Valve-related terms

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Strength performance: The strength performance of a valve refers to its ability to withstand the pressure of the medium. Valves are mechanical devices that are subjected to internal pressure; therefore, they must possess sufficient strength and stiffness to ensure they do not crack or deform over long-term use. Sealing performance: The sealing performance of a valve refers to the ability of its various sealing elements to prevent the leakage of the medium, and it is the most important technical parameter for valves. There are three sealing areas in a valve: the contact point between the moving part and the two sealing surfaces of the valve seat ； The interface between the packing and the valve stem as well as the packing box ； The connection between the valve body and the valve cover. The leakage in the former case is called internal leakage, which is what is commonly referred to as poor sealing; it affects the valve’s ability to stop the flow of the medium. For cut-off valves, internal leakage is not allowed. The leaks in the latter two locations are called external leaks, that is, the medium leaks from inside the valve to outside it. Leaks can lead to material loss, environmental pollution, and in severe cases, accidents. For flammable, explosive, toxic, or radioactive media, leaks are absolutely unacceptable; therefore, valves must possess reliable sealing properties. Flowing medium: As the medium passes through the valve, pressure loss occurs (that is, a pressure difference before and after the valve), meaning the valve presents a certain resistance to the flow of the medium. The medium must expend energy in order to overcome this resistance. From the perspective of energy conservation, when designing and manufacturing valves, it is necessary to minimize the resistance exerted by the valves on the flowing medium as much as possible. Opening force and opening torque: The opening force and opening torque refer to the force or torque that must be applied in order to open or close a valve. When closing the valve, it is necessary to create a certain sealing pressure between the sealing surfaces of the moving part and the seat. At the same time, it is also required to overcome the friction forces between the valve stem and the packing, between the threads of the valve stem and the nut, at the support points at the end of the valve stem, and in other friction-prone areas. Therefore, a certain closing force and closing torque must be applied. During the opening and closing process of the valve, the required opening and closing forces and torques change, with their maximum values occurring at the final moment of closing or the initial moment of opening. When designing and manufacturing valves, efforts should be made to reduce their closing force and closing torque. Opening and closing speed: The opening and closing speed is expressed as the time required for a valve to complete one opening or closing action. Generally, there are no strict requirements regarding the opening and closing speed of valves, but certain operating conditions impose specific demands on this speed. For example, in some cases rapid opening or closing is required to prevent accidents, while in other cases slow closing is necessary to avoid water hammer effects. These factors should be taken into consideration when selecting the type of valve. Response sensitivity and reliability refer to the degree to which a valve is sensitive to changes in medium parameters and can respond accordingly. For valves such as throttle valves, pressure reducing valves, and control valves that are used to regulate the parameters of a medium, as well as valves with specific functions like safety valves and steam traps, their functional sensitivity and reliability are very important technical performance indicators. Service life: It indicates the durability of a valve, is an important performance indicator for valves, and holds great economic significance. It is usually expressed in terms of the number of opening and closing cycles required to ensure the sealing requirements, or it can also be expressed in terms of the time of use. Type: Classification of valves based on their purpose or main structural characteristics.
Model: Identification of valves according to type, drive method, connection style, structural features, material of the valve seat sealing surface, and nominal pressure.
Connection dimensions: Dimensions of the part where the valve connects to the pipeline.
General dimensions: Height of the valve when open or closed, diameter of the handwheel, as well as connection dimensions.
Type of connection: Various methods used to connect the valve to pipelines or machinery and equipment (such as flange connection, threaded connection, welded connection, etc.).
Seal test: A test to evaluate the sealing performance of the moving parts and the valve body’s sealing surfaces.
Back seal test: A test to assess the sealing performance of the seal between the valve stem and the valve cover.
Seal test pressure: The pressure specified for conducting a seal test on the valve.
Suitable medium: The types of media that the valve can handle.
Suitable temperature: The temperature range within which the valve can function properly.
Sealing face: The two contact surfaces where the moving parts come into close contact with the valve seat (valve body) to ensure sealing.
Moving part/disc: A general term for components used to stop or regulate the flow of media, such as the gate in a gate valve or the valve disc in a throttle valve.
Packing: A filler placed in the packing box to prevent media from leaking from around the valve stem.
Packing seat: A component that supports the packing and helps maintain its sealing effect.
Gland: A component used to compress the packing in order to achieve sealing.
Yoke: A component on the valve cover or valve body that serves to support the valve stem nut and the drive mechanism.
Dimension of connecting channel: The structural dimensions of the part where the moving part is connected to the valve stem.
Flow area: The minimum cross-sectional area from the inlet end of the valve to the valve seat sealing surface (not the “area of the curtain”), used to calculate the theoretical flow rate under conditions with no resistance.
Flow diameter: The diameter corresponding to the flow area.
Flow characteristics: The functional relationship between the outlet pressure and flow rate of a pressure reducing valve under stable flow conditions, when parameters such as inlet pressure remain constant.
Flow characteristics derivation: The change in outlet pressure resulting from changes in flow rate in a pressure reducing valve under stable flow conditions, when parameters such as inlet pressure remain constant.
General valve: Valves that are commonly used in pipelines across various industrial enterprises.
Self-acting valve: A valve that operates automatically due to the properties of the medium itself (liquid, air, steam, etc.).
Actuated valve: A valve that is operated using manual force, electricity, hydraulics, or pneumatics.
Hammer blow handwheel: A handwheel design that uses impact forces to reduce the effort required to operate the valve.
Wormgear actuator: A device that uses a worm gear mechanism to open, close, or regulate the valve.
Pneumatic actuator: A driving device that uses air pressure to open, close, or regulate the valve.
Hydraulic actuator: A driving device that uses hydraulic pressure to open, close, or regulate the valve.
Hot condensate capacity: The amount of condensate that can be discharged by a steam trap under given pressure differences and temperatures ； Rhinoceros large weight; Steam loss – the amount of fresh steam that leaks out of the steam trap per unit of time