Boiler blowdown device

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· The blowdown system refers to the blowdown short pipes within the boiler itself, the blowdown valves, and the internal blowdown ducts of the boiler drum. · 　　The waste discharge conduit must be long enough and installed horizontally, with one end of the conduit sealed. Each boiler should be equipped with an independent blowdown pipe. The waste pipe should have as few bends as possible to ensure smooth waste flow and to be connected to a safe location. The connections between the drain pipes and the boiler drum, header, and drain valves must be secure and free from corrosion. · 　　Globe valves, sector valves, or inclined cut-off valves are suitable for use as discharge valves. For boilers with a nominal diameter of the blowdown valve ranging from φ20 to 65 mm, and a rated evaporation capacity of ≥1 t/h or an operating pressure of ≥0.7 Mpa, two blowdown valves connected in series should be installed on the blowdown pipe. During discharge, the discharge valve is subjected to the impact of high-temperature liquids and wear from dirt; after discharge stops, it gradually cools down to room temperature. To improve the performance of the blowdown valves under harsh operating conditions such as frequent exposure to large pressure differences, scaling, corrosion and wear, vibration, and thermal shock, there is a specific sequence for operating these valves in series. The connection order is: boiler drum (or lower header) – Valve 1 (slow valve), Valve 2 (fast valve). When performing blowdown, Valve 1 should be opened first, followed by Valve 2 (since Valve 2 is exposed to high pressure differences and is more prone to damage) ； When stopping discharge, close valve 2 first, then valve 1 (valve 2 is subjected to pressure differences and is prone to damage); this allows valve 1 to open and close without any pressure difference, resulting in better operating conditions and a longer lifespan. During major repairs, it is sufficient to inspect or replace valve 2 in particular. Valve 1 is a slow-opening valve; it is usually a inclined-ball type drain valve or a slow-opening gate-type drain valve, that is, an ordinary gate valve. However, it must have the ability to resist alkaline corrosion from furnace water ； Valve 2 is a quick-opening valve; swing gate or rack and pinion gate types are commonly used to meet the requirements regarding the operation and timing of waste discharge.