PLC chain alarm control circuit used in production process

According to the above requirements, the control relationship structure can be drawn
.
    The symbols a, b and i-io in the figure are input signals, and their meanings are as follows: a: Reset button of PV-102; b: Reset
button ; 1 : Air compressor stops; 2: Central control room emergency stop; 3: Ammonia superheater outlet gas ammonia temperature is extremely low l 4; Oxidation furnace platinum mesh 1 temperature
is extremely low; 5: Oxidation furnace platinum mesh 1 temperature is extremely high; 6: The hydrogen temperature at the outlet of the ammonia superheater is extremely low; 7: The ammonia/air ratio is extremely high; 8: The ammonia/air ratio is extremely low;
9: The temperature of the platinum mesh 2 of the oxidation furnace is extremely high; 10: The temperature of the platinum mesh 2 of the oxidation furnace is extremely low. PV-102 is the ammonia gas valve at the outlet of the ammonia superheater, xV-lol is the interlocking quick-closing valve
    in front of the ammonia filter , and XV-102 is the remote control vent valve before the ammonia filter.     (2) PLC selection In order to realize the interlock alarm control function of the atmospheric pressure nitric acid plant during the production process , taking into account the system requirements, Siemens S7-200 series PLC is used as the controller. It has the advantages of compact structure, small size, light weight and strong functions . The input power of the PLC is provided by external 24V DC, and the outputs are all relay type. Taking into account the input and output of other signals and future expansion applications, a total of 30 input nodes and 26 output points are designed (including 14 input points and 10 output points on the CPU module).