How to Choose the Right Split Flange for Your System

Choosing the correct split flange is a critical step in designing or maintaining any hydraulic, pipeline, or fluid power system. A poor selection can lead to system failure, costly downtime, and safety hazards. But with a wide range of types, materials, pressure ratings, and connection styles available, how do you select the right split flange for your specific application? 

In this guide, we’ll walk you through everything you need to know, from what a split flange is to the key factors you need to consider when choosing one. Whether you're working with high-pressure hydraulics or low-pressure fluid systems, this article will help ensure you're making a well-informed decision.

What Is a Split Flange?

A split flange is a two-piece flange assembly commonly used to connect hydraulic lines or piping systems. Instead of being a solid ring like traditional flanges, a split flange consists of two halves that clamp around a fitting and bolt together, securing the connection.

Split flanges are especially useful in systems where:

• Space is limited

• Access to the end of the pipe is restricted

• Retrofitting or maintenance needs to be done without disassembling the system

Benefits of Split Flanges

• Easy Installation & Disassembly – Perfect for tight spaces where welding or rotating pipes is not practical.

• High Pressure Tolerance – Most split flanges are designed to handle high-pressure hydraulic or pneumatic applications.

• Reusability – Split flanges can often be reused after disassembly, reducing long-term costs.

• Leak Prevention – When paired with an O-ring face seal, split flanges offer excellent leak protection in fluid systems.

Key Applications of Split Flanges

Split flanges are used across industries, including:

• Hydraulic systems in construction and agricultural equipment

• Offshore and marine applications

• Oil & gas pipelines

• Power plants and utilities

• Aerospace and defense systems

• Manufacturing plants

Types of Split Flanges

When choosing the right split flange, understanding the different types is the first step.

1. SAE Split Flanges (Code 61 / Code 62)

• Code 61: Medium pressure, up to 3,000 PSI

• Code 62: High pressure, up to 6,000 PSI

These are standardized by the SAE J518 and are widely used in hydraulic systems.

2. Square Flanges (JIS B 2291)

Common in Asian markets, especially Japanese machinery. Typically used in lower pressure hydraulic systems.

3. ISO 6162 Flanges

These follow international standards and are compatible with many global OEM systems.

Factors to Consider When Choosing a Split Flange

Choosing the wrong split flange can lead to leaks, damage, pressure failure, or misalignment. Below are the most critical factors you must evaluate:

1. System Pressure Rating

Split flanges come with pressure ratings that must match or exceed your system’s maximum operating pressure.

• Low-Pressure Systems: Typically under 500 PSI. A basic square or light-duty split flange may suffice.

• Medium-Pressure Systems: 500–3,000 PSI. Code 61 flanges are commonly used here.

• High-Pressure Systems: 3,000–6,000 PSI and above. Code 62 flanges are recommended.

Tip: Always factor in surge pressure or pressure spikes that might exceed normal operating pressure.

2. Material Compatibility

The flange material must be compatible with:

• The fluid type (hydraulic oil, water, chemicals, etc.)

• The environmental conditions (corrosion, temperature, vibration)

Common Split Flange Materials:

• Carbon Steel: Standard for hydraulic applications

• Stainless Steel: Ideal for corrosive or marine environments

• Aluminum: Lightweight, suitable for low-pressure systems

• Ductile Iron: Offers strength and resistance to cracking

3. Seal Type

Split flanges typically use O-ring face seals (ORFS). Choosing the correct O-ring material is crucial for system integrity.

Always match the seal material to the fluid's chemical properties and operating temperature.

4. Flange Size and Port Compatibility

Ensure the flange dimensions (bolt hole spacing, diameter, thickness) match the port size on the pipe, hose, or manifold. Use manufacturer or SAE J518 size charts to cross-reference dimensions.

5. Bolt Strength and Torque

Bolts secure the split flange halves together. If under-torqued or mismatched in grade, they can lead to leakage or failure.

• Always use high-tensile bolts (typically Grade 8 or 10.9)

• Follow the manufacturer’s recommended torque specs

• Use locking washers or thread locking compounds to prevent loosening under vibration

6. Environmental Conditions

Think beyond pressure and fluid compatibility. Consider:

• Corrosive environments (e.g., saltwater)

• Temperature extremes

• Vibration or dynamic load

• Ease of access for maintenance

These factors influence whether you choose stainless steel over carbon steel or add protective coatings such as zinc plating or black oxide.

Step-by-Step Guide to Selecting a Split Flange

Here’s a simplified process you can follow:

1. Define your application (fluid type, system pressure, temperature)

2. Identify your port/fitting standard (SAE J518, ISO 6162, JIS B2291)

3. Measure port size and required flange dimensions

4. Choose the right pressure-rated flange (Code 61 or Code 62)

5. Select appropriate material and seal type

6. Verify bolt type and torque specs

7. Ensure environmental suitability (coatings, corrosion resistance)

8. Order from a reputable supplier with certifications (ISO 9001, etc.)

Common Mistakes to Avoid

• Mixing Code 61 and Code 62 flanges — They may look similar but are not interchangeable.

• Using incorrect bolt torque — Leads to leakage or flange cracking.

• Skipping seal compatibility checks — A mismatched O-ring can fail quickly.

• Underrating system pressure — Always account for potential spikes or surges.

• Ignoring material corrosion resistance — Especially in marine or chemical environments.

Conclusion

Choosing the right split flange is about more than just matching size—it's about understanding the entire system, from pressure ratings and environmental conditions to material and seal compatibility.

A well-chosen flange will ensure:

• Reliable sealing

• Easy maintenance

• Long service life

• Safety and regulatory compliance

When in doubt, consult with flange or hydraulic system experts, or choose suppliers that offer technical support and custom engineering assistance.

Need help selecting the right flange for your hydraulic system?

DIKAI offers a wide range of Code 61 and Code 62 split flanges in carbon steel, stainless steel, and specialty materials. Contact our technical support team or download our free flange selection chart today!