Theme: lifts and escalators
Lift and escalator development has resulted in more efficient movement of passengers.
For lifts there is also a growing role in evacuation of buildings, and the current challenge to provide access for wheelchair users, required by the Disability Discrimination Act Significant advances have been made in both lift and escalator technology during the past decade. These advances, coupled with new legislation, a greater awareness of the possibility of using lifts for evacuation and the needs of the disabled, have pushed lifts to the top of the agenda.
Lifts without machine rooms have been on the market since 1995 and Kone recently celebrated the sale of its 50,000th MonoSpace lift. Competition from companies such as Otis, Schindler, Thyssen, Fujitec and Mitsubishi has led to the launch of similar products during the past four years.
Models were initially limited by factors such as travel distance, capacity, speed and robustness. Now they can be provided with travel distances of up to 70m (or 23 storeys), capacities of between eight people (630kg) and 21 people (1,600kg), and contract speeds of up to 1.6m/s. With four-car groups available, this will cater for the majority of the industry.
Units can withstand moderate damage, but don't be fooled by the VR (vandal resistant) range. In a vandal-prone application, lifts can become severely damaged. Subject to design load, therefore, it is worth considering lining the car interior and doors with a heavier-gauge stainless steel. A number of suppliers can also provide glazed vision panels within the car to achieve a semi-transparent aesthetic. However the external car construction can be somewhat unsightly.
The Kone MonoSpace range recently extended to the provision of healthcare lifts with capacities ranging from 1,600kg to 2,000kg, and goods lifts with a load capacity of up to 3,500kg. These lifts are 4:1 roped and, due to the machine torque, acceleration and rope speed, the maximum rated speed is currently limited to 1m/s, which is acceptable for healthcare and goods-lift applications.
During 2003 Kone is extending the MonoSpace range and Otis is doing likewise with its Gen2 range. These new passenger lifts will have contract speeds of up to 2.5m/s in either six- or eight-car group configurations. Fujitec also plans to launch an MRL product with a contract speed of 2.5m/s using its recently developed Tallon Drive system. These developments will make the selection of MRL lifts standard for the majority of construction projects.
Destination hall call systems Destination hall call (DHC) uses a neuralnetwork control algorithm to sector calls dynamically. People waiting in the lift lobby use a flat-screen touch pad to input their destination floor before they reach the lift.
The control system, armed with data on both the departure and destination floors of everyone waiting, assigns cars to stacks of floors to meet the demand. These screens can be wall-mounted or placed in a column or pedestal. They can provide restricted access to floors using identification codes, and building access-control systems can be integrated to input a call automatically.
When a call is accepted and sectored, the screen advises the waiting passenger to which lift the call is assigned. When the passenger enters the car, no additional commands are required. A display panel confirms the levels served for that trip, and normal position indicators advise the levels reached.
The efficiency and performance of this system can increase the normal 'up peak' handling capacity by up to 30 per cent depending on the building type and specification. The other major benefit is a reduction in passenger transit time to the destination level. DHC systems are best suited to existing buildings where the population has increased significantly to above the original design capacity. They are also suitable for buildings with different storey heights that are served by a central bank of lifts.
DHC systems are not intended to reduce the number of lifts required for a new development. Although during up peak modes the lifts will handle more traffic than the same number of lifts with a conventional system, in the two-way and down peak modes the traffic handling will be the same.
DHC systems are currently available from Schindler and Thyssen, which claim there are more than 800 installations worldwide. Schindler is currently installing its first UK DHC system on a four-car group of new lifts at 58 Fenchurch Street, London, by Kohn Pedersen Fox. With two lifts serving 17 floors and two lifts serving 12 floors, the use of DHC controls is intended to give equal service provision for the high- and low-rise levels in a far less complex way than by using traditional lift controls. Thyssen was recently commissioned to install this system at the landmark Centre Point building in New Oxford Street, London.
Escalators learn to stop Escalators are best used where there is a heavy and constant requirement to move people between levels, such as airports, retail centres and exhibition centres. New developments include energy-saving devices that reduce the speed of the escalator when vacant, but return it to normal when sensors at either end are activated. Many escalators are used for intermittent periods and this enables significant energy savings.
Curved escalators, manufactured by Mitsubishi, have been available for a number of years. They look fantastic, but come at a price. Only a handful of installations exist worldwide, mainly in retail centres.
Dual braking on lifts Lifts are required by EN81 to have a means to arrest the downward movement of an overspeeding car in the event of traction failure. The worst-case scenario is the detachment of all main hoist ropes from the car.
There are no reported instances of all ropes failing by material deterioration or mechanical failure. The cumbersome system used - a device to detect lift speeds above rated levels, that operates a rope to pull in safety gear on the car and clamps against the guide rails - should be questioned. EN81 does, however, allow the upward movement of the car to be arrested by alternative methods, such as sheave or rope brakes. These will then arrest the downward movement of the counterweight, if there are spaces below the lift pit.
If the code changed and sheave or rope brakes could be adopted to arrest the movement of the car and counterweight in either direction, the car construction would not have to withstand the forces applied during the operation of safety gear. This would also reduce the mass of the crown bar above the car that carries most of the load and maintains the verticality of the lift car under load conditions. In turn, the overall weight of the car and counterweight would be reduced, requiring less power and torque to operate the motor and therefore becoming more energy efficient. The reduction in car construction would also mean the guide rails and brackets would become smaller and the shaft dimensions would reduce, both laterally and vertically.
The main issue with this design is the human factor - the acceptance that uncontrolled movement of the car will be arrested by brake pads hydraulically operated against the polished surface of a drive sheave.
Sounds familiar? Motorcars have used this system for decades to great effect!
Evacuation lifts v stairs The current means of evacuating a building in the UK is via staircases. Indeed the message preached to all building occupants is:
'In the event of a fire do not use the lifts'. This is reinforced by lifts returning automatically to the main lobby - often empty - when fire alarms are activated, leaving occupants to search for alternative, perhaps unfamiliar, exit routes.
In the UK, provision is made in some buildings for means of escape via lifts with dual power supplies. BS 5588 Part 8 Code of practice for means of escape for disabled people allows the use of evacuation lifts provided they are operated by activating an 'evacuation switch.' This isolates lift call points and sends the lift directly to the exit floor.
Locating the lift in a protected enclosure and giving access via a protected lobby provides safety for occupants awaiting rescue.
Growing concern over the ability of occupants to negotiate staircases safely is leading to the search for alternative means of escape. Most research is based on the need to provide means of escape for both permanently and temporarily disabled occupants.
This could vary from an occupant requiring the use of a wheelchair, to a person who may find the ordeal of descending 10, 20 or even 50 storeys exhausting.
In Hong Kong, the 1996 Code of Practice on Means of Escape in Case of Fire was focused on high-rise buildings in excess of 80 storeys. All buildings, post-1996, must be provided with evacuation lifts departing from a refuge floor located every 15-20 storeys. Occupants make their way down staircases to refuge floors, where they board lifts designed specifically for escape.
Queuing only takes place on the refuge floor.
This is separated by compartment construction and smoke lobbies from adjacent floors.
The refuge floors should not be used as office accommodation.
High-rise projects in the UK are rare and do not generally exceed the 52-storey Canary Wharf Tower. It is unlikely that developers would accept a concept of 'losing' floors for typically lower UK buildings given the high costs of building here and loss of lettable space.
An alternative in the UK is to adopt a combination approach using staircases and lifts. The lifts could evacuate occupants who would find the staircases either impossible or uncomfortable to use. These lifts could be linked to the fire-alarm and detection system, (especially where phased evacuation is used), isolating the lift control panel and sending the lifts to priority areas.
Constructing the lift shaft and lobbies in fire-resisting materials would protect occupants from fire. Providing an air pressurisation system, which keeps the lobby at a higher pressure than the fire floor, would prevent smoke egress into either the lift or the lobby.
The biggest drawback of this design is the provision of a lift lobby big enough to ensure that lift evacuees are waiting in a protected environment. The potential occupancy of each floor level requiring escape via the lifts needs careful assessment, and could lead to large lift lobbies with a corresponding loss of net lettable space.
There is no doubt that the strategy of evacuation lifts will have increased benefits in safeguarding means of escape from highrise buildings. It requires careful analysis and should be used as a bespoke solution, tailored to the requirements of a particular building. The use of refuge floors could be combined with other features such as the provision of conference areas, museums, sky bridges or viewing galleries, while the use of refuge lobbies on each floor could incorporate the security or reception areas.
It is unlikely anyone will ever be able to startle the design team by chanting the mantra: 'The stair is dead long live the evacuation lift', considering the redundancy that staircases provide. However, it may be possible to reduce the size and number of staircases.
Lifts and the DDA The Disability Discrimination Act 1995, (DDA), Part III: Service Provision, has placed new responsibilities on service providers to accommodate the needs of disabled people. Since December 1996 it has been unlawful to treat disabled people less favourably than the able-bodied. Since October 1999, service providers have been required to make reasonable adjustments for disabled people and it is intended that from October 2004, reasonable adjustments should be made to premises to overcome physical barriers to access.
The implications of the DDA as far as lifts are concerned obviously differ between new and existing buildings. In the case of new buildings, incorporating the required features should be an exercise at the design stage. With existing buildings, accommodating the requirements will be more onerous - few buildings are easy to modify.
Step 1: Find a practical solution! BS:
6440, (1999), allows a platform without an enclosure or floor penetration to travel vertically a maximum of 2m in public buildings, (this can be 4m with an enclosure), and 4m in private dwellings. Travel of up to 9m, with three stops, can be achieved with an enclosed car and shaft.
The minimum internal platform dimensions defined by BS: 8300, (2001), and prEN81-70 to accommodate type A and B wheelchairs are 1,100mm wide by 1,400mm deep. Where type C wheelchairs are to be accommodated, the width increases to 2,000mm.
With a vertical shaft space for packaged equipment available, an MRL lift, in either traction or hydraulic configurations, may be suitable, but can be expensive. Excavation is needed to provide, for example, a 1,400mm pit, while the headroom of 3,800mm may necessitate roof alterations. A shaft wall is also required. Not surprisingly, some building layouts prohibit such alterations.
The second option is to use standard lifts designed for retrofitting within buildings, such as the Prestige unit by Moveman. These can be provided within a mild-steel sheet or part-glazed enclosure, while the 50mm pit and 2,300mm headroom are minimal. Such disabled-access units are designed for low use and, with a simple 240V single-phase design, are considerably more energy efficient than an MRL lift. The limitation of these is the restriction of 9m total travel distance over three floors. By comparison, MRL lifts can travel up to 70m with a capacity of 26 people or 2,000kg.
Both lift types can accommodate type A and B wheelchairs. However, the increased width requirement for type C wheelchairs is outside the general range of disabled lifts and an MRL lift would be required.
Step 2: Research the building layout and structure to locate common areas on each floor that may line through vertically, such as storage areas. These areas then need a structural check to see if cutouts can be formed to suitable dimensions. The area in front of the proposed location must be at least 1.5m by 1.5m to allow a wheelchair to turn and reverse in or out of the lift.
Step 3: Ensure the proposed lift meets the requirements of the DDA - that:
lthe call stations are clear and indicate the lift is coming;
lthe door open time is a minimum of five seconds and a reopening device is provided;
lthe destination and emergency buttons in the lift are as clear as on the landing and are located at least 400mm in from the front wall;
lthe car and landing buttons are between 900mm and 1,200mm above floor level; and lthe car is equipped with audible announcements and visual displays, and an emergency intercom is provided with an induction loop for hearing aid users.
Some projects that complete works to comply with DDA may achieve the criteria for partial exemption or zero rating of VAT.
Simon Russett is principal of the Hoare Lea Lift Engineering Group. He can be contacted on 020 7890 2632 or email simonrussett@ london. hoarelea. com READER ENQUIRIES Axess 4 All 1400 Britton Price 1401 Fujitec UK 1402 HighLift Systems 1403 Kone 1404 Mitsubishi Electric Europe 1405 Moveman 1406 Otis 1407 Schindler 1408 Schmersal UK 1409 Thyssen Lifts and Escalators 1410 An extensive list of UK companies supplying all lift types can be found at www. leia. co. uk.
Enquire at www. ajplus. co. uk/ajdirect