Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
SAE J518-2 (Code 62) Hydraulic Flanged Connections: Design, Dimensions, and Best Practices
This article provides an overview of the SAE J518-2 standard for four-screw flange connections rated for 42 MPa (Code 62). The standard covers dimensional and material specifications for flanged heads, flange clamps, split flange clamps, and port designs used in industrial and commercial hydraulic systems. Understanding these specifications is critical for ensuring reliable, leak-free connections at high pressure.
Scope and Key Specifications
The SAE J518-2 standard addresses Code 62 connections intended for tube, pipe, and hose assemblies where threaded connections are undesirable. It defines both metric (Type 1) and inch (Type 2) versions, although Type 2 is not recommended for new designs. The rated working pressure of an assembly is determined by the lowest-rated component, emphasizing the need for careful system design.
| Component | Minimum Yield Strength (MPa) | Minimum Elongation at Fracture |
|---|---|---|
| Flanged Heads | 215 | 10% per ASTM E8 or ISO 6892-1 |
| Flange Clamps and Split Flange Clamps | 330 | 3% per ASTM E8 or ISO 6892-1 |
Screws must be property class 10.9 or higher, conforming to ISO 4017 or ISO 4762. O-rings should comply with ISO 3601-1, with a hardness of 90 IRHD ±5, and satisfy Grade N requirements of ISO 3601-3. Unless otherwise specified, NBR (nitrile) material is required.
⚠️ Important Note on Type 2 Flanges: Type 2 (inch) flange clamps and split flange clamps are not intended for new designs. The standard recommends using Type 1 (metric) to promote global standardization and reduce complexity.
Design Insights and Pressure Rating
The maximum working pressure of a flange assembly is limited by the weakest component. For example, if a flanged head meets the 215 MPa minimum yield but the clamp meets 330 MPa, the pressure rating of the assembly may be governed by other factors such as O-ring material or port design. Always verify the pressure ratings of each component against the system requirements.
Interchangeability with ISO 6162-2 is maintained for most sizes, with exceptions for -40 and -48 inch-sized connections that exist only in SAE J518-2. This ensures compatibility across global supply chains when using metric flanges.
🛠️ Engineering Insight: The standard provides dimensional tables (Tables 1A and 1B) with maximum working pressures for each flange size. Always use the latest revision (2023) to ensure correct values, as previous issues may have different column headings.
Tolerances for unspecified dimensions must conform to ISO 2768-1 Class M and ISO 2768-2 Class C, and clearance holes per ISO 273 medium series. Surface texture requirements are specified in accordance with ISO 21920-1.
Common Mistakes and Frequently Asked Questions
Common Mistakes
- Using Type 2 inch flanges for new designs despite the standard stating they are not for new design.
- Ignoring the weakest component rule when calculating system pressure rating.
- Confusing Code 61 (35 MPa max) with Code 62 (42 MPa) and applying incorrect dimensions or clamps.
- Overlooking corrosion protection requirements; components must pass salt spray testing per ASTM B117 or ISO 9227.
Frequently Asked Questions
What is the difference between Code 61 and Code 62 flanges?
Code 61 flanges are rated for pressures from 3.5 to 35 MPa, while Code 62 flanges are rated for 42 MPa. They have different dimensions and are not interchangeable. SAE J518-1 covers Code 61; SAE J518-2 covers Code 62.
Why is Type 2 (inch) not recommended for new designs?
The standard aims to transition to a single global metric system. Type 2 flanges are retained only for existing installations and legacy maintenance. New systems should use Type 1 metric flanges to ensure long-term compatibility with international standards like ISO 6162-2.
How is the maximum working pressure of an assembly determined?
The assembly’s rated working pressure is the minimum of the pressure ratings of all components in the connection, including flanged heads, clamps, port bodies, O-rings, and fasteners. The standard specifies maximum working pressures for each flange size in Tables 1A and 1B.
What O-ring material and hardness are required?
Unless otherwise specified, O-rings must be NBR (nitrile) with a hardness of 90 IRHD ±5 IRHD, meeting ISO 3601-1 class A tolerances and Grade N quality per ISO 3601-3. For non-petroleum fluids, alternate elastomers may be used but must meet the working temperature range.
