Regarding the low outlet pressure interlock in the vacuum furnace
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Regarding the low outlet pressure interlock in the vacuum furnace, the interlocks triggered by low inlet flow rate and high outlet temperature both result in the shutdown of the gas valve for the main burner, thereby preventing dry burning or coking. However, in addition to the shutdown of the main burner valve, the interlock triggered by low outlet pressure also causes the feed valve and the furnace outlet valve to shut down as well. I don’t understand why this is the case. I would appreciate it if experts could help explain this. Thank you
Reply 1# man19501: In my opinion, such a interlock should be one for detecting leaks in the furnace tubes； If the furnace outlet temperature is too high, it is sufficient to shut down the fuel supply via interlock; shutting down the feed supply is not acceptable. Continuing or increasing the feed supply can help lower the furnace outlet temperature ； This is not appropriate; you need to discuss and study it thoroughly with the design team
Reply to 2# linweihua6: Thank you for your answer; this explanation is quite reasonable. Thank you again
I agree with the opinion above: the gas supply is cut off in case of a fault, but the feed supply remains active to prevent the furnace tubes from being damaged by high temperatures. This is also related to the design of the wind-on and wind-off valves – the gas valve is a wind-on valve, while the feed air valve is a wind-off valve.