Steel Structure Requirements for Mineral Processing Equipment

1. Structural Strength and Stiffness Requirements

• High load-bearing capacity: Must be able to withstand the equipment's own weight, the weight of fully loaded materials, impact loads (e.g., in crushers), vibration loads (e.g., in screening machines), and potential accidental overloads.
• Excellent fatigue resistance: As the equipment usually runs continuously 24 hours a day and bears alternating stress, the steel structure must have good fatigue resistance to prevent crack initiation due to fatigue.
• Sufficient stiffness: Ensure that the deformation under load is within the allowable range. For example, excessive deformation of the cylinder of large ball mills will affect the lining plates and grinding efficiency; insufficient stiffness of large frames will lead to poor gear meshing.

2. Wear Resistance and Impact Resistance Requirements

• Strengthening of key wear-prone areas: For parts in direct contact with materials or susceptible to scouring (e.g., structures around jaw plates/lining plates of crushers, chutes, hoppers, conveyor bottom plates, etc.), wear-resistant steel plates (e.g., NM series) should be adopted, or wear-resistant hard alloys should be surfacing welded on the surface, or replaceable wear-resistant lining plates (e.g., high-chromium cast iron, rubber lining plates) should be installed.
• Impact-resistant design: For equipment processing large, hard materials (e.g., jaw crushers, cone crushers), the steel structures of key parts such as frames and bearing blocks should have good toughness, and reinforcing plates should be used to disperse impact energy.

3. Corrosion Resistance Requirements

• Humid and chemical environments: Processes such as flotation, thickening and hydrometallurgy involve water, chemicals, acid and alkali media, which make steel structures highly susceptible to corrosion.
• Protective measures:
  • Coating system: Adopt heavy-duty anti-corrosion coating systems (e.g., epoxy zinc-rich primer, epoxy micaceous iron oxide intermediate coat, polyurethane topcoat), and determine the coating thickness according to the environmental class.
  • Material selection: In severely corrosive areas, weathering steel or local stainless steel (e.g., 304/316L) can be used.
  • Structural design: Avoid dead corners where water and corrosive media are easy to accumulate, and provide good drainage and ventilation.

4. Process and Manufacturing Quality Requirements

• Welding quality: This is the lifeline of steel structure performance. Requirements include:
  • Formulate strict Welding Procedure Specifications (WPS) and Procedure Qualification Records (PQR).
  • Welders must hold valid certificates to work.
  • Welds shall be full, free of cracks, slag inclusions, porosity and other defects. Critical stress-bearing welds (e.g., main welds of frames) generally require full penetration welding and non-destructive testing (e.g., ultrasonic testing - UT or radiographic testing - RT).
• Dimensional accuracy and tolerance: The manufacturing accuracy of large equipment components (e.g., cylinder sections of large rotary kilns) directly affects the efficiency of on-site installation as well as the concentricity and balance of equipment operation.
• Stress relief: For important welded parts, annealing treatment must be carried out to eliminate welding residual stress and prevent subsequent deformation and stress corrosion cracking.

5. Safety and Reliability Requirements

• Intrinsically safe design: The structure must have sufficient safety factors, and critical connections (e.g., bolts) must be equipped with anti-loosening measures. Consideration should be given to facilitating the installation of safety protection devices.
• Reliability design: The structural design should facilitate condition monitoring (e.g., setting vibration monitoring points) and non-destructive testing for predictive maintenance.
• Humanized design: Take into account the convenience of operation and maintenance, such as setting up reasonable maintenance platforms, lifting lugs and maintenance space.

6. Standardization and Modularization Requirements

• Design standardization: Adopt standard profiles, plate thicknesses and connection methods to facilitate procurement, manufacturing and spare parts management.
• Modular design: Large equipment should be designed into modular structures as much as possible to facilitate factory manufacturing, quality control, transportation and rapid on-site installation.

7. Material Selection Requirements

• Main structure: Generally use ordinary carbon structural steels or high-strength low-alloy steels such as Q235B and Q355B, with qualified material certificates required.
• Special parts: According to the needs of wear resistance, corrosion resistance or strength, select wear-resistant plates (e.g., NM360/NM400), weathering steel (e.g., Q355NH), stainless steel or higher-strength alloy steels.
• Material traceability: Important components must have complete traceability records for their materials.

Summary