Often steam exhaust from the boiler goes into the stack, the force of the steam shooting out of it, helps drawl the fire more inside the flues.

通常锅炉排出的蒸汽会进入到烟囱，喷涌出的蒸汽由于气压差的引力，会把更多的火带入火管。

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Second: to assist in cutting out a boiler, when ceasing to fire. In this case, the disc automatically closes and prevents header pressure from entering the boiler.

其次，有助于切断锅炉，当停火后，阀瓣自动关闭，防止热水器压力进入锅炉。

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