Explosion-proof discharge helium ionization detection system and preparation method thereof

Abstract

The invention belongs to the technical field of gas chromatographic analysis, and particularly relates to an explosion-proof discharge helium ionization detection system and a preparation method thereof. A discharge chamber and an ionization chamber are coaxially arranged on the inner sides of the upper end and the lower end of a detector main body respectively, and the discharge chamber and the ionization chamber are communicated through a needle-shaped small hole; a dual-electrode feed-through flange upper cover is fixed at the upper end of the discharge chamber in a sealing manner; dual electrodes in the dual-electrode feed-through flange upper cover coaxially extend into the discharge chamber and are respectively connected with a positive electrode and a negative electrode of a high-voltage power supply; a current sensor is fixed at the lower end of the ionization chamber in a sealing manner, and the current sensor extends into the ionization chamber through a parallel pole plate and is used for acquiring ion current; the explosion-proof housing wraps the detector main body and is provided with a sealing hole for a coaxial cable to pass through. According to the invention, the influence of gas path sectional area change on carrier gas flow velocity and gas path pressure drop is reduced, so that the detection performance is improved.

Description

Technical Field

[0001] This invention belongs to the field of gas chromatography analysis technology, and more specifically, relates to an explosion-proof discharge helium ionization detection system and its preparation method. Background Technology

[0002] The integrated development of high-end manufacturing fields such as aerospace, precision manufacturing, and semiconductor production, as well as the rapid large-scale development of the power and petrochemical industries, have created a demand for the analysis of high-purity and ultrapure gases and their trace impurities. This places higher demands on detection methods and equipment, requiring detection limits to reach the ppb level. Gas chromatography is a classic technique for separating and detecting components in complex gas mixtures, with its core components being the chromatographic column and detector.

[0003] The discharge helium ion detector is a general-purpose gas detector with a detection limit in the ppb range, capable of detecting trace gases. However, during excitation, the electrode tips of the discharge helium ion detector are subjected to high voltage and high current, and it continuously experiences corona discharge during operation. This poses a risk in situations where the test environment is suddenly exposed to flammable or explosive materials.

[0004] Furthermore, achieving a lower detection limit depends on plasma stability and high-fidelity acquisition of weak current signals. A stable power supply with low output ripple and noise enables the detector to excite a more stable plasma, while power supply and signal collection cables with excellent conductivity, insulation, and shielding properties, matched to the detector's impedance, can improve the detector's detection limit and sensitivity.

[0005] Current research on improving the performance of gas chromatograph detectors often focuses on optimizing the internal chamber volume, the position and distance of the bias electrode and the gas path opening; while neglecting the design to improve its airtightness, the high-voltage excitation power supply configured in the detector, and the baseline noise introduced by the signal acquisition unit. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the purpose of this invention is to propose an explosion-proof discharge helium ionization detection system and its preparation method, providing a reference for the mass production of explosion-proof discharge helium ion detectors, and improving the overall detection limit and sensitivity.

[0007] To achieve the above and other related objectives, the present invention provides an explosion-proof discharge helium ionization detection system, comprising: The detector body has a discharge chamber and an ionization chamber coaxially arranged on the inner sides of its upper and lower ends, respectively, and the discharge chamber and the ionization chamber are connected through a pinhole. The dual-electrode feedthrough flange cover is sealed and fixed to the upper end of the discharge chamber. The dual electrodes inside the dual-electrode feedthrough flange cover extend coaxially into the discharge chamber and are respectively connected to the positive and negative terminals of the high-voltage power supply. A current sensor is sealed and fixed at the lower end of the ionization chamber. The current sensor extends into the ionization chamber through parallel plates to obtain the ion current. The weak signal is collected by a weak current acquisition module. An explosion-proof housing covers the detector body and is provided with threaded through holes and straight slots for cables and stainless steel pipes to pass through.

[0008] In one embodiment of the present invention, Also includes: The first air inlet is located on the side of the discharge chamber, and helium carrier gas is introduced through the first air inlet; The second air inlet is located on the side of the ionization chamber, through which sample gas is introduced; An exhaust port, located on the side of the ionization chamber, discharges a mixture of ionized gases.

[0009] In one embodiment of the present invention, the connection sides of the discharge chamber, the ionization chamber and the needle-shaped orifice all contract towards the needle-shaped orifice and become conical, that is, the needle-shaped orifice is the apex of the confluence of two funnel shapes, and the discharge chamber, the ionization chamber and the needle-shaped orifice are located on the same axis.

[0010] In one embodiment of the present invention, the cone angle of the detector body is 135°.

[0011] In one embodiment of the present invention, the diameter of the pinhole of the detector body is greater than the height of the pinhole.

[0012] In one embodiment of the present invention, the detector body has an outer contour of a cylinder with one side milled flat, and the discharge chamber and ionization chamber are generally cylindrical cavities.

[0013] In one embodiment of the present invention, the electrode of the dual-electrode feed flange cover includes a nickel metal rod extending through a 99% ceramic hollow column and connected to a metal end cap at the tail end; the volume of the ionization chamber is no more than 500 microliters, and the volume of the discharge chamber is 5-10 times or more the volume of the ionization chamber.

[0014] In one embodiment of the present invention, the lower end of the dual electrode column of the dual electrode feed flange cover is located in the discharge chamber. A tungsten needle is welded and fixed to the end of one nickel rod, and a platinum electrode is fixed to the end of the other nickel rod. The tungsten needle and the platinum electrode are respectively connected to the negative and positive terminals of the high voltage power supply. The end of the tungsten needle is a sharp point, and the end of the platinum electrode is spherical. A high potential difference from the high voltage power supply is formed between the end of the tungsten needle and the end of the platinum electrode.

[0015] In one embodiment of the present invention, a stainless steel pipe is further included, which is welded to the first air inlet, the second air inlet, and the exhaust port.

[0016] This invention also provides a method for preparing an explosion-proof discharge helium ionization detection system, comprising the above-mentioned explosion-proof discharge helium ionization detection system, wherein the method for preparing the explosion-proof discharge helium ionization detection system includes: S1. Insert an oxygen-free copper sealing ring between the upper end of the discharge chamber of the detector body and the CF16 flange opening of the dual-electrode feedthrough flange cover, tighten the diagonal screws to make the metal ring seal, and fix the discharge end bracket at the same time. S2. Insert the parallel plate end of the current sensor into the ionization chamber, tighten the through-hole bolts to seal the metal edge of the current sensor with the arc line at the lower end of the ionization chamber, and fix the ionization end bracket to the lower end of the detection body with screws. S3. Weld stainless steel pipes to the first air inlet, the second air inlet, and the exhaust port respectively, and install an explosion-proof fixing / heat dissipation ring on the outside of the explosion-proof shell; S4. Fix the temperature control module: heating rod and PT100 output wires to the explosion-proof housing using explosion-proof connectors; introduce helium carrier gas into the gas pipe corresponding to the first air inlet, which is the helium carrier gas pipe; introduce sample gas into the gas pipe corresponding to the second air inlet, which is the sample gas inlet pipe; and exhaust pipe corresponding to the exhaust port, which is the tail gas exhaust pipe, through the straight slot hole of the explosion-proof housing, and fix them to the explosion-proof housing and the explosion-proof fixing / heat dissipation ring respectively using explosion-proof connectors.

[0017] As described above, the explosion-proof discharge helium ionization detection system and its preparation method of the present invention have the following beneficial effects: The present invention provides an explosion-proof discharge helium ionization detection system that enables the carrier gas and sample gas to accurately reach the ionization region, stabilizes the gas flow path, reduces the impact of changes in the gas path cross-sectional area on the carrier gas flow rate and gas path pressure drop, thereby improving detection performance.

[0018] The present invention discloses an explosion-proof discharge helium ionization detection system. The design of the discharge chamber flange simultaneously meets the considerations of airtightness and product standardization, thereby improving the stability of product production. The lower end of the ionization chamber is designed with an annular raised arc surface and is fixed with threaded adhesive, which enables the ionization chamber structure to cope with certain sudden vibrations, improves the airtightness of the ionization chamber, and thus improves the detection performance of the detector.

[0019] The present invention discloses an explosion-proof discharge helium ionization detection system for online testing of flammable and explosive industrial applications, enabling industrial chromatographs equipped with this detector to be widely used in petroleum, chemical, and defense industries. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the structure of an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention; Figure 2 This is a cross-sectional structural schematic diagram of an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention; Figure 3 This is a cross-sectional structural schematic diagram of an explosion-proof discharge helium ionization detection system according to another embodiment of the present invention; Figure 4 This is a block diagram connection schematic of an explosion-proof discharge helium ionization detection system according to another embodiment of the present invention; Figure 5 This is a test result of 1 ppm methane mixed standard gas from an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention.

[0021] The components include: 1. Detector body; 2. Discharge chamber; 3. Ionization chamber; 4. Dual-electrode feedthrough flange cover; 5. Current sensor; 6. First air inlet; 7. Second air inlet; 8. Exhaust port; 9. Discharge end bracket; 10. Ionization end bracket; 11. Explosion-proof housing; 12. Explosion-proof connector; 13. Explosion-proof fixing / heat dissipation ring. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0023] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] Terms such as "first" or "second" may be used to describe various components, but these components are not limited by the terms described above. The terms described above are used to distinguish one component from another; for example, without departing from the scope of the concept according to this disclosure, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0025] Furthermore, "connected / linked" indicates that one component is directly electrically connected to another component or indirectly electrically connected through another component. Unless otherwise explicitly stated in the sentence, the singular form may include the plural form. Additionally, the terms "comprising / including" or "containing / including" as used in this specification indicate the presence or addition of one or more components, steps, operations, and elements. Specific structural or functional descriptions of examples of embodiments of the concepts disclosed in this specification are merely illustrative to describe examples of embodiments of the concepts, and examples of embodiments of the concepts can be implemented in various forms, but these descriptions are not limited to the examples of embodiments described in this specification.

[0026] Based on the concept, various modifications and changes can be applied to examples of embodiments, such that examples of embodiments will be illustrated in the accompanying drawings and described in the specification. However, examples of embodiments based on the concept are not limited to specific embodiments, but include all changes, equivalents, or substitutions included within the spirit and scope of this disclosure.

[0027] It should be understood that when describing an element as "connected" or "linked" to another element, the element may be directly connected or linked to the other element, or it may be connected or linked to the other element via a third element. Conversely, it should be understood that when an element is described as "directly connected to" or "directly linked to" another element, no other element is placed between them. Other expressions describing relationships between components (i.e., "between" and "directly between" or "adjacent to" and "directly adjacent to") need to be interpreted in the same way.

[0028] The terminology used in this specification is for the purpose of describing specific examples of implementations only and is not intended to limit this disclosure. The singular form may include the plural form unless there is an explicit contrary meaning in the context. It should be understood in this specification that the terms "comprising" or "having" indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein (including technical or scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art. If a term is not clearly defined in a common dictionary in this specification, it shall be interpreted as having the same meaning as in the context of the relevant art, and not as an ideal or overly formal meaning.

[0030] Descriptions of known components and processing techniques may be omitted to avoid unnecessarily obscuring the embodiments of this disclosure.

[0031] Throughout this specification, the same reference numerals refer to the same elements. Therefore, even if a reference numeral is not mentioned or described with reference to one drawing, it may be mentioned or described with reference to another drawing. Furthermore, even if a reference numeral is not shown in one drawing, it may be mentioned or described with reference to another drawing.

[0032] Additionally, the logic level of a signal may be different from or opposite to the logic level described. For example, a signal described as having a logic "high" level may optionally have a logic "low" level, and a signal described as having a logic "low" level may optionally have a logic "high" level.

[0033] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0034] Please see Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 1 This is a schematic diagram of the structure of an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention; Figure 2 This is a cross-sectional structural schematic diagram of an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention; Figure 3 This is a cross-sectional structural schematic diagram of an explosion-proof discharge helium ionization detection system according to another embodiment of the present invention; Figure 4 This is a block diagram of another embodiment of the explosion-proof discharge helium ionization detection system of the present invention. The present invention provides an explosion-proof discharge helium ionization detection system, comprising: a discharge chamber 2 and an ionization chamber 3 coaxially disposed on the inner sides of the upper and lower ends of a detector body 1, the discharge chamber 2 and the ionization chamber 3 being connected through a pinhole; a dual-electrode feedthrough flange cover 4 sealed and fixed to the upper end of the discharge chamber 2, the dual electrodes inside the dual-electrode feedthrough flange cover 4 coaxially extending into the discharge chamber 2 and respectively connected to the positive and negative terminals of a high-voltage power supply; a current sensor 5 sealed and fixed to the lower end of the ionization chamber 3, the current sensor extending into the ionization chamber 3 through parallel plates to acquire ion current, the weak signal being collected by a weak current acquisition module; and an explosion-proof housing 11 covering the detector body 1, and provided with threaded through holes and straight slots for cables and stainless steel pipes to pass through.

[0035] The present invention provides an explosion-proof discharge helium ionization detection system, which further includes: a first air inlet 6 located on the side of the discharge chamber 2, through which helium carrier gas is introduced; a second air inlet 7 located on the side of the ionization chamber 3, through which sample gas is introduced; and an exhaust port 8 located on the side of the ionization chamber 3, through which mixed ionized gas is discharged.

[0036] Specifically, the connection sides of the discharge chamber 2, ionization chamber 3, and the needle-shaped orifice all taper towards the needle-shaped orifice, forming a conical shape. That is, the needle-shaped orifice is the confluence apex of two funnel-shaped structures, and the discharge chamber 2, ionization chamber 3, and needle-shaped orifice are located on the same axis. The cone angle of the cone shape of the detector body 1 is 135°. The diameter of the needle-shaped orifice in the detector body 1 is greater than the height of the needle-shaped orifice. The outer contour of the detector body 1 is a cylinder milled flat on one side, and the discharge chamber 2 and ionization chamber 3 are generally cylindrical cavities. The electrodes of the dual-electrode feedthrough flange cover 4 include nickel rods extending through a 99% ceramic hollow column and fitted with metal end caps at the tail end. The volume of the ionization chamber 3 is no more than 500 microliters, and the volume of the discharge chamber 2 is 5-10 times larger than the volume of the ionization chamber 3. It also includes a stainless steel tube, which is welded to the first air inlet 6, the second air inlet 7, and the exhaust port 8.

[0037] In one embodiment of the present invention, the detector body 1 has an outer contour of a cylinder milled flat on one side, with a discharge chamber 2 and an ionization chamber 3 respectively located on the inner sides of the upper and lower ends. The discharge chamber 2 and ionization chamber 3 are generally cylindrical cavities, connected by a pinhole. The connection sides of both chambers to the pinhole narrow towards the pinhole, forming a conical shape (with a cone angle of 135°). That is, the pinhole is the confluence of two funnel-shaped structures. The discharge chamber 2, ionization chamber 3, and pinhole are located on the same axis. The diameter of the pinhole inside the detector is greater than its height. In one embodiment of the present invention, the detector body 1 has a first air inlet 6, a second air inlet 7, and an exhaust port 8 on its milled side, arranged vertically from top to bottom along the center line of the plane; the first air inlet 6 is located on the side of the discharge chamber 2, and the second air inlet 7 and the exhaust port 8 are both located on the side of the ionization chamber 3; helium carrier gas is introduced through the first air inlet 6, sample gas is introduced through the second air inlet 7, and the mixed ionized gas is discharged through the exhaust port 8. A stainless steel tube with an outer diameter of 1 / 16 is welded to the first air inlet 6, the second air inlet 7, and the exhaust port 8 using a welding process.

[0038] In one embodiment of the present invention, at a constant discharge carrier gas flow rate, the small-volume ionization chamber exhibits excellent sensitivity, and the gas turnover is relatively fast. Due to the high sensitivity requirements of concentration-dependent detectors, the volume of the ionization chamber of the discharge helium ion detector is no greater than 500 microliters, while the volume of its discharge chamber is limited to 5-10 times or more the volume of the ionization chamber (e.g., the discharge chamber volume is approximately 3.20 m³). 3 The ionization chamber volume is approximately 0.23 m³. 3 This allows the ionization chamber to maintain a large glow discharge plasma reserve.

[0039] In one embodiment of the present invention, the dual-electrode feedthrough flange cover 4 is constructed by first having a nickel rod pass through a 99mm ceramic hollow column and be fitted with a metal end cap at the tail end, then welding the three together to form an electrode assembly. Next, the dual electrodes pass through two electrode transition rings and then through a CF16 flange cover with double circular holes, and the three together are welded to form the dual-electrode feedthrough flange cover. The design of each component must consider the difference in expansion coefficients between the metal and ceramic during welding, design a pre-reserved solder groove, and specify tolerances to ultimately achieve the sealing, pressure resistance, and insulation requirements of the dual-electrode feedthrough flange cover.

[0040] Another method for manufacturing the dual-electrode feed-through flange cover 4 is to use a double-hole CF16 flange cover as a base, and then sinter bimetallic nickel rods into the double holes using glass to achieve sealing, pressure resistance, and insulation functions. In this case, the metal material used to process the double-hole CF16 flange cover is Kovar alloy 4J50.

[0041] In one embodiment of the present invention, the main body of the current sensor 5 is made of a metal cavity ring combined with glass-sintered metal pins. The metal part is made of Kovar alloy and is gold-plated on the metal surface. A pair of parallel nickel plates are laser-welded to the two pins at the upper end of the current sensor 5. By preparing welding fixtures, the current sensor 5 can be mass-produced. The two exposed pins at the lower end of the current sensor 5 are covered with heat-shrink tubing after heating to avoid signal interference caused by external factors.

[0042] In one embodiment of the present invention, the invention further includes four through-board BNC connectors and four external coaxial cables (two providing excitation voltage, and two providing bias voltage and signal acquisition functions respectively). The contact and fit between the BNC connectors and the cables are stable and will not produce impedance changes. In addition, the selected cables have internal resistance that matches the detector impedance and have excellent conductivity, insulation and shielding performance, which can accurately transmit the weak electrical signals captured by the detector itself and reduce the noise introduced during signal transmission.

[0043] Specifically, all four through-plate connectors are BNC female connectors, fixed to two openings on each of the discharge end bracket 9 and ionization end bracket 10. The positive and negative terminals of the external high-voltage power supply are connected to two coaxial cables, and the other end of the coaxial cables is soldered / crimped with two BNC male connectors that connect to the BNC female connector on the upper end of the detector body 1. The high-voltage excitation of the gas plasma in the discharge chamber by the external high-voltage power supply is achieved through the plug-in connection of the BNC male and female connectors. In order to improve the detection performance, a high-voltage power supply module with the characteristics of "low output ripple and low noise, high stability, low temperature coefficient, arc protection and short circuit protection, and actual output voltage controllable by external potentiometer or external control" was selected for the high-voltage power supply for exciting helium plasma.

[0044] The first air inlet 6 corresponds to the air pipe, the sample gas enters the second air inlet 7 corresponds to the air pipe, and the exhaust port 8 corresponds to the exhaust pipe. No cables are included. Figure 1 The six curves shown in the diagram represent wires or conductors. The upper diagram indicates that two wires are actually welded to the upper end of the nickel rod on the feedthrough dual-electrode flange cover, with the other end welded to the two upper through-plate BNC female connectors. The two lower curves, due to the sufficient length pre-designed for the lower pins of the weak current sensor 5, can be directly welded to the two lower through-plate BNC female connectors. The two curves on the side represent the heating rod inserted into the pre-drilled holes inside the detector body and the PT100 output wire, respectively.

[0045] In one embodiment of the present invention, an explosion-proof design is also provided, including an explosion-proof housing 11 outside the detector body 1, and check valves, flow sensors, flame arresters, etc., added to each gas inlet and outlet of the detector body 1. The upper and lower covers of the explosion-proof housing 11 each have two holes for four through-plate BNC female connectors; straight slots are made on the busbar on the cylindrical side of the explosion-proof housing 11 for three 1 / 8-inch stainless steel gas pipes to pass through, and then fixed to the explosion-proof fixing / heat dissipation ring 13 via explosion-proof connectors 12.

[0046] This invention also provides a method for preparing an explosion-proof discharge helium ionization detection system, comprising the above-mentioned explosion-proof discharge helium ionization detection system, wherein the method for preparing the explosion-proof discharge helium ionization detection system includes: S1. Insert an oxygen-free copper sealing ring between the upper end of the discharge chamber 2 of the detector body 1 and the CF16 flange opening of the dual-electrode feedthrough flange cover 4, tighten the diagonal screws to make the metal ring seal, and fix the discharge end bracket 9 at the same time. S2. Insert the parallel plate end of the current sensor 5 into the ionization chamber 3, tighten the through-hole bolt to seal the metal edge of the current sensor 5 with the lower arc line of the ionization chamber 3, and fix the ionization end bracket 10 to the lower end of the detection body 1 with screws. S3. Weld stainless steel pipes to the first air inlet 6, the second air inlet 7, and the exhaust port 8 respectively, and fit an explosion-proof fixing / heat dissipation ring 13 on the outside of the explosion-proof housing 11. S4. Fix the outlet wires of the temperature control module, heating rod and PT100 to the explosion-proof housing 11 using explosion-proof connectors 12; introduce helium carrier gas into the gas pipe corresponding to the first air inlet 6, which is the helium carrier gas pipe; introduce sample gas into the gas pipe corresponding to the second air inlet 7, which is the sample gas inlet pipe; and exhaust pipe corresponding to the exhaust port 8, which is the tail gas exhaust pipe, through the straight slot hole of the explosion-proof housing 11, and fix them to the explosion-proof housing 11 and the explosion-proof fixing / heat dissipation ring 13 respectively using explosion-proof connectors 12.

[0047] Specifically, for the second air inlet (6), the exhaust port (7), and the exhaust port (8), two wires are taken, one end of which is welded to the dual electrodes of the dual-electrode feedthrough flange cover (4), and the other end is fully welded to the two BNC solder cups fixed at the upper end of the DID detector. In addition, the two gold-plated pins at the lower end of the current sensor (5) are welded to the two BNC solder cups at the lower end of the detector. The temperature control module (heating rod and PT100 output wires), the helium carrier gas pipe corresponding to the first air inlet (6), the sample gas pipe corresponding to the second air inlet (7), and the exhaust pipe corresponding to the exhaust port (8) are connected to the explosion-proof housing (11) opening and fixed with the explosion-proof connector (12).

[0048] In one embodiment of the present invention, the present invention also provides a method for preparing an explosion-proof discharge helium ionization detection system, wherein the discharge chamber 2 and the ionization chamber 3 of the detector body 1 are both required to be sealed and assembled.

[0049] The sealing assembly method for the discharge chamber 2 is as follows: the upper opening of the discharge chamber 2 of the detector body 1 is designed according to the standard dimensions of a CF16 flange, and the upper cover 4 of the dual-electrode feedthrough flange is also designed according to the CF16 flange standard, with reduced surface roughness. A CF16 standard oxygen-free copper ring is sandwiched between the flange openings of the two components. These three components form a sandwich structure, ensuring the sealing interface is free of dust and debris. During installation, six screws are installed around the flange opening and tightened gradually and orderly in a diagonal pattern, achieving a sealing effect with the copper ring.

[0050] The sealing assembly method of the ionization chamber 3 is as follows: an internal thread with a diameter larger than its own inner diameter is machined at the lower opening of the ionization chamber 3. After the long needle end of the current sensor 5 is passed through the matching through-hole bolt, the parallel electrode end is placed into the ionization chamber and fixed with the bolt. Specifically, a concentric, downward-convex arc surface is machined at the upper end of the internal thread hole, ensuring its surface roughness and smoothness; the upper surface of the metal edge of the weak current sensor contacts the convex arc surface, and the lower end contacts the top of the thread of the through-hole bolt. During installation, the threaded bolt is tightened to achieve the sealing effect of the ionization chamber.

[0051] The pair of parallel nickel electrodes at the upper end of the current sensor 5 are fixed by laser welding and powered by an external bias power supply inside the ionization chamber, forming a parallel electric field. Sample gas is introduced into the second gas inlet 7 inside the ionization chamber, entering the electric field at a uniform speed and colliding with the excited-state helium ion gas cloud flowing out of the upper needle-shaped hole. Therefore, during assembly, the direction of the parallel electrodes is kept parallel to the gas inlet direction, allowing the ion gas cloud to pass through and be captured.

[0052] The lower end of the dual electrode column of the dual electrode feed flange cover 4 is located in the discharge chamber 2. A tungsten needle is welded and fixed to the end of one nickel rod, and a platinum electrode is fixed to the end of the other nickel rod. The tungsten needle and the platinum electrode are respectively connected to the negative and positive terminals of the high voltage power supply. The end of the tungsten needle is a sharp point, and the end of the platinum electrode is spherical. A high potential difference from the high voltage power supply is formed between the end of the tungsten needle and the end of the platinum electrode.

[0053] Please see Figure 5 , Figure 5 This is a test result of 1 ppm methane mixed standard gas from an explosion-proof discharge helium ionization detection system according to an embodiment of the present invention.

[0054] Helium plasma is excited using a DC high-voltage power supply module, and a miniature high-voltage power supply module provides the bias voltage for the mixed gas plasma clusters in the ionization chamber. The figure shows the entire explosion-proof DID detection system designed in this patent, integrated into a chromatographic analysis system. Testing was performed using a 1 ppm methane mixed standard gas, which was then diluted stepwise using a diluent. The results showed that all components in the mixed standard gas were detected with good peak shapes: H2, O2+Ar, N2, CH4, and CO. All components were detectable at a dilution to 50 ppb, with signal-to-noise ratios exceeding 10. Therefore, the design, fabrication, and performance optimization methods of this explosion-proof DID detection system ultimately yielded high sensitivity, meeting the application requirements of various industries involved in high-purity and even ultra-high-purity gas analysis.

[0055] In summary, the explosion-proof discharge helium ionization detection system of this invention allows the carrier gas and sample gas to accurately reach the ionization region, stabilizes the gas flow path, and reduces the impact of changes in the gas path cross-sectional area on the carrier gas flow rate and pressure drop, thereby improving detection performance. The design of the discharge chamber flange of this invention simultaneously meets considerations of airtightness and product standardization, improving product manufacturing stability. The lower end of the ionization chamber features an annular raised arc surface design and is secured with threaded adhesive, enabling the ionization chamber structure to withstand certain sudden vibrations, improving the airtightness of the ionization chamber, and thus enhancing the detector's detection performance. This invention is designed for online testing of flammable and explosive industrial applications, making industrial chromatographs equipped with this detector widely applicable in the petroleum, chemical, and defense industries.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An explosion-proof discharge helium ionization detection system, characterized in that, include: The detector body (1) has a discharge chamber (2) and an ionization chamber (3) coaxially arranged on the inner sides of its upper and lower ends, respectively. The discharge chamber (2) and the ionization chamber (3) are connected through a pinhole. The dual-electrode feed-through flange cover (4) is sealed and fixed to the upper end of the discharge chamber (2). The dual electrodes inside the dual-electrode feed-through flange cover (4) extend coaxially into the discharge chamber (2) and are respectively connected to the positive and negative poles of the high-voltage power supply. A current sensor (5) is sealed and fixed at the lower end of the ionization chamber (3). The current sensor extends into the ionization chamber (3) through parallel plates to obtain ion current. The weak signal is collected by the weak current acquisition module. An explosion-proof housing (11) covers the detector body (1) and is provided with threaded through holes and straight slots for cables and stainless steel pipes to pass through.

2. The explosion-proof discharge helium ionization detection system according to claim 1, characterized in that, Also includes: The first air inlet (6) is located on the side of the discharge chamber (2), and helium carrier gas is introduced through the first air inlet (6); The second air inlet (7) is located on the side of the ionization chamber (3), through which sample gas is introduced; An exhaust port (8) is located on the side of the ionization chamber (3) from which the mixed ionized gas is discharged.

3. The explosion-proof discharge helium ionization detection system according to claim 2, characterized in that: The discharge chamber (2), ionization chamber (3) and the needle-shaped hole are connected on the side of the needle-shaped hole and the diameter of the needle-shaped hole is reduced to a conical shape. That is, the needle-shaped hole is the apex of the two funnel shapes, and the discharge chamber (2), ionization chamber (3) and the needle-shaped hole are located on the same axis.

4. The explosion-proof discharge helium ionization detection system according to claim 3, characterized in that: The cone angle of the detector body (1) is 135°.

5. The explosion-proof discharge helium ionization detection system according to claim 1, characterized in that: The diameter of the pinhole in the detector body (1) is greater than the height of the pinhole.

6. The explosion-proof discharge helium ionization detection system according to claim 1, characterized in that: The detector body (1) has an outer contour of a cylinder with one side milled flat, and the discharge chamber (2) and ionization chamber (3) are generally cylindrical cavities.

7. The explosion-proof discharge helium ionization detection system according to claim 1, characterized in that: The electrodes of the dual-electrode feed flange cover (4) include a nickel metal rod that passes through a 99% ceramic hollow column and is fitted with a metal end cap at the tail end; the volume of the ionization chamber (3) is no more than 500 microliters, and the volume of the discharge chamber (2) is 5-10 times or more the volume of the ionization chamber (3).

8. The explosion-proof discharge helium ionization detection system according to claim 7, characterized in that: The lower end of the dual electrode column of the dual electrode feed flange cover (4) is located in the discharge chamber (2). A tungsten needle is welded and fixed to the end of one nickel rod, and a platinum electrode is fixed to the end of the other nickel rod. The tungsten needle and the platinum electrode are respectively connected to the negative and positive terminals of the high voltage power supply. The end of the tungsten needle is a sharp point, and the end of the platinum electrode is spherical. A high potential difference from the high voltage power supply is formed between the end of the tungsten needle and the end of the platinum electrode.

9. The explosion-proof discharge helium ionization detection system according to claim 1, characterized in that: It also includes a stainless steel pipe, which is welded to the first air inlet (6), the second air inlet (7), and the exhaust port (8).

10. A method for preparing an explosion-proof discharge helium ionization detection system, characterized in that, The explosion-proof discharge helium ionization detection system according to any one of claims 1 to 9, wherein the preparation method of the explosion-proof discharge helium ionization detection system includes: S1. Insert an oxygen-free copper sealing ring between the upper end of the discharge chamber (2) of the detector body (1) and the CF16 flange opening of the double electrode feed-through flange cover (4), tighten the diagonal screws to make the metal ring seal, and fix the discharge end bracket (9). S2. Insert the parallel plate end of the current sensor (5) into the ionization chamber (3), tighten the through hole bolt to seal the metal edge of the current sensor (5) with the lower arc line of the ionization chamber (3), and fix the ionization end bracket (10) to the lower end of the detection body (1) with screws. S3. Weld stainless steel pipes to the first air inlet (6), the second air inlet (7), and the exhaust port (8) respectively, and fit an explosion-proof fixing / heat dissipation ring (13) on the outside of the explosion-proof housing (11). S4. Fix the outlet wires of the temperature control module, heating rod and PT100 to the explosion-proof shell (11) with explosion-proof connector (12); pass the helium carrier gas into the gas pipe corresponding to the first air inlet (6), which is the helium carrier gas pipe; pass the sample gas into the gas pipe corresponding to the second air inlet (7), which is the sample gas inlet pipe; pass the exhaust pipe corresponding to the exhaust port (8), which is the tail gas exhaust pipe, through the straight slot hole of the explosion-proof shell (11), and fix them to the explosion-proof shell (11) and the explosion-proof fixing / heat dissipation ring (13) respectively with explosion-proof connector (12).

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