MT 447-1995 Technical requirements for electrochemical oxygen sensors for coal mines
Some standard content:
Coal Industry Standard of the People's Republic of China
Electrochemical oxygen sensors for coal mines
Technical conditions
1 Subject content and scope of application
MT 447--1995
This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of electrochemical oxygen sensors for coal mines.
This standard applies to electrochemical oxygen sensors (hereinafter referred to as sensors) used in underground coal mine environmental monitoring. 2 Reference standards
GB191 Packaging, storage and transportation graphic signs
GB2423.1 Basic environmental test regulations for electric and electronic products Test A: Low temperature test method GB2423.2 Basic environmental test regulations for electric and electronic products Test B: High temperature test method GB 2423. 4
Basic environmental test regulations for electric and electronic products Test Db: Alternating damp heat test method GB 2423.5
Basic environmental test regulations for electric and electronic products Test Ea: Impact test method
Basic environmental test regulations for electric and electronic products Test Ed: Free fall test method GB 2423. 8
Basic environmental test regulations for electric and electronic products Test Fc: Vibration (sinusoidal) test method GB 2423. 10
GB3836.1 General requirements for explosion-proof electrical equipment for explosive atmospheres Increased safety electrical equipment e"
GB3836.3 Explosion-proof electrical equipment for explosive atmospheres GB3836.4 Explosion-proof electrical equipment for explosive atmospheres Intrinsically safe circuits and electrical equipment "i" GB/T4942.2 Protection levels of low-voltage electrical enclosures Method for random sampling using random numbers GB10111
GB12358 Gas detection in working environments General technical requirements for measuring alarm JJG365 Electrochemical electrode gas oxygen analyzer MT/T408 DC regulated power supply for coal mines
3 Technical requirements
3.1 The product shall comply with the requirements of this standard and be manufactured in accordance with the drawings and technical documents approved by the prescribed procedures. 3.2 Working conditions: www.bzxz.net
Temperature: 0~40℃,
Relative humidity: ≤98%;
Atmospheric pressure: 80~110kPa;
Speed: 0~~8 m/s.
3.3 Storage temperature is -40～60℃.
3.4 The sensor must adopt intrinsically safe explosion-proof structure and meet the relevant provisions of GB3836.1, GB3836.3 and GB3836.4.
Ministry of Coal Industry of the People's Republic of China approved 304 on March 8, 1996
Implemented on August 1, 1996
3.5 Power supply:
Should meet the requirements of MT/T408.
3.6 Output signal format:
MT 447--1995
Current: DC1~5mA (load resistance 0~~500Ω); frequency: 5~15Hz, 200~1000Hz (pulse width greater than 0.3ms); 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 1.5mm2, and 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-spark, moisture-proof) insulating paint at least twice. 3.11 When the sensor adopts a split structure, the length of the external cable of the probe should not be less than 5m. 3.12 The sensor should indicate the measured value in percentage volume concentration. When the digital indicator is used to indicate the measured value, the resolution should be 0.1%O2
3.13 Basic error:
The basic error of the sensor should comply with the provisions of Table 1: Table 1
Measurement range
3.14 Load capacity:
Basic error
±3% (full scale)
When the load resistance of the sensor with the output signal format of current changes within the range of 0~~500, the change of its output value should not exceed the provisions of 3.13.
3.15 Stability:
The basic error of the sensor for continuous operation for 7 days should not exceed the provisions of 3.13. 3.16 Response time:
The response time of the sensor should not exceed 60s. 3.17 Alarm function:
3.17.1 Sensors with alarm function should be able to set alarm points at any time within the measurement range, and the difference between the alarm value and the set value should not be greater than 0.5%02.
3.17.2 The sound pressure level of the sound signal at a distance of 1m from the alarm should not be less than 80dB(A), and the light signal should be clearly visible at a distance of 20m in a dark environment.
3.18 The drift of the display value of the sensor under the condition of a wind speed of 8m/s should not be greater than ±0.5%O2. 3.19 The sensor should comply with the provisions of 3.13 during the working temperature test. 3.20 The sensor should comply with the provisions of 3.13 after the storage temperature test. 3.21 The sensor should comply with the provisions of 3.13 after the wet heat test. 3.22 After the vibration test, the connectors and components of the sensor should not be loose or fall off; and comply with the provisions of 3.13. 3.23 After the impact test, the sensor shall have no signs of damage, and the connectors and parts shall not be loose or fall off, and shall comply with the provisions of 3.13. 3.24 After the drop test, the connectors and parts shall not be loose or fall off, and shall comply with the provisions of 3.13. 4 Test method
4.1. Environmental conditions
Unless otherwise specified in the environmental test or relevant standards, the test shall be carried out under the following environmental conditions: temperature: 15-35℃;
relative humidity: 45%-75%,
atmospheric pressure: 86-106kPa.
4.2 Test gas samples and instruments
4.2.1 Test gas
4.2.1.1 Standard push gas of oxygen in nitrogen:
MT447--- 1995
The uncertainty is ±1% (hereinafter referred to as standard push gas). 4.2.1.2 Oxygen-free gas (hereinafter referred to as nitrogen): 99.9% industrial pure nitrogen.
4.2.1.3 Gas pressure reducing valve and pressure gauge used in conjunction with standard gas cylinders. 4.2.2 Test instruments
4.2.2.1 Gas flow meter:
Measuring range: 30~300ml./min; accuracy: 2.5 level. 4.2.2.2 Stopwatch:
Division value is 0.015.
4.2.2.3 Potentiometer:
Input impedance greater than 100M0: 0.5 level.
4.2.2.4 DC milliammeter:
0~~100 mA, 0.2 level.
4.2.2.5 Frequency meter:
0~1000kHz accuracy: ≤1×10-6
4.2.2.6 DC regulated power supply:
Output voltage: 030V, output current: 2A. 4.3 Basic error determination
The basic error determination device is shown in Figure 1.
Figure 1 Schematic diagram of basic error determination
1-Test chamber 2-Sensor: 3-Gas injection device: 4-Preheating coil: 5-Flowmeter 5-Clean air bottle, 7-Test gas sample bottle: 8-Regulating valve
MT 447-1995
Use the gas injection device provided by the manufacturer to sequentially introduce nitrogen, 15% O, and 25% O2 into the sensor according to the flow rate during calibration. After each concentration of gas sample is introduced for 3 minutes, read the display value and output signal value (converted to oxygen concentration value). Repeat the measurement 4 times and take the arithmetic mean of the next 3 times, which should not exceed the requirements of 3.12. Calculate the error △(%) according to formula (1):
Where: A; the average value of the displayed value or output signal value; An—the oxygen content of the standard gas;
Am——the measurement range.
4.4 Load characteristic test
(1)
When the sensor stably displays the air content, connect an external load resistance of 500Q, measure its output signal value Sa, and then measure the signal value Sb when the output circuit is short-circuited, and calculate α(%) according to formula (2): S - s.
Where: Sb——the output signal value when the load resistance is 500α, mA, S——the output signal value when the load resistance is 0α, mA. 4.5 Stability determination
Put the adjusted sensor into the device shown in Figure 1 and run it continuously for 7 days. Measure the oxygen content in the air every 12 hours and record the indicated value and output signal value. The sensor shall not be adjusted during the test. Calculate the stability W (%) according to formula (3):
Amx _ An ×100
Where: Amax-
Maximum reading:
Amin—Minimum reading:
Am——Measurement range.
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. 4.6.1 Calibrate the sensor with air
4.6.2 Determination
(3)
Introduce nitrogen. When the displayed value stabilizes, stop introducing nitrogen and immediately introduce air at the calibrated flow rate. After 3 minutes, record the time when the sensor display value reaches 90% of the oxygen content in the air. Repeat the measurement three times and take the arithmetic mean. 307
MT 447—1995
Figure 2 Schematic diagram of response time determination
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 Alarm function test
4.7.1 Determination of the difference between the alarm value and the set value Set the sensor alarm point to the value specified at the factory. After the sensor display value stabilizes, slowly pass in a gas sample slightly lower than the oxygen concentration value of the set alarm point, record the sensor display value at the moment when the sound and light signals appear, and calculate the difference between the oxygen concentration value of the set alarm point and the display value.
4.7.2 Measurement of alarm sound level intensity
The alarm sound intensity is measured with a sound level meter. 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 mean. 4.7.3 Alarm light signal
The test is observed in a dark environment at a distance of 20m from the sensor. 4.8 Wind speed influence test
The sensor is suspended in the test wind tunnel, and the sensor display value when the wind speed is zero is used as the reference point. Then the wind speed is adjusted to 8+°5m/s, and the sensor is artificially rotated around the suspension axis to find the position affected by the wind speed. Fix it at this position, record the indication value once every 30s, record it 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 gas sample to be introduced into the sensor during the test should be consistent with the test requirement temperature. 4.9.1 Low temperature working test
Perform according to the test Ab method in GB2423.1. Under the condition of 0±3℃, the sensor is powered on and stabilized for 2h, and the basic error is measured. The basic error is measured once every 1 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 Bb method 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 1 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 Ab method in GB2423.1. The duration is 16 hours at a temperature of -10±3℃. The sensor is not packaged, powered on, and no intermediate testing is performed. After the test, the test box is restored to the conditions specified in 4.1 for 4 hours, and then the basic error is measured. 308
4.10.2 High temperature storage test
MT 447-1995
Perform according to the test method Bb in GB2423.2. The duration is 16h at a temperature of +45±2℃. The sensor is not packaged, not powered, and no intermediate detection is performed. After the test, restore to the conditions specified in 4.1 in the test chamber for 4h, and then measure the basic reading error. 4.11 Humidity test
Perform according to the test method Db in GB2423.4. The temperature is 40±2℃, the relative condensation is 93%±3%, and the duration is 12. The sensor is not packaged, not powered, and no intermediate detection is performed. After the test, restore to the conditions specified in 4.1 for 2h, and then measure the basic error. 4.12 Vibration test
Perform according to the test method Fc in GB2423.10. Severity level: sweep frequency range 10~150Hz, acceleration amplitude 50m/s, vibration number 5 times. The sensor is not packaged, not powered, and no intermediate inspection is performed. After the test, an appearance inspection is performed, and then the basic error is determined. 4.13 Impact test
Performed according to the test Ea method in GB2423.5. Severity level: peak acceleration is 500m/s*, pulse duration is 11±1ms, and 3 axes are impacted continuously in each direction for 3 times (a total of 18 times). The sensor is not packaged, not powered, and no intermediate inspection is performed. After the test, an appearance inspection is performed, and then the basic error is determined.
4.14 Drop test
Performed according to the test Ed method in GB2423.8. Severity level: drop height is 0.5m, free fall onto a smooth, hard concrete surface in the normal use direction for a total of 2 times. The sensor is not packaged, not powered, and no intermediate inspection is performed. After the test, an appearance inspection is performed, and then the basic error is determined.
4.154.10~4.14 After each test and before checking the function, the sensor can be recalibrated. 4.16 The explosion-proof performance test method of the sensor shall be carried out by the authorized explosion-proof inspection agency in accordance with the provisions of GB3836.1, GB3836.3 and GB3836.4.
5 Inspection rules
5.1 Factory inspection
5.1.1 The quality inspection department of the manufacturer shall conduct the inspection on each unit. The product can only leave the factory after passing the inspection and issuing the certificate of conformity. 5.1.2 The factory inspection items are shown in Table 2.
Technical requirements clauses
Factory inspection
Type I inspection
Note: ○ indicates items that must be carried out.
5.2 Type inspection
MT 447-1995
Continued Table 2
Technical requirements clauses
Type inspection should be carried out in the following cases: New products or old products are transferred to the factory for production trial and type identification Factory inspection
After formal production, if there are major changes in structure, materials, and processes, which may affect product performance: Normally produced sensors are inspected once every 2 years#
When production is resumed after more than 2 years of suspension,
When the factory inspection results are significantly different from the previous type inspection When the national quality supervision and inspection agency makes a request. Type inspection items are shown in Table 2.
Type inspection should be carried out by the quality supervision and inspection agency authorized by the Ministry of Coal Industry. 5.2.4 Sampling:
Type inspection
It is carried out according to the method specified in GB10111 from sensors that have passed the factory inspection. The sampling base shall be no less than 10 units, and the sampling quantity shall be no less than 3 units.
5.2.5 Judgment rules:
There are 3 sensors to be inspected. If one of the items in 3.10, 3.13~3.23 fails, or two of the items in other items excluding 3.13, 3.15 and 3.17.1 fail, the batch of products shall be judged as unqualified. If one of the items in other items excluding 3.13, 3.15 and 3.17.1 fails, all items shall be re-inspected twice. If there are still failures, the batch of sensors shall be judged as unqualified. 6 Marking, packaging, transportation and storage
6.1 Marking
6.1.1 The outer shell of the sensor shall be marked with "Ex", "MA" and measuring instrument markings in obvious places. 6.1.2 The nameplate of the sensor should have the following information: a
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;
Manufacturing factory name;
Factory number or date.
6.1.3 Packaging mark:
The shipping mark should comply with the relevant transportation regulations; MT447-1995
The operation mark should comply with the provisions of GB191.
6.2 Packaging
6.2.1 The packaging should adopt a composite protective packaging type with rainproof, moisture-proof, dustproof and vibration-proof capabilities. 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 transportation by road, rail, water or air. 6.4 Storage
Should be stored in a well-ventilated warehouse without corrosive gas. 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 by the Chongqing Branch of the China Coal Research Institute. The main drafters of this standard are Guo Zengsheng, Zou Jiyuan, Guo Peng, and Chen Yang. This standard is entrusted to the Chongqing Branch of the China Coal Research Institute for interpretation. 311
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