SAE Flanges (Code 61 / 62)

On large-bore, high-pressure hydraulic lines, SAE flanges provide a safer and more service-friendly connection than threaded fittings. The flange head on the end of the hose or tube is clamped against the port with four bolts, using two split flange halves or a one-piece flange; sealing is provided by the O-ring on the face of the head. Because the connection is not rotated, the hose is connected without twisting, and installation is easier in tight spaces where a wrench will not fit on large sizes. ISO 6162-1 defines the Code 61 series (called SAE 3000 in the field) and ISO 6162-2 the Code 62 series (SAE 6000).

SAE 3000 vs SAE 6000 flanges (Code 61 / Code 62)

"3000 PSI" and "6000 PSI" are series names; the permissible working pressure varies with nominal size and, in Code 61, drops at larger sizes. The pressure rating should be checked in the table for the size concerned. Even at the same nominal size, the two series are not interchangeable.

Components of an SAE flange connection

• Split flange clamp: made of two halves; it can be fitted and removed without disconnecting the line, which makes installation easier in tight spaces.
• Mating flange: connects the tube to the port via a weld neck, socket-weld or threaded connection.
• Blind flange: closes off an unused port or the end of a flanged line.
• Flange blocks: combine elbow, spacer, reducer and distribution functions in a single body; non-standard blocks are machined to technical drawings.
• Flanged hose ends: connect the hose assembly directly to a Code 61 or Code 62 port.

Selection criteria: identifying the series of an existing port

The choice between Code 61 and Code 62 should be based on nominal size, working pressure, port geometry and installation space. The series of an existing port is identified by measuring the bolt spacing and the diameter and thickness of the flange head. Whether the bolt thread is inch (UNC) or metric must also be checked separately; ISO 6162 covers both bolt options. AISI 316/316L options are the preferred choice in plants where corrosion resistance is important.

Installation: O-ring and criss-cross tightening

The O-ring groove and port face must be clean and free of scratches; the O-ring should be lightly lubricated with a suitable oil. The split flanges are seated parallel to the head, and the bolts are tightened first by hand, then in a criss-cross pattern and in stages up to the table torque. Fully tightening one bolt on its own tilts the flange and crushes the O-ring on one side.

Which industries use them?

Press, mill roll and power unit lines in rolling mills; lifting equipment and power units on drillships; compact power units in the defense industry; corrugated board (corrugator) machine hydraulics in board mills; and pump outlets in ship engine rooms.