure of the equipment, different equipment and different technical links, and the setting pressure is different and needs to be determined according to the relevant national safety technical regulations. Thus, the safety valve will generally not act in use as long as there is no overpressure. Sometimes, manual or pneumatic tests are required as per the protocol. However, the conventional spring type safety valve is generally prone to the following problems in daily use:

1) After long-term use, the valve core is misplaced, so that the valve core is not tightly closed, or the valve core is difficult to seat and open;

2) Because the existing spring type safety valve only depends on the spring force of the spring to act, the problems of insufficient spring force, spring deformation, rust of the spring, spring fracture and the like are easily caused after the existing spring type safety valve is used for a long time;

3) The valve rod and the spring are easily exposed to working media, so that the service lives of the spring and the valve rod are influenced, and the problems of deflection, deformation, rust, crack and the like of the valve rod are caused.

Disclosure of Invention

Aiming at the problems of the prior spring type safety valve, the invention aims to provide a novel pneumatic spring type safety valve.

The invention is realized by adopting the following technical scheme:

the pneumatic spring type safety valve comprises a valve body, wherein the valve body comprises an equipment interface and an exhaust port, a valve seat of a valve cavity in the valve body is provided with a valve core and an adjusting ring, the valve core is matched and positioned in the adjusting ring, a valve cover is arranged on the adjusting ring, the bottom surface of the valve cover is an arc surface, and a closed recoil cabin is formed among the valve cover, the valve core and the adjusting ring; the valve cover is positioned at the lower end of the valve rod, namely the lower end of the valve rod is propped against the conical groove on the surface of the valve cover. The upper surface of the valve body is provided with a valve body upper end cover, the valve body upper end cover is fixedly provided with a pressure cabin bracket, and the pressure cabin bracket is provided with a pressure cabin body; the pressure cabin body is internally provided with a pressure cabin lower piston, a pneumatic element and a pressure cabin upper piston in sequence from bottom to top; the valve rod penetrates through the valve body and the upper end cover of the valve body and then penetrates through the sealing guide pipe, and the upper end of the valve rod enters the pressure cabin and is fixedly connected with the lower surface of the lower piston of the pressure cabin; a spring is arranged in a back plug cavity of the piston on the pressure cabin, a spring gland is arranged above the spring, and the spring gland can move up and down along the plug cavity; the upper end of the pressure cabin body is provided with a pressure cabin upper cover, a fixed lifting nut is arranged outside an upper opening of the pressure cabin upper cover, a spring pressing rod is arranged in the fixed lifting nut in a threaded manner, and the bottom end of the spring pressing rod abuts against the spring pressing cover after the spring pressing rod stretches into the pressure cabin upper cover; the upper part of the spring compression bar is locked by screwing in a fixing nut, and the fixing nut is positioned above the fixed lifting nut.

When the closed device works, the closed device is timed, when the working pressure is slightly larger than the setting pressure of the pressure transmission mechanism, the valve core leaves the valve seat to drive the valve rod to act upwards, and the valve rod drives the piston under the pressure cabin to move upwards, so that the valve core reaches the maximum opening displacement. At this time, the pressure transmitting mechanism performs the following operation: because the ratio of the area of the lower piston to the area of the valve core in the pressure cabin is larger than 1, the setting pressure transferred to the lower piston by the valve rod is reduced. Meanwhile, the lower piston moves upwards (the ascending displacement is the displacement of the valve core), the pneumatic element in the pressure cabin body is extruded, the pressure in the cabin body is increased and changed, the upper piston in the cabin body is pushed to move upwards, and the pressure of the valve core is transmitted to the movable spring due to the upward movement of the upper piston. The spring simultaneously compresses the upper piston downwards until the spring force and the pressure in the pressure cabin body reach the balance position, and the pressure displayed by the checking table is the setting pressure. Because the valve core acts to discharge medium, the pressure of the equipment is lower than the pressure of the movable spring at the balance position, and under the action of the spring pressure, the valve core is closed through the pressure transmission mechanism, so that one setting process of the safety valve is completed. Thus, the safety valve is arranged on the equipment to continuously and repeatedly act, so that the safe use of the equipment is ensured.

Further preferably, a limiting ring protrusion is arranged on the inner bottom surface of a plug cavity of the piston on the pressure cabin, and the distance between the limiting ring protrusion and the spring gland is the maximum height of the valve core opening. The main function of the limiting ring is to prevent the pneumatic element from excessively extruding the spring through the piston on the pressure cabin if the working pressure is too high, and at the moment, the limiting ring is in contact with the spring gland, so that enough space is reserved for the spring.

Further preferably, the side surface of the upper cover of the pressure cabin is provided with an exhaust hole, and when the upper piston and the lower piston move, the gas in the cabin is exhausted.

Further preferably, a valve cap is arranged at the top of the upper cover of the pressure cabin, and the valve cap is fixedly connected with the fixed lifting nut through a tightening screw.

Further preferably, the bottom end installation part of the pressure cabin body is inserted into the installation hole on the upper surface of the pressure cabin support and then locked by the fastening nut, so that the pressure cabin body is stably installed on the pressure cabin support.

Further preferably, a sealing cap is mounted on the top of the sealing guide tube.

Further preferably, the pneumatic element is an encapsulated airbag pre-filled with air or nitrogen.

Further preferably, the area ratio of the piston to the valve core under the pressure cabin is 1-3, so that the setting pressure is reduced, the spring load is reduced, and the working condition of the spring is improved.

The invention has reasonable design, mainly changes the high pressure setting pressure into the low pressure setting pressure by arranging the pressure transmission mechanism (pneumatic element), reduces the spring displacement, protects the elasticity of the spring, improves the working condition of the spring, avoids the fatigue problem of the spring, greatly prolongs the service life of the spring, reduces the use cost and has good practical application and popularization value.

Drawings

Fig. 1 shows a schematic structural view of a pneumatic spring type safety valve according to the present invention.

In the figure: 1-valve body, 2-equipment interface, 3-exhaust port, 4-valve seat, 5-valve cover, 6-adjusting ring, 7-valve core, 8-valve rod, 9-valve body upper end cover, 10-sealing guide tube, 11-sealing cap, 12-pressure cabin support, 13-pressure cabin body, 14-bottom mounting part, 15-pressure cabin lower piston, 16-pneumatic element, 17-pressure cabin upper piston, 18-plug cavity, 19-limit ring bulge, 20-spring, 21-spring gland, 22-pressure cabin upper cover, 23-spring compression bar, 24-fixed lifting nut, 25-fixed nut, 26-valve cap, 27-tightening screw, 28-fastening nut, 29-exhaust hole, 30-taper groove.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

A pneumatic spring type safety valve comprises a valve body 1, a valve cover 5, an adjusting ring, a valve core 7, a valve rod 8, a valve body upper end cover 9, a pressure cabin bracket 12, a pressure cabin body 13, a pressure cabin lower piston 15, a pneumatic element 16, a pressure cabin upper piston 17, a spring 20, a spring gland 21, a pressure cabin upper cover 22, a spring compression bar 23, a fixed lifting nut 24, a fixed nut 25, a valve cap 26 and other components.

As shown in fig. 1, the valve body 1 has an equipment interface 2 (i.e., an intake port) and an exhaust port 3, which are connected to equipment through port flanges, respectively. Valve seat 4 department of valve pocket in valve body 1 is equipped with case 7 and adjusting ring 6 in proper order, then case 7 cooperation is located adjusting ring 6, is equipped with valve gap 5 on the adjusting ring 6, and valve gap 5 bottom surface is the cambered surface, forms airtight recoil storehouse between valve gap 5, case 7 and the adjusting ring 6, and the whole valve port that is used for closing and opening the disk seat. The valve cap 5 is located at the lower end of the valve stem 8, i.e. the lower end of the valve stem 8 abuts in a conical groove 30 in the surface of the valve cap 5. The structure is basically the same as that of the existing spring safety valve, and belongs to the prior art.

As shown in fig. 1, the upper surface of the valve body 1 is provided with a valve body upper end cover 9 through a screw, the valve body upper end cover 9 is fixedly provided with a pressure cabin support 12 through a screw, a pressure cabin body 13 is arranged on the pressure cabin support 12, and in specific implementation, a bottom end mounting part 14 of the pressure cabin body 13 is inserted into a mounting hole on the upper surface of the pressure cabin support 12 and then is locked through screwing a fastening nut 28 through a thread structure, so that the pressure cabin body is fixedly arranged on the pressure cabin support.

As shown in fig. 1, a pressure cabin lower piston 15, a pneumatic element 16 and a pressure cabin upper piston 17 are sequentially arranged in the pressure cabin body 13 from bottom to top; the pneumatic element 16 is an encapsulated air bag pre-filled with air or nitrogen, and serves as a pressure transmission mechanism. The valve body upper end cover 9 is integrally provided with a sealing guide pipe 10, the valve rod 8 penetrates through the valve body 1 and the valve body upper end cover 9 and then penetrates through the sealing guide pipe 10, and the sealing guide pipe has the function of accurately guiding the valve rod so that the valve core is reset on the valve seat. The top of the sealing guide tube 10 is provided with a sealing cap 11 through which the valve rod 8 also passes. Moreover, only the lower end of the valve rod 8 is exposed to the medium, so that corrosion of the internal parts of the pressure chamber body is avoided.

As shown in fig. 1, the upper end of the valve rod 8 is fixedly connected with the lower surface of the lower piston 16 of the pressure cabin after entering the pressure cabin; a spring 20 is arranged in a back plug cavity 18 of the piston 17 on the pressure cabin, a spring gland 21 is arranged above the spring 20, and the spring gland 21 can move up and down along the plug cavity 18; and the bottom surface in the plug cavity of the piston 17 on the pressure cabin is provided with a limiting ring bulge 19, and the distance between the limiting ring bulge 19 and the spring gland 21 is the maximum height of the valve core 7 for opening.

As shown in fig. 1, the upper end of the pressure chamber body 13 is provided with a pressure chamber upper cover 22 by screw threads, and the side surface of the pressure chamber upper cover 22 is provided with an exhaust hole 29 for exhausting gas in the chamber body due to the up-and-down movement of the upper piston and the lower piston. The upper opening of the pressure cabin upper cover 22 is externally provided with a fixed lifting nut 24 through threads, the fixed lifting nut 24 is internally provided with a spring pressing rod 23 through threads, the bottom end of the spring pressing rod 23 abuts against the spring pressing cover 21 after extending into the pressure cabin upper cover 22 (downward pressure is applied to the spring pressing cover in a normal state), the spring pressing rod moves downwards along the fixed lifting nut, after the spring pressing cover is pressed down to a proper position (the spring is pressed down), the upper part of the spring pressing rod 23 is screwed into a fixing nut 25 through threads (the fixing nut 25 is positioned above the fixed lifting nut 24) and then locked, and the positioning of the spring pressing rod is realized. A valve cap 26 is arranged on the top of the upper cover 22 of the pressure chamber, and the valve cap 26 is fixedly connected with a fixed lifting nut 24 through a tightening screw 27.

The working principle of the pneumatic spring type safety valve is as follows:

the safety valve converts the larger valve core setting pressure into smaller setting pressure through an air pressure (transmission) element, the pressure setting of the safety valve is finished by means of the elasticity of a movable spring, and the pressure setting of the safety valve is operated by means of the balance relation between the elasticity of the spring and the setting pressure of equipment.

When the safety valve is set, an air bag with fixed pressure needs to be preset in the pressure cabin body (the air bag for packaging airtight gas is used as a pneumatic element, and the airtight gas can be air or nitrogen). When the sealing equipment is set, when the working pressure is slightly larger than the 'setting pressure' of the pressure transmission mechanism (the setting pressure converted by the transmission mechanism), the valve core is separated from the valve seat to drive the valve rod to act upwards, and the valve rod drives the piston under the pressure cabin to move upwards, so that the valve core reaches the maximum opening displacement (namely the diameter of the throat). At this time, the pressure transmitting mechanism performs the following operation: because the ratio of the area of the lower piston to the area of the valve core in the pressure cabin is larger than 1 (recommended that the ratio of the area of the lower piston to the area of the valve core in the pressure cabin is controlled between 1 and 3), the setting pressure transmitted to the lower piston by the valve rod is reduced. Meanwhile, the piston moves upwards (the ascending displacement is the displacement of the valve core) under the pressure cabin, the pneumatic element in the pressure cabin is extruded, the pressure in the cabin is increased and changed, the upper piston in the cabin is pushed to move upwards, and the upper piston and the movable spring on the pressure cabin are two sides of a component, so that the upward movement simultaneously transmits the pressure of the valve core to the movable spring. The spring simultaneously compresses the upper piston downwards until the spring force and the pressure in the pressure cabin body reach the balance position, and the pressure displayed by the checking table is the setting pressure. Because the valve core acts to discharge medium, the pressure of the equipment is lower than the pressure of the movable spring at the balance position, and under the action of the spring pressure, the valve core is closed through the pressure transmission mechanism, so that one setting process of the safety valve is completed. Thus, the safety valve is arranged on the equipment to continuously and repeatedly act, so that the safe use of the equipment is ensured.

The specific calculation process comprises the following steps:

1. first section (valve core section)

Valve core stress and working pressure relation: f=p ₁ *S ₁ ；

Wherein the F-valve core is stressed (namely a valve rod or a piston under a pressure bin), N/cm ² ；P ₁ -working pressure (1.05-1.1P) ₁ =setting pressure), mpa; s is S ₁ Valve core area, cm ² 。

2. Second section (pressure cabin lower piston)

The stress relation between the lower piston of the pressure cabin and the valve core: p (P) ₁ *S ₁ =P ₂ *S ₂ ；

Wherein P is ₂ -pressure, mpa, generated by the piston under the pressure chamber due to the force transmitted by the valve stem; s is S ₂ Area of piston under pressure chamber cm ² 。

Then: p (P) ₂ =P ₁ *S ₁ /S ₂ Because of S ₁ ＜S ₂ The method comprises the steps of carrying out a first treatment on the surface of the Then P is ₂ ＜P ₁ And P is ₂ With area coefficient (k=s ₂ /S ₁ It is recommended that: 1 < K.ltoreq.3) and a ratio P ₁ And decreasing by a coefficient.

3. Third section (piston on pressure cabin)

Pressure change relationship in pressure bin: p (P) ₂ *V ₂ =P ₃ *V ₃ ；

Wherein P is ₃ The piston under the pressure cabin is moved up by the bottom of the pressure cabin for a certain displacement, and then the pressure in the cabin is changed, and the pressure is Mpa; the initial pressure of the pneumatic element (recommended that the initial pressure in the pneumatic element is set between 0.05 and 0.5 mpa) is related to the rising displacement of the piston under the pressure cabin; v (V) ₃ -pressure chamber lower piston is raised by a certain displacement from the bottom of the pressure chamber to the inner chamber volume, pi/4*D ² *H ₃ ，cm ³ ；V ₂ -cabin volume, pi/4*D, of the pressure cabin prior to displacement of the piston under the pressure cabin ² *H ₂ ，cm ³ ；

P ₃ =P ₂ *V ₂ /V ₃ =P ₂ *H ₂ /H ₃ =P ₂ *(H ₃ +h)/H ₃ =P ₂ *(1+h/H ₃ );

Wherein: k1 =h/H ₃ Setting coefficients for the pneumatic element; h, valve core opening height is the rising displacement of the piston under the pressure cabin; h ₃ Compression displacement of the pneumatic transmission element when it reaches the setting pressure (springs with different values, determined by tests, different preset pressure levels, different area coefficients K, different elastic coefficients); h ₂ The height of the effective volume of the pressure chamber, i.e. the height of the pneumatic element between the upper and lower pistons, is not subjected to any external forces before the setting of the safety valve.

4. Fourth section (spring section)

Pressure change relation between piston and movable spring on pressure bin: p (P) ₃ *V ₃ =K ₂ X；

Wherein K is ₂ -the spring rate of the spring; x-displacement of the spring when reaching the set pressure.

The pneumatic spring type safety valve has the following advantages:

(1) The greatest difference between the invention and the traditional spring safety valve is that a pressure transmission mechanism (namely a pneumatic element) is arranged, and the valve and the pressure transmission mechanism are respectively arranged but are mutually related. The pressure transmission mechanism is used for transmitting the pressure to change the high pressure setting pressure into the low pressure setting pressure, so that the spring displacement is reduced, the elasticity of the spring is protected, the working condition of the spring is improved, and the fatigue problem of the spring is avoided.

(2) Only the valve body, the valve core, the adjusting ring, the valve cover and part of the valve rod are positioned under the environment condition of the working medium of the equipment, the parts are reduced, the inside is simple, and the guide sleeve is not arranged, so that the valve core is sensitive to open and close, and the positioning is accurate.

(3) The pressure transmission mechanism ensures that the valve rod and the valve core are always on the same central line through the support and the sealing guide pipe on the flange of the upper end cover of the valve body, and ensures that the valve core accurately falls back on the valve seat under the action of the valve rod.

(4) The spring in the piston on the pressure cabin can reduce displacement due to the effect of pressure transmission, so that the spring has the effect of reducing the spring force under the condition that the spring force is unchanged.

(5) The valve rod and the spring are isolated from the medium, so that the working condition of the pressure component is improved.

Finally, it should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and although the detailed description is given with reference to the embodiments of the present invention, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, and it should be covered by the scope of the claims of the present invention.

Claims

1. The utility model provides a pneumatic spring type relief valve, includes valve body (1), valve body (1) include equipment interface (2) and gas vent (3), valve seat (4) department of valve pocket in valve body (1) are equipped with case (7) and adjusting ring (6), case (7) cooperation are located adjusting ring (6), be equipped with valve gap (5) on adjusting ring (6), valve gap (5) bottom surface is the cambered surface, form airtight recoil storehouse between valve gap (5), case (7) and adjusting ring (6); the valve cover (5) is positioned at the lower end of the valve rod (8), and the lower end of the valve rod (8) is propped against the conical groove (30) on the surface of the valve cover (5);

the method is characterized in that: the upper surface of the valve body (1) is provided with a valve body upper end cover (9), the valve body upper end cover (9) is fixedly provided with a pressure cabin bracket (12), and the pressure cabin bracket (12) is provided with a pressure cabin body (13); a pressure cabin lower piston (15), a pneumatic element (16) and a pressure cabin upper piston (17) are sequentially arranged in the pressure cabin body (13) from bottom to top; the valve body upper end cover (9) is provided with a sealing guide pipe (10), the valve rod (8) penetrates through the sealing guide pipe (10) after penetrating out of the valve body (1) and the valve body upper end cover (9), and the upper end of the valve rod (8) is fixedly connected with the lower surface of the lower piston (15) of the pressure cabin after entering the pressure cabin; a spring (20) is arranged in a back plug cavity (18) of the piston (17) on the pressure cabin, a spring gland (21) is arranged above the spring (20), and the spring gland (21) can move up and down along the plug cavity (18); the upper end of the pressure cabin body (13) is provided with a pressure cabin upper cover (22), a fixed lifting nut (24) is arranged outside the upper opening of the pressure cabin upper cover (22), a spring pressing rod (23) is arranged in the fixed lifting nut (24) in a threaded manner, and the bottom end of the spring pressing rod (23) abuts against the spring pressing cover (21) after the spring pressing rod (23) stretches into the pressure cabin upper cover (22); the upper part of the spring compression bar (23) is locked by screwing in a fixing nut (25), and the fixing nut (25) is positioned above the fixing lifting nut (24).

2. A pneumatic spring type safety valve according to claim 1, wherein: the bottom surface in the stopper chamber of piston (17) on the pressure cabin is equipped with spacing ring protruding (19), spacing ring protruding (19) and spring gland (21) between the distance be the maximum height that case (7) opened.

3. A pneumatic spring type safety valve according to claim 1 or 2, characterized in that: the side face of the pressure cabin upper cover (22) is provided with an exhaust hole (29).

4. A gas spring type safety valve according to claim 3, wherein: and a valve cap (26) is arranged at the top of the pressure cabin upper cover (22), and the valve cap (26) is fixedly connected with the fixed lifting nut (24) through a tightening screw (27).

5. A pneumatic spring type safety valve according to claim 4, wherein: the bottom end mounting part (14) of the pressure cabin body (13) is inserted into a mounting hole on the upper surface of the pressure cabin bracket (12) and then locked by a fastening nut (28).

6. A pneumatic spring type safety valve according to claim 5, wherein: the top of the sealing guide pipe (10) is provided with a sealing cap (11).

7. A pneumatic spring type safety valve according to claim 6, wherein: the pneumatic element (16) is an encapsulated balloon pre-filled with air or nitrogen.

8. A pneumatic spring type safety valve according to claim 7, wherein: the ratio of the area of the piston (15) to the area of the valve core (7) under the pressure cabin is larger than 1.

9. A pneumatic spring type safety valve according to claim 8, wherein: the area ratio of the piston (15) to the valve core (7) under the pressure cabin is less than or equal to 3.