暗杆-内螺纹结构用于青铜和铸铁闸阀。
Non-rising-inside screw stems are used in bronze and iron gate valves.
按阀杆的螺纹位置划分，可分为明杆闸阀和暗杆闸阀两种。
Position by the valve stem threads are divided into clear and dark bar bar gate valve two...
按阀杆的螺纹位置划分，可分为明杆闸阀和暗杆闸阀两种。
Position by the valve stem threads are divided into clear and dark bar bar gate valve two...
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