Dears:
In our plant the hot oil system contains hot oil heater which is fitted with inlet and outlet shutdown valves (Shutdown valves were not exist in the original design by heater supplier but the adding of these valves due to HAZOP recommendation and the cause to add such recommendation is tube leak in burner box which may be lead to out of control fire)
Accordingly HAZOP team recommend to add ESD valves at the inlet and outlet of the heater!
Hope to know, to add ESD valves at heater inlet/outlet to avoid out of control fire due to tube leak in burner box is valid recommendation or not, Specially heater BMS provide TAHH at the heater stack to trip the heater by close shutdown valves on fuel gas supply?
Also, there is a PSV between the heater and the outlet shutdown valve. The design case for this PSV is Abnormal heat input (PSV has relieving temperature of 400 oC and the flaring flow rate equal to inlet flow rate to the heater)
The problem is that this PSV is connected to LP flare header (design temp. 200 oC) , and such connection will cause a potential over temperature leading to abnormal stresses and loss of containment due to venting from hot source.
Hope to know:
Does the connection of mentioned PSV to flare header right?
Is it right to consider relieving load due to abnormal heat input to be equal the total flow rate to the heater or not?
Also, consider that the design pressure of the hot oil system is 10 barg (the system is 300# rating due to design temperature 350 oC)