Reducing the noise generated by a jaw crusher is crucial for worker safety, environmental regulations, and community relations. Jaw crushers are inherently noisy due to the high-impact nature of rock crushing. Here’s a breakdown of methods to reduce jaw crusher noise, categorized for clarity.

How To Reduce The Noise of Jaw Crusher

1. Source Control (Modifying the Crusher/Process):

Optimize Feed:

Consistent Feed Rate: Avoid large, sudden drops of material. A steady, choked feed (keeping the crushing chamber relatively full) can sometimes dampen impact noise slightly, although it might increase overall operational noise. Experiment to find the optimal balance.

Scalping: Pre-screen the feed material to remove fines that don’t need crushing. This reduces the amount of material going through and can lower noise.

Proper Maintenance:

Lubrication: Ensure all bearings and moving parts are adequately lubricated to reduce mechanical noise.

Tighten Fasteners: Loose bolts and components can vibrate excessively, creating noise. Regularly check and tighten all fasteners.

Replace Worn Parts: Worn jaw plates, bearings, and drive components can operate less efficiently and generate more noise. Replace them promptly.

Balance Rotating Parts: Ensure flywheels and drive components are properly balanced to minimize vibration.

Operational Settings: Ensure the crusher is operating at the recommended speed and Closed Side Setting (CSS) for the material being processed. Incorrect settings can increase stress and noise.

2. Path Control (Blocking or Absorbing Noise Transmission):

Enclosures:

Full Enclosure: Build a soundproof or sound-reducing enclosure around the crusher itself. This is often the most effective method but also the most expensive.

Considerations include:

Materials: Use heavy materials with good sound transmission loss (e.g., concrete, thick steel) combined with internal sound absorption materials (e.g., mineral wool, acoustic foam).

Ventilation: Enclosures require adequate ventilation systems, which themselves need silencers to prevent noise leakage.

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For more detailed information on how to reduce the noise of jaw crusher, please click here: https://www.yd-crusher.com/a/news/how-to-reduce-the-noise-of-jaw-crusher.html

Reducing noise from tunnel lining equipment is crucial for worker health and safety, environmental compliance, and maintaining good relations with nearby communities. Noise in tunnels is often amplified due to the confined space and hard, reflective surfaces. Here’s a breakdown of strategies, following the hierarchy of controls (elimination/substitution, engineering controls, administrative controls, PPE).

How to Reduce Tunnel Lining Equipment Noise

1. Source Control (Elimination, Substitution & Engineering Modifications): This is the most effective approach.

Equipment Selection (Procurement):

Specify Low-Noise Equipment: When purchasing or renting equipment (TBMs, segment erectors, grout pumps, ventilation fans, locomotives), specify maximum noise emission levels in the tender documents. Request noise data from manufacturers (sound power levels).

Choose Quieter Technologies: Opt for electric or hydraulic systems over noisier pneumatic ones where feasible. Use variable speed drives (VSDs) for fans and pumps so they only run as fast as needed. Consider modern, quieter engine designs for diesel equipment.

Engineering Modifications to Existing Equipment:

Engine/Motor Enclosures: Install well-sealed acoustic enclosures around noisy engines, motors, and pumps (e.g., grout pumps, generators). Ensure adequate ventilation for cooling, often requiring silenced air inlets and outlets.

Silencers/Mufflers: Fit high-performance silencers to engine exhausts and ventilation fan inlets/outlets. Ensure they are correctly sized and maintained.

Vibration Isolation: Mount noisy components (engines, pumps, gearboxes) on vibration isolators (rubber mounts, springs) to prevent vibration from transferring into the equipment structure or tunnel lining, which then radiates noise.

Hydraulic System Noise: Use low-noise hydraulic pumps, accumulators to dampen pulsations, and flexible hoses instead of rigid pipes where possible to reduce vibration transmission.

Conveyor Systems: Use low-noise rollers, belt materials, and ensure proper alignment and tension to minimize noise. Enclose drive units.

Grouting Equipment: Use pulsation dampeners on pumps. Enclose mixers and pumps if possible.

Segment Erectors: Ensure smooth hydraulic operation. Maintain components to prevent jerky movements or impacts.

Damping Materials: Apply damping materials (e.g., constrained layer damping) to large vibrating panels on equipment (like enclosures or guards) to reduce noise radiation.

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More detailed information on how to reduce noise from tunnel lining trolleys can be found at: https://www.gf-bridge-tunnel.com/a/blog/how-to-reduce-tunnel-lining-equipment-noise.html

Tunnel lining trolleys, also known as tunnel formwork systems or tunnel shuttering machines, are essential equipment used for in-situ concrete lining in tunnel construction. Depending on tunnel structure, size, and construction methods, tunnel lining trolleys can be classified into several types. These are large, mobile structures used inside tunnels to support the formwork for cast-in-place concrete linings or to install precast concrete segments.

Tunnel Lining Trolley Type

The primary categorization is based on the type of lining they are designed for:

Formwork Trolleys (for Cast-in-Place Concrete Lining):

These trolleys carry large sections of steel formwork. They position the formwork against the excavated tunnel profile, concrete is pumped behind it, and once the concrete cures sufficiently, the trolley lowers (strips) the formwork and moves forward (travels) to the next section.

Sub-types based on Formwork Configuration:

Full-Round Formwork Trolley: Carries formwork for the entire tunnel cross-section (invert, walls, and arch) allowing for a single pour. Complex and heavy, often used for circular or near-circular tunnels.

Arch (or Crown/Sidewall) Formwork Trolley: Carries formwork only for the upper arch and sidewall sections. This is used when the invert (floor) is cast separately first (often using simpler screeding or a dedicated invert form). This is very common for horseshoe or D-shaped tunnels.

Invert Formwork Trolley: Specifically designed to carry the formwork for casting the tunnel floor (invert). Often used in conjunction with an Arch Formwork Trolley.

Telescopic Formwork Trolley: The formwork sections are designed to retract inwards (like a telescope) after stripping. This allows the entire trolley to move forward through the previously cast lining section without needing extensive dismantling. This is the most common type for longer tunnels due to efficiency.

Non-Telescopic (Collapsible) Formwork Trolley: Sections may hinge or collapse, but might not fully telescope. Movement might require more clearance or partial dismantling. Less common for continuous tunnel drives.

Portal Formwork: While not strictly a “trolley” in the travelling sense, specialized formwork systems are used at the tunnel entrances/exits (portals).

Segment Erector Trolleys (for Precast Concrete Segments):

These are used primarily in tunnels excavated by Tunnel Boring Machines (TBMs), although variations exist for conventional tunnels installing precast linings.

Their main function is to pick up precast concrete segments (delivered usually by multi-service vehicles or segment cars), rotate them to the correct orientation, and precisely place them to form a complete ring against the TBM’s shield or the previously installed ring.

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More detailed information about tunnel lining trolley types can be found at: https://www.gf-bridge-tunnel.com/a/blog/tunnel-lining-trolleys-type.html

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.

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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