Stainless Steel SAE Flange Components (Code 61 & Code 62)

Understanding Stainless Steel SAE Flange Fittings (Code 61 & Code 62): A Guide

Stainless Steel SAE Flange fittings (SAE J518 / ISO 6162) represent the premium choice for high-pressure hydraulic connections in environments demanding maximum corrosion resistance and durability. Available in both Code 61 (Standard Duty) and Code 62 (Heavy Duty) pressure ratings, these fittings combine the robust, large-bore connection capability of the SAE flange system with the superior material properties of stainless steel (typically Grade 316 SS).

Core SAE Flange Sealing Principles

The fundamental design relies on:

• O-Ring Face Seal: A captive O-ring seated in a groove on the flat face of the flange head creates the primary seal when compressed against a smooth port surface.
• Bolted Connection: Four high-strength bolts (typically stainless steel bolts for stainless flanges) pass through split flange halves (or a captive flange) to clamp the flange head securely to the mating port, providing mechanical strength and generating the force needed to compress the O-ring.
• Code 61 vs. Code 62: Code 62 uses a thicker flange head, larger bolt diameter, and wider bolt spacing compared to Code 61 for the same nominal size, allowing it to handle significantly higher pressures (up to 6000 PSI). Code 61 is rated for lower, though still substantial, pressures (3000-5000 PSI depending on size). Components are NOT interchangeable between codes.

Advantages of Stainless Steel Flanges

Using stainless steel provides significant benefits over standard plated carbon steel flanges:

• Ultimate Corrosion Resistance: Essential for marine, offshore, subsea, chemical processing, food/beverage, and pharmaceutical industries where saltwater, aggressive chemicals, or sanitary conditions preclude carbon steel. 316 SS offers excellent protection against pitting and crevice corrosion.
• High Pressure & Temperature Capability: Combines the high-pressure strength of the flange design (especially Code 62) with the wide operating temperature range of stainless steel.
• Chemical Compatibility: Suitable for a vast array of process fluids and chemicals.
• Longevity in Harsh Environments: Significantly extends the service life of connections exposed to corrosive elements.
• Hygienic Properties: Meets requirements for sanitary applications.
• Robust & Reliable Seal: Retains the excellent leak resistance of the O-ring face seal design under demanding conditions.

Common Stainless Steel Grade

• Grade 316 (SS316 / UNS S31600): The standard choice for stainless steel hydraulic flanges due to its superior corrosion resistance, particularly against chlorides, thanks to its molybdenum content.

Considerations for Stainless Steel Flanges

• Higher Cost: Stainless steel components (flanges, bolts) are substantially more expensive than their carbon steel equivalents.
• O-Ring Selection: The O-ring material must be compatible with the system fluid, temperature, and pressure. For stainless steel applications, **Viton® (FKM) O-rings (OFL2 Series)** are typically recommended due to their better temperature and chemical resistance compared to standard Buna-N (OFL1 Series).
• Torque Criticality: Correct and even bolt tightening using a torque wrench and a cross pattern is vital to ensure uniform O-ring compression and prevent flange distortion or leaks. Torque values for stainless bolts may differ slightly from steel bolts.
• Port Requirements: Still requires a precisely machined flat port face with the correct tapped bolt pattern (Code 61 or Code 62).

Common Applications

Stainless Steel SAE Flanges are specified for the most demanding high-pressure hydraulic connections:

• Offshore Oil & Gas Platforms: Resisting corrosive seawater and process fluids under high pressure.
• Marine Hydraulic Systems: Deck machinery, steering systems, ballast systems on ships and submarines.
• Chemical Processing Plants: Handling corrosive materials in high-pressure reactors and piping.
• Pharmaceutical & Food Processing: Hygienic, corrosion-resistant connections for high-pressure processing lines.
• Subsea Equipment: ROVs, underwater tools, and installations requiring maximum durability.
• Desalination Plants: Handling high-pressure saltwater.
• Pulp & Paper Mills: Resisting corrosive processing chemicals.

Installation Best Practices

• Verify All Components: Ensure flange head, split halves, bolts, washers, and O-ring are the correct size, code (61/62), and appropriate stainless steel grade/material. Use stainless steel bolts and washers.
• Clean Meticulously: All sealing faces, O-ring grooves, O-rings, and threads must be perfectly clean.
• Inspect & Lubricate O-Ring: Check O-ring (preferably Viton®) for damage. Apply compatible lubricant.
• Lubricate Bolt Threads: **Crucially, apply a suitable anti-seize lubricant** to the threads of the stainless steel bolts to prevent galling during tightening.
• Assemble Components: Seat O-ring, position flange head against port, place split halves, insert bolts/washers.
• Tighten Bolts Evenly & Incrementally: Snug bolts lightly by hand. Use a calibrated torque wrench to tighten bolts progressively in a diagonal/cross pattern to the specified torque value for the size, code, and bolt grade. Multiple passes may be needed to achieve even clamping.
• Check for Leaks: Test thoroughly after system pressurization.

Stainless Steel SAE Flange fittings offer the highest level of reliability and durability for critical high-pressure hydraulic connections in corrosive or demanding environments. Delphi Fittings provides quality stainless steel flange components to meet these rigorous industry needs.