SAE 4-bolt flange connections are commonly used on heavy mobile equipment and other high-pressure applications.
There are two SAE series of flanges as well as Caterpillar's® newer proprietary version.
Code 61 denotes the standard series and Code 62 the high pressure series flanges.
Code 62 flanges have larger and thicker head diameters and use a different bolt size, bolt grade (8 instead of 5), and bolt hole pattern.
Caterpillar® style flanges feature a thicker 0.560" flange head and require special flange halves that do not conform to Code 62 bolt hole patterns.
Flange heads have a machined groove where the o-ring seats and sealing is achieved when the o-ring is compressed between the flange head and the smooth faced port.
The flange head is secured to the port by two split flange clamp halves and four bolts.
Other less common flanges include the Komatsu style flange in -10, and the very rare French Poclain style flanges.