Unthreaded Arc Weld Stud ISO 13918 UD Technical Datasheet
ISO 13918 UD Unthreaded Weld Studs are smooth cylindrical studs designed for permanent attachment to metallic substrates using the drawn arc stud welding process. Unlike threaded weld studs, UD studs feature a plain shank that serves as a robust anchoring point for insulation systems, refractory linings, locating fixtures, mounting posts, and custom-engineered assemblies.
Manufactured in accordance with ISO 13918, these studs are widely used in industrial boilers, furnaces, heat exchangers, pressure vessels, industrial ovens, process plants, railway equipment, structural fabrication, and heavy engineering. Their ability to provide a permanent welded anchor makes them particularly suitable for securing thermal insulation and refractory materials, helping improve energy efficiency while reducing heat loss from high-temperature equipment.
The studs are installed using drawn arc stud welding, creating a full-strength metallurgical bond without drilling, tapping, or requiring access to the reverse side of the workpiece.
Table of Contents
ITEM CODE: 1068
Standard
ISO 13918 UD
Dimensions
| d1 ±0.1 | 6 | 8 | 10 | 12 | 14.6 | 16 |
| d3 | 8.5 | 11 | 13 | 16 | 18.5 | 21 |
| h4 | 4 | 4 | 4 | 5 | 6 | 7 |
| α ±7° | 140° | 140° | 140° | 140° | 140° | 140° |
| l1 ±1 | l2 + 2.4 | l2 + 2.6 | l2 + 2.8 | l2 + 3.4 | l2 + 3.9 | l2 + 3.9 |
all dimensions in mm
| Note | Description |
|---|---|
| a | Length l₁ applies to 140° angle only (without tolerance). |
| b | The given values are for guidance only. |
Dimensions Tolerances:
General dimensional tolerances for standard metric fasteners—including thread diameter, overall length, head diameter, head height/thickness, across flats, and washer dimensions—are available in our Standard Dimensional Tolerances for Common Metric Fasteners guide.
Certain product-specific features, such as drive recess dimensions, socket depth, countersink geometry, under-head radii, and other special characteristics, are governed by the applicable DIN or ISO product standard and may not included in this datasheet.
Download Technical Datasheets
| Material | Download |
|---|---|
| Steel | ⬇️ Download Datasheet |
| Stainless Steel A2 | ⬇️ Download Datasheet |
Material Characteristics and Recommended Applications
| Material | Characteristics | Typical Applications |
|---|---|---|
| Low Carbon Steel | High strength, economical | Boilers, structural fabrication, industrial machinery |
| Stainless Steel A2 (304) | Good corrosion resistance | Food processing equipment, architectural applications |
| Stainless Steel A4 (316) | Excellent corrosion resistance | Marine, offshore, chemical plants |
Technical Specifications
| Property | Specification |
|---|---|
| Product Type | Unthreaded Arc Weld Stud |
| Standard | ISO 13918 UD |
| Welding Process | Drawn Arc Stud Welding |
| Stud Configuration | Smooth Cylindrical Stud |
| Thread | None |
| Weld End | Arc Welding Tip (140°) |
| Installation | One-sided Stud Welding |
| Base Materials | Carbon Steel, Stainless Steel |
| Surface Finish | Plain, Zinc Plated (where applicable) |
| Standard Diameter Range | Ø6–Ø16 mm |
| Standard Lengths | As specified in ISO 13918 |
| Corrosion Resistance | Material dependent |
Applications
Thermal Insulation & Refractory Systems
ISO 13918 UD weld studs are extensively used for retaining insulation and refractory materials in:
- Industrial Boilers
- Steam Boilers
- Waste Heat Recovery Boilers (WHRB)
- Heat Exchangers
- Pressure Vessels
- Furnaces
- Industrial Ovens
- Kilns
- Ducting Systems
- Chimneys
- Thermal Insulation Panels
- Acoustic Insulation Systems
Industrial Manufacturing
- Heavy Machinery
- Structural Steel Fabrication
- Railway Equipment
- Material Handling Equipment
- Mining Equipment
- Power Generation
- Process Plants
- Conveyor Systems
- Machine Guards
- Positioning Fixtures
- Mounting Posts
- OEM Equipment
Advantages
- Manufactured in accordance with ISO 13918
- Permanent metallurgical bond
- No drilling or tapping required
- Smooth cylindrical profile for versatile applications
- Excellent vibration and fatigue resistance
- Fast installation using drawn arc stud welding
- Suitable for automated production
- Ideal for securing insulation and refractory systems
- Supports high-temperature industrial applications
- Improves thermal efficiency by reducing heat loss
- Strong anchoring point for insulation clips and retaining washers
- One-sided installation
Thermal Insulation & Refractory Anchoring
One of the most common applications for ISO 13918 UD weld studs is the installation of thermal insulation systems in boilers, furnaces, and process equipment.
The studs are welded directly onto the equipment shell and are used together with insulation clips or retaining washers to secure:
- Mineral Wool
- Ceramic Fibre Blankets
- Calcium Silicate Boards
- Rock Wool
- Refractory Linings
- High Temperature Insulation Panels
These systems help to:
- Reduce heat loss
- Improve energy efficiency
- Maintain process temperatures
- Protect personnel from hot surfaces
- Extend equipment life
- Reduce operating costs
Installation Best Practices
Do
- Clean the welding surface thoroughly before installation.
- Select the correct welding current and time.
- Ensure proper grounding.
- Use recommended ceramic ferrules where required.
- Verify stud alignment before welding.
- Perform visual inspection after welding.
Don’t
- Weld onto painted or contaminated surfaces.
- Use bent or damaged studs.
- Ignore welding parameter recommendations.
- Weld on unsuitable base material thickness.
- Skip weld quality inspections.
Common Installation Problems & Solutions
| Problem | Possible Cause | Recommended Solution |
|---|---|---|
| Weak weld | Low welding current | Increase welding current |
| Porosity | Surface contamination | Clean base material |
| Misaligned stud | Incorrect gun positioning | Maintain perpendicular alignment |
| Excessive spatter | Incorrect welding settings | Recalibrate welding equipment |
| Poor fusion | Inadequate grounding | Improve grounding connection |
Frequently Asked Questions
What is an ISO 13918 UD weld stud?
ISO 13918 UD is a smooth cylindrical weld stud designed for permanent attachment using the drawn arc stud welding process.
What are UD weld studs used for?
They are commonly used for securing thermal insulation, refractory linings, locating fixtures, mounting posts, and custom engineered assemblies in industrial equipment.
Are UD weld studs suitable for boilers?
Yes. They are widely used in boilers, furnaces, heat exchangers, and process plants to retain insulation systems and refractory linings.
What welding process is used?
ISO 13918 UD studs are designed for drawn arc stud welding using compatible stud welding equipment.
What materials are available?
Standard materials include low carbon steel, stainless steel A2 (304), stainless steel A4 (316), and selected heat-resistant grades.
Can custom sizes be manufactured?
Yes. Custom diameters, lengths, and materials can be supplied subject to minimum order quantities.
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