Iso 13920-bf - En

The designation EN ISO 13920-BF refers to a specific set of general tolerances for welded constructions, combining two distinct classes of accuracy defined by the ISO 13920 standard. Breakdown of the Code

The code BF specifies the precision level required for the manufacturing of a welded part:

B: Represents the tolerance class for linear and angular dimensions. Class B is considered "medium" or "customary workshop accuracy".

F: Represents the tolerance class for shape and position (such as straightness, flatness, and parallelism). Tolerance Tables for EN ISO 13920-BF

These tolerances apply when no specific tolerance is indicated for a dimension on a technical drawing. 1. Linear Dimensions (Class B)

Tolerances for lengths, such as external sizes, internal sizes, and step sizes. Range of nominal sizes (mm) Tolerance (mm) ±1plus or minus 1 ±2plus or minus 2 120 to 400 ±2plus or minus 2 400 to 1000 ±3plus or minus 3 1000 to 2000 ±4plus or minus 4 2000 to 4000 ±6plus or minus 6 2. Shape and Position (Class F) Tolerances for straightness, flatness, and parallelism. Range of nominal sizes (mm) Tolerance (mm) Up to 1000 1000 to 2000 2000 to 4000 4000 to 8000 Application in Industry This standard is commonly cited in technical drawings for:

Steel Construction: Used by firms like Hazemag and C.C. JENSEN to ensure structural components fit together without excessive machining costs.

Mechanical Engineering: Often paired with ISO 2768-mK (which covers tolerances for machined parts) to provide a complete specification for assemblies that include both welded and machined features.

Quality Control: Serves as the basis for inspection reports to determine if a welded assembly meets the functional requirements of the design. Specification Steel Construction - hazemag

This guide explains the technical specifications for EN ISO 13920-BF, an international standard used to define general tolerances for welded constructions. Overview of EN ISO 13920

The ISO 13920 standard specifies general tolerances for linear and angular dimensions, as well as for shape and position of welded structures. It is designed to ensure functional suitability in manufacturing without requiring excessive precision that could increase costs unnecessarily. Breaking Down "BF"

When a drawing specifies EN ISO 13920-BF, it is identifying two specific tolerance classes:

B (Tolerance Class for Linear and Angular Dimensions): This is the "Medium" class for lengths and angles. It defines the allowable deviation for measurements like the length of a beam or the degree of an angle.

F (Tolerance Class for Shape and Position): This specifies the allowable variations for geometric attributes such as straightness, flatness, and parallelism. Key Tolerance Areas

The standard covers four main categories of dimensional variations: Linear Dimensions: Lengths of welded parts. Angular Dimensions: Angles between welded components.

Straightness and Flatness: How "true" a surface or edge must be.

Parallelism and Alignment: Ensuring parts are correctly positioned relative to each other. Application and Usage

Drawings: Engineers indicate this standard in the "General Tolerances" block of a technical drawing (e.g., "General Tolerance: EN ISO 13920-BF") to avoid labeling every single dimension with a specific tolerance.

Industry Use: It is commonly used in heavy-duty fabrication, such as for filtration distributors, corona rings, and offshore mattressing structures.

Revision Note: The original 1996 version (EN ISO 13920:1996) was revised by the updated ISO 13920:2023 standard. ISO 13920 An Explained Guide to Welding General Tolerances

The feature EN ISO 13920-BF is a combined designation for general tolerances in welded constructions. It specifies an accuracy level for both dimensional and geometric variations on technical drawings. The designation breaks down as follows:

EN ISO 13920: The international standard defining general tolerances for welded structures, covering lengths, angles, straightness, flatness, and parallelism. B: The tolerance class for linear and angular dimensions.

F: The tolerance class for shape and position (straightness, flatness, and parallelism). Typical Applications

This specification is commonly found on drawings for industrial equipment where standard welding precision is required without the need for high-precision machining. Examples include:

EN ISO 13920-BF is a technical specification used in engineering drawings to define general tolerances for welded constructions. It ensures that parts are manufactured to a consistent, economically viable level of precision without requiring individual tolerances for every dimension. Breakdown of the Specification

EN ISO 13920: The international standard for general tolerances of welded structures, covering lengths, angles, shape, and position.

Class B: Represents the tolerance class for linear and angular dimensions. "B" is generally considered a "medium" or "fine" grade for welding. en iso 13920-bf

Class F: Represents the tolerance class for straightness, flatness, and parallelism. Core Tolerance Areas This standard provides specific allowable deviations for:

Linear Dimensions: Lengths of components and distances between them.

Angular Dimensions: Accuracy of angles between welded parts.

Form and Position: Ensuring surfaces are sufficiently flat and edges are straight. Why It Is Used

Simplifies Drawings: Engineers don't have to label every single weld with a specific tolerance; they simply cite "ISO 13920-BF" in the title block.

Standardizes Quality: It provides a clear benchmark for what is considered an acceptable "standard" build in industrial fabrication.

Cost Efficiency: By using general tolerances, manufacturers can avoid the high costs of unnecessary high-precision machining where it isn't functional. Typical Applications

You will most often see this code on technical drawings for: Industrial Frames: Large structural steel assemblies. High Voltage Equipment: Such as corona rings and shields.

Piping Systems: Filtration distributors and cable attachment flanges.

Here is the breakdown:

  • EN ISO 13920 is the standard for Welding — General tolerances for welded constructions (though sometimes confused with ISO 9692 for edge preparation). However, in workshop practice, "BF" is defined in ISO 9692-1 (and adopted as EN ISO 9692-1).
  • BF stands for "Backing Flange" or more precisely a Backing run edge preparation. Specifically, BF designates a symmetrical double-V or double-bevel preparation with a backing strip or retained root face.

When to refer to other standards

  • For weld quality/acceptance (e.g., ISO 5817 / ISO 6520) — use those standards alongside EN ISO 13920.
  • For structural steel tolerances and fabrication (e.g., EN 1090) — coordinate requirements.

8. Summary Table

| Term | Standard | Meaning | |------|----------|---------| | EN ISO 13920 | ISO 13920 | General tolerances for welded constructions | | Class C, D, E, F | ISO 13920 | Tolerance grades (C finest → F coarsest) | | BF | ISO 9692-1 | Butt weld preparation with Backing + Flat root face | | EN ISO 13920-BF | Invalid combo | Likely means: Tolerance Class F + Weld prep BF |

8. Recommendations

  • Clarify BF meaning in drawing title block or project WPS
  • Attach ISO 2553 weld symbol with backing flag if needed
  • Confirm backing type (permanent/removable) in welding specification

If you need me to:

  • Convert this into a PDF-ready Word/Markdown file
  • Add an ISO 13920 tolerance table (linear, angular, flatness)
  • Include an example drawing symbol for BF

Just let me know.

EN ISO 13920-BF is a specific technical designation used in engineering drawings to define general tolerances for welded constructions. It combines two distinct precision levels from the ISO 13920 standard to ensure that welded parts fit together correctly without needing individual, complex dimensioning for every single weld. Breaking Down the Code: "BF"

The suffix BF tells the manufacturer exactly which tolerance "bracket" to use for different types of measurements:

B (Linear & Angular Dimensions): This represents the "Medium" or "Mean" tolerance class. It is the most commonly used class in general engineering and steel construction. It provides a balance between functional accuracy and cost-effective fabrication.

F (Shape & Position): This refers to the tolerance for straightness, flatness, and parallelism. While linear dimensions use letters A through D, shape and position tolerances use E through H. Class F is the second-most precise level in this category (often considered "Medium" for shape). Why Use EN ISO 13920-BF?

Using this standard shorthand simplifies communication between designers and fabrication shops. Instead of calculating individual limits for every length and angle, a single note—EN ISO 13920-BF—applies a pre-defined set of rules based on the size of the component.

Neutral Benchmarking: It acts as a universal language for international contracts, ensuring a manufacturer in Europe and a client in the Middle East have the same expectations for accuracy.

Cost Efficiency: Specifying "Class B" avoids the high costs associated with the ultra-precise "Class A," while preventing the safety or assembly risks of the looser "Class C".

Broad Application: This standard is widely used in machine construction, steel structures, rail vehicles, and shipbuilding. Tolerance Tables Overview

The actual permissible deviation (in millimeters or degrees) depends on the nominal size of the part. For example, a 1,000 mm beam in Class B will have a specific allowed variation, whereas a 10,000 mm beam will have a larger allowable margin. Type of Measurement Class for "BF" Key Focus Areas Linear Dimensions B (Medium) Length, width, and height of parts. Angular Dimensions B (Medium) Deviations in angles and slopes. Shape & Position F (Medium) Straightness, flatness, and parallelism. Testing and Verification

Compliance with EN ISO 13920-BF is verified using standard workshop tools such as steel straightedges, tape measures, and vernier callipers. It is important to note that this standard covers dimensional accuracy, not weld quality (like cracks or porosity), which is instead governed by ISO 5817. IS0 13920 - iTeh Standards

Understanding EN ISO 13920-BF: A Guide to Welding Tolerances

The designation EN ISO 13920-BF refers to a specific set of general tolerances for welded constructions. It combines two distinct tolerance classes defined by the international standard ISO 13920: Class B for linear and angular dimensions, and Class F for straightness, flatness, and parallelism.

This standard is essential for ensuring consistency and quality in structural steel fabrication when individual tolerances are not specified on a drawing. 1. Breakdown of the "BF" Designation The designation EN ISO 13920-BF refers to a

The "BF" suffix is a shorthand used in engineering drawings to indicate the level of accuracy required for a welded assembly.

Class B (Medium): This is the most common tolerance class used in general engineering and construction. It covers linear dimensions (lengths, widths, heights) and angular dimensions.

Class F: This class specifically governs the geometric tolerances of the weldment, including how straight a part is or how flat a surface must be. 2. Tolerance Tables for Class B (Linear & Angular)

According to technical guides from Scribd and Modulus Metal, the permitted deviations for Class B depend on the size of the component: Range of Nominal Size (mm) Linear Tolerance (± mm) Over 30 to 120 Over 120 to 400 Over 400 to 1,000 Over 1,000 to 2,000

For Angular Dimensions in Class B, the tolerance is determined by the length of the shorter leg of the angle: Up to 400 mm: ± 45 minutes of a degree. Over 400 to 1,000 mm: ± 30 minutes. Over 1,000 mm: ± 20 minutes. 3. Geometric Tolerances for Class F

Class F defines the allowable variation for the shape and position of the structure. Common tolerances for Class F include: Over 30 to 120 mm: +1 mm. Over 120 to 400 mm: +1.5 mm. Over 400 to 1,000 mm: +3 mm. 4. Why Use EN ISO 13920-BF?

Adopting these general tolerances simplifies the design and manufacturing process by:

ISO 13920 Welding General tolerances for welded constructions

In the world of metal fabrication, EN ISO 13920-BF isn't just a string of characters—it's the set of rules that keeps heavy structures from being "crooked." If you're building something like a heavy-duty roll trailer desorber unit , this standard is your blueprint for precision. The Story of the "Perfectly Imperfect" Weld

Imagine a team of engineers designing a massive steel frame. They know that when you apply intense heat to metal during welding, it expands, contracts, and twists. Without a shared "tolerance" agreement, the person welding the frame might think a 5mm warp is fine, while the person installing the machinery on top thinks it's a disaster. This is where EN ISO 13920 steps in. It provides a common language for general tolerances for welded constructions Breaking Down the "BF" The suffix

is the specific "handshake" between the designer and the workshop: B (Linear/Angular Dimensions):

This is the "Medium" tolerance class. It’s like saying, "We need this to be accurate, but we aren't building a watch." It allows for small variations in length and angles that are typical for professional workshop accuracy. F (Shape and Position):

This refers to how straight or flat the structure is. Class "F" is a common standard for general engineering, ensuring the final piece isn't so distorted that it won't fit into its designated space. Why it Matters By specifying EN ISO 13920-BF on a drawing, a company like NOVATECH ApS

ensures that their 13-ton trailers are built to a consistent quality. It prevents expensive "re-work" and ensures that if a part is made in one factory, it will perfectly match a part made in another. exact measurement tables for the "B" and "F" classes to use on a technical drawing?

Understanding EN ISO 13920-BF: General Tolerances for Welded Constructions

In the world of metal fabrication, precision is relative. Achieving surgical accuracy on a massive steel girder is neither practical nor cost-effective. This is where EN ISO 13920 comes into play. It provides a standardized framework for general tolerances in welded structures, ensuring that parts fit together without requiring the impossible level of precision typically reserved for machined components.

The designation "EN ISO 13920-BF" refers to a specific combination of tolerance classes within this international standard. What does "BF" stand for?

The code "BF" consists of two distinct tolerance classes defined in ISO 13920:

B (Linear and Angular Dimensions): This is the "intermediate" class for lengths and angles. It defines the allowable deviation for dimensions such as the length of a beam or the angle of a joint. For a 1-meter span, class B might allow a variation of a few millimeters, providing a balance between functional fit and manufacturing speed.

F (Shape and Position): This refers to tolerances for straightness, flatness, and parallelism. Class F is the "intermediate" tier for these geometric features. It ensures that a welded frame is sufficiently "square" and flat for its intended use without requiring expensive post-weld machining. Why use "BF" instead of other classes? The ISO 13920 standard offers four classes for dimensions ( ) and four for shape ( are the finest (tightest) and are the coarsest. Intermediate Very Coarse Dimensions (Length/Angle) B Shape & Position F

BF is widely considered the "standard workshop accuracy" class. It is the "Goldilocks" zone for general mechanical engineering—tight enough to ensure parts align during assembly but loose enough to be achieved by a skilled welder without specialized jigs or constant measurement. Practical Application

When a technical drawing specifies EN ISO 13920-BF, it acts as a "safety net" for the manufacturer. Any dimension on the drawing that does not have a specific tolerance assigned to it automatically falls under the rules of Class B (for length/angle) and Class F (for shape). This is critical in industries such as:

Construction: Ensuring structural beams meet at the correct angles.

Heavy Machinery: Designing foundations for pumps or blowers. Transport: Fabricating chassis or frames for vehicles.

Specifying EN ISO 13920-BF is a clear signal to the fabrication floor: "Build this with standard professional care." It eliminates the need for individual tolerance notes on every single weld, streamlining the design process and ensuring that everyone from the engineer to the quality inspector is on the same page regarding what "good enough" looks like.

Understanding EN ISO 13920-BF: The Standard for General Tolerances for Welded Constructions and Parts EN ISO 13920 is the standard for Welding

In the world of engineering and manufacturing, precision and accuracy are crucial for ensuring the quality and reliability of products. One of the key aspects of achieving this precision is by adhering to specific standards and guidelines that dictate the acceptable limits of variation in the dimensions and tolerances of various components and constructions. One such standard that plays a significant role in the fabrication and inspection of welded constructions and parts is EN ISO 13920-BF.

What is EN ISO 13920-BF?

EN ISO 13920-BF is a European standard that specifies general tolerances for welded constructions and parts. The standard is part of the ISO 13920 series, which provides guidelines for the tolerancing of welded parts and assemblies. The "BF" in the designation refers to the specific part of the standard that deals with general tolerances for welded constructions.

Scope and Application

EN ISO 13920-BF applies to the fabrication of welded constructions, including but not limited to, steel structures, machinery, and equipment. The standard is relevant to various industries, such as construction, automotive, aerospace, and shipbuilding, where welded joints are commonly used. The standard provides a set of general tolerances that can be applied to welded parts and assemblies, taking into account the inherent variability associated with welding processes.

Tolerances and Deviations

The standard defines various types of tolerances and deviations that are relevant to welded constructions, including:

  1. Linear Tolerances: These refer to the acceptable variations in linear dimensions, such as length, width, and height.
  2. Angular Tolerances: These refer to the acceptable variations in angular dimensions, such as angles and orientations.
  3. Geometric Tolerances: These refer to the acceptable variations in the shape and orientation of features, such as flatness, straightness, and circularity.

EN ISO 13920-BF provides a range of tolerance classes, each with its own set of specific tolerance values. The tolerance classes are designated by a letter (e.g., f, m, c, or v), which corresponds to a specific level of precision. For example, the "f" class represents a fine tolerance, while the "v" class represents a very coarse tolerance.

Welded Joint Tolerances

The standard also provides specific guidelines for the tolerancing of welded joints. Welded joints are classified into different types, such as butt joints, fillet joints, and lap joints. For each type of joint, EN ISO 13920-BF specifies the acceptable variations in joint dimensions, such as weld throat thickness, weld leg length, and joint misalignment.

Inspection and Verification

EN ISO 13920-BF emphasizes the importance of inspection and verification to ensure that welded constructions and parts meet the specified tolerances. The standard provides guidelines for the measurement and inspection of welded joints and parts, including the use of non-destructive testing (NDT) methods.

Benefits and Advantages

The use of EN ISO 13920-BF offers several benefits and advantages, including:

  1. Improved Quality: By adhering to specific tolerances and guidelines, manufacturers can ensure that their products meet the required quality standards.
  2. Increased Interchangeability: The standard promotes interchangeability between components and assemblies, making it easier to replace or substitute parts.
  3. Reduced Costs: By minimizing variations and deviations, manufacturers can reduce costs associated with rework, repair, and scrap.
  4. Enhanced Safety: The standard helps to ensure that welded constructions and parts are safe for use, reducing the risk of accidents and injuries.

Conclusion

EN ISO 13920-BF is an essential standard for manufacturers and fabricators of welded constructions and parts. By understanding and applying the guidelines and tolerances specified in the standard, manufacturers can ensure that their products meet the required quality and precision standards. The standard promotes consistency, interchangeability, and safety, ultimately contributing to the overall efficiency and reliability of engineering and manufacturing processes.

Additional Resources

For more information on EN ISO 13920-BF, readers can refer to the following resources:

  • ISO 13920:2016 - Welding - General tolerances for welded constructions and parts
  • EN ISO 13920:2016 - European Standard for general tolerances for welded constructions and parts
  • National and international standards organizations, such as ISO, CEN, and ANSI.

FAQs

Q: What is the difference between EN ISO 13920-BF and other tolerance standards? A: EN ISO 13920-BF is specifically designed for welded constructions and parts, providing guidelines for the tolerancing of welded joints and assemblies.

Q: How do I determine the tolerance class for my welded construction? A: The tolerance class depends on the specific application, industry, and required level of precision. Refer to the standard or consult with a qualified engineer or inspector.

Q: Can EN ISO 13920-BF be used for non-welded constructions? A: No, the standard is specifically designed for welded constructions and parts. Other standards may apply to non-welded constructions.

Q: Is EN ISO 13920-BF a mandatory standard? A: The standard may be mandatory in certain industries or countries. Check with local regulations and industry associations for specific requirements.

4. Application rules (typical)

| Parameter | Requirement | |-----------|--------------| | Weld type | Butt weld, single V, or U with backing | | Backing location | Root side | | Backing material | Steel, ceramic, or permanent (specified separately) | | Dimensional tolerance | Class C (medium) or Class D (coarse) per EN ISO 13920 | | Inspection | Visual after backing, then after final weld |

4. Advantages of Specifying EN ISO 13920-BF

  1. Drawing Simplification: Eliminates the need to tolerance every individual dimension on a fabrication drawing.
  2. Cost Efficiency: It avoids "over-specifying." If you specify ISO 2768-m (machining tolerances) on a weldment, costs will skyrocket unnecessarily. BF acknowledges the inherent shrinkage and distortion of welding.
  3. Fit-Up Reliability: Class B linear tolerances are tight enough to ensure that bolt holes (unless slotted) will generally align

How to Read the Tolerance Tables

If you are operating under Class B, you must consult the tables within the ISO 13920 standard.

2. Scope of EN ISO 13920

This standard specifies tolerance classes (fine, medium, coarse) for:

  • Linear dimensions
  • Angular dimensions
  • Straightness
  • Flatness
  • Welded assemblies

It does not define welding symbol positions (covered by ISO 2553), but ISO 13920-BF is an internal drawing notation referencing backing weld requirements in conjunction with tolerances.