Repairing weld cracks in steel structures is a critical task that requires careful planning, execution, and inspection to ensure the structural integrity is restored and the crack doesn’t return. This is a job for critical structures and should ALWAYS be performed by qualified welders following approved procedures under the supervision of experienced engineers or inspectors.

Repairing Cracks in Steel Structure Welds

1. Assessment and Planning:

Safety First: Implement all necessary safety precautions. This includes proper PPE (welding mask, gloves, leathers, respirator if needed), fire watch, ventilation, hot work permits, lockout/tagout procedures if near machinery, and securing the area.

Identify the Crack: Locate the crack precisely. Determine its full extent (length, depth, and whether it extends through the thickness). Non-Destructive Testing (NDT) methods like Magnetic Particle Testing (MT), Liquid Penetrant Testing (PT), or Ultrasonic Testing (UT) are often essential to find the crack tips accurately.

Determine the Cause (Crucial!): This is the MOST important step to prevent recurrence. Why did the crack form?

Fatigue: Cyclic loading leading to crack initiation and propagation.

High Residual Stress: From the original welding or fabrication process.

Hydrogen Embrittlement: Hydrogen trapped in the weld/Heat Affected Zone (HAZ). Often causes delayed cracking (hours or days after welding).

Poor Weld Quality: Lack of fusion, lack of penetration, porosity, slag inclusions acting as stress risers.

Incorrect Weld Procedure: Wrong consumables, incorrect preheat/interpass temperature, wrong parameters.

Poor Joint Design: Creates stress concentrations.

Overload: The structure was subjected to loads beyond its design capacity.

Base Metal Defects: Laminations or inclusions in the steel itself.

Consult Codes and Standards: Refer to relevant welding codes (e.g., AWS D1.1 Structural Welding Code – Steel, Eurocode 3, etc.) and project specifications for requirements regarding crack repair.

Develop a Repair Procedure: Based on the cause, material type, thickness, location, and code requirements, a detailed Welding Procedure Specification (WPS) for the repair must be developed or selected. This specifies:

Method of crack removal.

Joint preparation details.

Welding process (SMAW, FCAW, GMAW, SAW).

Filler metal type and size.

Preheat requirements.

Interpass temperature control.

Post-Weld Heat Treatment (PWHT) if required.

NDT requirements before, during, and after repair.

Qualified Personnel: Ensure the welders performing the repair are qualified according to the specific WPS and relevant codes. Ensure qualified NDT technicians and inspectors are involved.

2. Repair Execution:

Crack Removal: The entire crack, including its tips, must be completely removed. This is typically done by:

Gouging: Air Carbon Arc Gouging (CAC-A) is common and efficient but requires care not to introduce excessive carbon into the base metal (usually followed by grinding). Plasma Arc Gouging (PAG) is another option.

Grinding: Using abrasive wheels. More controlled but slower, suitable for smaller cracks or finishing after gouging.

…

For more detailed information on how to repair steel structure welding cracks, please click here: https://www.meichensteel.com/a/news/repairing-cracks-in-steel-structure-welds.html

Steel structure construction is a widely adopted method in modern architecture and engineering due to its strength, durability, and efficiency. From high-rise buildings and industrial warehouses to bridges and stadiums, steel provides a versatile solution for a wide range of construction needs.

The steel structure construction process involves a series of systematic steps that ensure the structural integrity and safety of the final build. These steps typically include planning and design, material procurement, fabrication, transportation, site preparation, and on-site erection. Each phase plays a crucial role in transforming raw steel components into a fully functional, load-bearing framework.

Steel structure construction process

Phase 1: Planning and Design

Conceptual Design & Feasibility: The client, architect, and engineers define the project requirements, budget, and overall building concept. Initial studies determine if a steel structure is the most suitable option.

Structural Engineering & Analysis: Structural engineers perform detailed calculations to determine loads (dead load, live load, wind, seismic, etc.) and design the steel frame. This includes selecting appropriate steel grades, member sizes (beams, columns), connection types (bolted, welded), and bracing systems for stability.

Detailed Drawings & Specifications: Architects and engineers produce detailed construction drawings (plans, elevations, sections, connection details) and technical specifications. These documents outline exactly how the structure should be built, the materials to use, and the quality standards required.

Shop Drawings: The steel fabricator (selected later) will create highly detailed shop drawings based on the engineering drawings. These drawings specify exact dimensions, cuts, hole locations, weld types, bolt types, surface finishes, and assembly marks for each individual steel member. These must be reviewed and approved by the structural engineer before fabrication begins.

Erection Plan: Often developed collaboratively between the engineer, fabricator, and erector, this plan outlines the sequence of lifting and assembling the steel members on site, crane locations, safety procedures, and temporary bracing requirements.

Phase 2: Fabrication (Off-Site)

This happens in a controlled factory environment (the fabrication shop):

Material Procurement: The fabricator orders the required raw steel shapes (I-beams, W-sections, channels, angles, plates, hollow sections) from steel mills based on the approved shop drawings and material specifications.

Cutting & Shaping: Steel members are cut to precise lengths using saws, shears, or thermal cutting (plasma, oxy-fuel).

Drilling/Punching: Holes for bolts are accurately drilled or punched according to the shop drawings.

Fitting & Welding: Components (e.g., base plates, connection plates, stiffeners) are fitted together and welded as specified in the shop drawings. Skilled, certified welders perform this work.

Surface Treatment: Steel members are cleaned (usually by shot blasting) to remove mill scale and rust. Then, a primer paint or other specified coating (like galvanizing) is applied for corrosion protection.

Quality Control (QC): Throughout fabrication, QC checks are performed (dimensional checks, weld inspection using visual or non-destructive testing methods like UT/MT/PT, coating thickness checks).

Marking & Labeling: Each finished piece is clearly marked with an identification number/code corresponding to the shop drawings and erection plan, ensuring it can be easily identified on site.

Phase 3: Transportation

Loading & Logistics: Fabricated steel members are carefully loaded onto trucks or trailers in a sequence that often aligns with the planned erection sequence on site.

Shipping: Steel is transported from the fabrication shop to the construction site. Special permits and escorts may be required for oversized loads.

Phase 4: Site Preparation

This happens concurrently with or before fabrication/transportation:

Foundation Construction: Concrete foundations (footings, pile caps, raft foundations) are constructed based on the engineering design. Crucially, anchor bolts are accurately embedded into the concrete where steel columns will be placed. Their position and elevation are critical.

Site Logistics: The site is prepared with clear access roads, designated laydown areas for storing steel deliveries, and stable pads for crane setup.

Phase 5: Erection (On-Site Assembly)

This is the process of assembling the steel frame on site:

Receiving & Sorting: Steel deliveries are received, checked against delivery tickets, and sorted in the laydown area according to their erection marks and the erection plan.

Crane Setup: Mobile or tower cranes capable of lifting the heaviest steel members are positioned strategically on site.

…

For more detailed information about the steel structure construction process, please click here: https://www.meichensteel.com/a/news/steel-structure-construction-process.html

Adjusting the clearance of a slewing bearing is crucial for ensuring smooth operation, reducing wear, and extending its service life. The process varies depending on the bearing type (single-row ball, double-row ball, or cross-roller) and the manufacturer’s specifications.

Slewing Bearing Clearance Adjustment Method

1. Initial Assessment

Before adjusting the slewing bearing clearance, it’s important to assess the condition of the bearing and machinery:

Inspect the Bearing: Look for signs of wear, damage, or corrosion. If the bearing is significantly worn or damaged, it may require replacement.

Check Manufacturer Specifications: Ensure you know the recommended clearance values provided by the bearing manufacturer. These values are essential for setting the correct adjustment.

2. Required Tools

To adjust slewing bearing clearance, you will need the following tools:

Dial indicator or laser measurement tool

Feeler gauges

Torque wrench

Shims or spacers (if applicable)

Jack (if lifting the structure is necessary)

Lubrication (specific grease or oil for the bearing)

3. Measuring Existing Clearance

Before making any adjustments, it is important to measure the current clearance. This will help determine whether the bearing is within the desired tolerance or if adjustments are needed.

Axial Clearance:

Place a dial indicator perpendicular to the raceway.

Lift the upper structure (if applicable) slightly using a jack or lifting mechanism.

Measure the axial movement along the bearing’s axis.

Radial Clearance:

Attach the dial indicator parallel to the bearing’s radial surface.

Apply side force to the structure to check the movement in the radial direction.

Tilting Clearance:

Measure the angular clearance by placing the dial indicator at multiple points along the bearing. Check for any tilting or angular movement.

Record the measurements and compare them with the specifications. If the clearance is out of the acceptable range, proceed to adjustment.

4. Adjusting the Clearance

The adjustment process will vary depending on the bearing design. There are two main types of slewing bearings: adjustable bolt-type and gear-type.

For Adjustable Bolt-Type Bearings:

…

For more detailed information on how to adjust the slewing bearing clearance, please click here: https://www.mcslewingbearings.com/a/news/slewing-bearing-clearance-adjustment-method.html

A flange slewing bearing has mounting holes directly drilled into the face of either the inner or outer ring (or both). This flange allows for direct bolting to the supporting structure without needing separate clamping rings, often simplifying the mounting arrangement.

Flange slewing bearing installation

Safety First!

PPE: Wear appropriate Personal Protective Equipment (safety glasses, gloves, steel-toed boots).

Lifting: Slewing bearings can be heavy. Use appropriate lifting equipment (cranes, hoists, slings) and techniques. Never lift by the seals or gear teeth if applicable.

Use designated lifting points if provided.

Lockout/Tagout: Ensure the machinery the bearing is being installed on is properly de-energized and locked out/tagged out before starting work.

Clear Area: Keep the work area clean and free of obstructions.

Tools and Materials Needed:

The new flange slewing bearing

Manufacturer’s installation manual

Appropriate lifting gear

Correct grade, size, and length fasteners (bolts, potentially nuts and washers) – Crucially important! Use new fasteners of the grade specified by the bearing or equipment manufacturer (often Grade 10.9 or 12.9).

Calibrated torque wrench(es) covering the required torque range

Feeler gauges

Cleaning supplies (lint-free cloths, appropriate solvent)

Lubricant for bolt threads (if specified by manufacturer, e.g., molybdenum disulfide paste)

Grease gun and the correct type/grade of grease (as specified by the manufacturer)

Measuring tools (tape measure, calipers)

Soft mallet (optional, for minor adjustments)

Pry bars (use with extreme caution and protection to avoid damage)

Installation Steps:

Phase 1: Preparation

Read the Manual: Thoroughly read and understand the specific installation manual provided by the bearing manufacturer. Pay close attention to torque values, bolt grades, tightening sequences, and lubrication requirements.

Inspect the Bearing:

Carefully unpack the bearing. Check for any shipping damage.

Verify the part number matches your requirements.

Check the manufacturing date (grease has a shelf life).

…

For more detailed information about flange slewing bearing installation, please click here: https://www.mcslewingbearings.com/a/news/flange-slewing-bearing-installation.html

Tempering furnaces for the architectural glass industry are designed to meet strict performance, safety, and quality standards. And the key properties of tempering furnaces specifically designed for the architectural glass industry. These furnaces are distinct due to the scale, quality requirements, and types of glass used in buildings.

Performance of tempering furnaces for the architectural glass industry

Large Size Capacity:

Architectural glass often comes in large sheets (standard float sizes, jumbo sizes). Furnaces must accommodate dimensions frequently reaching 3.3 meters wide and 6, 7, or even 12+ meters long.

The transport system (rollers) must be robust enough to handle the weight and dimensions of these large lites without causing damage or excessive deflection.

Advanced Convection Heating:

Crucial for Coated Glass (Low-E): Modern architectural glass heavily utilizes Low-E (low-emissivity) coatings for energy efficiency. These coatings reflect infrared heat. Pure radiation heating struggles to heat coated glass evenly and efficiently without overheating the coating.

Forced Convection: These furnaces employ powerful forced convection systems (using heated air) alongside radiation. This allows for:

Faster heating cycles.

More uniform temperature distribution across the glass surface and through its thickness, regardless of coatings.

Reduced risk of overheating and damaging sensitive soft coatings.

Better processing of thicker glass.

Types of Convection: Can be top convection only, or more commonly, top and bottom convection for maximum efficiency and uniformity. Some use compressed air-assisted convection for even higher heat transfer rates.

Precise Temperature Control and Uniformity:

Achieving a consistent temperature (around 620-650°C / 1150-1200°F) across the entire large sheet is critical for avoiding optical distortion and ensuring proper tempering.

Sophisticated control systems use numerous thermocouples and/or pyrometers to monitor glass temperature in multiple zones within the furnace.

Advanced algorithms adjust heating elements (and convection flow) dynamically to ensure uniformity, compensating for edge effects or variations in glass loading.

High-Performance Quenching System:

The quenching (rapid cooling) section uses high-pressure air blown through precisely positioned nozzles (top and bottom).

Must deliver powerful, uniform, and controllable airflow across the entire glass surface to create the necessary surface compression for strength and safety fragmentation.

Control over air pressure, nozzle distance, and potentially oscillating patterns is needed to optimize quenching for different glass thicknesses and types, minimizing distortion.

…

For more detailed information on the properties of tempering furnaces in the architectural glass industry, please click here: https://www.shencglass.com/en/a/news/performance-of-tempering-furnaces-for-the-architectural-glass-industry.html