Vacuum Circuit Breaker Bellows Assembly for Gas Insulated Switchgears (GIS)

Bellows and expansion joints are critical components in Gas Insulated Switchgears (GIS) / High Voltage Circuit breakers, especially in systems using SF6 (Sulfur Hexafluoride) gas due to its superior insulating and arc-quenching properties. Among these, the bellows assembly plays a vital role in ensuring mechanical flexibility, pressure containment, and operational reliability in vacuum circuit breakers.

Pliant Bellows has extensive experience and technical expertise in the design and manufacturing of bellows assemblies specifically tailored for SF6 circuit breakers. These assemblies are designed to perform in high-voltage environments, enduring repeated mechanical movements and pressure fluctuations while maintaining gas tightness and structural integrity.

Main Components of the Bellows Assembly:

• Transmission Shaft
  • Material: SS304 / 304L / 316 / 316L / 321
  • Selected based on customer requirements and application-specific factors such as corrosion resistance, mechanical strength, and temperature range.
  • Precision-machined to ensure seamless integration with bellows and flanges.


• Metallic Bellows
  • Material: SS304 / 304L / 316 / 316L / 316Ti / 321
  • Designed to absorb axial, lateral, and angular movements resulting from circuit breaker operations.
  • Engineered for high fatigue life and superior flexibility under repeated cycling.


• Welding Flange (for Bellows & Shaft Integration)
  • Material: SS304 / 304L / 316 / 316L / 321
  • Enables secure and leak-proof joining of the bellows to the transmission shaft.
  • Ensures compatibility with SF6 gas environment and high-pressure operation.


• Mounting Flange with O-ring Groove
  • Material: SS304 / 304L / 316 / 316L / 321
  • Features a precision-machined groove to accommodate an O-ring for enhanced sealing.
  • Facilitates easy installation into the switchgear assembly while maintaining a gas-tight environment.

Manufacturing and Quality Assurance:

• All components are fabricated and assembled in an ISO 3834-2 certified facility, ensuring high-quality welding standards and traceable manufacturing processes.


• Welding Process:
  • Conducted using automated TIG welding with Argon gas or advanced laser welding techniques.
  • Weld joints are ultrasonically cleaned prior to welding to eliminate contamination.
  • Special care is taken to strengthen joints to withstand mechanical shocks and vibrations during circuit breaker operation.


• Design Validation:
  • Every design is tested for durability using an in-house cycle life testing machine, simulating real-world operational stresses.
  • Designs are verified in compliance with EJMA 10 (Expansion Joint Manufacturers Association) standards to ensure long-term performance and safety.

Testing & Inspection:

• To ensure leak-proof and reliable performance, each bellows assembly undergoes rigorous testing, including:
• 100% Pneumatic Testing (Air Bubble Test):
  • Performed at 2 bar pressure in a submerged water tank to visually detect any leaks or defects.


• Optional Testing Based on Customer Request:
  • Hydrostatic Pressure Testing – Verifies structural strength and pressure retention capability.
  • Helium Leak Detection Testing – Highly sensitive method for detecting minute leaks and ensuring gas-tight performance, especially critical for SF6 containment.

Why Choose Pliant Bellows for Your SF6 Circuit Breaker Needs?

• • Custom Bellows Manufacturing to match your exact specifications
• • Wide material options for shaft, bellows, and flanges
• • Precision welding and assembly in certified facilities
• • Trusted by OEMs and utilities worldwide
• • Proven design validation and long cycle life