In the BPCS (basic process control system) layer for a highly exothermic reaction, we better be sure that the temperature T stays within the allowed range. The measure we protect against an error in the temperature sensor (reading too low) causing a dangerously high temperature could be to install a second temperature sensor that can detect any erroneous reading from the first sensor. This will alert the BPCS system and result in appropriate actions. The failure position of a control valve is selected to yield the safest condition in the process, so for the reactor with exothermic reaction, we should select "fail-open" valve, which will open the valve during a failure, to prevent the reaction from building pressure. This will avoid any catastrophic situation such as a sudden explosion.
In the SIS (safety interlock system to stop/start equipment), the reason why we do not use the same sensor that is used in BPCS is that if there is an issue with the primary sensor, then the secondary sensor, which is in SIS, will not give the same reading as the primary. This will activate the SIS system and result in appropriate action to maintain the safety of the process. In relief system, the goal is usually to achieve reasonable pressure (prevent high pressure or prevent low pressure). The capacity should be for the "worst-case" scenario, the action is automatic (it does not require a person), and it is entirely self-contained (no external power required).
The reason why it needs no electricity is that in case of an emergency like a power cut, the relief valve still must function. Therefore, it has to be self-contained to operate in the absence of any external power.
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The number of moles of CO² which contain 8. 00g of oxygen is