What is Internal Bore Welding (IBW)?

Article

Introduction to Internal Bore Welding (IBW)

Internal bore welding (IBW), sometimes referred to as inner bore welding, is an advanced welding technique that enables precision TIG welding from inside a tube or pipe joint. Originally developed over 50 years ago for shell and tube heat exchanger production, this method provides a superior alternative to traditional through-tube construction, ensuring a crevice-free, high-integrity joint.

Typical applications of IBW range across multiple industries, including power generation, aerospace, nuclear energy, and marine engineering. This technique is particularly beneficial for scenarios where access from the outside is restricted or where traditional welding methods may compromise joint integrity.

The Advantages of Internal Bore Welding

IBW offers several advantages over conventional through-tube construction:

Crevice-Free Joints: Ensures long-term reliability and minimises the risk of corrosion.
High-Pressure Resistance: Ideal for applications requiring robust joint integrity, such as feedwater heaters and steam condensers.
Precision and Consistency: Automated orbital welding systems ensure high repeatability and minimal defects.
Improved Structural Strength: By welding at the back face of the tube plate, IBW enhances the overall strength and longevity of the joint.e

Key Applications of IBW

Internal bore welding has been widely adopted in industries requiring high-quality, high-performance welded joints. Some notable applications include:

Power Generation: Essential for high-pressure feedwater heaters and steam condensers.
Aerospace and Aviation: Used to manufacture critical engine components requiring high precision.
Nuclear Energy: Employed in the construction of nuclear propulsion and fusion research equipment.
Industrial Heat Exchangers: Provides a robust solution for heat exchanger tube-to-tubeplate joints.

Joint Design Considerations for IBW

For successful IBW application, the tube plate must be prepared to a high level of precision with a machined groove around the hole, creating a small stub or upstand. This precision allows for a secure fit of the tube end into the tube plate, forming the basis for a strong and consistent weld.

Such detailed preparation also enhances accuracy throughout the welding process and creates the optimal conditions needed for achieving high-integrity welds. Proper tube-to-plate alignment is critical to ensuring the long-term performance of the welded joint.

IBW Weld Head Design and Functionality

A specialised IBW weld head is designed to position the tungsten electrode inside the tube bore while providing:

Rotational Drive: Enables precise movement of the electrode along the joint line.
Axial Positioning Adjustments: Allows fine-tuning for precise electrode to joint alignment.
Water Cooling: Essential for maintaining welding efficiency and to prevent overheating of low mass components in an aggressive thermal environment.

IBW Welding Process and Operator Training

As with all orbital welding applications, meticulous weld procedure development and operator training are critical for success. Cost-effective methods such as individual test pieces are used to minimise material waste and to produce weld samples. This approach allows for comprehensive testing, ensuring optimal welding performance before full-scale implementation.

IBW Welding Sequence and Methodology

The IBW process follows a systematic approach:

Weld Head Setting: The weld head is positioned within the tubeplate, and adjusted to ensure correct alignment between the electrode and the joint line. Key dimensions are recorded and the weld head removed before:

Tube Alignment and Positioning: The tube is carefully inserted and secured using axial clamping where necessary.
Borescope Inspection: Internal joint alignment is inspected and adjusted as needed.
Weld Head Positioning: The weld head is inserted for welding, taking into account any required joint offsets to ensure optimal positioning.
Welding: Backing gas/flux is applied to the joint OD and the welding sequence is executed using the Orbital TIG system.
Final Inspection: The weld is visually inspected internally and externally to confirm compliance with visual requirements. Additional pressure tests and NDT (non destructive testing) are completed in accordance with the project requirements.

Inspection and Quality Control

Ensuring weld quality is paramount, as access for defect repairs becomes challenging as construction progresses. Standard inspection techniques include:

Visual Inspection: Assessment of weld profile and surface appearance.
Dye Penetrant Inspection (DPI): Detects surface-breaking defects.
Pressure Testing: Individual tube loops undergo pressure testing as part of the QC process.

Why Choose Orbitec for Internal Bore Welding Solutions?

With over 40 years of experience in implementing the orbital welding process across a wide range of industries and applications, Orbitec delivers Internal Bore Welding (IBW) solutions tailored to meet diverse industrial needs. Our comprehensive expertise includes joint configuration, custom tooling, procedural development, operator training, and strict quality assurance, ensuring the highest standards in orbital welding.

For more information on our IBW solutions, contact Orbitec at info@orbitecuk.com or call +441332 296193