五月综合人人永久精品_51日日夜夜精品视频,日日夜夜精品视频天天7799_囯产夜轮视屏_国产免费永久在线观看__久久精品在线观看_日韩黄频_起视碰看97视频免费_天天干夜操_永久精品大片www.

Bronze valves and brass valves are mainly made of different materials. Copper has corrosion resistance, long service life, and higher prices. The difference is several times. For example, for a gate valve, a copper core means that the smooth sealing surface is copper, just a small circle. For a DN100 gate valve, that circle is only two fingers wide, and the thickness may be 3mm. In other places, there is a copper or iron sleeve, and everything else is iron. Copper valves, except for the screw rod, are all copper.