Welcome to My Blog!
Before we dive into the content, if you’re interested in our products or have any questions, please feel free to visit our Contact Us page on the website. Our team is ready to assist you with inquiries, orders, or any support you may need.
Now, let’s get started on our journey together. I hope you find the content here insightful, engaging, and valuable.
Table of Contents
Introduction
Rotary unions play a critical role in fluid and gas transfer between rotating and stationary components in various industrial systems. Whether in high-pressure hydraulic systems, steam applications, or chemical processing, rotary unions ensure smooth fluid transmission without leakage, even under high stress and extreme conditions. However, choosing the right rotary union for a specific application can be challenging due to the variety of types and materials available. In this 2025 guide, we’ll provide you with essential information on rotary unions, their types, uses, and expert selection tips to help you make the right choice for your needs.
What Are Rotary Unions?
Basic Definition
A rotary union is a device that allows the transfer of fluid or gas between stationary and rotating parts, maintaining continuous flow despite rotation. It typically connects a rotating shaft or drum to a fluid supply line. Rotary unions are designed to withstand various temperatures, pressures, and rotational speeds while ensuring leak-free performance.
Key Components Explained
A rotary union consists of several key components:
- Rotor: The rotating part that allows the transfer of fluid or gas.
- Stator: The stationary part that connects to the supply line.
- Seals: Prevent leakage and maintain pressure.
- Bearings: Support the rotor and reduce friction.
- Passages: Channels through which fluid or gas flows.
How Rotary Unions Work
Flow Path & Sealing Principle
The fluid or gas flows through the stationary part of the rotary union (the stator) and enters the rotating rotor. The sealing mechanism between the rotor and stator prevents leaks, ensuring a continuous and smooth flow of the medium as the rotor turns. The seals are designed to handle varying pressures, temperatures, and rotational speeds, providing an efficient transfer of fluids or gases.
Single vs Multi-Passage Designs
Rotary unions can be designed with a single passage or multiple passages.
- Single-Passage: Best for simpler applications with a single flow medium, such as hydraulic systems.
- Multi-Passage: Used for complex applications requiring the transfer of multiple fluids or gases simultaneously, such as in plastic injection molding machines or CNC machine tool spindles.
Main Types & Materials
High-Temperature Steam Unions
Heating end dedicated rotary joint
Anti-spherical seal design 2. Graphite or antimony-impregnated graphite seal materials as standard 3. Dual oil-free bearing support 4. Maximum support spacing 5. Extended seal life and reliability 6. Easy to replace 7. Rotating or fixed siphon equipment
| Specifications | |
| Maximum speed | 120RPM |
| Maximum temperature | 120℃ |
| Maximum pressure | 1.5MPa |
| Applicable media | Steam, hot water |
High-temperature steam rotary unions are designed to handle steam at elevated temperatures and pressures, making them essential in industries like power generation, chemical processing, and food production. Constructed from materials like stainless steel or titanium, they ensure minimal leakage and maximum durability under harsh conditions.
High-Pressure Hydraulic Unions
High pressure metallurgy special rotary joint
Special series cooling, bottom blowing, top blowing, large ladle turntable rotary joint, Adaptable from 20 tons to 350 tons converter, Adaptable from single water cooling to nitrogen and hydrogen system, Single channel to more than 30 channels
| Specifications | |
| Maximum speed | 50RPM |
| Maximum temperature | 80℃ |
| Maximum pressure | 32.5MPA |
| Applicable media | Water, ethylene glycol, hydraulic oil |
High-pressure hydraulic rotary unions are built to manage intense pressures, commonly found in manufacturing and aerospace industries. Made with robust materials such as hardened steel, these unions are engineered for fluid power applications that require consistent performance under extreme pressure and temperature conditions.
Corrosion-Resistant Chemical Unions
These rotary unions are designed for industries handling aggressive chemicals, acids, or solvents. Using corrosion-resistant materials like titanium or specialized alloys, they offer excellent durability and leak protection. They are ideal for chemical processing, pharmaceutical production, and other environments where fluid and gas contamination risks are high.
Industrial Applications
Plastic Injection Molding
In plastic injection molding, rotary unions facilitate the transfer of cooling water or other fluids to rotating molds during the injection process. The union’s ability to prevent leakage is crucial in ensuring product quality and reducing downtime, making them indispensable in high-volume plastic manufacturing operations.
Paper Drying Cylinders
High-speed paper machine special rotary joint
Balanced seal design Multi-spring seal compensation mechanism Floating seal technology Imported antimony-impregnated seal package Weighted cantilever fixed siphon High-strength overall horizontal sheath tube Maintenance-free design High reliability and long life Suitable for all types of high-speed wide-width paper machines
| Specifications | |
| Maximum speed | 2000RPM |
| Drying cylinder width | <7000mm |
| Shaft head inner diameter | <90mm |
| Drain pressure difference | <0.15bar |
Rotary unions are used extensively in the paper industry for steam transfer into drying cylinders. These unions enable controlled steam flow for efficient moisture removal from paper sheets during production. Designed to withstand high temperatures and maintain constant pressure, they contribute to smoother, faster drying processes in paper mills.
CNC Machine Tool Spindles
CNC spindle water outlet rotary joint
Single channel coolant or MQL Closed seal, automatic line-like applications Full flow design, no debris and hair to clog Bearing support with threaded rotor for easy installation Deep groove ball bearings for smooth operation Labyrinth system and large leakage port to protect ball bearings Balanced mechanical seal made of silicon carbide Long service life even in harsh operating environments Anodized chrome housing for corrosion protection
| Specifications | |
| Maximum speed | 5000RPM |
| Maximum temperature | 70℃ |
| Maximum pressure | 11MPa |
| Applicable media | Coolant |
In CNC machining, rotary unions provide cooling fluids and lubricants to the rotating spindles of the machine. These unions help maintain optimal cutting conditions, extend tool life, and reduce wear and tear on the machine components. The selection of durable, high-performance rotary unions is vital to maintain precision and reduce maintenance costs.
Step-by-Step Selection Tips
Define Media, Pressure & Temperature
Selecting the right rotary union starts with understanding your system’s media, operating pressure, and temperature. Whether you’re transferring hydraulic fluids, steam, or chemicals, knowing these parameters helps determine the right material and sealing technology needed to ensure efficient and leak-free operation.
Port Size & Connection Type
Choosing the correct port size and connection type is crucial for seamless integration into your system. Rotary unions come with various connection options such as flanged, threaded, or quick-connect. Proper sizing and compatibility are essential to avoid leakage and ensure consistent fluid flow through the union.
Maintenance Access & Seal Life
Consider maintenance access and seal life when selecting a rotary union. Opt for unions that allow for easy maintenance and seal replacements. Longer-lasting seals made from high-performance materials, such as graphite or carbon, will reduce maintenance intervals and increase the overall efficiency of your system.
Installation & Maintenance
Alignment & Torque Best Practices
Proper installation and alignment are key to ensuring the rotary union operates effectively and lasts longer. Alignment should be within specified tolerances, and the torque applied during installation must meet the manufacturer’s recommendations to avoid damaging seals and components. Misalignment can lead to premature wear and leaks.
Common Problems & Quick Fixes
Leaks & Troubleshooting
Leaks are the most common problem with rotary unions and are often caused by worn seals, improper installation, or using the wrong materials. Regularly check seals for wear, inspect connections for damage, and ensure that the union is properly aligned. Replacing seals and tightening connections promptly can solve most leak issues.
Overheating Solutions
Overheating can occur when the rotary union fails to handle the required temperature or when fluid flow is restricted. Solutions include ensuring proper lubrication, using seals designed for high-temperature applications, and optimizing flow rates. Regular monitoring of system temperatures will help detect early signs of overheating.
2025 Product Spotlight
New Compact Multi-Passage Series
Our 2025 compact multi-passage rotary union series is engineered for applications with limited space but high fluid transfer requirements. This advanced design allows simultaneous fluid handling through multiple passages while maintaining a small footprint. It is ideal for tight installations without sacrificing performance.
Free Selection
To simplify the process of selecting the right rotary joint for your application, please fill out your requirements in the form below. Upon receipt, we will guide you through the selection process based on key parameters such as medium type, pressure, temperature, and connection type, making it easier than ever to find the ideal product for your system.
Conclusion
Selecting the appropriate rotary unions requires understanding your system’s media, pressure, temperature, and application requirements. Proper selection, installation, and maintenance are critical for achieving optimal performance and service life. Modern Sealing offers a wide range of high-quality, customizable rotary unions for various industrial applications. Contact us today for a free consultation to ensure you select the rotary union that best meets your needs.
FAQ
How do I choose the right rotary unions for my application?
To choose the right rotary union, define the type of media, pressure, temperature, and flow rate required. Also, consider your system’s space constraints and the connection type. Our selection guide and calculator can help you make the right choice.
Can rotary unions handle both high-pressure and high-temperature applications?
Yes, rotary unions can be designed to handle both high-pressure and high-temperature applications. Ensure you select materials and seals that are compatible with your system’s operating conditions.
What maintenance is required for rotary unions?
Routine maintenance includes regular inspections for leaks, replacing seals as needed, and ensuring proper lubrication. Regular checks can extend the life of your rotary union and prevent unexpected downtime.
Latest News
Insights & Innovation
