Regarding throttle stop valves and throttle stop vent valves

Throttling shut-off is the function of a regular shut-off valve. The vent shut-off valve needs to open quickly, and the noise generated during venting must be calculated. There is no need to analyze the characteristics of the valve; instead, it is necessary to analyze the characteristics of the two process positions. Valves are designed to serve the process.

Thanks, brother upstairs, but a throttle valve might not just serve the function of an ordinary valve. Ordinary stop valves are usually not used for adjustment. For example, a project specification listed a throttle stop valve and a throttle stop vent valve; the equipment models submitted by the valve manufacturer were LJ41Y (throttle stop valve) and FJ41Y (throttle stop vent valve), respectively. Also, it was confirmed that the throttle stop valve is not a regular stop valve (J41Y), but the specific difference could not be stated. So the actual question now should be the difference between a throttle stop valve, a throttle stop vent valve, and a regular stop valve. As far as I remember, ordinary stop valves are usually used as shut-off valves and not for regulation. Although the throttle valve uses a structure similar to that of a globe valve, its sealing surface has been treated

Don’t make it too complicated. There are tons of terms related to throttling and shutdown. It should properly be called throttling, not restriction. Interception is the same as cutoff. Stop valves can be classified into many types based on their function. A standard stop valve is mainly used for shutting off, cutting off, and blocking flow. It belongs to the category of on-off valves. Regulating stop valve: the valve serves to regulate flow; it is usually of small size, but it is not a regulating valve. The blowdown stop valve is the result of giving special emphasis to practical applications in ordinary stop valves. The main characteristics of this type of valve are similar to those of safety valves: first, if the valve does not operate for a long time, there is a risk that it may fail to open when it is needed most. Second: The valve used for the vent must be of quick-opening type; depending on your requirements, it should open upon receiving a signal. Third: The vent valve must be subject to noise calculation, and noise reduction measures must be properly implemented. Otherwise, it will be even worse during high-pressure venting. Whether the sealing surface needs to be treated depends on the medium and the sealing level required by the process stage. The type of valve that is produced depends on the manufacturing process used

In ammonia refrigeration systems, since they are closed systems, are there vent valves?

Two things, right. A throttle stop valve is a stop valve to which a throttling function has been added; in other words, the head of the valve’s plug is designed to provide a constant or linear flow rate characteristic, and the valve is also equipped with a scale to indicate the degree of opening. The valve possesses the regulating capabilities of a manual control valve, while its sealing performance is higher than that of a control valve, achieving zero leakage similar to that of a globe valve. A throttle-shut-off vent valve requires not only all the functions of a throttle-shut-off valve but also the capability to vent. Gases are typically the media for which such a function is needed, and venting gases presents significant challenges; as can be seen from calculations, the flow velocity at the valve outlet is high, resulting in considerable noise. In such cases, valves generally require a multi-stage pressure reduction and noise reduction design. Moreover, due to the relatively large pressure difference, valves are typically designed with a soft + hard sealing mechanism to ensure reliable sealing performance and thus extend the service life of the valve seat. Therefore, the throttle-stop vent valve is much more troublesome than a throttle-stop valve. The above are my humble opinions; please feel free to correct me.

1. Closed position: The hard seal on the valve disc presses against the protrusion of the valve seat, creating a hard seal; simultaneously, the soft seal embedded in the valve disc presses tightly against the end face of the valve seat, forming a second seal. This dual-seal structure ensures zero leakage from the valve. Moreover, the presence of balance holes in the valve disc results in less force acting on it during closing and opening, which in turn reduces the torque required to open and close the valve. 2. Pressure-relief state: When the bottom end of the valve disc is away from the sealing surface of the valve seat, since the bottom surface of the valve disc is close to the bottom edge of the groove in the cage sleeve, a seal is formed between the valve disc and the inner diameter of the cage sleeve at this time. And it does not release pressure directly, thereby achieving a mitigating effect. 3. Throttling state: The bottom of the valve disc moves away from the valve seat, allowing further opening; a first stage of throttling occurs at the small throttle area. The high-speed fluid flows directly toward the small valve disc after passing through the pressure-reducing throttle. Since the edge of the valve sleeve window serves as the final throttling surface, when the high-pressure medium strikes the throttling passage, vortices are generated at the bottom of the valve disc due to the change in flow direction, which reduces the direct impact of the medium on the valve disc. As a result, the valve seat seal is also protected from direct exposure to the medium. Additionally, because the sealing surface of the valve disc is conical, it is possible to remove dirt and impurities from this sealing surface, thereby protecting it and extending the service life of the valve. 4. Fully open state: When the valve disc is in the fully open position, the entire valve is in a state of complete drainage; the resistance of the fluid flow through the valve is low, which reduces the drainage time and improves the efficiency of drainage by the valve.