Abstract: The invention relates to an intensifier using liquid, comprising at least one cylinder which has plural pistons and a lubricating chamber between them.

Abstract: In a swivel joint which leads high-pressure liquid in a fixed pipe into a rotatable pipe coupled slidably to said fixed pipe, a lubricating chamber is provided in the neighborhood of sliding area between the fixed and rotatable pipes, and lubricant having at least same pressure as that of said high-pressure liquid is led into said lubricating chamber for smooth rotation and prevention of leakage of the high-pressure liquid and abrasion of the sldiing area.

Abstract: The present invention comprises an apparatus for producing high pressure fluid by means of a cylinder having a reciprocatingly sliding ram inside, suction and pressurization of the fluid being performed by the reciprocation of said ram. In the apparatus, an oil chamber is positioned on the intensifying side within said cylinder, and lubricating oil in said oil chamber is caused to have a pressure equivalent to that of the high pressure fluid produced. This oil pressure is transmitted to the slidable contact portions of the ram. The apparatus is capable of detecting the lack of lubricating oil, when such lack of lubricating oil occurs.