Project Details
Dual Gas Detector Installation at Pohang City Sewage Sludge Recycling Facility
RS Korea completed two simultaneous fixed-gas-detector installations at the Pohang City Sewage Sludge Recycling Facility — a municipal wastewater treatment and resource-recovery plant that collects household food-waste effluent and converts the resulting sludge into reusable material. Following multiple pre-construction site surveys and coordination meetings, a two-team crew of four technicians completed both installations in a single day. Site 1 (sludge receiving bay) received a FIX800 multi-gas detector configured for O₂, H₂S, and EX (LEL), paired with an outdoor status display board. Site 2 (dried-sludge storage tank) received a FIX800 CO detector with an advanced extractive pre-treatment unit and a free-standing stainless-steel enclosure.
Installation Specifications
| Item | Details |
|---|---|
| Detector model | FIX800 (fixed multi-channel gas transmitter) |
| Site 1 — Sludge Receiving Bay | FIX800 configured for O₂ / H₂S / EX (LEL); outdoor LED status display board; wall-mount installation with concrete core-drilling |
| Site 2 — Dried-Sludge Storage Tank | FIX800 configured for CO; advanced extractive pre-treatment unit with PTFE sampling hose; free-standing SUS enclosure; 4–20 mA signal output wired to facility DCS |
| Installation environment | Enclosed / confined-space (sludge bay sealed by shutter after unloading); large indoor storage tank with combustible off-gas accumulation risk |
| Construction schedule | 2 teams × 2 technicians, 1-day concurrent installation |
Hazard Characteristics and Key Safety Considerations at Sludge Recycling Facilities
- Confined-space asphyxiation and H₂S exposure: After the unloading shutter closes, the sludge receiving bay becomes a sealed confined space. Decomposing organic sludge continuously generates H₂S and displaces O₂, creating an immediately dangerous atmosphere for any worker who enters without prior gas clearance.
- Explosive gas accumulation in storage tanks: Dried sludge in the storage tank off-gasses combustible hydrocarbons, including methane. Even a minor ignition source can trigger a fire or deflagration; continuous CO monitoring provides an early indicator of smouldering or incomplete combustion before an event escalates.
- Extractive sampling for high-humidity environments: The storage-tank environment contains elevated moisture and particulates. The advanced pre-treatment unit (filter, pump, dryer) conditions the sample gas before it reaches the electrochemical CO sensor, preventing sensor contamination and ensuring measurement accuracy.
- 4–20 mA signal integration: Both detectors output industry-standard 4–20 mA analog signals, enabling direct integration with the facility's existing PLC/DCS and enabling automated alarm relay and data logging without additional signal converters.
- Pre-construction coordination as a key success factor: Installation point selection, power-supply routing, and GAS IN/OUT port welding were all agreed and prepared during pre-site meetings, allowing the actual field work to be completed cleanly in one shift with no rework.
Frequently Asked Questions
What gases must be monitored in a sewage sludge receiving bay?
At minimum, O₂ (oxygen deficiency), H₂S (hydrogen sulphide from organic decomposition), and EX/LEL (explosive gases such as methane) should be monitored simultaneously. Because the bay becomes a confined space when the shutter is closed, multi-gas detection is required under Korean Occupational Safety and Health regulations for confined-space entry.
Why is CO monitoring used in the dried-sludge storage tank rather than LEL?
Dried sludge can undergo slow smouldering combustion before any visible flame or significant heat is detectable. CO is produced at the very earliest stages of this process, making it the most sensitive early-warning indicator for incipient fire. LEL sensors detect flammable gas concentrations but respond later in the combustion sequence, so CO monitoring provides an additional layer of protection for this application.
What is an extractive pre-treatment unit, and why is it required here?
An extractive pre-treatment unit actively draws a gas sample through a filter, moisture separator, and often a pump, conditioning it before it reaches the sensor. In high-humidity or dusty environments such as a sludge storage tank, raw ambient sampling would quickly foul or saturate electrochemical sensors and produce erroneous readings. The pre-treatment unit maintains measurement integrity over the long service intervals typical of municipal infrastructure.
How is the FIX800 powered in facilities where electrical fit-out is not yet complete?
In this project the dried-sludge storage-tank unit was commissioned using a portable power bank to verify correct sensor readings and alarm thresholds before the permanent 220 V supply was energised. This approach allows functional verification and client handover training to proceed on schedule, with permanent power connected by the facility's electrical team at a later date.
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