The gas itself is toxic, flammable and explosive. According to the combustion characteristics of the gas in the furnace, attention should be paid to the safe use of each stage during the use of the gas boiler burner.
1. Pre-blowing
Before the burner is ignited, there must be a period of pre-blowing to blow away or dilute the remaining air in the furnace and flue. Because there is inevitably remaining gas in the working chamber of the burner, if it is ignited without pre-blowing, there is a danger of explosion. The remaining gas must be blown off or diluted to ensure that the gas concentration is not within the explosion limit. The pre-blowing time is related to the furnace structure and the blowing volume, generally set to 15-60 seconds.
2. Automatic ignition
Gas burners should be ignited by electric sparks to facilitate automatic control. The high-voltage ignition transformer can be used to generate arc ignition, and its output energy is required to be: voltage ≥ 3.5K V, current ≥ 15 mA, and the ignition time is generally: 2 to 5 seconds.
3. Burning status monitoring
The combustion state must be dynamically monitored. Once the flame detector detects the flameout signal, it must be fed back to the burner in a very short time, and the burner will enter the protection state and cut off the gas supply at the same time.
The flame detector must be able to sense the flame signal normally, neither sensitive nor dull. Because of its sensitivity, if the combustion state fluctuates, it is easy to cause malfunction and sluggishness, and the feedback flame signal is lagging, which is not conducive to safe operation.
It is generally required that the response time from flameout to flameout signal sent out by the flame detector should not exceed 0.2 seconds.
4. Protection after ignition failure
When the burner is ignited, gas is introduced, and the gas ignites and burns. The ignition action requires that the ignition temperature field be formed before the gas is introduced to facilitate ignition and combustion. If the ignition fails, the flame detector cannot sense the flame signal, and the burner enters the protection state.
The time from ignition to entering the protection state should be appropriate, neither too short nor too long. If it is too short, it will not have time to form a stable flame; if it is too long, a large amount of gas will enter the furnace when it fails to ignite. Generally, it is required that the burner judges the flame signal sensed by the flame detector within 2-3 seconds after the gas is turned on. If it is not on fire, it will enter the protection state, and if it is on fire, it will maintain combustion.
5. Burner flameout protection
During the combustion process of the burner, if the flame is accidentally extinguished, the burner will enter the protection state. Because the furnace is hot. The gas is prone to deflagration, so it must enter the protection state in a very short time and cut off the gas supply.
From the occurrence of flameout to the protection state of the burner, the response time of this process requires no more than 1 second.
6. Gas pressure high and low limit protection
The gas burner has a certain range for stable combustion, and only allow gas pressure to fluctuate within a certain range. The purpose of limiting the high and low pressure of the gas is to ensure flame stability: no flameout, no flameout or backfire, and at the same time limit the output heat power of the burner to ensure the safe and economic operation of the equipment. When the gas pressure exceeds this range, the burner should be locked to work.
7. Insufficient air pressure protection
The gas burner is designed with high heat intensity, and its combustion method adopts forced air blasting. If the fan fails and the air is interrupted or the air is insufficient, immediately cut off the gas, otherwise the furnace will deflagrate or flash back to the fan. Therefore, while improving the quality of the fan, the gas control must be interlocked with the air pressure. When the air pressure is insufficient, the gas supply should be cut off immediately. Generally, a gas pressure switch is used to sense the air pressure signal and output a switch quantity signal to control the corresponding operation of the gas solenoid valve.
8. Power-off protection
When the burner is suddenly cut off during the working process, the gas supply must be cut off immediately to protect the safety of the equipment. The gas control solenoid valve must be normally closed. Once the power is cut off, it will automatically close and cut off the gas supply. The response time of solenoid valve closing is less than or equal to 5s.
9. Measures to prevent gas leakage accidents
Gas leakage may cause the boiler to explode. There are several ways to solve the problem of leakage in the gas furnace: one is to strengthen the pre-blowing time and the amount of blowing to blow or dilute the gas in the furnace; the second is to use two solenoid valves in series for the gas pipeline. Improve the safety of the system; the third is to use the pipeline leakage detection device to detect the gas pipeline before ignition. If the gas leakage reaches a certain amount, the burner will be locked.