This connection is commonly used in fluid power systems. There are two pressure ratings. Form R (Code 61) is referred to as the “standard duty” series, and Form S (Code 62) is the “heavy duty” series.
The design concept for both series is the same, but the bolt hole spacing and flanged head diameters are larger for the higher pressure, Form S connection. Both metric and inch bolts
are used.The female (port) is an unthreaded hole with four bolt holes in a rectangular pattern around the port.
The male consists of a flanged head, grooved for an o-ring, and either a captive flange or split flange halves with bolt holes to match the port. The seal takes place on the o-ring, which is compressed between the flanged head and the flat surface surrounding the port. The threaded bolts hold the connection together