ISO 6164:1994 Preview
Hydraulic fluid power -- Four-screw, one-piece square-flange connections for use at pressures of 25 MPa and 40 MPa (250 bar and 400 bar)
This standard was last reviewed and confirmed in 2003. Therefore this version remains current.
Gives complete general and dimensional specifications. For flange connections, a design factor of 2,5 is valid, not including weld joints, for which special instructions exist. Also specifies the dimensions of the seals to be used, as well as the grooves to house the seals.