Will a valve that is set to \"open in case of failure\" close in the event of a failure?

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Without a doubt, the answer is yes; otherwise we wouldn’t be asking such a question! In piping and instrumentation diagrams (P&ID) or other process safety information (PSI), valves can be indicated as \"fail open,\" \"fail close,\" and \"fail in place.\" This indicates what action the valve should take in the event of a failure in the supply medium (usually instrument air or power supply issues). In the batch reaction system shown in Figure 1, the material inside the reactor is first heated by steam from the heat exchanger. Once the material in that batch reaches the desired reaction temperature, the steam valve of the heat exchanger is closed and cooling water is introduced to control the temperature of the reactor. The water flow is controlled by valve 1, which is a \"fail-open\" valve that requires instrument air pressure to close. On the day the incident occurred, the temperature of the reactor began to rise, triggering a high-temperature alarm. The operator observed that the signal for valve 1 was “fully open”. The temperature of the reactor continued to rise, eventually triggering alarms for high temperature and low cooling water flow. The operator was unable to identify the problem within 7 minutes, nor did they activate the emergency cooling water bypass to increase the flow of cooling water to the reactor. The final action of the emergency shutdown system is to discharge the material inside the reactor into the accident tank. Although no injuries were caused, it constituted an environmental release incident. Do you know? • The positioner of valve 1 (the gray box in the diagram), which is connected to the mechanical linkage, converts the received control signals and transmits them to the valve actuator. • With the help of the working linkage mechanism, the valve stem moves from the open position (Figure 2) to the closed position (Figure 3) as the air pressure signal changes. When the linkage fails (Figure 4), the valve remains closed. • In addition to the failure of the utility medium, it should be understood that valves may also fail to operate for many other reasons: mechanical components may malfunction or become detached. Valve components may get stuck due to rust or dirt. The material inside the valve can also cause it to stick. What can you do? It is necessary to identify the valve position when critical safety-related valves in the plant fail. It should be noted that P&ID diagrams usually indicate the valve status in the event of a failure of utility media (such as power supply, instrument air, etc.). It is important to recognize that valves may fail to operate for many other reasons besides the failure of the medium supplied to them. It is important to go to the site to observe the operation of the valves in order to identify and report any issues with them. If you are involved in hazard identification activities such as Process Hazard Analysis (PHA), Change Management (MOC) reviews, or design reviews, you need to consider the consequences of a valve failing to operate as designed; this includes the valve not functioning at all, or failing to remain in the position specified for it in the event of a failure of the process medium.