Explosion-proof surface gap online detection method

Abstract

The invention provides a flame-proof surface gap online detection method, and belongs to the technical field of flame-proof equipment joint surface gap detection. According to the technical scheme, a nitrogen pressurizing and leakage detection mode is adopted, a mathematical model of the flame-proof surface gap, the pressure and the leakage flow of the flame-proof equipment is constructed, the size of the flame-proof surface gap can be accurately reflected in real time, and needed equipment comprises the flame-proof equipment, a gas storage bottle, a gas filling pipeline, a gas pressure meter and a flow meter; and the gas storage bottle is filled with nitrogen. Compared with a traditional detection method, the online detection method for the gap of the flameproof surface has the advantages that the problem that real-time and accurate detection cannot be achieved is solved, the safety risk of traditional detection is avoided, and the online detection method has important practical engineering application value.

Description

Technical Field

[0001] This invention relates to the field of explosion-proof equipment mating surface gap detection technology, and more particularly to an online detection method for explosion-proof surface gap. Background Technology

[0002] The research on explosion-proof electrical technology originated from coal mining. In the early 19th century, due to the development of production, mechanized production gradually replaced heavy manual labor. The driving power of machinery is provided by electric motors and their electrical control systems. Because electrical equipment often generates sparks, arcs, and dangerous temperatures during starting, stopping, and operation, explosion accidents frequently occur in production. People began to study and explore explosion accidents. In 1883, the world's first research institution, the Chicago Insurance Institute in the United States, was established. Soon, many advanced countries established similar research institutions. These research institutions conducted a series of experimental studies on the combustion and explosion process of methane in coal mines, as well as the relationship between the physical quantities generated during the explosion, providing a wealth of results for exploring corresponding explosion-proof measures. Between 1903 and 1943, researchers in countries such as Britain, Germany, and Russia successively invented explosion-proof electrical equipment of the flameproof, increased safety, and intrinsically safe types. Later, they developed explosion-proof electrical equipment such as sand-filled, plastic-sealed, and pressurized types, and established corresponding manufacturing standards and installation specifications.

[0003] To improve the quality of explosion-proof products, countries worldwide have incorporated explosion-proof products into mandatory certification management. Major certification bodies include the international IECEx certification system and the European ATEX certification system, with certification primarily based on indoor explosion-proof testing. Internationally, there are mainly EN series standards, IEC series standards, and North American series standards. These standards classify hazardous areas and specify requirements for the selection, installation, inspection, and maintenance of explosion-proof electrical equipment, but do not include relevant indicators and content for testing and evaluation technologies. Domestic electrical explosion-proof standards and specifications are similar to international IEC standards, based on the GB3836 series standards. Domestic standards specify requirements for the manufacture, installation, use, and maintenance of explosion-proof electrical equipment, but do not include requirements for testing parameters and indicators. Electrical explosion-proof testing mainly focuses on indoor type certification testing. Before explosion-proof electrical equipment is officially marketed, it must undergo type certification testing at a nationally designated explosion-proof certification body. Tests include: flameproof testing, spark testing, constant temperature and humidity environment simulation testing, and thermal shock testing, to verify whether the explosion-proof performance of the electrical flameproof equipment meets the requirements. However, these tests are all destructive explosion tests, and this testing technology cannot be applied on-site without disassembling the equipment.

[0004] The inspection and testing of electrical explosion-proof equipment primarily involves visual inspection, with key influencing parameters including grounding resistance, operating temperature, and the gap between explosion-proof surfaces. Explosion-proof equipment is the most widely used electrical equipment in industries such as coal, petroleum, and chemicals. This type of equipment uses a high-strength explosion-proof outer shell, tightly secured to resist potential internal combustion and explosion. Therefore, the explosion-proof joint surface is a core performance indicator of explosion-proof equipment. The gap between explosion-proof surfaces is generally measured using a feeler gauge; however, this poses a safety risk when the equipment is energized in the field, and the measurement results are prone to error, seriously affecting the assessment of the explosion-proof equipment's performance.

[0005] In summary, electrical explosion-proof equipment is widely used in explosive hazardous locations such as coal mines, petroleum plants, and chemical plants. Relevant standards have also clearly defined the inspection requirements for equipment performance. However, current inspection and testing primarily rely on indoor experiments, making online testing of the equipment impossible. As a core indicator affecting the performance of explosion-proof equipment, the gap between the explosion-proof surfaces is susceptible to safety risks and errors when measured using feeler gauges. Furthermore, abnormalities in the gap cannot be detected promptly.

[0006] Current testing methods for explosion-proof electrical equipment primarily rely on indoor experiments, lacking on-site testing techniques that do not require disassembly of the equipment. Currently, the gap measurement of the explosion-proof surface uses feeler gauges, which poses safety risks and inaccuracies, and makes it difficult to detect changes in the gap in a timely manner. This invention provides an online measurement method for the explosion-proof surface gap, enabling quantitative description of the gap and achieving online testing without disassembling the equipment, thus reflecting the size of the explosion-proof surface gap in real time and accurately. Summary of the Invention

[0007] The purpose of this invention is to provide a simple and effective online detection method for the gap between explosion-proof surfaces.

[0008] This invention is achieved through the following measures:

[0009] An online detection method for explosion-proof surface gaps is characterized by employing nitrogen pressurization and leakage detection to construct a mathematical model of the explosion-proof surface gaps, pressure, and leakage flow rate in explosion-proof equipment. This model can accurately reflect the size of the explosion-proof surface gaps in real time. The specific method is as follows:

[0010] S1. Fill the explosion-proof device with nitrogen gas. After the nitrogen pressure P inside the explosion-proof device stabilizes, measure the filling flow rate Q. in The value of the filling flow rate Q at this time in The leakage flow rate Q of nitrogen gas leaking from inside the explosion-proof device to the outside. out equal;

[0011] S2. Assuming that the gap S between the flameproof surfaces is uniform, the relationship between the flameproof surface area A and the gap S is: A=S×L, where L is the perimeter of the flameproof surface, obtained by measurement.

[0012] S3, based on leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is used to obtain the formula for calculating the flameproof surface gap S, and the value of S is calculated based on the known parameters.

[0013] The invention also has the following specific features:

[0014] The detection calculation method is as follows:

[0015] (1) Determine the relationship between the flameproof surface area A and the flameproof surface gap S:

[0016] When the nitrogen filling reaches a stable state, the leakage flow rate of nitrogen through the explosion-proof surface gap of the equipment is equal to the filling flow rate, thus:

[0017] Q out =Q in (3-1)

[0018] Assuming the gap between the flameproof surfaces is uniform, the relationship between the flameproof surface area A and the flameproof surface gap S is as follows:

[0019] A = S × L (3-2)

[0020] (2) Determine the leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is as follows:

[0021] When the pressure reaches a stable state (a pressure change of less than 0.1 MPa within 1 minute is considered a stable pressure), the leakage flow rate Q of nitrogen from the explosion-proof surface gap of the equipment is... out Equal to the imported filling flow rate Q in The nitrogen pressure P inside the explosion-proof device is detected, and the external pressure of the explosion-proof device is P0. Based on the leakage velocity of the gas at the gap in the explosion-proof surface of the device, the following two leakage flow rates Q can be obtained. out The relationship between the flameproof surface area A and the flameproof surface area A is as follows:

[0022] (a) When hour,

[0023] That is, the nitrogen leakage rate is relatively fast. At this time, the internal pressure of the explosion-proof device is high, and the expansion factor of the nitrogen needs to be considered. Therefore, the leakage flow rate Q out The relationship between the explosion-proof surface area A and the surface area A is as follows:

[0024]

[0025] In the formula, Y is the gas expansion factor, and the calculation formula is as follows:

[0026]

[0027] (b) when hour,

[0028] That is, the leakage rate of nitrogen is relatively slow, and the leakage flow rate Q out The relationship between the explosion-proof surface area A and the surface area A is as follows:

[0029]

[0030] (3) Determine the formula for calculating the gap S between the flameproof surfaces:

[0031] From (3-1), (3-2), and (3-3), the formula for calculating the gap between the explosion-proof surfaces is as follows:

[0032]

[0033] or

[0034]

[0035] In the formula:

[0036] P—Nitrogen pressure inside the explosion-proof equipment, Pa;

[0037] P0 — Ambient pressure, Pa;

[0038] Q in — Refill flow rate, m 3 / s;

[0039] K – the adiabatic index of the gas; the adiabatic index of the nitrogen gas used is 1.40.

[0040] Cg—Gas leakage coefficient, taking 0.90 considering the shape of the explosion-proof joint surface as a rectangle;

[0041] Y—Gas expansion factor;

[0042] A – Area of ​​the explosion-proof surface of the equipment, mm 2 ;

[0043] S—gap between explosion-proof surfaces, mm;

[0044] L—Circumference of the explosion-proof surface of the equipment, mm;

[0045] M – molecular weight, nitrogen has a molecular weight of 28;

[0046] R—universal gas constant, J / mol·K, usually taken as R = 8.31436;

[0047] T—Gas temperature, K;

[0048] Q out —Leakage flow, m 3 / s.

[0049] The nitrogen is supplied by a gas storage cylinder, and the gas storage cylinder's filling port is connected to the redundant cable inlet of the explosion-proof equipment via a gas filling pipeline.

[0050] The filling flow rate Q in The value is measured by a flow meter installed on the inflation line.

[0051] The nitrogen pressure P is measured by a pressure gauge (6) connected to the redundant cable inlet 2 of the explosion-proof equipment.

[0052] The thread type of the connection interface between the air inlet, the air pipeline, the redundant cable inlet one, the pressure gauge, and the redundant cable inlet two must be consistent to achieve the sealing protection requirements.

[0053] The beneficial effects of this invention are as follows:

[0054] This invention proposes an online detection method for the gap between explosion-proof surfaces. Compared with traditional detection methods, it solves the problem of not being able to detect in real time and accurately, avoids the safety risks of traditional detection, and has important practical engineering application value.

[0055] This invention relates to explosion-proof electrical equipment used in explosive atmospheres. This type of equipment is widely used in industries such as coal, petroleum, and chemicals, and is produced in large quantities. This invention has significant engineering application value in the routine inspection of explosion-proof equipment. Attached Figure Description

[0056] Figure 1 This is a front view of an embodiment of the present invention.

[0057] Figure 2 This is a side view of an embodiment of the present invention.

[0058] The attached diagram is labeled as follows: 1. Gas storage; 2. Flow meter; 3. Explosion-proof device; 4. Explosion-proof surface gap; 5. Gas filling pipeline; 6. Pressure gauge. Detailed Implementation

[0059] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0060] Example 1

[0061] See Figures 1-2This invention discloses an online detection method for the explosion-proof surface gap. Using nitrogen pressurization and leakage detection, a mathematical model is constructed to determine the relationship between the explosion-proof surface gap 4 and pressure and leakage flow in explosion-proof equipment. This model can accurately reflect the size of the explosion-proof surface gap 4 in real time. The specific method is as follows:

[0062] S1. Fill the explosion-proof equipment with nitrogen gas. After the nitrogen pressure P inside the explosion-proof equipment stabilizes, measure the filling flow rate Q. in The value, at this time the filling flow rate Q in The leakage flow rate Q of nitrogen gas from inside the explosion-proof equipment to the outside. out equal;

[0063] S2. Assuming that the gap S between the flameproof surfaces is uniform, the relationship between the flameproof surface area A and the gap S is: A=S×L, where L is the perimeter of the flameproof surface, obtained by measurement.

[0064] S3, based on leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is used to obtain the formula for calculating the flameproof surface gap S, and the value of S is calculated based on the known parameters.

[0065] Example 2

[0066] See Figures 1-2 This invention discloses an online detection method for the explosion-proof surface gap. Using nitrogen pressurization and leakage detection, a mathematical model is constructed to determine the relationship between the explosion-proof surface gap 4 and pressure and leakage flow in explosion-proof equipment. This model can accurately reflect the size of the explosion-proof surface gap 4 in real time. The specific method is as follows:

[0067] S1. Fill the explosion-proof equipment with nitrogen gas. After the nitrogen pressure P inside the explosion-proof equipment stabilizes, measure the filling flow rate Q. in The value, at this time the filling flow rate Q in The leakage flow rate Q of nitrogen gas from inside the explosion-proof equipment to the outside. out equal;

[0068] S2. Assuming that the gap S between the flameproof surfaces is uniform, the relationship between the flameproof surface area A and the gap S is: A=S×L, where L is the perimeter of the flameproof surface, obtained by measurement.

[0069] S3, based on leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is used to obtain the formula for calculating the flameproof surface gap S, and the value of S is calculated based on the known parameters.

[0070] The detection calculation method is as follows:

[0071] (1) Determine the relationship between the flameproof surface area A and the flameproof surface gap S:

[0072] When the nitrogen filling reaches a stable state, the leakage flow rate of nitrogen through the explosion-proof surface gap of the equipment is equal to the filling flow rate, thus:

[0073] Q out =Q in (3-1)

[0074] Assuming the flameproof surface gap 4 is uniform, the relationship between the flameproof surface area A and the flameproof surface gap S of the equipment is as follows:

[0075] A = S × L (3-2)

[0076] (2) Determine the leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is as follows:

[0077] When the pressure reaches a stable state (a pressure change of less than 0.1 MPa within 1 second is considered to indicate that the pressure has reached a stable state), the leakage flow rate of nitrogen from the explosion-proof surface gap of the equipment is equal to the inlet filling flow rate, i.e., Q. out =Q in The nitrogen pressure P inside the explosion-proof equipment is measured, while the external pressure is P0. If the nitrogen leakage rate is relatively fast, that is:

[0078]

[0079] At this point, the internal pressure of the explosion-proof equipment is relatively high, and the expansion factor of nitrogen needs to be considered. Therefore, the leakage flow rate Q... out The relationship between the flameproof surface area A and the flameproof surface area A is:

[0080]

[0081] In the formula, Y is the gas expansion factor, and the calculation formula is as follows:

[0082]

[0083] (3) Determine the formula for calculating the gap S between the flameproof surfaces:

[0084] From (3-1), (3-2), and (3-3), the formula for calculating the explosion-proof surface gap 4 is:

[0085]

[0086] In the formula:

[0087] P—Nitrogen pressure inside the explosion-proof equipment, Pa;

[0088] P0 — Ambient pressure, Pa;

[0089] Q in — Refill flow rate, m 3 / s;

[0090] K – the adiabatic index of the gas; the adiabatic index of the nitrogen gas used is 1.40.

[0091] Cg—Gas leakage coefficient, taking 0.90 considering the shape of the explosion-proof joint surface as a rectangle;

[0092] Y—Gas expansion factor;

[0093] A – Area of ​​the explosion-proof surface of the equipment, mm 2 ;

[0094] S—gap between explosion-proof surfaces, mm;

[0095] L—Circumference of the explosion-proof surface of the equipment, mm;

[0096] M – molecular weight, nitrogen has a molecular weight of 28;

[0097] R—universal gas constant, J / mol·K, usually taken as R = 8.31436;

[0098] T—Gas temperature, K;

[0099] Q out —Leakage flow, m 3 / s.

[0100] Nitrogen is supplied by gas cylinder 1, and the filling port of gas cylinder 1 is connected to the redundant cable inlet of explosion-proof equipment 3 through filling pipeline 5.

[0101] Refill Flow Q in The value is measured by the flow meter 2 installed on the inflation line 5.

[0102] The nitrogen pressure P is measured by a pressure gauge 6 connected to the redundant cable inlet 2 of the explosion-proof device 3.

[0103] The thread type of the connection interface between the air inlet, air pipeline 5, redundant cable inlet 1, air pressure gauge 6, and redundant cable inlet 2 must be consistent to meet the sealing protection requirements.

[0104] Example 3

[0105] See Figures 1-2 This invention discloses an online detection method for the explosion-proof surface gap. Using nitrogen pressurization and leakage detection, a mathematical model is constructed to determine the relationship between the explosion-proof surface gap 4 and pressure and leakage flow in explosion-proof equipment. This model can accurately reflect the size of the explosion-proof surface gap 4 in real time. The specific method is as follows:

[0106] S1. Fill the explosion-proof equipment with nitrogen gas. After the nitrogen pressure P inside the explosion-proof equipment stabilizes, measure the filling flow rate Q. in The value, at this time the filling flow rate Q inThe leakage flow rate Q of nitrogen gas from inside the explosion-proof equipment to the outside. out equal;

[0107] S2. Assuming that the gap S between the flameproof surfaces is uniform, the relationship between the flameproof surface area A and the gap S is: A=S×L, where L is the perimeter of the flameproof surface, obtained by measurement.

[0108] S3, based on leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is used to obtain the formula for calculating the flameproof surface gap S, and the value of S is calculated based on the known parameters.

[0109] The detection calculation method is as follows:

[0110] (1) Determine the relationship between the flameproof surface area A and the flameproof surface gap S:

[0111] When the nitrogen filling reaches a stable state, the leakage flow rate of nitrogen through the explosion-proof surface gap of the equipment is equal to the filling flow rate, thus:

[0112] Q out =Q in (3-1)

[0113] Assuming the flameproof surface gap 4 is uniform, the relationship between the flameproof surface area A and the flameproof surface gap S of the equipment is as follows:

[0114] A = S × L (3-2)

[0115] (2) Determine the leakage flow rate Q out The relationship between the flameproof surface area A and the flameproof surface area A is as follows:

[0116] When the pressure reaches a stable state (a pressure change of less than 0.1 MPa within 1 second is considered to indicate that the pressure has reached a stable state), the leakage flow rate of nitrogen from the explosion-proof surface gap of the equipment is equal to the filling flow rate at the inlet, i.e., Q. out =Q in The nitrogen pressure P inside the explosion-proof equipment is measured, while the external pressure is P0. If the nitrogen leakage rate is slow, that is:

[0117]

[0118] Then the leakage flow Q out The relationship between the flameproof surface area A and the flameproof surface area A is:

[0119]

[0120] (3) Determine the formula for calculating the gap S between the flameproof surfaces:

[0121] From (3-1), (3-2), and (3-3), the formula for calculating the explosion-proof surface gap 4 is:

[0122]

[0123] In the formula:

[0124] P—Nitrogen pressure inside the explosion-proof equipment, Pa;

[0125] P0 — Ambient pressure, Pa;

[0126] Q in — Refill flow rate, m 3 / s;

[0127] K – the adiabatic index of the gas; the adiabatic index of the nitrogen gas used is 1.40.

[0128] Cg—Gas leakage coefficient, taking 0.90 considering the shape of the explosion-proof joint surface as a rectangle;

[0129] Y—Gas expansion factor;

[0130] A – Area of ​​the explosion-proof surface of the equipment, mm 2 ;

[0131] S—gap between explosion-proof surfaces, mm;

[0132] L—Circumference of the explosion-proof surface of the equipment, mm;

[0133] M – molecular weight, nitrogen has a molecular weight of 28;

[0134] R—universal gas constant, J / mol·K, usually taken as R = 8.31436;

[0135] T—Gas temperature, K;

[0136] Q out —Leakage flow, m 3 / s.

[0137] Nitrogen is supplied by gas cylinder 1, and the filling port of gas cylinder 1 is connected to the redundant cable inlet of explosion-proof equipment 3 through the filling pipeline 5.

[0138] Recharge Flow Q in The value is measured by the flow meter 2 installed on the inflation line 5.

[0139] The nitrogen pressure P is measured by a pressure gauge 6 connected to the redundant cable inlet 2 of the explosion-proof device 3.

[0140] The thread type of the connection interface between the air inlet, air pipeline 5, redundant cable inlet 1, air pressure gauge 6, and redundant cable inlet 2 must be consistent to meet the sealing protection requirements.

[0141] The technical features of this invention not described can be implemented by or using existing technology, and will not be repeated here. Of course, the above description is not a limitation of this invention, and this invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention should also be within the protection scope of this invention.

Claims

1. A method for online detection of flameproof surface gap, characterized in that: The specific method is as follows: S1. Fill nitrogen into the flameproof equipment, and measure the filling flow rate Q after the nitrogen pressure P in the flameproof equipment is stable. in The value of the filling flow Q in The leakage flow rate Q of the nitrogen leaking from the inside of the flameproof equipment to the outside out equal; S2. When the flameproof surface gap S is considered to be uniform, the relationship between the flameproof surface area A and the flameproof surface gap S is: A = S × L, where L is the perimeter of the flameproof surface, obtained by measurement; S3, according to the leakage flow Q out The relationship between the flameproof surface area A and the flameproof surface gap S is obtained, and the value of S is calculated based on the known parameters.

2. The method for online detection of flameproof surface gap according to claim 1, characterized in that: For step S3, when hour, That is, the leakage speed of the nitrogen is fast. At this time, the internal pressure of the explosion-proof equipment is high. The expansion factor of the nitrogen needs to be considered. The leakage flow rate Q of the nitrogen is out The relationship between it and the flameproof surface area A is: Where Y is the calculated gas expansion factor, and the calculation formula is as follows: In the formula: P is the nitrogen pressure in the explosion-proof equipment; P0 is the ambient pressure; K is the adiabatic index of the gas; Cg is the gas leakage coefficient; R is the universal gas constant; T is the gas temperature; M is the molecular weight; and Y is the gas expansion factor.

3. The method for online detection of flameproof surface gap according to claim 1, characterized in that: For step S3, when hour, That is, the leakage rate of the nitrogen is slow, and the leakage flow rate Q of the nitrogen is out The relationship between it and the flameproof surface area A is: Where: P is the nitrogen pressure in the explosion-proof equipment; P0 is the ambient pressure; K is the adiabatic index of the gas; Cg is the gas leakage coefficient; R is the universal gas constant; T is the gas temperature; M is the molecular weight.

4. The method for online detection of flameproof surface gap according to claim 2, characterized in that: For step S3, the calculation formula for the flameproof surface gap S is obtained as follows: Where: P is the nitrogen pressure in the explosion-proof equipment; K is the adiabatic index of the gas; Cg is the gas leakage coefficient; R is the universal gas constant; T is the gas temperature; M is the molecular weight; Y is the gas expansion factor; Q in is the filling flow rate; L is the circumference of the flameproof surface.

5. The method for online detection of flameproof surface gap according to claim 3, characterized in that: For step S3, the calculation formula for the flameproof surface gap S is obtained as follows: Where: P is the nitrogen pressure in the explosion-proof equipment; K is the adiabatic index of the gas; Cg is the gas leakage coefficient; R is the universal gas constant; T is the gas temperature; M is the molecular weight; Q in is the filling flow rate; L is the circumference of the flameproof surface.

6. The method for online detection of flameproof surface gap according to claim 1, characterized in that: The nitrogen is provided by a gas storage bottle (1), and the filling port of the gas storage bottle (1) is connected to a redundant cable introduction port of the flameproof equipment (3) through a filling pipeline (5).

7. The method for online detection of flameproof surface gap according to claim 6, characterized in that: The filling flow rate Q in The value is measured by a flow meter (2) installed on the inflation line (5).

8. The method for online detection of flameproof surface gap according to claim 7, characterized in that: The value of the nitrogen pressure P is measured by a barometer (6) connected to the redundant cable inlet port 2 of the flameproof equipment (3).

9. The method for online detection of flameproof surface gap according to claim 8, characterized in that: The thread types of the connection interfaces among the inflation port, the inflation pipeline (5), the redundant cable inlet port 1, the pressure gauge (6) and the redundant cable inlet port 2 must be consistent so as to meet the sealing protection requirements.

Images