【2025: Understand at a Glance】Understanding the requirements for valve actuation time in one diagram

The following responses are not included in the attachment and are provided for reference only: The main functional difference between an emergency shut-off valve and a regular on/off valve is that the emergency shut-off valve can still operate promptly in the event of an accident; therefore, higher requirements are placed on the selection of such valves.

During the design process, in addition to adhering to SH/T 3005-2016 \"Code for Selection and Design of Automation Instruments in Petrochemical Industries\", the \"Regulations on Selection and Design of Emergency Shutoff Valves for Liquefied Hydrocarbon Spheres\" (Sinopec Document No. Jian 518) was also referred to extensively. These regulations provide detailed specifications regarding the technical performance of emergency shutoff valves, the materials used for these valves, the selection of actuators, as well as inspection and testing procedures.

Ball valves, gate valves, and butterfly valves can all be used as emergency shut-off valves in tank farms. Ball valves have a simple structure and good sealing performance, but large-diameter ball valves are expensive; therefore, they are generally used in pipes with a diameter of DN200 or less, or in situations where the full diameter of the pipe is required ； Butterfly valves have poor sealing performance but are inexpensive; however, for high-performance three-eccentric butterfly valves with higher manufacturing precision, the sealing performance improves but the cost also increases accordingly, resulting in a low overall cost-effectiveness ； Gate valves offer good sealing performance and require less effort to operate; they are suitable for large-diameter pipelines. Therefore, gate valves are commonly used in tank areas. Double-gate valve assemblies are typically used at the inlets and outlets of storage tanks, while single-gate valves have the capability to regulate flow rate and are generally used in the pipelines leading out from feed pumps.

The \"Specifications for the Selection and Design of Emergency Shutoff Valves for Liquefied Hydrocarbon Spheres\" stipulate that pneumatic emergency shutoff valves should be used when the tank area is equipped with a reliable instrument air system； When the tank area does not have a instrument air system but does have a power supply system classified as a Class 1 load, emergency shut-off valves driven by electro-hydraulic actuators or electric actuators should be used. In practical applications, electric control valves respond slowly and cannot achieve a fail-safe state; therefore, they are not recommended for use as emergency shut-off valves. In the absence of instrumented air supply, electro-hydraulic control valves should be preferred. When the actuator of the shut-off valve is of pneumatic type, a fail-safe single-acting cylinder actuator is the preferred choice ； When using a pneumatic double-acting cylinder actuator, an air reservoir should be provided ； If an electric actuator must be used, it should be powered by an electrical supply classified as a particularly important primary load.

Shut-off time is one of the important parameters for emergency shut-off valves. Literature stipulates that the maximum actuation time for such valves should not exceed 10 seconds, while the \"Specifications for the Selection and Design of Emergency Shut-Off Valves for Liquefied Hydrocarbon Spheres\" require a time of \"1 second per inch of valve diameter\". The larger the valve diameter, the more unfavorable it is for the shut-off time; in practical applications, an appropriate shut-off time should be selected based on the process requirements. For pneumatic actuators, the shut-off time is also related to factors such as the size of the cylinder and the dimensions of the air supply pipeline. Valve manufacturers generally conduct calculations based on the actual operating conditions, and take measures such as enlarging the cylinder, increasing the diameter of the air supply pipe, or installing air-controlled valves to meet the shutdown time requirements of emergency shut-off valves.

Whether emergency shut-off valves need to be designed with fire protection features should be determined based on process requirements. The \"Guidelines for Addressing Hidden Dangers in Tank Areas\" (Group Work Order Anfeng No. 39) state that for storage tanks that require an independent SIS, the tank base valves and emergency shut-off valves located on their inlet and outlet pipelines must have fire protection measures in place, and they should also possess manual operation capabilities.

Fire protection design for emergency shut-off valves in tank areas is highly necessary. The reason is that the substances stored in these areas are flammable and explosive, resulting in a high likelihood of fire accidents; such accidents can cause severe damage. Since emergency shut-off valves are usually located in areas at risk of fire, it is essential to implement appropriate fire protection measures to ensure that they can still function effectively in case of a fire, thereby maintaining the safety of the tank area.

The selection of the valve body, seat, internal components, cover, and packing for emergency shut-off valves shall comply with API-607-2016 \"Fire Resistance Testing of 90° Rotating Valves and Valves with Nonmetallic Seats\" or API 6FA-1999 \"Code for Fire Resistance Testing of Valves\". Literature generally refers to valves that rotate 90°, such as ball valves, plug valves, butterfly valves, etc., and is mainly concerned with the fire resistance testing of valves with soft seat assemblies ； Literature provides universal standards that can be applied to hard-sealed valves, and the choice is made based on actual requirements in the design process.

The actuator and its accessories used for emergency shut-off valves should have fire protection measures, with fireproof covers being the preferred option. The fire protection shield shall comply with UL1709-2007, the standard for rapid heating combustion tests of protective materials for structural steel, and be able to resist hydrocarbon fires at 1093°C for 30 minutes.

For pneumatic actuators, when it is not practical to install a fire protection cover from an economic perspective, a fusible plug can be installed on the cylinder. In the event of a fire, due to the rapid rise in temperature, the temperature of the cylinder reaches or exceeds the melting point of the fuse plug; the fuse plug then melts, allowing the pressure inside the cylinder to be released. This enables the spring on the other side of the cylinder or the compressed air in the air reservoir to push the piston, thereby closing the valve automatically.