What is an SAE Flange and How is it Used in 2025?

Hydraulic SAE flanges are integral components in modern hydraulic systems, providing secure, leak‑free connections between critical components such as pipes, hoses, pumps, and valves. Developed to meet strict international standards like SAE J518 and ISO 6162, these flanges have evolved significantly over the decades to offer robust performance even under extreme pressure and dynamic operating conditions.

In this article, we explore the fundamentals of SAE flanges—their design, materials, and varied applications—and provide detailed installation guidelines along with expert tips on how to select the right flange for your system.

What Is SAE Flange?

SAE flanges designed to specifications such as SAE J518 and ISO 6162 and feature a four-bolt assembly and O-ring seals to provide secure, leak-free connections even under high pressures. SAE is the abbreviation of Society of Automotive Engineers. Hydraulic SAE flanges are a standardized, high-performance connector used to connect components such as pipes, hoses, pumps, and valves in hydraulic systems.

History of SAE flange

The origins of hydraulic SAE flanges can be traced back to the mid-20th century, when the hydraulic and fluid power industry was working to standardize connections. SAE flanges provide a unified way to connect components such as pumps, hoses and valves. As hydraulic systems have become indispensable in various fields such as automotive, aerospace, construction and industrial machinery, the use of SAE flanges has grown and has now developed into a trusted industry standard solution.

Types of SAE flange

SAE flanges are produced to meet strict international standards, ensuring compatibility and interchangeability across various hydraulic systems. They are available in two main types—Code 61 (designed for lower to moderate pressure) and Code 62 (suitable for higher pressure requirements).

Code 61 (3000 Series):

Designed for moderate pressure applications, Code 61 flanges are often used in systems where pressures range from approximately 34 bar (500 psi) up to about 345 bar (5000 psi). They typically feature a flat-face design with an O‑ring groove to achieve a seal at lower tightening torques.

Code 62 (6000 Series):

Built for high-pressure applications, Code 62 flanges can withstand pressures up to around 414 bar (6000 psi). These flanges generally have a more robust construction and may include design modifications (such as increased bolt sizes) to secure better sealing under higher pressures.

In addition to classification based on pressure level and design specifications, there are many other classification methods:

By Connection Type: SAE flanges can be classified according to how they attach to the piping system. Socket weld SAE flanges involve inserting the pipe into a recessed flange area that is then welded in place, making them ideal for smaller diameters (typically up to 2 inches) to ensure a compact, leak‑free joint. Butt weld SAE flanges are welded directly to the pipe, creating a continuous and durable connection preferred for larger pipe sizes and high‑pressure applications, while threaded SAE flanges join components using screw threads (such as NPT, BSPP, or metric), which facilitates disassembly and maintenance.

By Structural Configuration: Single‑part or integral flanges are manufactured as a single unit for permanent, robust connections and can be found in socket weld, butt weld, or threaded variants; split flanges are assembled from two halves, offering easy disassembly for maintenance or repair in restricted spaces; blind flanges are used to seal off pipe ends, maintaining system integrity by closing an unused connection without an active flow path.

By Face Design: O‑ring face flanges are machined with a groove to seat an O‑ring, delivering a reliable, soft seal even under varying bolt torques and minimizing leaks; flat face flanges feature a completely flat sealing surface that relies on the precision of the mating surfaces to form a seal, though they may require higher bolt torques and more precise machining to prevent leakage.

SAE flange material

The primary materials used in the manufacturing of SAE flanges include various grades of carbon steel and stainless steel, each offering distinct properties tailored to different operational requirements.​

1. Carbon Steel SAE Flanges

Carbon steel is widely utilized for SAE flanges due to its strength and cost-effectiveness. Common grades include:​

ST52.3: A low-alloy, high-strength structural steel known for excellent weldability and machinability. It is often employed in hydraulic components that must withstand high pressure and mechanical stress.

S355J0: This grade offers good tensile strength and is suitable for general structural purposes.

C45 (EN/DIN 1.0503): A medium carbon steel providing good wear resistance and moderate tensile strength, making it appropriate for parts subjected to higher mechanical loads.

2. Stainless Steel SAE Flanges

For applications requiring enhanced corrosion resistance, especially in harsh environments or where exposure to moisture and chemicals is prevalent, stainless steel is the preferred material. Notable grades include:​

AISI 316L (EN/DIN 1.4404): A low-carbon variation of AISI 316, offering superior corrosion resistance and excellent performance in aggressive environments.

AISI 304 (EN/DIN 1.4301): A widely used austenitic stainless steel known for its good corrosion resistance and formability, suitable for a variety of applications.

AISI 316Ti (EN/DIN 1.4571): This grade includes titanium stabilization, enhancing resistance to intergranular corrosion, particularly useful in high-temperature environments.

3. Duplex Stainless Steel SAE Flanges

In situations demanding both high strength and excellent corrosion resistance, duplex stainless steels are employed. These steels have a mixed microstructure of austenite and ferrite, providing enhanced mechanical properties and resistance to stress corrosion cracking. ​

Surface Treatments

To further enhance the performance and longevity of carbon steel SAE flanges, various surface treatments are applied:​

Zinc Coating (Galvanization): Applying a layer of zinc provides corrosion protection. Options include white zinc plating with a thickness exceeding 8 µm and yellow galvanized zinc.

Phosphating: This process imparts a black finish that offers moderate corrosion resistance and serves as a good base for painting.

Nickel Plating: Provides a hard, corrosion-resistant surface, enhancing the flange's durability in aggressive environments.

Advantages of SAE Flange

SAE flanges offer significant benefits in hydraulic systems compared to alternative connection methods. One key advantage is that, compared to other connection types, SAE flanges distribute torque to four bolts, reducing the need for bulky tools and enabling simpler, more even tightening. This design feature helps ensure a secure and leak‑free seal while easing installation and maintenance tasks.

Additionally, SAE flanges are manufactured to strict international standards (such as SAE J518 and ISO 6162), which guarantees consistent quality and compatibility across different components and systems. Their robust sealing mechanism—often incorporating O‑ring faces—provides reliable performance under high‑pressure and dynamic loading conditions. Overall, SAE flanges combine ease of assembly, durability, efficient torque distribution, and standardized construction to deliver a safe, cost‑effective solution for complex hydraulic applications.

How to Use SAE Flange?

A complete SAE flange kit consists of a flat flange and an O-ring flange. The O-ring flange has a machined groove that accommodates a rubber O-ring, typically made of NBR. When assembled, this setup creates a seal by compressing the O-ring between the flat flange surface and the semi-circular groove on the opposing flange as bolts are tightened to draw the two halves together.

Installation process of SAE flanges

1. Preparation: Ensure that both mating surfaces are clean, free of debris and damage.

2. O‑Ring Placement: Carefully insert the appropriately sized O‑ring into the flange groove to provide a proper sealing surface.

3. Alignment: Align the flange with the mating component to ensure that bolt holes match perfectly.

4. Bolt Insertion: Insert bolts and washers through the corresponding bolt holes in a crosswise pattern.

5. Hand Tightening: Hand-tighten the bolts uniformly to seat the O‑ring without causing uneven pressure.

6. Torque Application: Use a calibrated torque wrench to tighten the bolts in diagonal sequence to the manufacturer’s specified torque.

7. Final Inspection: Inspect the assembled flange connection for proper alignment, seal integrity, and absence of leaks before putting the system into operation.

Applications of SAE flanges

• Industrial Hydraulic Systems: SAE flanges are used to connect pumps, valves, and actuators in heavy industrial machinery ensuring leak‑free performance.
• Mobile Hydraulics: They are widely applied in construction equipment, agricultural machinery, and other mobile hydraulic systems where vibration and shock resistance are critical.
• Aerospace Systems: SAE flanges provide reliable connections in aircraft hydraulic systems, contributing to safety and efficiency.
• Marine Applications: They are ideal for hydraulic systems in shipbuilding and offshore platforms, where corrosion resistance and durability are essential.
• Manufacturing and Process Industries: SAE flanges support reliable high‑pressure connections needed in complex manufacturing processes and automation.
• Automotive Systems: They are employed to join hydraulic components in automotive power steering and braking systems, ensuring precise fluid control.

Technical Specifications of SAE Flange

Below is the specification sheet of Jiayuan Hydraulics' Split Flange Clamps Code 61/62 FL/FS:

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The SAE split flange specification table of Jiayuan Hydraulics is shown below:

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Frequently Asked Questions

Q1: What are the differences between Code 61 and Code 62 SAE Flanges?

A: Code 61 flanges (often referred to as the 3000 series) are designed for moderate pressures, while Code 62 flanges (the 6000 series) are built to withstand higher pressures; the primary differences include variations in construction, bolt sizes, and pressure ratings.

Q2: Which materials are typically used for manufacturing SAE Flanges?

A: SAE flanges are generally made from carbon steels—such as ST52.3 or S355—as well as stainless steels (commonly AISI 304, 316L, or 316Ti) to provide the necessary strength, corrosion resistance, and durability in demanding hydraulic environments.

Q3: Can SAE Flanges be reused after disassembly?

A: Yes, if they are inspected and found to be undamaged, SAE flanges can be reused; however, components like O‑ring seals should be replaced to maintain the integrity of the connection.

Q4: What maintenance practices ensure the long‑term performance of SAE Flanges?

A: Regular inspections for leaks or damage, periodic re‑torquing of bolts to the recommended specifications, and timely replacement of seals or gaskets are essential for maintaining SAE flange performance.

Q5: How do I choose the right SAE Flange for my application?

A: Selecting the right SAE flange involves evaluating several key factors:

• Pressure Requirements
• Material Considerations
• Connection Type
• Design and Structural Configuration
• Seal and Face Design

For expert advice and a wide range of high-quality SAE flanges that meet international standards, we recommend Jiayuan Hydraulics. Their products are recognized for durability and reliability, making them a trusted partner in optimizing your hydraulic system’s performance.

Conclusion

In summary, SAE flanges provide a dependable solution for achieving leak‑free, high‑performance connections in hydraulic systems. Their standardized designs, diverse material options, and versatile configurations ensure that these components meet the rigorous demands of a wide range of applications—from industrial and mobile hydraulics to aerospace and marine systems. By understanding the types, installation processes, and key factors in choosing the right flange, engineers can enhance system reliability and streamline maintenance procedures.
For those seeking expert advice and high-quality products, Jiayuan Hydraulics stands out as a trusted partner in delivering durable, precision‑engineered SAE flanges that help keep your hydraulic systems running smoothly.

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