**Abstract:** Relief valves, emergency shutoff valves, and emergency opening valves are relatively new types of valves that have gained significant attention in the construction and fire protection water supply industries. These devices have been widely discussed due to their critical roles in ensuring system safety and efficiency. This paper explores the design, application, and technical considerations related to these valves, with a focus on pressure relief, emergency shutoff, and emergency opening functions. Keywords: Pressure relief valve, emergency shutoff valve, emergency opening valve, hydraulic control valve, fire-specific. **1. Pressure Relief Valve** A pressure relief valve is installed on the outlet pipe of a fire pump and typically remains closed. It automatically opens when the pressure in the fire water distribution network exceeds the set value, preventing damage caused by overpressure. Overpressure can occur due to several reasons, such as a steep pump performance curve, which may lead to overpressure during low-flow operation (e.g., during self-tests or early-stage fires). Additionally, if the pump stops suddenly (e.g., due to power failure), water hammer effects can also cause overpressure. Proper installation of the pressure relief valve requires careful consideration of its location, size, pressure setting, and accompanying components. According to the draft revision of GBH84-1985, "Automatic Sprinkler System Design Code," it is recommended to install a control valve on the outlet pipe of each group of pumps, and if necessary, a pressure relief valve should be added. The relief valve can be placed near the fire pump or fire water tank. If located before the check valve, it can help prevent overpressure caused by low flow. When placed after the check valve, it not only manages overpressure from low flow but also mitigates pressure surges caused by pump shutdowns. In terms of sizing, two common approaches exist: one where the valve matches or is slightly smaller than the main fire water pipe, and another using standard sizes like DN100 or DN150. Larger valves offer faster discharge capacity, reducing pressure more effectively. However, larger valves increase costs. Therefore, for practical applications, a fixed size is often used. For example, if the fire water main pipe diameter is ≤ 150 mm, a DN100 valve is used; for diameters > 150 mm, a DN150 valve is preferred. The pressure setting of the relief valve should be higher than the pump's operating pressure. In systems with a booster pump, the pressure setting must account for both the pump’s on and off states. To avoid unintended activation due to water hammer, reliable measures must be in place to suppress pressure surges. Additionally, the relief valve should be installed on a branch line connected to the fire water supply pipe, with a signal valve or butterfly valve in front for maintenance purposes. A bypass pipe should also be included to ensure continuous flow during valve maintenance. **2. Emergency Shutoff Valve** An emergency shutoff valve is designed to close automatically when the pipeline pressure exceeds a set value, preventing fire pump water from entering the fire water tank and protecting the system from overpressure. In China, life and fire water supply systems are commonly used, where the initial pump pressure is low, and the fire pump generates much higher pressure upon activation. According to the "Building Fire Protection Code," fire pump water should not enter the fire water tank during a fire. To address this, an emergency shutoff valve should be installed on the pipe leading into the fire water tank. However, the correct pressure setting of the emergency shutoff valve is crucial. If the pressure is set too low, the valve may close prematurely during the life pump operation. Conversely, if the pressure is too high, the valve may fail to close when the fire pump starts. Generally, the pressure setting should be higher than the zero-pressure value of the life pump and lower than the fire pump’s design flow pressure. Reliable measures must also be taken to prevent water hammer in the main water lines. **3. Emergency Opening Valve** Emergency opening valves are used in water spray fire suppression systems but have not yet been widely implemented in real projects. Normally closed, they open automatically when the network pressure reaches the set value, preventing premature water spray before the fire pump reaches its rated speed. These valves are similar to relief valves in function but differ in purpose: while a relief valve discharges water to reduce pressure, the emergency opening valve allows water to enter the sprinkler system to extinguish the fire. Both types of valves are classified as hydraulic control valves, and they rely on pilot needles and diaphragms. However, the needle valve is prone to clogging due to impurities, and the rubber diaphragm may age or wear over time. To mitigate these issues, multi-stage filters are installed before the needle valve to trap solid particles, and high-quality diaphragms with spring mechanisms are used to ensure reliable operation. Currently, relief valves, emergency shutoff valves, and emergency opening valves are treated as general-purpose valves, not specifically designed for fire protection. As a result, they do not undergo rigorous testing by fire product quality supervision centers. It is essential that these valves be recognized as fire-specific products and subjected to strict quality control to ensure their reliability in critical situations.

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