A few questions regarding the gas pressure control valve of the heating furnace～
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The gas flow path for the heating furnace in our unit is as follows: The system gas enters the unit through a gas total pressure control valve, then goes into a gas separation tank; from there, it is divided into a pilot light supply and main gas supply, which then enter the heating furnace. Gas temperature control valves and quick shut-off valves are installed in this section. The total gas pressure control valve does not have a low/low pressure interlock; in other words, in the event of an unexpected interruption in gas supply, it will not trigger the rapid shut-off valve to operate. So now, what I would like to ask is: from the perspective of safe production, during normal operation, should the bypass line of the total gas pressure control valve be left slightly open to maintain a surplus amount of gas?
What are you preventing by revealing the foreshadowing? The overall gas regulation failure causes automatic shutdown, resulting in low gas pressure; is a voltage line used to maintain a certain level of pressure in order to keep the furnace burning? Is that what you mean?
To prevent the pressure-controlled valve from opening or closing unexpectedly, which could cause the flame to go out; subsequently, the valve returns to its normal position on its own, allowing large amounts of gas to enter the furnace and trigger a flash explosion. The purpose of installing some bypass lines is to ensure that, even in the event of fluctuations in the pressure-controlled valve, the amount of gas in these bypass lines will be sufficient to keep the pilot light burning. But now there is a problem: if the eternal flame cannot burn properly, it becomes even more dangerous to turn on the auxiliary line
To prevent the pressure-controlled valve from opening or closing unexpectedly, which could cause the flame to go out; subsequently, the valve returns to its normal position on its own, allowing large amounts of gas to enter the furnace and trigger a flash explosion. The purpose of installing some bypass lines is to ensure that, even in the event of fluctuations in the pressure-controlled valve, the amount of gas in these bypass lines will be sufficient to keep the pilot light burning. But now there is a problem: if the eternal flame cannot burn properly, it becomes even more dangerous to turn on the auxiliary line
If it shuts down due to a simple fault, that’s not a problem; at worst, the plant can be shut down. What’s concerning is that it might turn on again on its own after shutting down due to a fault. If it isn’t detected right away, a large amount of gas will enter the heating furnace, which is very dangerous
It would be best to add a chain. . . Ovens should be designed with interlocks. . If there’s a shut-off valve, why isn’t a interlock installed? It doesn’t comply with the relevant standards. . .
Well, it should be equipped with interlocks, but it’s currently operating normally; the next maintenance session is scheduled for 2019, so the interlocks cannot be installed for now. There is another reason for not using interlocks: the gas pressure often fluctuates slightly, and if the interlock values are set improperly, it may lead to unexpected shutdowns of the furnace
Interlocks must be installed in heating furnaces; safety first should not remain just a slogan. From the perspective of Safety Instrumented Analysis (SIL), it is also necessary to add it
Our facility was built 16 years ago; the main gas control valve is a air-shut valve, while the temperature controls for each furnace are air-open valves. In my opinion, the wires for the pilot lights should be placed before the main control valve, so that they are not affected by it. The main gas pressure control valve and the total flow meter should be installed after the liquid separation tank, to prevent any impact on the operation of the control valves when there is liquid present. Having an accurate flow meter also helps in identifying problems more easily. Our facility does not have a low-pressure interlock system – it’s unlikely that the pressure will drop to such an extreme level. If the pressure really starts to drop significantly, the system should shut down automatically; otherwise, it becomes dangerous once the interlock activates. By taking proactive measures, it’s possible to safely close all the valves, but with an interlock system, internal leaks may cause some burners to stop functioning while gas continues to flow, leaving other burners still burning, which increases the risk of a flash explosion
This post was last edited by Yongan Environmental Protection on 2017-5-31 at 11:56. According to the rules, both gas and the permanent flame system should be equipped with low-low interlocks; the interlock value for the permanent flame should be lower than that for the fuel gas. This ensures that when the gas pressure drops below a certain level, the fuel gas burner shuts off first, while the permanent flame continues to burn, keeping a flame in the furnace and facilitating rapid resumption of operations. As the gas pressure continues to drop and falls below the interlock value for the pilot light, the pilot light interlock shuts it off. When igniting again, make sure to close the manual valve in front of the furnace, perform steam purging, and then ignite after analyzing the combustible gases. One must not give up eating just because of this issue, and remove the interlocks arbitrarily.