plug screw meaning in English

堵头螺钉
堵头螺丝
螺塞

Plug screws and flat sealing rings for welded - in screw caps for filling and sounding pipes
充料管和探测管用焊接盖板螺纹盖的螺塞和扁密封圈
Stud ends , ports , for fittings , valves - plug screw with whitworth pipe thread - general outlay of types
管件和阀门用管堵和螺纹孔.带惠氏管螺纹的螺塞.各类
Stud ends , ports , for fittings , valves - part 1 : plug screw with metric fine pitch thread ; general outlay of types
配件和阀门用螺柱端和孔.第1部分:带公制小螺距螺纹螺