I have worked extensively with hydraulic and piping systems, and I find that split flanges are an unsung hero in making maintenance fast, safe, and reliable. These mechanical fittings are essential components in industries where piping downtime must be minimized. In this guide, I’ll walk you through their origins, design variations, technical standards, and real-world performance—everything you need to know.
1. History & Evolution
Split flanges emerged during the mid‑20th century when hydraulic technology surged in industries like oil and gas, construction, and agriculture. Engineers sought ways to avoid welding or cutting pipelines for flange replacement. The result was a two-piece flange that could be installed around existing piping—dramatically reducing maintenance time. Over time, various designs (e.g., lap‑joint, ring‑type joint, Van Stone) evolved to serve different pressure, temperature, and alignment needs.
2. Technical Overview
Definition
A split flange is a flange assembly divided into two halves, bolted together to encircle an existing pipe or hose fitting. This design allows installation or replacement without disconnecting the remainder of the system.
Types
Here are the common split flange types:
-
Lap‑Joint Split Flange: A loose backing flange used with a stub end; offers easy alignment.
-
Ring‑Type Joint (RTJ) Split Flange: Uses a metal ring gasket for high‑pressure, high‑temperature sealing.
-
Van Stone Split Flange: A loose flange that spins at the pipe end, accommodating misalignment.
-
ANSI/B16.5 Split Flange: Complies with American flange standards—interlocked in two halves.
-
CAT‑Style Split Flange: Designed for Caterpillar hydraulic fittings with special geometry.
Standards & Specifications
Split flanges are commonly governed by standards like:
-
SAE J518 / ISO 6162 (Code 61 & Code 62) for hydraulic flanges.
-
SAE J2593 for bolt torque values.
-
ANSI B16.5 for pipe flanges.
Environmental durability, metallurgy, and pressure-temperature ratings follow ASTM/ASME norms.
3. Materials & Design Considerations
Material selection dictates durability, corrosion resistance, and pressure capability:
-
Carbon Steel: Affordable and strong, often coated for corrosion protection.
-
Stainless Steel (e.g., SS316): Ideal for harsh, chemical, or food‑grade environments.
-
Alloy Steels: For specialized, high‑temperature applications.
-
Plastic/Nylon: Used in low-pressure systems requiring corrosion resistance.
-
Seals & Gaskets: Typically NBR (Buna‑N), Viton optional for higher temperatures.
4. Installation & Maintenance
Selection Process
Choose the right items by evaluating:
-
Pressure rating: Code 61 (up to ~5,000 psi), Code 62 (~6,000 psi depending on size).
-
Temperature: Consider derating for higher temps per material specs .
-
Bolting patterns & torque specs: Follow SAE J2593 and ISO guidelines.
Torque & Sealing
Proper torque is critical:
-
Torque ranges (ft‑lb) for Code 61: 32–77; Code 62: 46–208.
-
Use O-rings (NBR, Viton) rated for your fluid and temperature.
-
Lubricate threads and sealing surfaces with recommended fluid to prevent galling.
5. Comparative Table
| Feature | Lap‑Joint | RTJ | Van Stone | ANSI Split Flange | CAT‑Style |
|---|---|---|---|---|---|
| Alignment Ease | ★★★★★ | ★★★★☆ | ★★★★★ | ★★★★☆ | ★★★★☆ |
| Pressure Rating | Moderate | Very High | Moderate | Moderate–High | High |
| Pressure Capability | ≤5,000 psi |
|
≤4,000 psi | Per ANSI spec | Per hydraulic theory |
| Install/Remove Ease | Very Easy | Moderate | Very Easy | Moderate | Moderate |
| Cost | Medium | Higher | Medium | Low–Medium | Medium |
| Common Use | Maintenance-heavy | Oil & gas, petro | Thermal/vibration | General piping | CAT equipment |
6. Case Study: Petrochemical Plant Retrofit
Background:
A petrochemical facility in Texas suffered frequent flange leaks during hot crude transfers. Shutdowns were costly—exceeding $50,000 per hour.
Solution:
We replaced existing weld-neck flanges with RTJ split flanges (SAE J518, Code 62) around the transmission lines. Custom machined RTJ rings and SS316 flanges were delivered in situ, allowing retrofit without cutting piping.
Outcome:
-
Downtime reduced by 60%.
-
Leak incidents dropped to zero in 24 months.
-
ROI achieved within 8 weeks.
7. Industry Applications
Split flanges are found in:
-
Industrial Hydraulics: Behind hydraulic presses, industrial presses.
-
Oil & Gas: High-pressure pipelines and maintenance-heavy loops.
-
Marine: Corrosion-resistant pipe joints on vessels.
-
HVAC: Connections for chillers and steam lines.
-
Automotive: In exhaust systems and hydraulic circuits.
8. Benefits & Limitations
Benefits:
-
Fast maintenance: No need to cut/weld existing pipes.
-
Leak prevention: O‑ring or RTJ seals ensure reliability.
-
Labor savings: Fewer specialists required.
-
System continuity: Avoids removing other components.
Limitations:
-
Cost premium: Higher than weld‑neck flanges.
-
Bolting access: May be restricted in cramped areas.
-
Gasket care: Improper torque or reuse may cause leaks.
9. Common Issues & Troubleshooting
-
Uneven torque: Causes sealing failure. Use torque wrenches and follow bolt sequence.
-
Incorrect O‑Ring: Leads to degradation. Match material to fluid and temperature.
-
Misalignment: Bolt holes misalign if dimensions mismatch.
-
Surface damage: Scratch or burr disables seal—inspect surfaces carefully.
10. Frequently Asked Questions
Q1. What is a split flange used for?
A split flange joins existing piping or hoses without cutting. Two halves clamp around a fitting or stub end, then sealed with O‑ring or gasket. Ideal for timely maintenance and retrofit.
Q2. What’s difference between SAе Code 61 and 62?
Code 61 handles up to ~5,000 psi; Code 62 up to ~6,000 psi depending on size. Code 62 has thicker metal and larger bolt diameter.
Q3. How do I torque split flange bolts?
Use manufacturer torque table. For Code 61/62, torque ranges from 32 to 208 ft‑lb depending on size and bolt grade . Lubricate threads before tightening and follow a crisscross pattern.
Q4. What material should I select: carbon vs stainless steel?
For general hydraulic use, carbon steel with coating is adequate. For corrosive or hygienic environments, 316 stainless steel is recommended.
Q5. Can I replace an RTJ flange with a lap‑joint flange?
Not directly. RTJ is for very high pressure and uses metal gasket. Swapping to lap‑joint reduces pressure rating and requires piping adjustment for bolt patterns.
11. Conclusion
As a hydraulic systems specialist, I appreciate split flanges’ impact on operational efficiency. They combine robustness with simplicity. Whether it’s lap‑joint for fast maintenance, RTJ for extreme conditions, or Van Stone for thermal movement—they are indispensable. With correct materials, precision, and torque control, split flanges are a long‑term, cost‑effective solution.
EN 
AR