Choosing Hydraulic Flange Fittings for High-Pressure Lines

Hydraulic connections join pipe, hose, or tube to another line or to components such as cylinders, pumps, valves, and ports. The goal is to keep the system connected and sealed under pressure.

In some configurations, a hydraulic flange fitting or separate flange is the best practical option. In others, it may be the only practical way to make a strong, serviceable, leak-resistant connection.

When Flanges Are Commonly Used

Flange connections are often used where pressure is high and the pipe or tube outside diameter is over 7/8 inch. The connection can be bolted together to join two sections of pipe, tube, or hose.

A flange can also be bolted or screwed to a component to secure a fitting or line section. This makes it useful around pumps, motors, valves, and other equipment ports.

Service Access and Assembly

Flanged joints can often be disassembled for inspection, cleaning, modification, or service access. That can be valuable in systems where large threaded connections would be difficult to break loose or reassemble.

Some flanges may be permanently welded to a line or port section. More commonly, the joint is made by bolting two flanges together with a gasket or seal between them.

Code 61 and Code 62

Two common hydraulic flange groups are SAE Code 61 and SAE Code 62. Code 61 is commonly used where working pressure falls in the 3,000 to 5,000 PSI range, depending on size and standard details.

Code 62 is used for higher-pressure applications and is commonly associated with working pressures up to 6,000 PSI. The two groups should not be treated as interchangeable.

Standards to Confirm

Hydraulic flange fitting standards include ISO 6162 and SAE J518. North American parts may use UNC thread arrangements, while international versions may use metric threads.

Before selecting a replacement, confirm the code, pressure class, bolt pattern, thread type, seal, port face, and whether the connection is being bolted to another flange or directly to a component.