What valves are used in steam pipelines?
①For valves suitable for steam pipelines with a temperature less than 425°C, you can basically choose: gate valves and stop valves.
②Select alloy valves for temperatures above 400℃.
③Gate valve is mainly used as the main steam valve of steam pipeline, which is a valve that is not frequently opened and closed.
④The stop valve is mainly used for valves that are close to the user’s equipment, because this kind of valve has a better regulating effect on the flow.
⑤The selection of valves for steam pipelines mainly depends on temperature, pressure, function and installation position.
So can butterfly valves be used on steam pipelines?
However, if the pipeline pressure is not very high (below 6.4Mpa), it can also be used. However, because of the high temperature, it is recommended to use a metal hard-sealed butterfly valve. An eccentric butterfly valve with a valve body WCB can be used. Pay attention to the flow direction when installing, and the pipeline must be try to keep it as clean as possible to prevent welding slag from getting stuck on the sealing surface, which may lead to loose sealing.
Why do steam pipes need drainage and install steam traps?
When hot steam flows in the pipe, part of the heat will be transferred to the surrounding environment. In a steam system, energy loss means reduced efficiency, so steam pipes need to be insulated to minimize these losses. But no matter how good the insulation material is and how thick the insulation is, there will always be a certain heat loss in the pipeline, which will cause the steam to condense along the length of the main pipe. If this condensate is not removed, it will accumulate in the pipes and cause problems such as corrosion.
The presence of water droplets in steam will dampen the steam, reducing the heat transfer potential of the steam. If water accumulates in the pipe, the effective cross-section of the pipe is reduced and the steam velocity increases, even exceeding the recommended upper limit. Wherever possible, steam main pipes should be arranged with a slope of not less than 1:100 along the flow direction (1 meter drop for every 100 meters). This slope will ensure that the condensate flows to the discharge point under the action of gravity and steam flow, where it can then be drained safely and efficiently. The trap must ensure that the condensate reaches the steam trap. Gravity will cause the water (condensate) to flow down the slope of the pipe to the low points where it will accumulate. Steam traps should therefore be located at these locations.
Large-diameter steam main pipes generate a large amount of condensed water during the start-up stage, so drain points need to be arranged every 30m to 50m, and they should also be arranged at the natural lowest point of the pipeline, such as the bottom of the ascending pipeline.
A more reliable way to remove condensate is to set up a water collection tank. When the diameter of the steam main pipe is within 100mm, the connection position of the drain pipe should be at least 25 to 30 mm from the bottom of the sump of the steam main pipe, and for the steam main pipe with a larger diameter, the distance should be at least 50mm. The lower space prevents pipe impurities and scale from entering the trap. A blind flange or drain valve may also be added to the bottom of the sump for cleaning purposes.
The valve should be as close as possible to the steam inlet, which can reduce the amount of condensed water in the branch pipe when the connected equipment may be closed for a period of time. Of course, branching pipelines also have low points. The most common case is that the downcomer is connected to a shut-off or control valve. Condensate will accumulate in front of the closed valve, and when the valve is opened again, the condensate will be carried away with the steam, so the drain point and steam trap group must be installed at the bottom before the filter and control valve.
