Abstract: This paper introduces the potential problems of the fuel gas manifold pressure control valve of the heating furnace in the air-open type (FC). It is more reasonable to change the gas-off type (FO). In the design of the refinery installation, the fuel gas system of the furnace directly affects the safety, smoothness and continuous operation of the installation, while the heating furnace fuel gas The pressure control loop on the manifold is again a vital control link in the furnace fuel gas system. When the entire plant fuel gas pipe network pressure fluctuations, the loop can guarantee the heating furnace fuel gas system pressure stability, so as to ensure the normal operation of the heating furnace. In the usual design, in order to ensure that in the event of a fault or accident timely cut off the heating furnace fuel gas to protect the furnace tube will not be burned or coking, to avoid the resulting accidents and reduce unnecessary economic losses, from failure From a safety point of view, it is generally considered that the pressure control valve of the fuel gas manifold should be of open air type (FC). The following to discuss the valve if you choose the open type (FC) problems and risks. 1 Ask a question Figure 1 shows a typical furnace fuel gas system process. PV is the fuel gas manifold pressure control valve. If the valve is open air (FC), when the PV valve fails, its accident status is off. In this case, the heater fuel gas is shut off due to the PV valve being closed. All heating The furnaces were forced to shut down due to the lack of fuel gas, causing unnecessary plant shutdowns. If a refinery 600 kt / a catalytic device, because the valve design is open air type (FC), driving the device due to the failure of the valve caused by abnormal parking, making start was interrupted for a few days, a great economic loss. 2 solution In fact, in the design, in order to ensure the safe operation of the furnace, the furnace will be designed for emergency parking interlock system, each furnace fuel gas manifold has an emergency shut-off valve ESDV (FC) At the time of the accident, the valve ESDV was actually functioning to shut off the furnace fuel gas, whereas the PV valve had no direct effect on the safe operation of the furnace, either in the air or in the air. Therefore, in order to reduce the possibility of abnormal stopping of the device due to the failure of the valve PV, the valve is more gas-tight (FO). Of course, when the PV (FO) valve fails, the valve is fully open and the pressure in the furnace fuel gas system is somewhat affected, but each furnace has a fuel gas flow control circuit (and Furnace outlet temperature cascade). This circuit also serves to stabilize the fuel gas pressure, so there is no need to worry about the problem of unstable fuel gas pressure due to valve PV (FO) failure. After several years of practice has proved that the valve design selection to the air-off (FO), to avoid many similar problems of abnormal parking, but also by the owners and relevant experts recognized. 3 Conclusion I have repeatedly participated in the review of large-scale oil refining projects and chemical projects, several found this problem, including the application of the United States UOP's patented technology project, this issue has been discussed with many experts, we agree with this Therefore, we recommend this practice to everyone in order to readers. -------------------------------------------------- -------------------------- About the author: Sun Bao (1967-), male, Jiangdu in Jiangsu Province, graduated from Xi'an Petroleum Institute in 1991 automation , Undergraduate, now China Petroleum East China Survey and Design Institute of Electronic Control Room engaged in petrochemical automation engineering design work.