Construction of Terminal 5 at
Helping to keep this huge construction project on schedule are Lee-Dickens Sitewatch Remote Terminal Units (RTUs) used as part of a remote inventory management and supply chain logistics system to ensure the estimated 1.5 million m3 of cement necessary for the project is continuously available.
The Terminal 5 programme extends far beyond the construction of just a terminal building. It also includes a total of 60 aircraft stands, two satellite buildings (one in phase 2), a 4,000 space multi storey car park, a new control tower, the diversion of two rivers and an airport perimeter road, and over 13km of bored tunnel, including extensions to the Heathrow Express and Piccadilly Line underground services. Just over 3000 construction workers are currently employed on the project.
A construction programme of this scale presents many engineering challenges, made ever more complex by being next to a busy airfield. One of the most vital logistical challenges to overcome to ensure the project runs to schedule is the timely availability of ordinary portland cement (OPC) and pulverised fuel ash (PFA) at the construction site.
Delivery of raw materials arrives at a rate of around 1000 tonnes of OPC and PFA a day, the equivalent of 35 lorries a day (peaking at 1400 tonnes of OPC/PFA or 45 lorry loads per day). With such large requirements BAA have installed 18 silos onsite to store the cement and PFA. This ensures that both are constantly available, thereby preventing any build downtime.
In order to co-ordinate and direct the delivering of cement and PFA to the site, Laing O’Rourke and AMEC, the principal civil contractors on the T5 project, are employing three Lee-Dickens’ Sitewatch Midi Remote Terminal Units (RTUs) to monitor in real time the levels of cement and PFA in silos.
The Lee-Dickens Sitewatch RTU’s use existing load cell sensors mounted on each of the silo’s stanchions to measure the current level in the tank and from that calculate the quantity of fill space available. This fill space determines where the delivery vehicles should be directed to on the site and that no areas will be allowed to run out of product.
The silos are positioned in three separate groups (Batchers) with a Sitewatch RTU sending fill space information from either four or six silos back to a master station computer via the Public Switched Telephone Network (PSTN). The real-time level data is then updated to a series of web pages every 15 minutes allowing the BAA site managers to best direct and control the delivery traffic and the product usage.
In addition to the RTU hardware, Lee-Dickens’ Systems Division is also providing BAA/Laing O’Rourke/AMEC with a `Bureau Service’ that takes care of the operation and maintenance aspects of the telemetry central master station. This involves the design, configuration and maintenance of the password protected HTML web pages that display product usage rates and recent history.
”There are a number of ways in which the information can be made available to the customer including, XML files, Email, Voice Mail, WAP Pages and SMS,” said Tony Meadows, System’s Division Director, Lee-Dickens. “HTML has proved to be particularly popular with BAA, Laing O’Rourke and AMEC as both real time and historical data can be viewed with a standard Internet browser, subject to account permissions. This gives the construction logistics managers the ability to view levels of any silo at anytime, anywhere on or off site.”
“We put the task of measuring the silo fill space into the hands of Lee-Dickens who provide the data back to us on our own set of private web pages. The data acquisition and online presentation of this data via their Bureau Service, allows us to focus on our core business and not concern ourselves with the day to day running of a remote data gathering system,” said Steve Honeybone, Bulk Material & logistic Centre Manager, BAA.