The HSC-A Hydraulic Stage Cementer features inner closing structure, opening through pressure difference. The closing plug drives the closing sleeve down and then shut circulation ports.

• 型压差式双级注水泥器为内关闭式结构，不需投重力塞，通过液体的压力差打开循环孔，关闭塞带动关闭套下行关闭循环孔。