What valve should be used for steam?
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Do we usually use cage-type control valves for steam here? I don’t know what the reason is! ! Some say to use ball valves – what are the advantages of that?
For valves on steam transmission pipelines, manual control valves or automatic control valves with good regulating performance are generally selected. Among valves with control functions, globe valves and plunger valves can meet general flow regulation requirements, while needle valves can be used for fine adjustments of very small flow amounts ； For stable regulation (pressure, flow rate) over a wide range of flow rates, a throttle valve is the appropriate choice. Among them, the globe valve is a type of valve widely used in chemical plants; it offers reliable sealing performance and is also suitable for regulating flow. It is generally installed at locations where flow regulation is needed, such as at the pump outlet, upstream of the flow meter in the bypass circuit of control valves, and elsewhere of similar nature.
The cage-type control valve is a pressure-balanced control valve; its internal components feature a pilot-operated spool guided by a sleeve. It relies primarily on the pressure of the fluid to enable rapid movement of the spool, resulting in low operating force. In addition, it features a single-seat seal design, with a high precision in its flow characteristic curve, meeting the IEC534-1 standard. The control valve features good dynamic stability, low noise, and blast resistance, making it suitable for controlling high-pressure differential fluids at various temperatures. It is equipped with a multi-spring diaphragm actuator or an electric actuator, featuring a compact structure and high output force. Ball valves generally cannot be used with steam.
For temperatures below 425 degrees, gate valves, globe valves, check valves, and metal-sealed butterfly valves can generally be chosen. The material of these valves is carbon steel WCB; they can be used in pipelines with steam temperatures below 425 degrees. For valves operating at temperatures below 600 degrees, the material is stainless steel, or chrome-molybdenum steel, chrome-molybdenum-vanadium steel, etc. For valves used in steam pipelines where the temperature is below 250 degrees, ball valves are generally a good choice; they offer excellent sealing performance, and the material can be carbon steel WCB.
Generally, globe valves are used for regulation, while gate valves are used for opening and closing (shutting off). Butterfly valves are also used for switching at low pressures, but they tend not to seal tightly. Hard sealing is generally chosen for valve sealing surfaces.
Steam is generally controlled using globe valves, which are inexpensive, resistant to high temperatures, adjustable, and easy to operate. Ball valves cannot be adjusted, and their sealing surfaces are prone to damage when operating at high temperatures for extended periods. Gate valves take up a lot of space and are also difficult to operate. Butterfly valves find it difficult to maintain sealing performance at high temperatures.
Plunger valves are generally used, while ball valves can be employed for smaller pipe diameters. . .
We have a lot of steam here, and quite a bit more was added during the renovations. Judging from the situation on site, butterfly valves are definitely not an option to consider. There is no butterfly valve for the steam! A globe valve is a good choice; it should be given priority. The flow is easy to control, and the sealing is also good. If quick opening and closing are required, a ball valve can be chosen; generally, the diameter should not exceed DN50. Gate valves are also not suitable for steam; they can be used as a makeshift solution when spare parts are truly unavailable.
Globe valves are generally used on steam pipelines, while gate valves, ball valves, and butterfly valves are used on water pipelines.
Globally, gate valves used for manual adjustment are more common