How to choose a manual steam valve

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How to choose manual steam valves: the valve disc and the shape of the valve flow channel are used to endow the valve with certain flow characteristics. This must be taken into account when selecting steam manual valves. For liquids such as condensate water, valves used to shut off or allow the flow of the medium are typically those with low flow resistance and a straight-through flow path (full-bore ball valves). Steam manual valves commonly use bellows-sealed globe valves. The structure of a bellows-sealed globe valve is that of a valve that closes downward; due to the complex flow path, its flow resistance is higher than that of other rotary valves. However, the spherical valve structure of globe valves facilitates the regulation and sealing of steam, and designers often modify the shape of the valve disc in such valves to use them for throttling purposes. It should be noted that using the adjustment of the opening height of the shut-off valve to achieve throttling has certain limitations in terms of application. Because, under throttling conditions in the pipeline, the flow velocity of the fluid is very high, which can cause the sealing surfaces to be eroded and worn, thereby reducing the effectiveness of the seal. For steam, proper throttling control can effectively regulate the startup speed of the steam system, thereby preventing issues such as thermal shock, as well as water hammer, vibration, and noise caused by inadequate drainage. Generally speaking, the equal percentage spool structure is more suitable for applications such as steam cylinder and pressure relief valve bypasses, as well as manual valves at equipment inlets. Watt’s experience in energy conservation shows that when a throttle valve element structure is used, the dryness of the steam (its moisture content) can cause cavitation at the valve element area, thereby preventing a proper seal. Quick-opening flat valve cores are less susceptible to erosion caused by steam dryness and cavitation, but 3D simulations show that quick-opening bellows-sealed steam stop valves tend to exacerbate steam turbulence, thereby leading to fatigue failure of the bellows. It reduces the service life of bellows globe valves, and can also cause water hammer during startup, leading to deformation of the valve stem. The flat valve core structure is prone to being affected by solid impurities such as welding slag, resulting in irreversible sealing failure. The quick-opening valve core structure with a rectifying step facilitates smooth flow of steam through the valve nozzle, and also reduces the impact of cavitation on the sealing surface. This structure is widely chosen for bellows-sealed steam stop valves. Traditional plunger-type valve core structures and conical valve core structures are not recommended for steam systems; such self-sealing valve core structures are not suitable for bellows-sealed globe valves. The valve disc of the steam valve, along with the shape of its flow passage, endows the valve with certain flow characteristics. The Watt energy-saving experience shows that this factor must be taken into account when selecting steam manual valves. The flow characteristics of valves that are suitable for these application features help to extend the service life of bellows-sealed steam stop valves.