Connection type of the valve
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I would like to ask whether there are any regulations regarding when valves in main steam pipelines should be connected using flanges and when welding should be used
This post was last edited by ylb913 on 2016-3-9 at 12:15. Valves that use welding are rarely useful, and this is even more true for steam valves.
1. Valve connections for low-pressure steam pipelines use flanges. Due to the relationship between the pressure and temperature of saturated steam, the temperature of low-pressure steam is generally not very high; as a result, the flange seal will not leak even in the presence of slight deformations. Therefore, valve connections for low-pressure steam pipelines typically employ flanges； 2. Valves in high-pressure steam pipelines are generally connected by welding. Since the temperature of high-pressure steam is very high, using flange connections could lead to leakage due to the possibility of the flanges deforming under such high temperatures. For example, in the connection of valves for high-temperature and high-pressure steam pipes in thermal power generation, welding is used as the connection method, with the aim of preventing leaks.
According to industry standards, temperatures above 540 degrees are not suitable for flange connections. In fact, when the temperature is above 350 degrees, welding is recommended. Flange connections require thermal tightening at high temperatures, which poses difficulties for installation companies; therefore, welding is a more reliable option.
Generally, valves come with flanges; welding is chosen at high pressures because the flange can be a source of leakage, and welding helps to prevent leaks under such conditions. Flange valves are generally chosen for steam
High temperature and high pressure; the remaining flanges are welded
Both temperature and pressure are crucial. Flange connections need to be heat-tightened when used in high-temperature environments; moreover, high temperatures place higher demands on the materials used for flanges and bolts. Flanges, bolts, and gaskets increase the investment costs and also add potential leakage points. Therefore, for high-temperature and high-pressure hazardous media, welding connections are generally used.
1. Temperature: Above 350 degrees, flanges are prone to leakage. 2. Pressure: In high-pressure applications, welding must be used, as flanges themselves are not suitable for such conditions and are prone to leakage. 3. Flanges are used for those parts that are prone to damage and require frequent replacement.