Engineer Jagvir Goyal discusses what makes freight elevators run.
Having a fast and efficient vertical transport system for passengers and goods is a crucial factor that must be factored while planning a high-rise building. No skyscraper can be successfully used unless it has efficient elevators installed in it. And no building beyond four storeys can be conceptualised without an elevator.
Last month, we discussed passenger elevators; this month, it is the turn of freight elevators. While passenger elevators can be of any shape, freight elevators need to be specially designed to suit the type and size of goods they need to carry and withstand rough and tough use. Here too, safety and fast travel remain basic requirements.
Hoisting system
Freight elevators use both geared and gearless traction to run goods cars. Machine room-less elevators are also used for goods transportation. Geared traction elevators are used when the lift rates are not required to be very fast. An electric motor drives a gear reduction unit that further drives the sheaves. The gear reduction helps choose an electric motor of lower horsepower. Normally, the speed of geared traction elevators is below 2.5 m per second and these are suitable to carry loads up to 125 tonne.
Gearless traction elevators have one end of the steel wire ropes attached to the top of the car and the other end to the counterweight. These can operate at high speeds of 2.5 m per second or even more. If well maintained, they don鈥檛 need any replacement. In these hoists, many lengths of wire ropes or cables are wrapped around the drive sheave in special grooves. Guide rails are provided for the counterweight鈥檚 movement. The car weight and counterweight press the wire rope into the sheave groove and the necessary traction is obtained from the sheaves run directly by the motor. The grooved sheave has a large diameter, varying from 0.5 m to 1.5 m. The electric motor required to turn it at hundreds of rpm also has to be very powerful.
In machine room-less elevators, the machine room is avoided by using smaller sheaves for geared and gearless traction elevators and redesigning the motor. The small-sized machine is mounted within the hoist way or shaft or duct itself. Elimination of machine room becomes possible when we use steel belts instead of heavy steel wire ropes. These belts are just 3 mm thick, as strong and flexible as steel wire ropes or cables, and make the use of smaller sheaves possible. Most reputed companies like Otis use flat, polyurethane-coated steel belts of 30 mm width and 3 mm thickness.
The capacity
Freight elevators can have a load-carrying capacity of anywhere between half a tonne to 5 tonne. For higher loads, elevator companies don鈥檛 back out but offer to provide solutions to meet the needs of the industry. KONE offers freight elevators of 500 kg to 3,000 kg capacity. Otis, the oldest elevator company, provides goods elevators suitable for any capacity between 1,300 kg and 5,440 kg. It further rates its elevators according to load categories. Class A elevators are for hand trucks, class B elevators for automobiles and class C elevators have the capacity to carry a commercial truck.
Essential features
Freight elevators need to be equipped with certain key features for optimal and trouble-free use. These include:
Safety systems: Safety remains the prime requirement in all elevators 鈥� passenger or goods. All elevators are provided with a governor that engages the cab鈥檚 brakes if the elevator starts falling down. Thereafter, the cab can be brought down slowly and smoothly to the desired level and an accident is avoided.
Automatic controls: The elevator control system must be fully automatic. An automatic control system uses the power of the microprocessor to control every aspect of elevator operation. It judges the acceleration of the cab and automatically controls it, thereby providing a uniform speed to the cab. It also decelerates it when it approaches a landing. It is programmable at site and can handle subsequent modifications.
The car: The cars for carrying goods should preferably have stainless steel wall panels. Otherwise, suitably painted, simple mild steel panels can be chosen. Doors for freight elevators may be automatic or manual as per the user鈥檚 requirement.
The movement: Freight elevators shouldn鈥檛 cause any noise pollution. While jerk-free, smooth and uniform speed movement is essential, noise levels should be kept very low, not higher than a refrigerator鈥檚 rumbling. Whenever goods elevators are designed for hospitals, utmost levelling accuracy and advanced sensor interception should be ensured to cause zero discomfort to bedridden or stretcher-ridden patients.
Energy-saving: Whether it is a passenger or freight elevator, energy-saving features are a compulsory requirement. The choice of a gearless drive system helps save electricity by 30-40 per cent. An elevator that requires less starting current requires a smaller backup generator and saves costs. The use of LED lights reduces the energy consumed in the cars by 60-70 per cent. In addition, these lights have a very long life. Elevator companies are working not only on the use of LED lights in the cars but also on the use of solar energy. KONE supplies a kit that connects the car light supply to a small solar panel system. Signalisation and car lights automatically switch to standby or off mode in many elevators when the car is not under use and turn 鈥榦n鈥� upon receiving a call.
Overload device: An overload device is necessary in freight elevators too. Such a device keeps the car doors open, sounds a buzzer and switches on a warning light whenever car load exceeds 10 per cent of rated capacity.
Freight elevator products
Almost every elevator producer, including the reputed companies, has added freight elevators to its product list. Some manufacturers produce even goods-specific elevators. For instance, KONE produces goods elevators for transportation of heavy loads in hotels, offices, high-rise residential buildings and industries. Its good elevators can handle loads of 0.5 tonne to 3 tonne and it promises to offer solutions for higher capacities. The speed variation is between 0.5 m to 1 m per second with a maximum travel height of 100 m. KONE offers solutions for higher speeds also. It provides exclusive designs of big-sized cars to handle large goods in industries. Both geared and gearless traction systems are used by KONE for its freight elevators. The company has evolved a custom-built V3F drive system for smooth and jerk-free movements of cabs. This system also helps them reduce the starting current, thus requiring a small backup generator for the system and saving costs.
Schneider has designated its freight elevators Schneider 2400, 2500 and 2600. Schneider 2400 is meant to carry shopping carts and people. As its car can be of extra large size, it is ideally suited to shopping malls, hotels and public places. The option of providing a mechanical or hydraulic hoisting system has been kept open for the buyer. Schneider 2500 is suitable for hospitals. It has been customised to carry beds and accompanying patients and medical equipment to operation theatres. Utmost precision has been used in its controls to avoid any discomfort to patients or any disruption in medical services. This elevator is also operational both on hydraulic and mechanical systems. For the heaviest freights, Schneider has brought out its 2600 elevator model, which is best suited to warehouses and industrial use.
Otis calls its freight elevator the FO-VF elevator. Under the FO series, Otis elevators are designed to carry loads of 630 kg to 5,000 kg. Full computer control technology for signal transmission and motion control has been provided in these elevators. Special attention has been paid to low noise and jerk-free smooth movement.
Special freight elevators
Apart of producing general freight elevators, specific elevators are also produced these days. Some notable categories are:
Car elevators: These can transport cars vertically and are best suited to multi-storeyed car parking buildings. The maximum size of cars and load capacity are precisely defined for these elevators.
Dust-proof elevators: These elevators are used in industries that operate in a dusty environment, such as power projects and cement plants. They are dust-proof with a capacity varying up to 3 tonne and speed varying from 0.5 m/sec to 1 m/sec. They comply to IP 54 level. IP ratings are used to specify environmental protection in electrical enclosures. These are developed by CENELEC, a European committee that assigns two or three numbers to an IP. The first number relates to solids, the second to liquids and the third to mechanical impacts. IP means Ingress Protection. IP54 means Ingress Protection with 5 as level of protection from solid objects and 4 as level of protection from liquids. The highest digit for total protection against dust is 6 while 5 means protection against dust with no harmful deposit. For liquids, 8 is the highest number; 4 means a protection against water sprayed from all directions. Therefore, IP54 protection in elevators is undoubtedly high dust-proof protection. KONE successfully produces these elevators.
Explosion-proof elevators: These are used in areas where explosions may occur owing to the presence of highly inflammable gases, flammable liquids or combustible dust. These are classified by location depending upon the properties of flammable gases, liquids or dust. The classification is in classes, groups and divisions. There are two classes, I and II, seven groups, A, B, C, D, E, F and G, and two divisions 1 and 2. Explosion-proof elevators are suitable for use in oil refineries, pharmaceutical plants and gas utility facilities. KONE produces a 2 C explosion-proof elevator. C group relates to ethylene. The elevator can have a capacity up to 3 tonne, speed up to 1 m/sec and travel distance up to 100 m.
Aircraft elevators: These shift aircraft from the runway area to hangar decks when the two are located at different levels. The capacity of these elevators has to be very high to bear the load of aircrafts while vertical travel has to be as minimal as possible.
Marine elevators: These are used in vertical transportation of ships. Owing to their peculiar use and customised design, they need to be handed over to a company for design, manufacture, installation, successful commissioning, running and maintenance. Marine elevators can be customised for cruises, yachts, ferries and cargo. Here too, the basic hoisting system remains the same: gearless traction and machine room-less technology. KONE manufactures marine elevators and is a worldwide supplier. Marine elevators need special attention because all their components need to be manufactured for operation in rough ocean conditions by withstanding heavy vibrations and tolerating rolling and pitching of ships.
Choosing the company
While selecting a freight elevator company, you should always ensure that the company specialises in the production of elevators for the desired freight or load. A company may be highly reputed but concentrating only on passenger elevators. The company should be finalised as early as possible at the initial stages, as this helps finalise hoist ways and other elevator-related features.
KONE produces many types of special freight elevators like marine elevators, explosion-proof elevators, dust-proof elevators and car elevators. Though it produces residential and commercial elevators, ThyssenKrupp specialises in hospital and transparent elevators. Schneider produces elevators for hospitals, shopping malls and even warehouses.
In addition to specialisation, the safety record and post-sales service record of the company should always be checked. There can鈥檛 be any compromise on safety and there shouldn鈥檛 be any accident record. Often, promises are many; factual maintenance visits few. A warranty and annual maintenance contract should always be signed with the elevator company. Otis has now evolved a remote elevator monitoring system to serve its elevators. Known as the REM system, it identifies problems before they actually occur by detecting failing components. Such a system ensures zero loss of service to the user. This system can further classify whether the problem is urgent or can wait. For urgent problems, an alert message is received by the service cell and mechanics arrive well in time. Internet services and telecom links established by elevator companies boost the confidence of the user who can be sure of the timely arrival of mechanics in case of a breakdown or emergency.
Quick Bytes
鈥� All elevators are provided with a governor that engages the cab's brakes if the elevator starts falling down.
鈥� The choice of a gearless drive system helps save electricity by 30-40 per cent.
鈥� The capacity of aircraft elevators has to be very high to bear the load of the aircrafts.
鈥� Always ensure that the freight elevator company specialises in the production of elevators for the desired freight or load.
Engineer Jagvir Goyal discusses what makes freight elevators run.
Having a fast and efficient vertical transport system for passengers and goods is a crucial factor that must be factored while planning a high-rise building. No skyscraper can be successfully used unless it has efficient elevators installed in it. And no building beyond four storeys can be conceptualised without an elevator.
Last month, we discussed passenger elevators; this month, it is the turn of freight elevators. While passenger elevators can be of any shape, freight elevators need to be specially designed to suit the type and size of goods they need to carry and withstand rough and tough use. Here too, safety and fast travel remain basic requirements.
Hoisting system
Freight elevators use both geared and gearless traction to run goods cars. Machine room-less elevators are also used for goods transportation. Geared traction elevators are used when the lift rates are not required to be very fast. An electric motor drives a gear reduction unit that further drives the sheaves. The gear reduction helps choose an electric motor of lower horsepower. Normally, the speed of geared traction elevators is below 2.5 m per second and these are suitable to carry loads up to 125 tonne.
Gearless traction elevators have one end of the steel wire ropes attached to the top of the car and the other end to the counterweight. These can operate at high speeds of 2.5 m per second or even more. If well maintained, they don鈥檛 need any replacement. In these hoists, many lengths of wire ropes or cables are wrapped around the drive sheave in special grooves. Guide rails are provided for the counterweight鈥檚 movement. The car weight and counterweight press the wire rope into the sheave groove and the necessary traction is obtained from the sheaves run directly by the motor. The grooved sheave has a large diameter, varying from 0.5 m to 1.5 m. The electric motor required to turn it at hundreds of rpm also has to be very powerful.
In machine room-less elevators, the machine room is avoided by using smaller sheaves for geared and gearless traction elevators and redesigning the motor. The small-sized machine is mounted within the hoist way or shaft or duct itself. Elimination of machine room becomes possible when we use steel belts instead of heavy steel wire ropes. These belts are just 3 mm thick, as strong and flexible as steel wire ropes or cables, and make the use of smaller sheaves possible. Most reputed companies like Otis use flat, polyurethane-coated steel belts of 30 mm width and 3 mm thickness.
The capacity
Freight elevators can have a load-carrying capacity of anywhere between half a tonne to 5 tonne. For higher loads, elevator companies don鈥檛 back out but offer to provide solutions to meet the needs of the industry. KONE offers freight elevators of 500 kg to 3,000 kg capacity. Otis, the oldest elevator company, provides goods elevators suitable for any capacity between 1,300 kg and 5,440 kg. It further rates its elevators according to load categories. Class A elevators are for hand trucks, class B elevators for automobiles and class C elevators have the capacity to carry a commercial truck.
Essential features
Freight elevators need to be equipped with certain key features for optimal and trouble-free use. These include:
Safety systems: Safety remains the prime requirement in all elevators 鈥� passenger or goods. All elevators are provided with a governor that engages the cab鈥檚 brakes if the elevator starts falling down. Thereafter, the cab can be brought down slowly and smoothly to the desired level and an accident is avoided.
Automatic controls: The elevator control system must be fully automatic. An automatic control system uses the power of the microprocessor to control every aspect of elevator operation. It judges the acceleration of the cab and automatically controls it, thereby providing a uniform speed to the cab. It also decelerates it when it approaches a landing. It is programmable at site and can handle subsequent modifications.
The car: The cars for carrying goods should preferably have stainless steel wall panels. Otherwise, suitably painted, simple mild steel panels can be chosen. Doors for freight elevators may be automatic or manual as per the user鈥檚 requirement.
The movement: Freight elevators shouldn鈥檛 cause any noise pollution. While jerk-free, smooth and uniform speed movement is essential, noise levels should be kept very low, not higher than a refrigerator鈥檚 rumbling. Whenever goods elevators are designed for hospitals, utmost levelling accuracy and advanced sensor interception should be ensured to cause zero discomfort to bedridden or stretcher-ridden patients.
Energy-saving: Whether it is a passenger or freight elevator, energy-saving features are a compulsory requirement. The choice of a gearless drive system helps save electricity by 30-40 per cent. An elevator that requires less starting current requires a smaller backup generator and saves costs. The use of LED lights reduces the energy consumed in the cars by 60-70 per cent. In addition, these lights have a very long life. Elevator companies are working not only on the use of LED lights in the cars but also on the use of solar energy. KONE supplies a kit that connects the car light supply to a small solar panel system. Signalisation and car lights automatically switch to standby or off mode in many elevators when the car is not under use and turn 鈥榦n鈥� upon receiving a call.
Overload device: An overload device is necessary in freight elevators too. Such a device keeps the car doors open, sounds a buzzer and switches on a warning light whenever car load exceeds 10 per cent of rated capacity.
Freight elevator products
Almost every elevator producer, including the reputed companies, has added freight elevators to its product list. Some manufacturers produce even goods-specific elevators. For instance, KONE produces goods elevators for transportation of heavy loads in hotels, offices, high-rise residential buildings and industries. Its good elevators can handle loads of 0.5 tonne to 3 tonne and it promises to offer solutions for higher capacities. The speed variation is between 0.5 m to 1 m per second with a maximum travel height of 100 m. KONE offers solutions for higher speeds also. It provides exclusive designs of big-sized cars to handle large goods in industries. Both geared and gearless traction systems are used by KONE for its freight elevators. The company has evolved a custom-built V3F drive system for smooth and jerk-free movements of cabs. This system also helps them reduce the starting current, thus requiring a small backup generator for the system and saving costs.
Schneider has designated its freight elevators Schneider 2400, 2500 and 2600. Schneider 2400 is meant to carry shopping carts and people. As its car can be of extra large size, it is ideally suited to shopping malls, hotels and public places. The option of providing a mechanical or hydraulic hoisting system has been kept open for the buyer. Schneider 2500 is suitable for hospitals. It has been customised to carry beds and accompanying patients and medical equipment to operation theatres. Utmost precision has been used in its controls to avoid any discomfort to patients or any disruption in medical services. This elevator is also operational both on hydraulic and mechanical systems. For the heaviest freights, Schneider has brought out its 2600 elevator model, which is best suited to warehouses and industrial use.
Otis calls its freight elevator the FO-VF elevator. Under the FO series, Otis elevators are designed to carry loads of 630 kg to 5,000 kg. Full computer control technology for signal transmission and motion control has been provided in these elevators. Special attention has been paid to low noise and jerk-free smooth movement.
Special freight elevators
Apart of producing general freight elevators, specific elevators are also produced these days. Some notable categories are:
Car elevators: These can transport cars vertically and are best suited to multi-storeyed car parking buildings. The maximum size of cars and load capacity are precisely defined for these elevators.
Dust-proof elevators: These elevators are used in industries that operate in a dusty environment, such as power projects and cement plants. They are dust-proof with a capacity varying up to 3 tonne and speed varying from 0.5 m/sec to 1 m/sec. They comply to IP 54 level. IP ratings are used to specify environmental protection in electrical enclosures. These are developed by CENELEC, a European committee that assigns two or three numbers to an IP. The first number relates to solids, the second to liquids and the third to mechanical impacts. IP means Ingress Protection. IP54 means Ingress Protection with 5 as level of protection from solid objects and 4 as level of protection from liquids. The highest digit for total protection against dust is 6 while 5 means protection against dust with no harmful deposit. For liquids, 8 is the highest number; 4 means a protection against water sprayed from all directions. Therefore, IP54 protection in elevators is undoubtedly high dust-proof protection. KONE successfully produces these elevators.
Explosion-proof elevators: These are used in areas where explosions may occur owing to the presence of highly inflammable gases, flammable liquids or combustible dust. These are classified by location depending upon the properties of flammable gases, liquids or dust. The classification is in classes, groups and divisions. There are two classes, I and II, seven groups, A, B, C, D, E, F and G, and two divisions 1 and 2. Explosion-proof elevators are suitable for use in oil refineries, pharmaceutical plants and gas utility facilities. KONE produces a 2 C explosion-proof elevator. C group relates to ethylene. The elevator can have a capacity up to 3 tonne, speed up to 1 m/sec and travel distance up to 100 m.
Aircraft elevators: These shift aircraft from the runway area to hangar decks when the two are located at different levels. The capacity of these elevators has to be very high to bear the load of aircrafts while vertical travel has to be as minimal as possible.
Marine elevators: These are used in vertical transportation of ships. Owing to their peculiar use and customised design, they need to be handed over to a company for design, manufacture, installation, successful commissioning, running and maintenance. Marine elevators can be customised for cruises, yachts, ferries and cargo. Here too, the basic hoisting system remains the same: gearless traction and machine room-less technology. KONE manufactures marine elevators and is a worldwide supplier. Marine elevators need special attention because all their components need to be manufactured for operation in rough ocean conditions by withstanding heavy vibrations and tolerating rolling and pitching of ships.
Choosing the company
While selecting a freight elevator company, you should always ensure that the company specialises in the production of elevators for the desired freight or load. A company may be highly reputed but concentrating only on passenger elevators. The company should be finalised as early as possible at the initial stages, as this helps finalise hoist ways and other elevator-related features.
KONE produces many types of special freight elevators like marine elevators, explosion-proof elevators, dust-proof elevators and car elevators. Though it produces residential and commercial elevators, ThyssenKrupp specialises in hospital and transparent elevators. Schneider produces elevators for hospitals, shopping malls and even warehouses.
In addition to specialisation, the safety record and post-sales service record of the company should always be checked. There can鈥檛 be any compromise on safety and there shouldn鈥檛 be any accident record. Often, promises are many; factual maintenance visits few. A warranty and annual maintenance contract should always be signed with the elevator company. Otis has now evolved a remote elevator monitoring system to serve its elevators. Known as the REM system, it identifies problems before they actually occur by detecting failing components. Such a system ensures zero loss of service to the user. This system can further classify whether the problem is urgent or can wait. For urgent problems, an alert message is received by the service cell and mechanics arrive well in time. Internet services and telecom links established by elevator companies boost the confidence of the user who can be sure of the timely arrival of mechanics in case of a breakdown or emergency.
Quick Bytes
鈥� All elevators are provided with a governor that engages the cab's brakes if the elevator starts falling down.鈥� The choice of a gearless drive system helps save electricity by 30-40 per cent.鈥� The capacity of aircraft elevators has to be very high to bear the load of the aircrafts.鈥� Always ensure that the freight elevator company specialises in the production of elevators for the desired freight or load.
