This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of low-concentration carrier catalytic methane sensors for coal mines. This standard applies to low-concentration (0-4%) carrier catalytic methane sensors and high and low-concentration methane sensors (hereinafter referred to as sensors) used in coal mine underground environmental monitoring, which use the carrier catalytic principle to measure low-concentration methane. MT 444-1995 Technical requirements for catalytic combustion low-concentration methane sensors for coal mines MT444-1995 Standard download decompression password: www.bzxz.net

Coal Industry Standard of the People's Republic of China
Technical Conditions for Low-Concentration Carrier Catalytic Methane Sensors for Coal Mines
1 Subject Content and Scope of Application
MT444--1995
This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of low-concentration carrier catalytic methane sensors for coal mines.
This standard applies to low-concentration (0-4%) carrier catalytic methane sensors and high and low-concentration methane sensors (hereinafter referred to as sensors) used in coal mine underground environmental monitoring, which use the carrier catalytic principle to measure low-concentration methane. 2 Reference standards
Packaging, storage and transportation pictorial marking
GB 191
Basic environmental testing procedures for electric and electronic products Test A: Low temperature test method
GB 2423. 1
GB 2423.4
Basic environmental testing procedures for electric and electronic products Basic environmental testing procedures for electric and electronic products Basic environmental testing procedures for electric and electronic products GB 2423.5
GB 2423. 8
GB 2423.10
GB 3836. 1
GB 3836. 2
GB 3836. 4
Test B: High temperature test method
Test Db: Alternating damp heat test method
Test Ea: Impact test method
Basic environmental test procedures for electric and electronic productsTest Ed: Free fall test methodBasic environmental test procedures for electric and electronic productsTest Fc: Vibration (sinusoidal) test methodGeneral requirements
Explosion-proof electrical equipment for explosive atmospheres
Explosion-proof electrical equipment for explosive atmospheres
Flameproof electrical equipment "d"
Increased safety electrical equipment\e"
Explosion-proof electrical equipment for explosive atmospheres
Explosion-proof electrical equipment for explosive atmospheresIntrinsically safe circuits and electrical equipment""GB/T4942.2 Protection level of low-voltage electrical enclosuresRandom sampling method using random numbersGB 10111
MT281 Carrier thermal catalytic element for methane detection in coal minesMT/T408 DC regulated power supply for coal mines
3 Technical requirements
3.1 The product shall comply with the requirements of this standard and shall be manufactured according to the drawings and technical documents approved by the prescribed procedures. 3.2 Working conditions:
Temperature: 0~40℃;
Relative humidity: ≤98% (25℃),
Atmospheric pressure: 86~116kPa;
Wind speed: 0~8 m/s.
3.3 Storage temperature is -40～60℃.
3.4 ​​The sensor shall adopt intrinsically safe and flameproof explosion-proof structure and shall comply with the relevant provisions of GB3836.1, GB3836.2, GB3836.3 and GB3836.4
Approved by the Ministry of Coal Industry of the People's Republic of China on March 8, 1996 and implemented on August 1, 1996
3.5 Power supply:
Should comply with the requirements of MT/T408.
3.6 Output signal format:
The following signal format should be selected:
MT 444-1995
Current DC 1~～5mA (preferred), 4～20mA (load resistance 0～500Q); frequency: 5～15Hz, 200~1000Hz (pulse width greater than 0.3ms); digital coding: transmission rate is 300, 600, 1200, 2400, 4800, 9600b/s, and the level is not less than 3V. 3.7 The sensor should have a suspension or support structure suitable for underground installation. 3.8 The protection performance of the sensor housing should comply with the IP54 protection level specified in GB4942.2 3.9 The cross-sectional area of ​​the sensor cable should not be greater than 1.5mm; the transmission distance of the sensor should not be less than 1km. 3.10 Anti-corrosion measures should be taken for the sensor housing, connectors and parts, and the coating and plating should be uniform, firm and consistent in color; the printed circuit board should be coated with three-proof (anti-corrosion, anti-mildew, and moisture-proof) insulating paint at least twice. 3.11 The sensor adopts a diffusion sampling method. The sampling head should be equipped with a dust and wind speed protection cover; the vent should be equipped with a fire-blocking element and should comply with the relevant provisions of GB3836.2. 3.12 The sensor should indicate the measured value in percent volume concentration. When a digital indicator is used to indicate the measured value, its resolution should be 0.01% CH4 and it should be able to indicate the positive or negative value of the displayed value. 3.13 When the methane concentration exceeds the upper limit of the measurement range, the sensor should have the function of protecting the carrier catalytic element and should keep the indicated value and output signal value of the sensor in the over-limit state. 3.14 Basic error:
The basic error of the sensor shall comply with the provisions of Table 1: Table 1
Measurement range
0. 00~1. 00
>1.00~2. 00
>2. 00~~4. 00
Basic error
3.15 When the load resistance of the sensor whose output signal format is current changes within the range of 0~500Ω, the change of its output signal value shall not exceed the provisions of 3.14.
When the load resistance of the sensor whose output signal format is frequency changes within the range of 0~500Ω, the change of its output signal value shall not exceed the provisions of 3.14, and its pulse width shall not be less than 0.3ms. 3.16 Stability:
The basic error of the sensor working continuously for 7d shall not exceed the provisions of 3.14. 3.17 Response time:
The response time of the sensor shall not exceed 30s. 3.18 Alarm function:
3.18.1 Sensors with alarm function should be able to set alarm points at any time within the measurement range. The difference between the alarm value and the set value should not be greater than ±0.05%CH4.
3.18.2 The sound pressure level of the sound signal at a distance of 1m from the alarm should not be less than 80dB(A); the light signal should be clearly visible at a distance of 20m.
3.19 The drift of the indicated value of the sensor under the wind speed of 8m/s should not be greater than ±0.01%CH4. 3.20 The sensor should comply with the provisions of 3.14 during the working temperature test. 3.21 After the storage temperature test, the sensor should comply with the provisions of 3.14. 282
MT 444—1995
3.22 After the damp heat test, the sensor should comply with the provisions of 3.14. 3.23 After the vibration test, the connectors and parts of the sensor should not be loose or fall off, and meet the requirements of 3.14. 3.24 After the impact test, the sensor should have no signs of damage, and the connectors and parts should not be loose or fall off, and meet the requirements of 3.14. 3.25 After the drop test, the connectors and parts of the sensor should not be loose or fall off, and meet the requirements of 3.14. 4 Test method
4.1 Environmental conditions
Unless otherwise specified in the environmental test or relevant standards, the test should be carried out under the following environmental conditions: temperature: 15~35℃,
relative humidity: 45%~75%,
atmospheric pressure: 86~106kPa.
4.2 Test gas sample and instrument
4.2.1 Test gas sample
Standard methane gas sample in air (hereinafter referred to as standard gas sample), with an uncertainty of 3%. 4.2.2 Test instruments
4.2.2.1 Gas flow meter
Measuring range: 30~300mL/min; accuracy: 2.5 grade. 4.2.2.2 Stopwatch
Division value: 0.01 s.
4.2.2.3 DC milliammeter
0~100mA, 0.2 grade.
4.2.2.4 Frequency meter
0～1 000 kHz; accuracy; ≤1×10-6. 4.2.2.5 DC regulated power supply
Output voltage: 0～30V; output current: 2A. 4.3 Basic error determination
According to the gas flow rate, ventilation time, gas injection device and ventilation steps specified in the product standard, the following method is used: Before the measurement, the sensor (hereinafter referred to as the calibration instrument) should be repeatedly calibrated with clean air and 2.0% standard gas sample, and it shall not be calibrated again in subsequent measurements.
After the zero point of the sensor is stable in clean air, three standard gas samples (0.5, 1.5, 3.5)% are introduced into the sensor in sequence according to the flow rate during calibration for 3 minutes each. Record the indicated value and output signal value of the sensor (converted into methane concentration value). Repeat the measurement 4 times and take the arithmetic mean of the next 3 times.
4.4 Load characteristic test
MT444—1995
Figure 1 Schematic diagram of basic error determination
1-Test box, 2-Sensor, 3-Gas injection device, 4-Preheating coil, 5-Flowmeter 6-Clean air bottle; 7-Test gas sample bottle: 8-Regulating valve 4.4.1 Load characteristic test of output signal as current quantity Make the sensor display stably in the air, record the difference of output signal value when the external load resistance is 500α and 0Q, and convert it into methane concentration value.
4.4.2 Load characteristic test of output signal as frequency quantity Make the sensor display stably in the air, record the difference of output frequency value when the external load resistance is 500α and 02, and convert it into methane concentration value.
4.5 Stability determination
Put the adjusted sensor into the device shown in Figure 1, and continuously pass 0.5% methane gas for 7 days. Every 12 hours, pass clean air and 1.5% standard gas sample in turn at the flow rate during calibration for 3 minutes each, and record the indication value and output signal value. The sensor shall not be adjusted during the test.
4.6 Response time determination
The determination device is shown in Figure 2. The gas injection device provided by the manufacturer should be used on the diffusion sampling head. At the flow rate during calibration, pass 2% methane gas sample for 3 minutes and read the indication value.
Then pass clean air. After the zero point of the sensor is stable, quickly replace the gas injection device that passes the original methane gas sample at the flow rate during calibration to the sampling head, and start recording the time required for the sensor indication value to reach 90% of the original indication value. Measure 3 times and take the arithmetic average.
4.7 Alarm function test
MT 444-- 1995
Figure 2 Schematic diagram of response time measurement
1-Clean air hose, 2-Clean air injection device, 3-Diffusion sampling head: 4-Sensor, 5-Exhaust port: 6-Ventilation hood support, 7-Test gas sample injection device, 8-Test gas sample hose 4.7.1 Determination of the difference between the alarm value and the set value Set the sensor alarm point to the value specified when the output is widened. After the zero point of the sensor is stable, slowly pass a gas sample slightly larger than the methane concentration value of the set alarm point, record the sensor indication value at the moment when the sound and light signals appear, and calculate the difference between the methane concentration value of the set alarm point and the indication value.
4.7.2 Measurement of alarm sound level intensity
The alarm sound intensity is measured with a sound level meter, and the ambient noise should be less than 50dB(A). Place the sound level meter 1m in front of the axis of the alarm sounder of the sensor, measure 3 times, and take the arithmetic average. 4.7.3 Alarm light signal
The test is carried out in a dark environment at a distance of 20m from the sensor. 4.8 Wind speed influence test
The sensor is hung in the test wind tunnel, and the reference point of the sensor is adjusted when the wind flow is zero. Then the wind speed is adjusted to 8+5m/s, and the sensor is artificially rotated around the hanging axis to find the position affected by the wind speed. Fixed at this position, record the indication value once every 30s, record 3 times in total, and take the difference between the arithmetic mean and the reference point as the drift. 4.9 Working temperature test
The temperature of the standard gas sample introduced into the sensor during the test should be consistent with the test required temperature. 4.9.1 Low temperature working test
It is carried out according to the test Ab method in GB2423.1. Under the condition of 0±3℃, the sensor is powered on, and after stabilization for 2h, the basic error is measured. The basic error is measured once every hour thereafter, for a total of 3 times. The arithmetic mean is taken as the measured value. 4.9.2 High temperature working test
Perform according to the test method Bb in GB2423.2. At a temperature of 40±2℃, the sensor is powered on and stabilized for 2 hours before the basic error is measured. The basic error is measured once every hour thereafter, for a total of 3 times. The arithmetic mean is taken as the measured value. 4.10 Storage temperature test
4.10.1 Low temperature storage test
Perform according to the test method Ab in GB2423.1. At a temperature of -40±3℃, the duration is 16 hours. The sensor is not packaged, powered on, and no intermediate inspection is performed. After the test, the sensor is restored to the conditions specified in 4.1 in the test chamber and maintained for 2 hours before the basic error is measured. 285bzxZ.net
4.10.2 High temperature storage test
MT 444 1995
Perform according to the test method Bb in GB2423.2. Under the condition of temperature of +60±2℃, the duration is 16h. The sensor is not packaged, not powered, and no intermediate inspection is performed. After the test, it is restored to the conditions specified in 4.1 in the test box for 2h, and then the basic error is measured. 4.11 Humidity test
Performed according to the test Db method in GB2423.4. Under the conditions of temperature of 40±2℃ and relative humidity of 93%±3%, the duration is 12d. The sensor is not packaged, not powered, and no intermediate inspection is performed. After the test, it is restored to the conditions specified in 4.1 for 2h, and then the basic error is measured. 4.12 Vibration test
Performed according to the test Fc method in GB2423.10. Severity level: sweep frequency range 10~150Hz, acceleration amplitude 50m/s, vibration number 5 times. The sensor is not packaged. The fixed sensor is not powered, and no intermediate inspection is performed. The airborne mobile sensor is powered and intermediate inspection is performed. After the test, the appearance inspection and basic error are measured. 4.13 Impact test
Perform according to the test Ea method in GB2423.5. Severity level: peak acceleration is 500m/s* pulse duration is 11±1ms, and the three axes are impacted continuously for 3 times in each direction (a total of 18 times). The sensor is not packaged. The fixed sensor is not powered and no intermediate test is performed. The airborne mobile sensor is powered and the intermediate test is performed. After the test, the appearance inspection and basic error determination are performed. 4.14 Drop test
Perform according to the test Ed method in GB2423.8. Severity level: The drop height is 0.5m, and it falls freely onto a smooth and hard concrete surface in the normal use direction for a total of 2 times. The sensor is not packaged, powered, and no intermediate test is performed. After the test, the appearance inspection is performed and the basic error is determined.
4.154.10~4.14After each test, before checking the performance, it is allowed to recalibrate the sensor. 4.16 The explosion-proof performance test method of the sensor shall be carried out by an authorized explosion-proof inspection agency in accordance with the provisions of GB3836.1, GB3836.2, GB3836.3 and GB3836.4.
5 Inspection rules
5.1 Factory inspection
5.1.1 It shall be carried out by the manufacturer's quality inspection department. Only after the inspection is passed and the certificate is issued can it be shipped out of the factory. 5.1.2 The factory inspection items are shown in Table 2.
5.2 Type inspection
5.2.1 Type inspection shall be conducted in any of the following cases: When a new product or old product is transferred to a factory for trial production and type identification; When there are major changes in structure, materials, and processes after formal production, which may affect product performance. C
For sensors in normal production, once every two years;
When production is resumed after more than two years of suspension;
When there is a significant difference between the factory inspection result and the last type inspection Table 2
Technical requirements clause
Outgoing inspection
Type inspection
Note: ○ indicates an item that must be conducted.
MT444-1995
Continued Table 2
Technical requirements clause
When the national quality supervision and inspection agency makes a request. 5.2.2 Type inspection items are shown in Table 2.
Factory inspection
5.2.3 Type inspection shall be conducted by the quality supervision and inspection agency designated by the Ministry of Coal Industry. Type inspection
5.2.4 Sampling
Sampling shall be conducted according to the method specified in GB10111 from the sensors that have passed the factory inspection. The sampling base shall not be less than 10 units, and the sampling quantity shall not be less than 3 units.
5.2.5 Judgment rules
There are 3 sensors to be inspected. During the inspection, if one of the items in 3.14, 3.15, 3.16 and 3.18.1 fails, or two of the items in other items fail, the batch of products shall be judged as unqualified. If one of the items in other items other than 3.14, 3.15, 3.16 and 3.18.1 fails, all items shall be doubled for re-inspection. If there are still unqualified items, the batch of sensors shall be judged as unqualified. 6 Marking, packaging, transportation, storage
6.1 Marking
The sensor housing should be marked with "\Ex", "MA" and measuring instrument markings in obvious places. 6.1.1
The nameplate of the sensor should have the following contents: product model and name,
"Ex\" mark in the upper right corner;
explosion-proof mark;
explosion-proof inspection certificate number;
coal mine safety mark number;
manufacturing measuring instrument license number,
related equipment model;
main technical parameters;
protection level;
manufacturer name;
factory number or date.
6.1.3 Packaging mark:
The shipping mark should comply with the relevant transportation regulations; a.
The operation mark should comply with the provisions of GB191.
6.2 Packaging
MT444-1995
6.2.1 The packaging should adopt composite protection The packaging type should be rainproof, moisture-proof, dustproof and vibration-proof. 6.2.2 The following documents should be included in the packaging box:
Product certificate;
Product instruction manual;
Packing list.
6.3 Transportation
The packaged products should be suitable for road, rail, water and air transportation. 6.4 Storage
Should be stored in a well-ventilated warehouse without corrosive gases. Additional notes:
This standard was proposed by the Coal Mine Safety Standardization Technical Committee of the Ministry of Coal Industry. This standard is under the jurisdiction of the Gas Detection and Rescue Equipment Branch of the Coal Mine Safety Standardization Technical Committee of the Ministry of Coal Industry. This standard was drafted at the expense of the Fushun Branch of the China Coal Research Institute. The main drafter of this standard is Miao Yaxin.
This standard is entrusted to the Fushun Branch of the China Coal Research Institute for interpretation. 288
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