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Burhani Engineering Technolog
Burhani Engineering Technolog

Flat Bottom Vacuum box for testing butt welds on flat surfaces

Bubble leak testing of tank bottom plate welds and shell to bottom plate welds

In the realm of welding, the quality and integrity of welding are paramount. Whether in the construction of pipelines, pressure vessels, or structural steel, the assurance of flawless butt welds is critical. To achieve this, rigorous testing methods are employed, and one tool that stands out is the flat bottom vacuum box. In this comprehensive guide, we will delve into the world of flat bottom vacuum boxes for testing butt welds on flat surfaces, exploring their benefits, various applications, setup techniques, and essential tips to ensure accurate and reliable weld inspections.

The Burhani Engineering Technology vacuum box has been designed for the operators according to API 650/653 recommendations. Bubble leak or vacuum box testing is an integral part of tank inspections as required by the American Petroleum Institute (API) and other international standards associations to establish the condition of tank bottom plate welds and shell-to-bottom plate welds.

Burhani Engineering Technolog Understanding Flat Bottom Vacuum Boxes in Weld Testing

Flat bottom vacuum boxes are specialized tools used in non-destructive testing (NDT) to assess the quality of butt welds, primarily on flat surfaces. These boxes create a sealed chamber over the weld joint, allowing for the application of a vacuum to create a pressure differential. By introducing a liquid (typically a dye penetrant or soapy solution) onto the weld surface, any defects or discontinuities in the weld will become visible as the liquid is drawn into the imperfections. This process, known as vacuum box testing, is an effective means of identifying weld defects, such as cracks, porosity, or lack of fusion.

The Benefits of Using Flat Bottom Vacuum Boxes for Weld Testing

1. High Sensitivity to Defects: Vacuum box testing is highly sensitive and can detect even minute defects in welds, ensuring the highest level of quality control.
2. Non-Destructive: Vacuum box testing is a non-destructive testing method, meaning it does not alter or harm the weld in any way. This allows for repeated inspections without compromising the integrity of the welded joint.
3. Versatile Application: Flat bottom vacuum boxes are adaptable to a wide range of flat surface welds, making them suitable for various industries, including construction, manufacturing, and infrastructure.
4. Cost-Effective: Vacuum box testing is a cost-effective means of weld inspection, as it does not require expensive equipment or materials.
5. Quick Results: This testing method provides immediate results, allowing for prompt decision-making and necessary repairs or modifications.
6. Reduces Rework: By identifying defects early in the welding process, vacuum box testing helps reduce the need for costly rework and ensures weld quality from the outset.
7. Enhanced Safety: Ensuring the integrity of welds through testing with vacuum boxes is vital in industries where safety is a top priority, such as the petrochemical and nuclear sectors.

Applications of Flat Bottom Vacuum Boxes in Weld Testing

Flat bottom vacuum boxes find applications in a range of industries, including:
1. Petrochemical: Vacuum box testing is extensively used in the petrochemical industry to assess welds on storage tanks, pipelines, and other critical equipment.
2. Construction: Welded connections in structural steel and buildings benefit from vacuum box testing to ensure their integrity and safety.
3. Manufacturing: Vacuum box testing is applied in the manufacturing of pressure vessels, heat exchangers, and various industrial equipment.
4. Infrastructure: The construction of bridges, tunnels, and other infrastructure relies on the quality of welds, which can be verified using vacuum box testing.
5. Shipbuilding: Shipbuilders use vacuum box testing to inspect welds on ship components, ensuring seaworthiness and safety.
6. Aerospace: Vacuum box testing is applied in the aerospace industry to assess welds in aircraft components, where the highest level of quality and safety is imperative.

Setting Up Your Flat Bottom Vacuum Box for Weld Testing

Proper setup and operation of your flat bottom vacuum box are crucial for accurate weld inspections. Follow these steps to set up your vacuum box:
1. Select the Right Vacuum Box: Choose a vacuum box that suits the size and type of welds you intend to inspect. Ensure it has a flat bottom design to match the surfaces you will be testing.
2. Safety Precautions: Always prioritize safety when working with weld testing equipment. Wear appropriate personal protective equipment, such as gloves and safety glasses, and ensure proper ventilation in your workspace.
3. Prepare Your Weld Surface: Ensure the weld surface is clean and free from contaminants, including oil, grease, and rust.
4. Prepare the Liquid Solution: Depending on the application, prepare the appropriate liquid solution for use in the vacuum box. This may be a dye penetrant for weld inspections.
5. Position the Vacuum Box: Place the flat bottom vacuum box over the weld joint, ensuring it forms a sealed chamber. Seal any gaps or openings to prevent air leakage.
6. Connect the Vacuum Source: Attach a vacuum source to the vacuum box. Ensure that the vacuum source is capable of creating the necessary pressure differential.
7. Start the Vacuum Pump: Turn on the vacuum pump and create a pressure differential within the vacuum box. This will draw the liquid solution onto the weld surface.
8. Inspect for Defects: Carefully examine the surface for indications of defects, such as cracks, porosity, or lack of fusion. These will appear as dark lines or areas on the surface where the liquid has been drawn in.
9. Document Findings: Record and document any defects found during the inspection, including their location and size.
10. Cleaning and Reuse: After completing the inspection, clean the vacuum box thoroughly and ensure it is ready for future use.

Tips for Accurate Weld Testing with Flat Bottom Vacuum Boxes
To ensure precise and reliable weld testing using flat bottom vacuum boxes, consider the following tips:
1. Calibration: Regularly calibrate your vacuum box to maintain accuracy in defect detection.
2. Proper Liquid Application: Ensure that the liquid solution is evenly applied to the weld surface to prevent false indications.
3. Surface Preparation: Thoroughly clean and prepare the weld surface before testing to avoid contaminants affecting the inspection.
4. Pressure Differential: Monitor and maintain the correct pressure differential in the vacuum box to ensure consistent and accurate results.
5. Careful Inspection: Conduct a meticulous visual inspection, and if defects are found, follow up with appropriate repairs or further testing as needed.
6. Training: Ensure that personnel conducting the testing are trained and experienced in vacuum box testing procedures to maximize accuracy.
7. Documentation: Keep detailed records of weld inspections, including photographs and reports, for quality control and future reference


  • Designed to API 650/653 recommendations
  • 750 mm (29.53 in) weld inspection length, improves inspection times and reduces operator fatigue
  • Integrated LED lights provide the required light intensity as specified by API and ASME inspection standards
  • Screen glare and shadows from external light sources are eliminated
  • Calibrated vacuum relief valve ensures the correct vacuum is generated, too high a vacuum can damage the vacuum box and cause injury to the operator
  • Superior build quality with robust cast aluminum body
  • Two-stage seal design to improve initial vacuum, especially on large lap welds
  • Electric vacuum pump or compressor driven


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