Common Problems and Solutions in Factory & Mining Equipment Production

Mining equipment typically operates in extremely harsh environments (high dust, high humidity, heavy loads, and continuous operation). This places exceptionally high demands on equipment installation, operation, and maintenance.
To facilitate review and discussion, these 50 common problems are divided into four major sections: Installation, Operation, Mechanical Maintenance, and Electrical & Automation.

Part 1: Equipment Installation (1-12)

Keywords: Industrial equipment installation, secondary grouting, alignment, thermal expansion in machinery.

1. What are the consequences of improper secondary grouting for foundations?

• Analysis: It leads to resonance during operation, loosening of anchor bolts, and eventually results in base fractures or premature bearing failure. Large hollow areas can cause subsidence under prolonged vibration, leading to severe equipment tilting, loss of center of gravity, and bearing damage.

1. Why must center-line deviation be strictly controlled during large ball mill installation?

• Analysis: Excessive deviation causes poor gear meshing, creating periodic impacts that accelerate wear or cause tooth breakage. Long-term eccentric meshing impacts the reducer shafts and bearings, reducing fatigue strength. It also causes current spikes in the motor due to unstable torque, affecting the coils.

1. What should be done if the drive drum and tail drum of a belt conveyor are not parallel during installation?

• Analysis: The bearing seat positions must be adjusted to ensure parallelism; otherwise, the belt will suffer severe permanent misalignment. If distortion occurs, the concentricity and level must be restored immediately to prevent tracking issues.

1. Causes of insufficient “NPSH” (Net Positive Suction Head) in mining pump installation?

• Analysis: Usually caused by an excessive installation height or high resistance in the suction pipeline, leading to cavitation (bubble collapse) that impacts the impeller. Check for foreign objects or crystals blocking the pipes. Standby units should be installed for timely switching. Cavitation is often identified by irregular abnormal noise in the pump body.

1. Why consider thermal expansion during coupling alignment?

• Analysis: Temperature rises during operation cause the shaft centerline to move upward. Cold installation requires a pre-calculated offset. Without room for expansion, heat can cause “cylinder topping” against connected equipment. Reserving axial clearance is essential for spherical roller bearings with internal play.

1. Impact of unbalanced spring installation on vibrating screens?

• Analysis: It causes the screen body to sway laterally and creates uneven stress, leading to structural tearing of the screen frame. Uneven spring height or position causes tilting and excessive impact on one side, eventually leading to fractures.

1. Hazards of insufficient or excessive bolt pre-tightening force?

• Analysis: Insufficient force causes bolts to loosen, leading to vibration, shifting, or impact cracking. Excessive force exceeds the material’s yield limit, leading to bolt elongation or fracture.

1. How to control welding deformation at the installation site?

• Analysis: Use symmetrical welding, segmental welding, and a reasonable welding sequence. Monitor the thermal stress deformation caused by workpiece temperature while ensuring symmetrical execution.

1. Principles for arranging equipment base shims (padding iron)?

• Analysis: Shims should be placed on both sides of anchor bolts and at concentrated load points. Each stack should not exceed 5 pieces. Minimize shim use during infrastructure construction to reduce displacement caused by vibration.

1. Precautions for dismantling and installing large underground equipment?

• Analysis: Strictly record the disassembly sequence and protect seals to prevent mine dust from entering precision surfaces. Due to limited space, protect parts from bumps and corrosion caused by underground mineral content.

1. Cleaning standards for hydraulic pipelines before installation?

• Analysis: Pipelines must undergo acid pickling or circulatory flushing to reach NAS Class 7 or equivalent cleanliness. Otherwise, hydraulic components will be easily damaged.

1. Why perform a 24-48 hour trial run after installation?

• Analysis: To wear in mating surfaces, observe temperature rise and vibration stability, and detect assembly hazards early. Check the tightness of fixing bolts and the overall mechanical coordination.

Part 2: Use and Operation (13-25)

Keywords: Mining equipment operation, crusher maintenance, hydraulic system troubleshooting, safety valves.

13. What happens if a crusher experiences “tramp iron” (unbreakable objects)?

• Analysis: Foreign objects can cause main shaft breakage, liner cracking, or transmission system collapse. In severe cases, it leads to “overspeeding” (runaway), resulting in massive economic losses.

13. Why is it strictly forbidden to start large conveyors under load?

• Analysis: The startup current or torque is too high, which can burn the motor or snap the belt. Without protection, the motor will be destroyed. Always empty the belt before stopping; never stop with material on the line.

13. Consequences of high fluctuations in ball mill feeding rates?

• Analysis: It affects grinding fineness and leads to “over-filling” or increased liner impact wear. Unbalanced loads cause current fluctuations, shorten motor life, and produce uneven mineral powder grain size.

13. How do operators judge faults by “listening, touching, seeing, and smelling”?

• Analysis: Listen for abnormal noise, touch for vibration/heat, see pressure gauges, and smell for burning odors. Use a listening rod to locate noise sources and identify the fault type quickly to prevent further damage.

13. Causes of unstable pressure in hydraulic systems?

• Analysis: Air intake in the oil pump, relief valve failure, or filter blockage. Check the oil level and quality via the sight glass. Pipeline leaks and valve malfunctions are primary causes.

13. Why follow the sequence “start downstream first, stop upstream first”?

• Analysis: To prevent material accumulation that could “choke” the machine or cause overflow. Starting empty ensures the system is safe before material enters.

13. Is a very high lubricating oil level beneficial?

• Analysis: No. Excessive oil causes churning and heat, increases power consumption, and leads to seal leakage. In dusty areas, leaked oil attracts dust, accelerating seal wear and damaging internal components.

13. What is the function of the pneumatic FRL (Filter, Regulator, Lubricator) triplet?

• Analysis: To filter air, regulate pressure, and provide oil mist lubrication to protect pneumatic components.

13. Why is it forbidden to stop a crusher when there is material in the chamber?

• Analysis: There is a high risk of “locked rotor” on the next start. This leads to excessive current, belt slippage, and potential breakage of the liner or main shaft.

13. Risks of overloading a hoist?

• Analysis: Accelerated wire rope fatigue and insufficient braking torque, which can lead to rope slippage or snapping, causing irreversible injury and equipment damage.

13. Why must standby equipment be turned (barring) regularly?

• Analysis: To prevent axial shaft bending or localized indentation/corrosion on bearings. Periodic barring reduces the impact of humidity and gravity on rotating parts.

13. What to note for outdoor equipment in freezing seasons?

• Analysis: Switch to low-viscosity lube oil, preheat hydraulic oil, and prevent pipe freezing. Drain cooling water from idle equipment to prevent cavity cracking.

13. Why can’t the setting pressure of a safety valve be adjusted higher at will?

• Analysis: It removes the overpressure protection, potentially leading to explosions or major structural failure. It forces the equipment to run beyond its fatigue limit.

Part 3: Mechanical Maintenance (26-38)

Keywords: Bearing failure analysis, gear reducer leak repair, non-destructive testing, preventative maintenance.

26. Five common causes of bearing overheating?

• Analysis: Lack of oil, excessive oil, contaminated grease, poor alignment, and insufficient bearing clearance. Also, cooling system failure or deteriorated grease.

26. How to manage oil leaks in gear reducers?

• Analysis: Check seals for wear, clear vent holes, and improve joint surface sealing. Inspect oil seals, observation ports, and joint gaskets for targeted repair.

26. Why do liner bolts loosen easily?

• Analysis: Severe material impact and vibration. Self-locking nuts should be used, and regular tightening checks are required.

26. How to detect metal wear debris in lubricating oil?

• Analysis: Ferrographic analysis. Take samples from the drain port for visual inspection and use analyzers to determine metal content.

26. Why must important rotating parts undergo dynamic balancing after repair?

• Analysis: Mass eccentricity creates massive centrifugal force at high speeds, leading to the destruction of bearings and bases.

26. Causes of “crawling” (stuttering) in hydraulic cylinders?

• Analysis: Air trapped in the system or excessive friction from seals.

26. When should wire ropes be scrapped?

• Analysis: When the number of broken wires within one lay length reaches the specified ratio or the local diameter reduces significantly (per Safety Codes for Lifting Appliances).

26. How to repair worn pin-type parts?

• Analysis: Use buildup welding followed by machining, thermal spraying, or replacing the wear sleeve.

26. Why are cold bonding or hot vulcanization better for belt joints than mechanical clips?

• Analysis: They offer higher strength, smoother operation, and do not damage drums or scrapers.

26. Causes of a drop in centrifugal pump head?

• Analysis: Severe impeller wear or seal failure in the suction pipe.

26. How to judge if a bearing has fatigue spalling?

• Analysis: Irregular vibration noise during operation. Upon disassembly, pitting or layered peeling is visible on the raceway.

26. What is “Maintenance over Repair”?

• Analysis: Strengthening inspections and proactive lubrication to prevent small issues from evolving into major accidents.

26. How to choose materials for wear parts?

• Analysis: Based on working conditions. Choose high-manganese steel for high impact and high-chromium cast iron or cemented carbide for high abrasion.

Part 4: Electrical & Automation (39-50)

Keywords: Motor overcurrent, VFD troubleshooting, PLC maintenance, mine explosion-proof electricals.

39. Causes of high motor operating current?

• Analysis: Overload, low supply voltage, three-phase imbalance, or mechanical jamming.

39. How to troubleshoot frequent “Overcurrent” faults in a VFD (Variable Frequency Drive)?

• Analysis: Check cable grounding, load fluctuations, and whether the startup acceleration time is too short.

39. Why must underground electrical equipment be explosion-proof?

• Analysis: To prevent electrical sparks from igniting methane gas or coal dust.

39. Causes of high interference in control system sensors?

• Analysis: Shielded wires not grounded or power lines laid parallel to signal lines.

39. Possible causes of PLC program freezing or loss?

• Analysis: Depleted lithium battery, external electromagnetic interference, or power supply quality fluctuations.

39. Why install temperature measuring elements (PT100) in large motors?

• Analysis: To monitor winding temperature in real-time and prevent insulation aging or burnout.

39. Difference between Soft Starters and Direct-on-Line (DOL) starting?

• Analysis: Soft starters reduce current impact on the grid and lower shear stress on mechanical transmission parts.

39. Why must control cabinets be cleaned regularly?

• Analysis: Mine dust can be conductive or block heat dissipation, leading to short circuits on circuit boards.

39. Causes of frequent proximity switch failure?

• Analysis: The sensing distance is set too close (mechanical impact) or the protection rating is insufficient (water ingress).

39. Logic design requirements for Emergency Stop buttons?

• Analysis: Must use “Normally Closed” (NC) contacts and have the highest priority for physical disconnection.

39. Core value of mine automation monitoring systems?

• Analysis: Achieving unmanned or reduced-staff operations, enhancing safety, and optimizing processes.

39. How to prevent cables from being snapped on mobile equipment?

• Analysis: Install cable reels and configure limit switches and tension protection switches.

1

• Primary Keywords: Mining equipment troubleshooting, factory machinery maintenance, industrial equipment installation, equipment failure solutions.
• Long-tail Keywords: How to fix ball mill gear wear, causes of conveyor belt misalignment, hydraulic pump cavitation solutions, preventing motor burnout in mines, PLC maintenance for industrial automation, explosion-proof electrical standards for mining.
  Conclusion:
  In actual production, “30% depends on installation, 70% depends on usage.” Most failures originate from minor installation deviations or operational violations.
  Recommendations: 1. Digital Logs: Turn these 50 points into a digital inspection checklist.

1. Preventative Maintenance (PM): Use condition monitoring to intervene before a breakdown.
2. Training: An operator’s ability to detect early signs is the first line of defense against major accidents.
   Would you like to delve deeper into a specific machine (e.g., Crusher, Hoist) or focus on a specific technical section?