Rotary Joint for Thermal Oil

What Is a Rotary Joint?

A Rotary Joint (also known as a rotary union) is a device that enables the transfer of fluid—such as Rotary Joint for Thermal Oil—between stationary and rotating parts of machinery. When dealing with thermal oil, the rotary joint must be designed to handle high temperatures, thermal expansion, and pressurized fluid safely and reliably.

Purpose of a Rotary Joint for Thermal Oil

Rotary Joint for Thermal Oil systems are commonly used for indirect heating in industrial processes. A rotary joint for thermal oil allows this high-temperature fluid to flow into rotating equipment—such as heated drums, rolls, or dryers—without leaking or losing heat.

It ensures:

• Continuous rotation with fluid transfer
  
  


• High thermal resistance
  
  


• Leak-free sealing under extreme conditions
  
  

Operating Conditions

Parameter	Typical Range
Temperature	Up to 350–400°C (662–752°F)
Pressure	Up to 10–40 bar (145–580 psi)
Rotational Speed	0–200 RPM (higher speeds require cooling)
Media Compatibility	Synthetic or mineral-based thermal oil

Key Components

1. Housing/Body
   
   
   
   
   
   • Made from steel or cast iron, sometimes with insulation to prevent heat loss.
     
     
   
   
   
   


2. Rotating Shaft (Rotor)
   
   
   
   
   
   • Transfers rotary motion; must withstand thermal stress.
     
     
   
   
   
   


3. Sealing Mechanism
   
   
   
   
   
   • Mechanical seals or graphite-based seals designed for high temperatures.
     
     
   
   
   
   


4. Bearings
   
   
   
   
   
   • Either lubricated or bearing-less (for high-temp operation).
     
     
   
   
   
   


5. Siphon Tube (Optional)
   
   
   
   
   
   • Used in rotating drums to control fluid exit; common in dryers.
     
     
   
   
   
   

Types of Rotary Joints for Thermal Oil

1. Single-Flow Rotary Joint

• Thermal oil flows in and out through separate components (inflow only through the joint, return via siphon or another path).
  
  


• Common in rotating drums, rollers.
  
  

2. Dual-Flow Rotary Joint

• Inlet and outlet channels are both integrated in the joint using an internal tube system.
  
  


• Suitable for compact systems where space is limited.
  
  

3. Self-Supported vs. Bearing-Supported

• Self-supported: Mounted directly to the machine, often smaller in size.
  
  


• Bearing-supported: Includes internal bearings, better for higher loads or misalignment.
  
  

Applications

Rotary joints for thermal oil are critical in:

• Textile drying machines
  
  


• Plastic film calendering
  
  


• Paper machinery heated rolls
  
  


• Rubber mills
  
  


• Laminating and embossing rollers
  
  


• Chemical and pharmaceutical reactors
  
  

Material & Seal Selection

Choosing the correct material and sealing technology is essential:

Component	Typical Material Choices
Body	Cast iron, stainless steel
Shaft	Chrome-plated steel, stainless
Seal Faces	Carbon-graphite, ceramic, tungsten carbide
O-rings	Viton®, Kalrez®, or PTFE-based materials

High-temp graphite seals are often preferred for long life and thermal resistance.

Design Considerations

When selecting a rotary joint for thermal oil:

1. Thermal expansion – Materials and seals must accommodate large thermal deltas.
   
   


2. Flow rate – Should allow sufficient oil circulation for heating.
   
   


3. Orientation – Some joints are designed for horizontal mounting only.
   
   


4. Siphon requirements – For draining or circulating within rotating drums.
   
   


5. Cooling needs – Some joints require cooling systems to protect seals or bearings.
   
   

Maintenance Tips

• Check for seal wear regularly, especially in high-temp cycles.
  
  


• Use clean thermal oil to prevent clogging and carbon buildup.
  
  


• Inspect for external leaks around the seal or body.
  
  


• Allow proper thermal expansion space when installing.
  
  


• Follow manufacturer-recommended torque settings and alignment procedures.
  
  

Advantages of Using Rotary Joints for Thermal Oil

• Energy efficiency – Allows recirculation of heated oil
  
  


• Process consistency – Ensures uniform temperature across rotating components
  
  


• Space-saving – Especially dual-flow designs
  
  


• High safety – Reliable sealing under harsh thermal conditions
  
  

Conclusion

A Rotary Joint for Thermal Oil is a vital component in systems that require the transfer of heat through rotating machinery. It must be precisely engineered to handle the challenges of high temperature, pressure, and continuous movement without compromising safety or efficiency. Proper selection, installation, and maintenance of the joint ensure stable operation and long equipment life.