The new lifts
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Replacement of the Fastest Lifts in the UK
Having undergone a thorough cleaning of its exterior, attention was then focussed upon the inner workings, namely the two "Express" lifts which provide the necessary access between floors.
Circa January 1999 BT Today Newsdesk reported: -
The two high-speed lifts at London's BT Tower, which have been in service for the past 35 years, are being replaced. The customer centre, including ground floor, will close on Monday 1st February, and is scheduled to re-open towards the end of the year, depending on how the work progresses.
Abridged from 'Elevator World' Feb 2000:-
Ove Arup R&D was chosen as the lift consultant to oversee the whole project with the aim of
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The original specification was for 2 lifts, each to carry up to 15 persons or a load of 2,250 pounds in a car 6 feet, 3 inches deep by 4 feet, 6 inches wide through a doorway of 3 feet, 6 inches wide by 7 feet high.
To transport the following:
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Visitors to the Tower would once have been welcomed by:
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A special feature was the removable ceiling giving an increase in height from 7' 9" to 12' when necessary to accommodate large aerial sections. Serving 30 floors the lift was designed to run at 1000 feet per minute, making a journey time from the 1st floor public entrance to the high-level galleries of about 40 seconds. This was the highest speed lift in the UK.
The driving sheave of 38" diameter and 13" wide was mounted directly onto the 90 horsepower d.c. motor without the use of reduction gears. Each lift was suspended by 6 double wrapped steel-wire ropes and the system was balanced by the use of compensating ropes between the counterweight and the bottom of the car.
Nineties Survey & Initial Planning
To quantify the work required a number of surveys were carried out:
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'The Tower is the only building in the country which is allowed to be evacuated by lift and, for this, Parliamentary legislation had to be passed.'
Originally, much of the Tower was filled with switchgear from the Strowger era, which occupied 17 apparatus floors. Nowadays, to fully utilise the empty floors, if more office space is provided with more people, then a reliable lift service is essential in providing a safe working environment. To this end, a five-minute building evacuation has to be met, thus the lift speed is critical in achieving this new profile.
Lift speeds
The existing lifts were designed to operate at 1,000 feet per minute. This was increased in the 1980s to 1,200 feet per minute The computer indicated that a speed of 1,400 feet per minute was possible within the limitations of the pit depths and overruns.
Arup fire developed a revised evacuation strategy as part of the 'total solution'.
The New Specifications
Work was focussed on 3 key areas:
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Project Management
The contract for the new cars was awarded to Thyssen Lifts. However, as most new work on the Tower is 'project managed' a 'briefing day' was called by Arup, the overall contractor responsible. This allowed all interested parties to meet up and give a co-ordinated approach to the work on hand...
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Planning
Time, budget and practicalities dictated that the existing lift shaft and motor room equipment would need to be removed and replaced in its entirety. Refurbishment or overhaul of the original lifts was not an option-the 'swinging sixties' cars were destined for the scrapheap, to be replaced with a more spacious 21st century design having a height of 3.7 metres (approx 12 feet).
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The massive (sixties designed) gearless machines had to be thermic lanced into small enough pieces so that the one remaining lift could safely handle the weight. For the liftmen and engineers whom had once maintained similar machines, this was a sad day. Of course, the new machines were to deliver a better quality ride, but this was little consolation for destroying what was once lift technology on a grand scale.
Removal of the old fixtures and fittings revealed deficiencies in the design...
The car guide rails were rigidly pinned to each fixing point. This meant that there was little (give) flexibility in the rails as the lifts moved over them. Additionally, for the length of the Tower, the building itself was subject to some slight (vertical) settlement and over the years this had severely distorted the guide rails, giving a poorer quality ride. Equally though, overhaul of the entire system was long overdue.
Design features of the new system...
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The New Lift Cars
At 3.7 metres, these are among the tallest single-decker cars in the UK. Full assembly at Thyssen's Nottingham factory was not feasible, so the streamlined cones, top and bottom, were transported directly to the Tower.
John Gale, correspondent for Elevator World writes about Car Interior No. 1 (Sky Flight)...
"The interior finishes of this car certainly add a sky-like atmosphere to the journey, along with a crisp, clear, spatial sparkle. This was achieved by the use of optical white glass, which does not have that green tint to it, and 16 fibre-optic down lights. The modernist feel in the lift car is continued by the use of flat-screen indicators, special glass touch key pads and a laser-cut Tower graphic with blue LED position bars."
By November 1999, tests on the north lift proved more than satisfactory and the project moved onto Phase 2...
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When the management of Light Straw visited the Tower on 19th October 2002, Car Interior No.2, the south lift, operated by Dave Lemm, was fully completed. |
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THYSSEN |
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The new look glass landing doors of the 34th floor lift. The doors automatically open into the room when the lift arrives. |
Specialist Contractors
Liftout Ltd
[www.liftout.net/]
"Having discussed contract requirements in detail with the client, our quotations are economically costed and then confirmed following a full site survey. Health & Safety Policy, Risk Assessments and a full Method Statement are supplied on receipt of order and Plant Test Certificates are always made available for on-site Health & Safety File."
Using Thermic Lance cutting equipment, Liftout’s highly qualified engineers set about the task of cutting through the massive 300 mm shaft of the old lift machinery. The bulky mass of the redundant gearless machines soon became manageable and was transported safely in small pieces to the ground.
Elevator World Feb 2000
Post Office Electrical Engineers Journals & publicity handouts.
Critical Path
Critical Path Method or Critical Path Node is a British idea that was devised in 1957 by the research department of CEGB (Central Electricity Generating Board). In America, a similar process was not adopted until 1958.
Critical Path charts & diagrams (rather like a graph) give an indication as to the latest times that certain activities need to be completed to ensure that the overall project is finished on time (and often budget).
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