CN111044332A

CN111044332A - An explosion-proof dilution sampling probe

Info

Publication number: CN111044332A
Application number: CN201911129201.0A
Authority: CN
Inventors: 吕琼; 魏巍
Original assignee: Bay Environmental Technology Beijing Corp
Current assignee: Bay Environmental Technology Beijing Corp
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-04-21

Abstract

The invention relates to an explosion-proof dilution sampling probe, which comprises a probe shell, a vacuum generator arranged in the probe shell, a sound velocity small hole communicated with the vacuum generator, a fixing device and a sampling probe pipe which is fixed on the outer wall of the probe shell and communicated with the sound velocity small hole; the vacuum generator comprises a mounting plate and an air distribution disc integrally connected to one side of the mounting plate; the sound velocity small hole comprises a flow stabilizing tube and an air guide tube integrally connected with the flow stabilizing tube, and the diameter of the air guide tube is smaller than that of the flow stabilizing tube; the fixing device comprises a base fixedly connected to the mounting plate and communicated with the vacuum generator and a fastener for fixing the air duct on the base when the air duct is inserted into the base. The invention has the advantages that the sound velocity small holes with different apertures can be conveniently replaced by workers to meet different environmental requirements, and meanwhile, the explosion-proof function is provided, so that the explosion-proof device is suitable for 1-zone and 2-zone dangerous places of explosive gas mixtures of groups IIA-IIC, T1-T3 and indoor and outdoor installation.

Description

Explosion-proof dilution sampling probe

Technical Field

The invention relates to a sampling probe, in particular to an explosion-proof dilution sampling probe.

Background

The sampling method of the pollutant on-line detection system has two kinds, namely a direct extraction method and a dilution extraction method. The idea of the direct extraction method is to heat the extraction pipeline to a temperature higher than the sample gas temperature so as to solve the problem of water vapor condensation on the sampling transmission pipeline. The method is divided into a dry method and a wet method, wherein the dry method is to remove moisture in the sample gas through a rapid cooling dehydration process before the sample gas reaches the instrument, and simultaneously, the temperature of the sample gas is reduced to room temperature so as to be convenient for the instrument to measure, and due to the dehydration process, the components such as hydrogen chloride, ammonia, hydrogen sulfide and the like which have lower concentration and are easy to dissolve in water in the sample gas cannot be measured. The wet measurement does not need dehydration, and the high-temperature and high-humidity sample gas is directly sent into an analyzer, but the requirement on the analyzer is very high, so that the whole system is expensive, and the method is mainly applied to measurement of multi-component, low-concentration and water-soluble gaseous pollutants. The gaseous pollutant analysis by direct extraction method generally adopts ultraviolet or infrared non-dispersive absorption, and is characterized by that it can analyze several pollutant components, but its measurement sensitivity is low, and it is not accurate to measure pollutant with lower concentration.

The starting point of the dilution extraction method is to dilute the sampled sample gas with a large amount of dry and pure air to reduce the water content in the sample gas and make the dew point temperature of the sample gas far lower than the room temperature (generally reaching-40 ℃) to solve the problem caused by water vapor condensation. The critical hole sampling technology adopted in the dilution sampling method can accurately ensure the dilution ratio. The critical pore means: when the pressure ratio across the critical orifice reaches above 0.53, the flow rate of the fluid through the critical orifice is limited to sonic velocity, and thus the flow rate of the fluid through the critical orifice is constant; it is easy to ensure that the pressure of the dilution gas is constant, i.e. the flow rate of the dilution gas is also a constant value, so that the dilution ratio of the sample gas is a constant value. The greatest benefits of the dilution sampling method are: the sample gas is accurately diluted in a large proportion, so that the long-distance transmission of the sample gas is simple and convenient, any component of the sample gas is not changed, and the measurement of the sample gas is accurate.

The critical aperture in the existing dilution sampling probe, also called sonic aperture, is mostly integrated with the dilution sampling probe, and can only detect the gaseous pollutants with a certain concentration gradient, so the applicability is low.

Disclosure of Invention

The invention aims to provide an explosion-proof dilution sampling probe which has the advantage that workers can conveniently replace small sound speed holes with different apertures to meet different environmental requirements.

The technical purpose of the invention is realized by the following technical scheme: an explosion-proof dilution sampling probe comprises a probe shell, a vacuum generator arranged in the probe shell, a sound velocity small hole communicated with the vacuum generator, a fixing device for detachably and fixedly connecting the sound velocity small hole to the vacuum generator, and a sampling probe tube fixed on the outer wall of the probe shell and communicated with the sound velocity small hole;

the vacuum generator comprises a mounting plate and an air distribution disc integrally connected to one side of the mounting plate;

the sound velocity small hole comprises a flow stabilizing tube and an air guide tube integrally connected with the flow stabilizing tube, and the diameter of the air guide tube is smaller than that of the flow stabilizing tube;

the fixing device comprises a base fixedly connected to the mounting plate and communicated with the vacuum generator and a fastener for fixing the air duct on the base when the air duct is inserted into the base.

Through adopting above-mentioned technical scheme, the mounting means that the sound velocity aperture passes through base and fastener detachable connection on vacuum generator makes things convenient for the staff to change the sound velocity aperture in different apertures as required to change the dilution ratio, so that detect the gaseous pollutant of different concentrations, improve the application scope who dilutes the sampling probe, satisfy different environmental requirements.

The invention is further configured to: the base is cylindrical, external threads are arranged on the outer wall of the base, three coaxial through holes are formed in the base and comprise a small hole, a middle hole and a large hole which are sequentially far away from the gas distribution disc, a first step surface is formed between the small hole and the middle hole, and a second step surface is formed between the middle hole and the large hole;

the fastener is including placing O type circle on first step face, the lower part is pegged graft in the centre bore and upper portion supports the lock nut on the second step face and threaded connection on the base so that the O type circle is supported tightly to the clamp sleeve, the air duct passes lock nut, clamp sleeve and O type circle in proper order and pegged graft on the base.

By adopting the technical scheme, the installation method comprises the following steps: placing an O-shaped ring on a first step surface, extending a lower barrel of a clamping sleeve into a middle hole and abutting against the O-shaped ring, supporting an upper barrel of the clamping sleeve on a second step surface, then preliminarily installing a locking nut on a base, taking a sound velocity small hole, forcibly penetrating an air guide pipe through the locking nut, the clamping sleeve and the O-shaped ring in sequence and extending into the small hole, then rotating the locking nut, abutting against the step surface in the locking nut on the clamping sleeve, and enabling the clamping sleeve to tightly press the O-shaped ring; the mounting method II comprises the steps that a locking nut, a clamping sleeve and an O-shaped ring are sequentially sleeved on an air duct, then the air duct is stretched into a small hole, the locking nut is rotated to enable the locking nut to be in threaded connection with a base, and the O-shaped ring and the clamping sleeve are sequentially pressed into the base in the rotating process to achieve fixed mounting; when the sound speed hole is replaced, the locking nut is loosened, and then the sound speed hole is taken down, so that the sound speed hole is very convenient.

The invention is further configured to: and the inner wall of the O-shaped ring is provided with an anti-falling conical surface.

Through adopting above-mentioned technical scheme, the setting of conical surface for increase the frictional force between air duct outer wall and the O type circle, prevent to deviate from easily after the air duct installation.

The invention is further configured to: the gas distribution disc is a disc with a hollow inner part, a standard gas port, a dilution gas port and a sample gas outlet which are communicated with the inner part of the gas distribution disc are fixedly connected to the outer wall of the gas distribution disc, and the dilution gas port and the sample gas outlet are oppositely arranged; the gas distributor is internally provided with a Venturi tube for communicating the inner port of the dilution gas port with the inner port of the sample gas outlet and a vacuum cavity for communicating the Venturi tube with the sonic hole, the outer port of the dilution gas port is connected with a gas source, and the outer port of the sample gas outlet is communicated with an analyzer.

Through adopting above-mentioned technical scheme, during the detection, install the probe shell body on the flue outer wall, the in-process of installation should ensure that the sampling probe is installed with-5 flagging angle or horizontal position, can not make the probe upwarp, then put through the air supply, dilution gas 0 gets into venturi by the dilution gas mouth, because the velocity of flow of dilution gas 0 is big, consequently form the negative pressure in the vacuum cavity department with venturi intercommunication, the sampling gas in the flue at this moment is inhaled to venturi in by the influence of pressure differential and is mixed with dilution gas 0 in, finally let in the analysis appearance through the appearance gas outlet and carry out the analysis and detection.

The invention is further configured to: and a three-way joint is arranged on the sample gas outlet, one path of the three-way joint is emptied, and the other path of the three-way joint is connected with an analyzer.

By adopting the technical scheme, the vacuum generator is ensured to generate enough vacuum degree by the emptying mode, and continuous power is realized.

The invention is further configured to: a cylindrical metal filter and a preheater are sequentially sleeved outside the sonic small hole;

one end of the preheater is fixed on the mounting plate through a hoop, and the other end of the preheater is fixed on the outer wall of the probe shell through a flange;

an internal thread hole is formed in the mounting plate by taking the base as the center, one end of the metal filter is connected to the mounting plate through a joint thread, and the other end of the metal filter abuts against the outer wall of the probe outer shell;

a circulation chamber is formed between the metal filter and the preheater, a stainless steel pipe communicated with an air source is connected and communicated with the side wall of the metal filter, and an air conveying pipe communicated with a dilution air port is arranged on the side wall of the preheater.

By adopting the technical scheme, when the dilution gas 0 is introduced from the stainless steel pipe, the dilution gas preferably enters the preheater to be preheated and then is output from the gas pipe, and the preheating function mainly prevents the water in the sampling gas from being liquefied.

The invention is further configured to: the gas distribution disc is further fixedly connected with a vacuum degree measuring port communicated with the inside of the gas distribution disc, one end of the vacuum degree measuring port is communicated with the vacuum cavity, and the other end of the vacuum degree measuring port is provided with a pressure gauge.

By adopting the technical scheme, the vacuum degree in the vacuum cavity is monitored in real time.

The invention is further configured to: and a glass filter is arranged in the flow stabilizing pipe.

Through adopting above-mentioned technical scheme, the setting of glass filter for impurity particle in the gas of sampling filters, avoids it to block up the pipeline.

The invention is further configured to: the sampling probe tube is fixed on the outer wall of the probe shell through a flange and is communicated with the sonic orifice in a sealing mode.

Through adopting above-mentioned technical scheme, easy to assemble and dismantlement.

The invention is further configured to: and one end of the sampling probe tube, which is far away from the probe shell, is fixedly connected with a flow baffle plate which inclines downwards.

Through adopting above-mentioned technical scheme, keep off the setting of flowing the board for reduce the volume that aqueous gas got into in the sampling probe tube, thereby guarantee the analytical accuracy of sample gas.

In conclusion, the beneficial technical effects of the invention are as follows:

1. the sound velocity small holes are detachably connected to the vacuum generator through the base and the fastening piece, so that workers can conveniently replace the sound velocity small holes with different apertures according to needs, the dilution ratio is changed, gaseous pollutants with different concentrations can be conveniently detected, the application range of the dilution sampling probe is expanded, and different environmental requirements are met;

2. the conical surface is arranged and used for increasing the friction force between the outer wall of the air guide pipe and the O-shaped ring and preventing the air guide pipe from being easily separated after being installed;

3. preheating the sampling gas through a preheater so as to prevent the water in the sampling gas from being liquefied to influence detection data;

4. by means of emptying, the vacuum generator is guaranteed to generate enough vacuum degree, and continuous power is achieved.

Drawings

FIG. 1 is a schematic view of the overall structure of the interior of a decapping probe housing embodying the present invention;

FIG. 2 is a top view of the internal structure of the probe housing;

FIG. 3 is a schematic structural diagram showing the connection relationship between the sonic orifice and the vacuum generator;

FIG. 4 is a schematic structural view showing a base;

FIG. 5 is an exploded view of the connection between the fastener and the base;

FIG. 6 is a schematic structural view showing the connection and positional relationship among the metal filter, the preheater, the stainless steel pipe and the gas pipe;

FIG. 7 is a schematic structural diagram showing interfaces on the gas distribution plate;

FIG. 8 is a schematic structural diagram embodying the sampling principle;

fig. 9 is a schematic structural diagram showing the operation state of the dilution sampling probe.

Reference numeral, 1, a probe housing; 11. an explosion-proof junction box; 12. an explosion-proof power supply junction box; 2. a vacuum generator; 21. mounting a plate; 211. an internally threaded bore; 22. a gas distribution plate; 23. a label port; 24. a diluent gas port; 25. a sample gas outlet; 26. a vacuum degree measuring port; 27. a venturi tube; 28. a vacuum chamber; 3. a sonic orifice; 31. a flow stabilizing pipe; 32. an air duct; 4. a fixing device; 41. a base; 411. a small hole; 412. a mesopore; 413. macropores; 414. a first step surface; 415. a second step surface; 42. a fastener; 421. an O-shaped ring; 422. a card sleeve; 423. locking the nut; 5. sampling probe tube; 51. a flow baffle plate; 6. a metal filter; 61. a stainless steel tube; 7. a preheater; 71. clamping a hoop; 72. a gas delivery pipe; 8. a pressure gauge; 9. a three-way joint; 91. an emptying pipe; 92. a stop valve; 93. a hose.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1, 2 and 3, the explosion-proof dilution sampling probe disclosed by the invention comprises a probe shell 1, a vacuum generator 2 arranged in the probe shell 1, a sound velocity small hole 3 communicated with the vacuum generator 2, a fixing device 4 for detachably and fixedly connecting the sound velocity small hole 3 to the vacuum generator 2, and a sampling probe tube 5 fixed on the outer wall of the probe shell 1 and communicated with the sound velocity small hole 3.

Sound speed aperture 3 passes through 4 detachable connections of fixing device on vacuum generator 2, makes the staff can change the dilution ratio through the sound speed aperture 3 of changing different apertures as required to detect the gaseous pollutant of different concentrations, improve the application scope who dilutes the sampling probe, satisfy different environmental requirement.

Referring to fig. 2 and 3, the probe casing 1 is assembled by a plurality of stainless steel plates, and is internally provided with an explosion-proof junction box 11 and an explosion-proof power supply junction box 12 which are connected by a power line; the vacuum generator 2 comprises a mounting plate 21 and a gas distribution plate 22 integrally connected to one side of the mounting plate 21; sound velocity aperture 3 includes flow stabilizing tube 31 and with flow stabilizing tube 31 an organic whole connected's air duct 32, the diameter of air duct 32 is less than flow stabilizing tube 31, install glass filter in flow stabilizing tube 31, when the sampling gas gets into flow stabilizing tube 31, the great impurity of granule can drop into in the tube that flow stabilizing tube 31 is located the glass filter front end under the effect of glass filter, and the less impurity of granule then can see through the tube that glass filter gets into flow stabilizing tube 31 and is located the glass filter rear end along with the sampling gas, because the junction between flow stabilizing tube 31 and the air duct 32 is the binding off structure, therefore, the less impurity of granule can make a round trip to collide with the inner wall of flow stabilizing tube at the in-process of motion, finally stay in flow stabilizing tube, mutually support between glass filter and flow stabilizing tube 31, realize the filtration to the impurity in the sampling gas.

Referring to fig. 3 and 4, the fixing device 4 includes a base 41 and a fastening member 42, the base 41 is fixed on the mounting plate 21 and is communicated with the vacuum port of the vacuum generator 2, when the air duct 32 is inserted into the base 41, the worker can fix the air duct 32 on the base 41 by the fastening member 42 cooperating with the base 41.

Referring to fig. 5 and 6, the base 41 is cylindrical, external threads are arranged on the outer wall of the base 41, three coaxial through holes are formed in the base 41, each through hole comprises a small hole 411, a middle hole 412 and a large hole 413 which are sequentially far away from the air distribution disc 22, a first step surface 414 is formed between the small hole 411 and the middle hole 412, and a second step surface 415 is formed between the middle hole 412 and the large hole 413; the fastener 42 comprises an O-ring 421, a ferrule 422 and a lock nut 423; the diameter of the O-shaped ring 421 is larger than that of the small hole 411, and the inner wall of the O-shaped ring 421 is provided with a conical surface for increasing the friction force between the outer wall of the air duct 32 and the O-shaped ring 421 so as to prevent the air duct 32 from being easily separated after being installed; the cutting sleeve 422 comprises an upper cylinder and a lower cylinder, the outer diameter of the lower cylinder is matched with the inner diameter of the middle hole 412, the outer diameter of the upper cylinder is matched with the inner diameter of the big hole 413, and the height of the upper cylinder is equal to the depth of the big hole 413; the locking nut 423 is cylindrical, a stepped hole is formed in the locking nut 423, and an internal thread matched with the external thread on the base 41 is arranged in a large hole of the stepped hole.

Two mounting methods are set forth herein with respect to the above-described mounting structure. The method comprises the following steps: placing the O-shaped ring 421 on the first step surface 414, extending the lower cylinder of the ferrule 422 into the middle hole 412 and abutting against the O-shaped ring 421, supporting the upper cylinder of the ferrule 422 on the second step surface 415, then primarily installing the locking nut 423 on the base 41, taking the sound velocity small hole 3, forcibly passing the air duct 32 through the locking nut 423, the ferrule 422 and the O-shaped ring 421 in sequence and extending into the small hole 411, then rotating the locking nut 423, and abutting against the step surface in the locking nut 423 on the ferrule 422, so that the ferrule 422 compresses the O-shaped ring 421.

In the second method, the locking nut 423, the ferrule 422 and the O-ring 421 are sequentially sleeved on the air duct 32, then the air duct 32 is inserted into the small hole 411, the locking nut 423 is rotated to enable the locking nut 423 to be in threaded connection with the base 41, and in the rotating process, the O-ring 421 and the ferrule 422 are sequentially pressed into the base 41 to achieve fixed installation.

When the sound velocity small hole is replaced, the locking nut 423 only needs to be unscrewed, and then the sound velocity small hole 3 is taken down, so that the sound velocity small hole is quite convenient.

In order to improve the mounting firmness, an annular groove for embedding the O-shaped ring 421 is arranged on the outer wall of the air duct 32.

Referring to fig. 6 and 7, a metal filter 6 and a preheater 7 are sequentially sleeved outside the sound velocity small hole 3; the preheater 7 is in a cylindrical shape, one end of the preheater is fixed on the mounting plate 21 through a hoop 71, and the other end of the preheater is fixed on the outer wall of the probe shell 1 through a flange; the specific structure of the metal filter 6 can refer to a filter of model JS-GL-001, an internal threaded hole 211 (see figure 3) is formed in the mounting plate 21 by taking the base 41 as the center, one end of the metal filter 6 is connected to the mounting plate 21 through a connector thread, and the other end of the metal filter 6 abuts against the outer wall of the probe shell 1. Through the mode of can dismantling the connection, make things convenient for the staff to clear up and change metal filter 6.

A circulation chamber is formed between the metal filter 6 and the preheater 7, the side wall of the preheater 7 is connected and communicated with a stainless steel pipe 61 and an air conveying pipe 72, the stainless steel pipe 61 is communicated with an air source, an explosion-proof heat tracing band is wound on the outer wall of the preheater 7, one end of the explosion-proof heat tracing band is connected with an explosion-proof terminal connector, the other end of the explosion-proof heat tracing band is connected with an explosion-proof power supply junction box 12, after the explosion-proof heat tracing band is wound, an insulating layer is coated outside, when dilution gas 0 is introduced from the stainless steel pipe 61, the dilution gas is preferentially introduced into the preheater 7 to be preheated, and then is output from the air conveying pipe 72.

Referring to fig. 6, 7 and 8, the gas distribution plate 22 is a hollow disc, a standard gas port 23, a dilution gas port 24, a sample gas outlet 25 and a vacuum degree measuring port 26 which are communicated with the inside of the gas distribution plate 22 are fixedly connected to the outer wall of the gas distribution plate 22, and the dilution gas port 24 and the sample gas outlet 25 are oppositely arranged; a venturi tube 27 for communicating the dilution gas port 24 with the inner port of the sample gas outlet 25 and a vacuum chamber 28 for communicating the venturi tube 27 with the small sonic hole 3 are arranged in the gas distributor 22; the free end of the gas pipe 72 is communicated with the outer port of the dilution gas port 24; one end of the vacuum degree measuring port 26 is communicated with the vacuum cavity 28, and the other end is provided with a pressure gauge 8 for detecting the vacuum degree in the vacuum cavity 28.

Referring to fig. 1, a three-way joint 9 is installed on the sample gas outlet 25, one path of the three-way joint 9 is vented through a vent pipe 91, namely is communicated with the atmosphere, so as to ensure that the vacuum generator 2 generates sufficient vacuum degree, and a stop valve 92 is installed on the vent pipe 91 and is used for controlling the on-off of the vent pipe 91; the other path of the three-way joint 9 is connected with an analyzer through a hose 93.

Referring to fig. 8 and 9, the sampling probe 5 is fixed on the outer wall of the probe housing 1 through a flange and a counter flange and is in sealed communication with the sonic orifice 3. A baffle plate is fixedly connected to the inner wall of the sampling probe tube 5 and used for dividing the interior of the sampling probe tube 5 into an upper cavity and a lower cavity, a baffle plate 51 inclined downwards is arranged at one end, far away from the probe shell 1, of the sampling probe tube 5, the baffle plate 51 is integrally connected with the baffle plate, when negative pressure is generated, sampling gas enters the sampling probe tube from the lower cavity, part of the sampling gas is sucked into the sonic holes 3, part of the sampling gas is circulated out from the upper cavity, and the baffle plate 51 is arranged and used for reducing the amount of water-containing gas entering the sampling probe tube 5, so that the analysis precision of the sampling gas is ensured.

The working principle is as follows: during detection, the probe shell 1 is arranged on the outer wall of a flue, the sampling probe 5 is arranged at a droop angle of minus 5 degrees or a horizontal position in the installation process, the probe cannot be tilted upwards, then an air source is connected, the diluent gas 0 is introduced into the preheater 7 through the stainless steel pipe 61 to be preheated, then enters the circulation chamber from the air pipe 72, and then enters the Venturi tube 27 through the air pipe 72 and the diluent gas port 24 in sequence, negative pressure is formed at the vacuum chamber 28 communicated with the Venturi tube 27 due to the large flow velocity of the diluent gas 0, and the sample gas in the flue is sucked into the Venturi tube 27 to be mixed with the diluent gas 0 sequentially under the influence of pressure difference through the sampling probe 5, the metal filter 6, the sound velocity small hole 3 and vacuum, and finally introduced into an analyzer through the sample gas outlet 25 to be analyzed and detected.

Compared with the prior art, the explosion-proof diluting sampling probe realizes the explosion-proof function through explosion-proof parts such as the probe shell 1, the explosion-proof junction box 11, the explosion-proof power junction box 12, the explosion-proof tracing band and the like, is suitable for 1-zone and 2-zone dangerous places of IIA-IIC level and T1-T3 group explosive gas mixtures and indoor and outdoor installation, and is particularly suitable for places such as thermal power plants, cement plants, steel plants, nonferrous metal smelting plants, paper mills, glass, plastic processing, pharmaceutical factories, petrochemical plants and the like.

The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.

Claims

1. An explosion-proof dilution sampling probe which characterized in that: comprises a probe shell (1), a vacuum generator (2) arranged in the probe shell (1), a sound velocity pore (3) communicated with the vacuum generator (2), a fixing device (4) which can detachably and fixedly connect the sound velocity pore (3) to the vacuum generator (2), and a sampling probe tube (5) which is fixed on the outer wall of the probe shell (1) and is communicated with the sound velocity pore (3);

the vacuum generator (2) comprises a mounting plate (21) and a gas distribution disc (22) integrally connected to one side of the mounting plate (21);

the sound velocity small hole (3) comprises a flow stabilizing pipe (31) and an air guide pipe (32) which is integrally connected with the flow stabilizing pipe (31), and the diameter of the air guide pipe (32) is smaller than that of the flow stabilizing pipe (31);

the fixing device (4) comprises a base (41) fixedly connected to the mounting plate (21) and communicated with the vacuum generator (2), and a fastening piece (42) used for fixing the air guide pipe (32) on the base (41) when the air guide pipe (32) is plugged onto the base (41).

2. An explosion-proof dilution sampling probe according to claim 1, wherein: the base (41) is cylindrical, external threads are arranged on the outer wall of the base, three coaxial through holes are formed in the base (41), each through hole comprises a small hole (411), a middle hole (412) and a large hole (413) which are sequentially far away from the gas distribution disc (22), a first step surface (414) is formed between each small hole (411) and each middle hole (412), and a second step surface (415) is formed between each middle hole (412) and each large hole (413);

the fastening piece (42) comprises an O-shaped ring (421) placed on the first step surface (414), a clamping sleeve (422) with the lower portion inserted in the middle hole and the upper portion supported on the second step surface (415), and a locking nut (423) in threaded connection with the base (41) to enable the clamping sleeve (422) to tightly press the O-shaped ring (421), and the air duct (32) sequentially penetrates through the locking nut (423), the clamping sleeve (422) and the O-shaped ring (421) and is inserted in the base (41).

3. An explosion-proof dilution sampling probe according to claim 2, wherein: the inner wall of the O-shaped ring (421) is provided with an anti-falling conical surface.

4. An explosion-proof dilution sampling probe according to claim 1, wherein: the gas distribution disc (22) is a disc with an internal middle hole (412), a gas marking port (23), a dilution gas port (24) and a sample gas outlet (25) which are communicated with the inside of the gas distribution disc (22) are fixedly connected to the outer wall of the gas distribution disc (22), and the dilution gas port (24) and the sample gas outlet (25) are arranged oppositely; be equipped with venturi (27) with the inner port intercommunication of gas dilution mouth (24) and sample gas export (25) and with vacuum chamber (28) of venturi (27) and speed aperture (3) intercommunication in gas distribution dish (22), the air supply is connected to the outer port of gas dilution mouth (24), the outer port of sample gas export (25) lets in the analysis appearance.

5. An explosion-proof dilution sampling probe according to claim 4, wherein: and a three-way joint (9) is arranged on the sample gas outlet (25), one way of the three-way joint (9) is emptied, and the other way is connected with an analyzer.

6. An explosion-proof dilution sampling probe according to claim 1, wherein: a cylindrical metal filter (6) and a preheater (7) are sequentially sleeved outside the sound velocity small hole (3);

one end of the preheater (7) is fixed on the mounting plate (21) through a hoop (71), and the other end of the preheater is fixed on the outer wall of the probe shell (1) through a flange;

an internal threaded hole (211) is formed in the mounting plate (21) by taking the base (41) as the center, one end of the metal filter (6) is connected to the mounting plate (21) through a joint thread, and the other end of the metal filter (6) abuts against the outer wall of the probe shell (1);

the metal filter (6) with form the circulation cavity between preheater (7), connect and communicate on the lateral wall of metal filter (6) have with communicating stainless steel pipe (61) of air supply, be equipped with on the lateral wall of preheater (7) and dilute gas mouth (24) the gas-supply pipe (72) of intercommunication.

7. An explosion-proof dilution sampling probe according to claim 1, wherein: still the rigid coupling has vacuum degree measurement mouth (26) with dividing the inside intercommunication of gas dish (22) on gas dish (22), the one end of vacuum degree measurement mouth (26) communicates on vacuum cavity (28), manometer (8) are installed to the other end of vacuum degree measurement mouth (26).

8. An explosion-proof dilution sampling probe according to claim 2, wherein: and a glass filter is arranged in the flow stabilizing pipe (31).

9. An explosion-proof dilution sampling probe according to claim 2, wherein: the sampling probe tube (5) is fixed on the outer wall of the probe shell (1) through a flange and is communicated with the sound velocity small hole (3) in a sealing mode.

10. An explosion-proof dilution sampling probe according to claim 9, wherein: one end of the sampling probe tube (5) far away from the probe shell (1) is fixedly connected with a baffle plate (51) which inclines downwards.