Project Details
FIX800 4-Gas Detector Relocation: Seoul Dongbuk Line Tunnel Construction, Nowon-gu
RS Korea's technical sales team carried out the relocation and reinstallation of FIX800 fixed 4-gas detectors (O₂, CO, H₂S, EX) across four confined-space worksites along the Seoul Dongbuk Light Rail tunnel construction corridor in Nowon-gu and Seongbuk-gu, Seoul. As excavation progressed, each detector unit was decommissioned, physically moved to the new working face, and recommissioned to maintain continuous gas monitoring throughout the advancing tunnel sections.
Installation Specifications
| Item | Details |
|---|---|
| Detector model | FIX800 fixed multi-gas detector |
| Gases monitored | O₂ (oxygen), CO (carbon monoxide), H₂S (hydrogen sulfide), EX (combustible gas / LEL) |
| Installation environment | Underground tunnel shafts and ventilation adits — confined space, high dust, water ingress risk |
| Mounting method | Originally magnetic bracket on H-beam steel; re-mounted with anchor bolts (cal-block) into cured concrete walls due to on-site conditions |
| Sites covered | Station 113 (Hagye-dong 266, Nowon-gu) · Vent 112E (Hagye-dong 266, Nowon-gu) · Vent 111E (Hagye-dong 271-7, Nowon-gu) · Vent 109E (Jangwi-dong 311-20, Seongbuk-gu) |
Key Hazard Considerations for Tunnel Confined-Space Gas Monitoring
- Blast-generated dust: Drill-and-blast excavation produces sustained airborne particulates that can clog sensor inlets; enclosures and sensor protection measures are essential for continuous reliable measurement.
- Water ingress: Groundwater and surface drainage collect inside ventilation shafts. At Vent 112E, accumulated water inside the enclosure (channelled by H-beam geometry and curing protective foam) caused contamination; units must be sited to prevent pooling rather than simply sheltered from direct rain.
- Repeated relocation requirement: Progressive tunnel excavation advances the hazardous zone, making the magnetic-bracket quick-release enclosure design a key operational feature — enabling rapid repositioning without specialist tooling under normal conditions.
- Oxygen deficiency and toxic gas accumulation: Confined tunnel shafts are susceptible to O₂ depletion, CO and H₂S build-up from machinery exhaust and ground gases, and LEL-range combustible gas pockets, all of which require simultaneous real-time monitoring.
- Wired communication integration: Each detector unit interfaces via hardwired communication lines with an LED display board at the shaft entrance; the full system (detector + cabling + display) must be safely de-energised before relocation and fully re-terminated and function-tested after reinstallation.
Frequently Asked Questions
Why are four gases (O₂, CO, H₂S, EX) monitored simultaneously in tunnel construction?
Underground excavation environments present multiple concurrent hazards: oxygen can be displaced by ground gases or combustion products (creating asphyxiation risk), CO and H₂S can accumulate from diesel machinery and geogenic sources to toxic concentrations, and combustible gases may reach explosive lower-explosive-limit (LEL) thresholds. Simultaneous monitoring of all four parameters ensures workers receive timely warnings for all relevant hazard types with a single fixed instrument.
What is the relocation procedure for the FIX800 during active tunnel construction?
The standard relocation sequence consists of four steps: (1) power off the detector and any wired display boards connected to it; (2) physically detach and move the detector unit to the new position; (3) re-lay and route the power and communication cabling; (4) reconnect wiring and verify normal operation with live gas readings before leaving the site.
Why was the mounting method changed from magnetic brackets to concrete anchors?
The original magnetic bracket design is intended for attachment to steel structural members (H-beams) for easy repositioning. At several sites, the available steel surfaces were obstructed by work vehicles and worker traffic, and the concrete lining had already been cured, making concrete anchor bolts (cal-blocks) the only secure and practical alternative. The change increased installation effort but ensured structural stability of the detector.
How should FIX800 detectors be protected against water ingress in shaft environments?
Detectors should be positioned to avoid locations where water can pool or channel onto the enclosure — in particular, the inner face of H-beams (rather than the flange face) can trap water redirected by safety foam and tarpaulins. At Vent 112E, internally accumulated water was found upon relocation; the unit was cleaned and confirmed operational, but the incident highlights that drainage path analysis at each mounting point is as important as shelter from direct precipitation.
