The space constraint has forced construction industry to move vertical in metro cities in India. As the building height increases, the need for enhanced elevator speed also increases. This has opened new avenues of technology for the elevator manufacturer in India. Rajnikant Lad, Chartered Engineer & Elevator consultant at Shree Jee Elevator Consultants gives an account of latest innovations and options available in the field of vertical transportation.
A building height is the main deciding factor for speed of the elevator. With increase in speed, we have to meet new challenges of riding comfort, operational efficiency, energy efficiency, earthquake consideration and many more aspect of safety and rescue during emergencies. This has made the elevator industry more and more technology driven.
We see a fast change in elevator requirement in the country which has gone up to 40,000-45,000 per year and is bound to increase year by year. The elevators with speeds of 0.65m/sec and 1.0m/sec to maximum 2.5m/sec were used till year 2000. Now elevators with speed of 2.5 m/sec are very common and the maximum elevator speed available is 6m/sec.
As per present rules, building above 70m is considered a high rise building. The same is under consideration for amendment to increase to 120m. This will further boost the highrise elevator market and in turn invite faster technological developmemt. The present market requirement and future business prospect in India has attracted the entire international leading elevator manufacturer to have their presence in India.
The business growth, presence of major International elevator players and increasing building height has given new dimensions to the Indian Elevator Industry. We have now all latest elevator technologies available in India. Whether it is touch screen system, intelligent elevator monitoring system, full length infra red door safety screen, hydraulic elevator, vacuum elevators, capsule elevator, destination control system, machine room less elevator, Variable Voltage Variable Frequency (VVVF) drive system, and gearless drive all are now available in India. In near future we may also witness Double Decker and Twin elevator systems in upcoming buildings. Some of the latest technological developments include:
Destination Control System
This is the latest in elevator control system. In this system one has to press the number of floor he intends to visit. The system will collect this information and analyze the movement and location of the elevators moving in that group. After analyzing, the call will be assigned to the elevator which will come in minimum time and provide minimum riding time to that passenger. The display system provides the lift number which will attend to the call of the passenger. The passenger notes the lift number and boards that elevator. There are no buttons provided inside the lift cabin.
Double Decker Elevators
The Double Decker system is used to optimize the core building area in tall buildings. We can have more free space area available in a building by incorporating two elevators in a same shaft. This system has its own advantages and disadvantages.
• It provides high efficiency during peak hours as car stops at two adjacent floors at the same time. But during light traffic heavy car masses have to move using unnecessary energy. Passengers may encounter waiting time when other car is loading /unloading.
• Two entry levels are required at all floors.
• All cars in a group must be double deck.
Double Decker elevators are preferred as express shuttle to serve sky lobbies and have not been introduced in India so far as they are not yet economically viable.
Twin Elevator System
(Two Elevators in same shaft)
In this case we have two cars moving independently in a same shaft. The cars use the same guide rails and the same landing doors. Minimum clearance between both cars is guaranteed by a special safety concept. With the use of double entrance, we can see excellent results of up-peak traffic. It consumes less energy compared to the Double Decker system and results in lower operational costs.Still this is not considered a commercially feasible solution in India.
The introduction of synchronous motor and VVVF drive system and PU coated flat wire ropes has made the elevator manufacturer job easy. This has helped in reducing the overall weight of the machine unit to a great extent. With reduction in size and weight of the machine unit, it has become possible to install it inside the elevator shaft. The size is so small that it can be installed inside the lift shaft at the top in a small space .These are now termed as machine room less MRL elevators. Beside small in size and light in weight, it is also energy efficient. With gear less unit and use of VVVF drive system we can save energy up to 50% as compared to the conventional elevators.
Full Length Infra red door safety system
The introduction of full length infra red door safety system has made the door closing operation more safe and reliable. The problem arising out from the use of mechanical safety and photocell system is now totally overcome. This latest safety system detects even a small obstruction during door closing operation. The doors immediately stop closing operation, avoiding possibility of any accident.
Need for professional approach
When the subject becomes more technology driven, you need to have experts from the field to assist you in planning the right thing for your requirement. Elevator consultant plays a great role in deciding right technology for a particular project. If he is involved from the drawing board stage with a particular project, he can be of much help in deciding elevators/escalators which can offer maximum efficiency, comfort and safety combined with cost effectiveness. Some of the points which need to be studied before finalizing the technical specification are:
• Type of project (residential, commercial, mix of residential and commercial, hospital, office building, mall etc.)
• Building height
• Building occupant population and floor area served
• Floating population and its timing in case of office, hospital, commercial complex
• Height restriction from the statutory point of view or from construction point of view
• Noise level requirement inside building or at particular floor/area
• Handling capacity and waiting time requirement(traffic analysis)
• Future expansion plan
• Possible change in building occupancy in future
While considering the speed, one has to follow that the elevator must be able to cover travel distance from bottom floor to the top floor in 60 seconds as required under fire lift norms. This gives a clear deciding factor for elevator speed. Besides height, one has to study the passenger handling requirement. For normal consideration, the elevator should be able to handle 10 to 15 percent of the building population in five minutes in a diversified building and the waiting time of passenger at various floor should not be more than 20 to 25 seconds.
The study of the type of passenger flow morning peak, evening peak, intermediate floor to floor traffic and lunch break traffic is based on the type of occupancy of the building. An office building will have different traffic pattern as compared to a mixed use commercial building having offices, restaurant, hospital and even residential blocks on top portion of the building.
In all our elevator decision, we should provide one stretcher elevator and one goods elevator with wide opening. Provision must be made for the use of elevators by differently-abled persons too. Furthermore, whether it is an office building or residential building, the need for stretches /good transportation is inevitable. Providing one elevator as stretcher and one as goods elevator will solve a number of problems of the users.
Elevator Safety Considerations
While designing elevator location in a building, one must consider possibility of use of elevator during fire emergencies. By locating few elevators which opens opposite to the normal wind direction (west opening), and are located on the outskirt of the building will facilitate better usage during fire.
The one important factor missed generally or not given due importance is the maintenance requirement for elevators. We must provide trap door in the top floor and in machine room floor which helps lifting/shifting heavy machine unit during major repair in the longer run. The elevator machine room approach and entrance must be kept wide enough (passage/steps minimum 1.5m wide and entrance door opening minimum 1.0m.)
The hydraulic lift/vacuum elevator is used in bungalows or duplex flats where space becomes the main constraint. This may lead to compromising on machine room space and safety. The machine room location, dimensions and approach must be made in such a way that during emergency, one can easily enter machine room and carry out repair/rescue work. There has to be good provision for inside passenger to communicate with the outside world through intercom/speak phone or any better communication means. This helps trapped passenger get connected with the outside world and stay relaxed.
The increase in elevator installations and building height has been forcing us to rethink on the related safety issues. The fire brigade has its own restrictions for the height of the ladders. We have to study further for better and suitable system to address emergency rescue during fire, earthquake and other emergencies.
The safety awareness is one of the means for ensuring safe travel in elevator. Safety training must be carried out by elevator contractors with frequent intervals. Considering the present elevator demand and continuous increase in the near future, it has become imperative for the elevator industry to create technical knowledge bank in the country. The technical institutions in India must consider the elevator subject as part of their regular study and create sufficient good quality technical work force.