Which of the following is NOT an acceptable overpressure protection device?

The manual shutoff valve is not considered an acceptable overpressure protection device because it is primarily designed to stop the flow of gas in the event of an emergency or for maintenance purposes, rather than to provide protective measures against overpressure conditions. Overpressure protection devices are specifically implemented to detect and relieve excess pressure that could lead to dangerous situations or equipment failure.

In contrast, a pressure relief valve is designed to open at a predetermined pressure to allow gas to escape, thereby preventing overpressure conditions from occurring. A monitor regulator helps maintain consistent downstream pressure by automatically controlling the flow of gas, and a series regulator is used to reduce pressure in multiple stages for more precise control. Each of these devices plays a critical role in managing pressure and ensuring the safe operation of LP gas systems, while the manual shutoff valve lacks that specific protective function against overpressure.