Introduction

In mining safety monitoring systems, smoke detectors are key sentinels for early fire warning. The response speed and reliability of these detectors directly affect personnel evacuation and incident control.

Compared with routine inspections, replacing smoke detectors is a high-risk operation. The underground environment is complex, with gas, coal dust, and electrical equipment coexisting, and any improper operation can amplify safety hazards.

Leveraging over 40 years of expertise in mining safety monitoring, Nexisense has systematically compiled key safety rules and operational points for underground smoke detector replacement, providing actionable and traceable guidance for field operations.

Core Principles of Underground Smoke Detector Replacement

Before starting the procedure, a fundamental consensus must be established: replacing a sensor is not simply "equipment swap," but a controlled safety operation. Core goals include:

• No introduction of new ignition sources

• Preservation of the integrity of existing monitoring systems

• Ensure post-replacement data is accurate, reliable, and usable

All operations should revolve around these three objectives.

Pre-Replacement Preparation

Operation Approval and Safety Protection

• Work Permit: Obtain approval from ventilation and safety management departments, specifying work time, location, and responsible personnel. Ensure complete power shutdown procedures.

• Environmental Gas Detection: Conduct on-site testing within 30 minutes before work. Required thresholds:

• CH₄ < 0.5%

• CO < 24 ppm

• O₂ 18%–22%

• Dedicated Supervision: At least two personnel cooperate, with one operating and one monitoring, maintaining real-time communication.

Equipment and Tool Check

• Sensor Unit: Must be the same model, with clear explosion-proof markings, valid MA certification, and parameters consistent with system configuration.

• Tools: Only intrinsically safe tools, such as copper wrenches and screwdrivers, with pressure resistance ≥1.5× working pressure.

• Standard Test Media: Smoke aerosol standard agent with typical concentration 0.2 dB/m for function and alarm testing.

• Auxiliary Materials: New sealing rings, explosion-proof clay, waterproof tape, etc., prepared in advance to avoid mid-operation retrieval.

  
  

Replacement Procedure

Power Shutdown and Site Isolation

• Disconnect smoke detector power (intrinsically safe and explosion-proof mining substation)

• Wait at least 3 minutes to release residual system charge

• Hang "Personnel Working, Do Not Energize" warning sign, confirmed by supervisor

Old Sensor Removal

• Record Wiring Information: Photograph wire sequence and color correspondence to prevent misconnection.

• Remove Interface Smoothly: Avoid forceful rotation or pulling to prevent cable thread and seal damage.

• Temporary Sealing: After removal, immediately seal the interface with explosion-proof clay to prevent dust and moisture entry.

New Sensor Installation

• Verify product model, communication method, and system configuration

• Replace with a new sealing ring for secure interface fit

• Reconnect according to original wiring sequence and tighten to prevent loose connection or stress concentration

• Confirm the sensor is firmly fixed with no movement after installation

Post-Replacement Mandatory Checks

Basic Function Testing

• Status Indicators: Power indicator normal and warning status according to device specifications

• Alarm Response: Trigger with smoke test agent; audible and visual alarm response ≤15 seconds

• Data Upload Verification: Ground monitoring system values match on-site status without delay or packet loss

Installation Quality Verification

• Seal Check: Apply soap water at interfaces; no bubbles should form

• Installation Angle: Sensor tilt ≤5°; use laser level if necessary

• Protection Measures: Add guard rails or protective covers in high-risk areas like belt galleries

Common Errors and Risk Mitigation

• Plugging/unplugging cables under power may cause sparks

• Mixing different sensor models can cause parameter mismatch

• Skipping calibration leads to cumulative measurement deviation

• Reusing sealing rings reduces protection grade

The key to avoiding these issues is strict adherence to procedures, not relying on experience alone.

Nexisense Professional Recommendations

• Use original or certified accessories to ensure system compatibility

• Maintain complete replacement records: time, personnel, and test data

• Regular Inspection:

• Monthly check of wiring and fixture status

  
  

• Quarterly function and alarm testing

These measures significantly enhance long-term system stability.

Emergency Handling Key Points

• Unexpected power outage: Restore sensor protective cover, stop work, evacuate to safe area

• False alarm: Immediately notify control center and reset within 5 minutes according to procedure

• Device abnormality: Pause work, report to ventilation or technical department, do not operate faulty equipment

Conclusion

Underground smoke detector replacement appears routine but tests safety awareness, procedural compliance, and professional competence. Through thorough preparation, standardized operation, and strict post-replacement verification, risks can be minimized, ensuring the monitoring system functions effectively when needed. Nexisense believes reliable safety monitoring depends not only on device performance but also on respect and diligence in every detail of operation.