combustible gas alarm can detect the concentration of combustible gas. its composition mainly includes the following 3 parts: monitor, detector and signal transmission part. after detecting the concentration value of combustible gas to be exploded, it can convert it to the percentage value of the lower explosion limit, give an alarm immediately, strengthen the control of the output of combustible gas, and then transmit the detection signal of the detector to the monitor. However, the combustible gas alarm needs to be verified before it is put into use, so what aspects should be paid attention to in the verification of combustible gas alarm ? The following is a detailed introduction to this problem.

aspects to be noticed in the verification of combustible gas alarm:

1. Precautions before verification

combustible gas alarm verification/testing laboratory should pay attention to opening doors and windows for ventilation, A fume hood shall be installed to allow the gas to diffuse out. Smoking and open fire are strictly prohibited in the detection area. The on-site verification shall ensure good ventilation, sufficient oxygen and no electromagnetic interference affecting the normal operation of the instrument.As there are many kinds of gas alarms on the market at present, and the combustible gas alarms produced by various manufacturers also have different characteristics, the verification personnel should first carefully read the product specification to understand the basic information involved in the detection of the working principle, range, alarm point, detection/calibration gas, etc. of the instrument, as well as the matters needing attention in operation and use. Secondly, make a preliminary judgment on whether the alarm is working normally, and observe whether it can be started normally, whether the key is valid, and whether the digital display is short of code.

2, verification of combustible gas standard substance

combustible gas is a mixture of various gases (mainly isobutane), therefore, what kind of standard gas is used as the medium for the verification of combustible gas report is a very important issue. In the JJG693-2011 "Combustible Gas Detection Alarm Verification Regulations", isobutane and propane are used as standard gases for verification of combustible gas alarms, but in practice, the use of these two gases to test combustible gas alarms will bring great inconvenience to manufacturers.The gas standard substance used by the metrological verification personnel in the verification of combustible gas alarm shall be the same as that of the gas to be measured, and the general instrument can be representative gas standard substance such as isobutane or propane. For non-universal instruments, try to use the same gas standard substance as the measured gas, otherwise, it can not determine whether the instrument is qualified.

3, verify the combustible gas alarm power supply

We usually use dry batteries or storage batteries as the power supply for combustible gas detection instruments. The power required by the instrument is clearly stated in the instrument manual. Therefore, the power required for normal operation of the instrument must be confirmed before verification. This kind of instrument is mainly composed of two modules: sensor and sampling pump. They all need large current under normal working conditions, so that the sensor can be heated to sufficient temperature and the sampling flow rate can be guaranteed. If the power is insufficient, the standard gas indication will be low, if the sampling flow is small, the instrument will be slow to respond to the standard gas, the response time is too large and the indication value is not allowed.Therefore, if the use of dry batteries or removable batteries of the instrument, the power supply should be carried out by voltage. For those batteries that cannot be disassembled, the current should be replenished first.

4. check the response time of combustible gas alarm

usually under the circumstances, the verification of the response time of the combustible gas alarm will adopt different methods or equipment according to the different environment, generally through the following two methods: the 1 is through manual shouting and then a stopwatch. In order to be able to accurately determine the response time of the alarm, the intercom is usually used to shout, instead of manual gesturing and manual shouting. The other 1 is done by watching the digital change of the host control coefficient.

under the condition of distance (60-80)m, if interphone is not used, manual shouting, gesturing and other methods are generally used to complete the verification of combustible gas alarm. at this time, the verification response time is obviously uncertain, as a result, the accuracy of the response time of the combustible gas detection alarm is affected. If it is at (80-150)m and there are partitions such as factory buildings and walls, the mutual shouting cannot be heard at all, and the interphone is not used for communication, which cannot be verified at all.

is realized by watching the digital change of the control coefficient of the host computer. the operation process is in the production workshop. the verification personnel blow air to the sensor of the instrument at a flow rate of about 500 ml/min according to the national standard, and record the time with a stopwatch. When the host control system personnel found that the number has changed, and then use the stopwatch timing, and this 1 process will produce an error of about 3s.

Do this repeatedly, and then take the average of the stopwatch, which is the response time of the system. Using this method will cause unnecessary waste of standard gas. In daily work, the first method is generally used to test the response time of combustible gas alarm. The use of the instrument is a walkie-talkie, stopwatch, the advantage of doing so is the operation of small timing error, accurate verification data, saving standard gas.

5. Check the place where the gas alarm is used

The use place of combustible gas alarm is related to the alarm level, when using the detector, to make the level of hazardous places conform to the explosion-proof mark of the instrument, the detector must also conform to the explosion-proof category, level and group of the explosion-proof gas mixture on site. It must not be used in the environment exceeding the explosion-proof mark, otherwise the explosion-proof function on site will disappear. The place where the combustible gas alarm is used is related to the main chemical element record in the annular joint. The detector cannot be used in the place containing sulfur, phosphorus, this is mainly because they will cause the detector in the detector element poisoning, at the same time the detector sensitivity is also reduced, and also shorten the service life, and even some will make the detector failure.Therefore, an anti-toxic catalytic combustion type detector or a semiconductor type detector is selected to detect the combustible gas containing the above-mentioned element compounds.

The above aspects that should be paid attention to in the verification of combustible gas alarm are shared here. Nowadays, combustible gas alarm has been widely used in many industries and can detect leakage in dangerous places, at the same time, the personal and property safety of the staff in the place can be fully guaranteed to avoid a series of problems such as environmental pollution, casualties, and property losses.