You might have seen different types of hydraulic lifts in your daily life but have you ever thought of how hydraulic elevators work? Read the article till the end of it to understand the working of Hydraulic Lifts and its various types.
Hydraulic elevators, which are heavy-duty elevators built for frequent and long term use work on a very simple working principle. They are best for their durability and are very quiet. Hydraulics is used for control, generation, and transmitting of power by using pressurized liquids. Some examples of hydraulic systems are hydraulic lifts which help to move goods or people vertically, hydraulic brakes, hydraulic steering, hydraulic jack, heavy equipment, hydraulic shock absorbers. The JCB truck uses hydraulics to carry heavy loads and lift them vertically.
The movement of Hydraulic elevators is done by a piston that moves inside a cylinder. The electric motor will pump the oil into the cylinder to move the piston. The building that is 5 to 6 stories generally uses hydraulic lifts. The first hydraulic elevators used water pressure as the source of power and it was used generally for conveying materials. A hydraulic elevator is supported by a piston, moving inside a cylinder and gets operated by water or oil pressure.
The two main types of elevator systems are traction and hydraulic. Traction elevator uses steel ropes or belts on a pulley. Hydraulic elevators are powered by a hydraulic jack, with fluid operated piston traveling in the cylinder. The installation, operation, and maintenance of hydraulic lift can be done only by trained technicians.
Usage Of Hydraulic Elevators
Hydraulic elevators are seen almost in every building, two main factors limit the heights they can reach. It requires some energy to lift the cab and these cabs are not generally used in high rise buildings. They operate at a speed 150 ft/minutes or less and due to this reason, these elevators travel at a slower speed. Hydraulic elevators are intended to operate in buildings having a maximum of 7 floors.
Different Types Of Hydraulic Elevators
There are different types of hydraulic elevators available now.
This hydraulic cylinder is extended to the ground and kept inside a drilled hole. The car of the elevator is kept on the piston that travels inside a cylinder. It travels a maximum distance of 60 feet.
Here there won’t be any drilled holes because of the restriction in the buildings. These can travel a maximum of 40 feet.
This can be classified further into 3 types.
- Telescopic hydraulic elevators: The telescopic hydraulic elevators are configured with telescopic pistons based at the pit and do not require any sheave or hole below and have 2 to 3 telescopic pistons. It can travel a distance of 50 feet.
- Non-telescopic hydraulic elevators: These are single-stage elevators which consist of only1 piston.
- Roped hydraulic: Cables and pistons used to attach sheaves for extending the rise of holeless hydraulic elevators. A governor is required to hold the cab as it uses a rope to hold up the elevator cab. These models are designed for 60 feet of travel.
Machine Room Less Elevator
In the machine room-less elevators, the hydraulic lift mechanisms are kept on the hoistway as there is no space for a machine room. This maximizes available spacing in the building.
Components Of Hydraulic Elevator
Hydraulic elevator and traction elevator differ in case of its two main components:
- Machine/ drive system
- Safety system
1. Machine / Drive system
The lift car is driven by a direct-acting or indirect-acting method. In a direct-acting system, the hydraulic arm is located on either side or at the back. The indirect-acting system is used in the case of a roped hydraulic elevator. The machine/drive system has the following components
The cylinder should be made of steel pipe of suitable thickness following safety guidelines and standards. The top of the cylinder consists of a cylinder head with an internal guide ring and a self-adjusting packing mechanism. The plunger is made of smoothly machined steel shaft of required diameter and it is provided with a welded stopper at the bottom to prevent the piston from leaving the cylinder.
1.b) Hydraulic Power Unit
The hydraulic power unit should be rated properly and provided with vibration isolators. The units must be operated with minimum noise and vibrations. The units are mounted on a vibration isolator above the machine room floor. A silencer is provided to eliminate airborne noise and to minimize the transmission of pulsations to the ram. The main components of the hydraulic power unit are
The tank should be designed of sufficient capacity and should have reserve quantity to prevent the entry of gas and air. A sight glass is provided for checking the oil level and minimum level marks are indicated. An oil level monitoring device shall be provided and there should be audible alarm provision in the control panel to indicate any faults. The main function of the tank is to store oil which is self-lubricating and non-compressible.
Pumps are used in hydraulic elevators to push the liquid into the cylinder to lift the elevator. The pumps are the submersible type with a variable speed system. A submersible pump is a pump that can be fully submerged in water. The motor of the pump is sealed perfectly and is close-coupled to the body of the pump. The pump and its motor should be mounted on the base plate and it needs to be rigid. The pump and the motor shall be aligned properly and maintained to operate smoothly in normal operating mode. The inlet of the pump shall be provided with an oil filter. A stop cock can be provided to clean the filter without much loss of oil. The pump motor shall be of single speed and it should run with less noise and vibrations.
The main function of the valve is to discharge liquid out of the system. The valve helps to increase the pressure when it is closed and decreases the pressure when it is open. The stopcocks are setting up between the control valve and cylinder, then between the reservoir tank and the pump.
An actuator is a device that converts fluid or electrical energy into mechanical energy. The elevators use oil pressure to power a ram that can raise or lower the lift car. Elevators that travel over six stories use cables and counterweights. The component installation should be done by well-trained technicians. There are a lot of job opportunities for well-trained technicians.
2. Safety system
The major features of the hydraulic elevator that help it dominate the market are its affordability to manufacture, install and service, and better safety record compared to other elevators. Hydraulic elevators are proven as a highly safe option especially in earthquake-prone areas. The safety system of hydraulic elevators includes various safety components such as Manual reset slack rope safety switch, Seismic valve for hydraulic elevators, Final Limit Switch, Anti-creep device, Buffers, easily accessible manual devices for emergency operation, Automatic bi-directional levelling, Pit switch, Pump run timer, etc.
The concept of hydraulic elevators is not so complex, now you might have got a clear understanding of the working of hydraulic elevators and the basic principle behind it.