monitoring air flow gas detection temperature sensors CASE STUDY GAS DETECTION SYSTEM AT LOWER LEA VALLEY CABLE TUNNELS For Murphy Group/National Grid

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1 CASE STUDY GAS DETECTION SYSTEM AT LOWER LEA VALLEY CABLE TUNNELS For Murphy Group/National Grid monitoring gas detection air flow temperature sensors

2 PROJECT OVERVIEW Project Name: Company Name: Application: The purpose of the overall project was to re-locate overhead line circuits, which crossed the Olympic site in the Lower Lea Valley area as part of the Power Lines Underground (PLUG) project. The project involved the design and construction of 2 cable tunnels running parallel between Hackney and West Ham over a route length of approximately 6km. One tunnel is 4.15m nominal diameter and connects into National Grid Company (NGC) substations; the other is 2.82m nominal diameter and connects into EDF Energy (EDFE) substations. For the National Grid Tunnel, Trolex provided a gas detection system to monitor the main shaft, shaft staircases and plantrooms. Junctions of the shaft and tunnel were also monitored and additional carbon monoxide sensors were fixed at the plantroom inlet/outlet grills. Methane sensors were fixed at top of shafts. Lower Lea Valley Cable Tunnels J. Murphy & Sons/National Grid Gas Detection and Air Velocity Monitoring System The alarms where the sensors are sited are classed as Zone 1 so required ATEX Grp II equipment. These fed back up to the control panels via intrinsically safe barriers to the non certified cubicles containing gas racks. The following gases needed to be monitored: Methane Carbon Monoxide Hydrogen Sulphide Oxygen The monitoring and control panels were located in the control office of each shaft head building. The trip amplifiers located in the control panels monitored the various gas levels. Control relays were tripped at alarm set points to initiate alarms.

3 PRODUCTS USED TX6373 Toxic Gas Detectors Fixed toxic gas monitoring for point-source hazards and perimeter protection, measuring Carbon Monoxide, Hydrogen Sulphide and Oxygen High-accuracy electrochemical gas sensing elements Pre-calibrated, plug-in gas sensing modules with standardised output signal for convenient placement and servicing TX6363 Infrared Gas Detector TX Plant-safety protection for methane and carbon dioxide in hazardous areas Infrared gas sensing element with long-term stability Choice of analogue output signal: 4 to 20mA, 0.4 to 2V or 5 to 15Hz TX6274 Temperature Sensor High-accuracy temperature sensor with integral signal transmitter Optional LCD temperature readout Semi-conductor sensor or PT100 sensing element compatibility TX5922 Air Flow Sensor High-accuracy response with dynamic linearity correction Clear readout of signal values and function mode parameters Simple pushbutton scaling to match on-site parameters No moving parts, self-cleaning vortex sensing head for longterm stability.

4 SYSTEM DRAWINGS WEST HAM SHAFT NGT-1 TX6373 TX6373 TX6373 CARPENTERS ROAD NGT-2 HACKNEY NGT-3 $%%&#!!"# TX6363 Methane Gas Detector TX6274 Temperature Sensor TX6373 Carbon Monoxide Sensor TX6373 Oxygen Gas Detector TX6373 Hydrogen Sulphide Gas Detector TX5922 Air Flow Sensor

5 CUSTOMER VIEW J. Murphy & Sons (JMS) has been procuring Trolex equipment for over 15 years and have been known to us through a number of TBM OEMs for the environmental monitoring systems they provide in and around the TBMs. JMS have developed a working relationship with Trolex and when fixed gas monitoring at regular intervals became a British Standard good practice in this country, Trolex were able to offer JMS an affordable system that we could install & maintain. The Trolex environmental monitoring systems can be readily installed by our own fully trained operatives and only require a Trolex service engineer to attend for commissioning and regular maintenance. Trolex have delivered sensors that seem to be more tolerant in the humid conditions naturally encountered within the existing ventilated tunnel network which has helped prior concerns with fixed monitoring systems where we had issues affecting the durability of the various sensors/cells remaining in calibration and failing within months rather than years in operational service. Trolex have always been an approachable company that are always willing to assist in mutually resolving problems & issues that can manifest themselves on challenging projects.

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