Hydraulic Lift Systems
Joseph Bramah, a British mechanic, is credited for developing the first hydraulic press. According to Bramah, if a small force on a small area could create a larger force in a larger area, then the only limit to the force machines can exert is the area on which that force is applied.
Quick links to Hydraulic Lift Systems Information
History of Hydraulic Lift Systems
Since the inception of the first hydraulic press in 1795, hydraulic lift systems have found their way into various applications, from small assembling companies to steel mills. Hydraulics allows operators to accomplish more work with a minimum mechanical linkage. These systems apply Pascal’s law, which observes that when pressure is applied to a confined fluid at any point, the pressure is transmitted throughout the fluid equally, in all directions, upon every part of the confining container.
Combining Pascal’s law and its application in developing the first hydraulic press, it is clear that applying a force of 100lbs on a 10-square-inch area will exert a pressure of 10lbs per square inch of the confining container. This pressure is enough to support a weight weighing 1000lbs if the hydraulic lift table is 100-square-inches. In the application of Pascal’s principle, lift hydraulic systems use hydraulic fluids to transmit energy from one point of the confining container to another. The unique property of hydraulic fluids is that they are incompressible; this allows them to transmit energy instantaneously.
A hydraulic lift system has many benefits. First off, it provides a comfortable working space, reducing injuries when workers are exposed to repetitive stress. When a more physically demanding job, a lift makes an ergonomic working space where workers do not strain much. These lifts also lift work materials and place them next to the workers, enhancing efficiency and the overall productivity of the workers.
The lifting equipment can move vertically or horizontally, moving workers or workstations where they are supposed to be. Many of the hydraulic systems, such as car lifts, are designed with a wheel, making them mobile; a good example is a forklift. However, in a place where repetitive work is done, a hydraulic lift cart can be fixed permanently, acting as part and parcel of the whole lift system.
Small hydraulic lifting equipment is used in manufacturing workshops to move items from one place to another. These, like forklifts, are created to move from one place to the next. For workers who are engaged in tasks that require them to stay in motion, a tilting lift comes in handy. There are also lifts with adjustment features, keeping the workers in comfortable positions.
The hydraulic lift system is used in production houses, as hydraulic car lift in auto-repair shops, docks, and warehouses, among others places. These lifts can be operated manually or automatically, depending on their use and their sizes.
Types of Hydraulic Fluids
Fluids form an integral part of hydraulics. They are responsible for transmitting energy and enabling the lifting process. Besides energy transmission, these fluids also lubricate systems, transfer heat, and control contamination. During the development of hydraulics, fluids are chosen based on their viscosity, base stock, and any other added property that will make them useful in transmitting energy. There are three main categories of hydraulic fluids:
- Petroleum Based and Mineral-Based
- These are common in many types of hydraulics including hydraulic elevator, hydraulic scissor lift, hydraulic lift cart and others. The property of a mineral based hydraulic fluid is determined by the quality of the original crude oil, the refining process and lastly the additives in the fluid. Additives in these fluids include anti-corrosion agents, antiwear, rust and oxidation resistors, demulsifiers, extreme pressure agents, defoamants, and VI improvers. These fluids are less costly and are more readily available.
- Water-Based Fluids
- Water-based fluids have a high water content, and as such, they are used where fire resistance is crucial. They are available as oil-in-water or water-in-oil emulsions and water glycol blends. Though needed for their fire resistant properties, these fluids cannot be used in hot environments as heat will lead to evaporation of water and consequently an increase in the fluid’s viscosity.
- Evaporation will still occur even under normal temperature conditions. To this end, distilled water has to occasionally be added to the system to balance the viscosity. Again, it has to be tested for compatibility before using a water-based hydraulic fluid. Unlike petroleum based fluids, water-based fluids have lower wear resistance.
- Synthetic Fluids
- These are man-made and fitted with all good characteristics needed for specific applications. They are designed to offer excellent lubrication in high temperature and high-pressure areas. Additionally, they have water resistance, friction resistance, and detergency properties. Thermally, these fluids are stable. Common synthetic fluids include organic esters, phosphate esters, and hydrocarbon fluids with esters. Synthetic fluids are more expensive compared to conventional hydraulic fluids. Again, they are toxic and require special disposal. Compatibility is another issue between synthetic fluids and standard seal materials.
- Custom Hydraulic Lifts
- Hydraulic lifts for specific applications are not produced in mass. Custom orders are, therefore, allowed by a high number of manufacturers. However, custom orders are not for all applications as some of the lifts are produced in mass, such as forklifts. Even then, consumers will still have a wide range of lifts from different companies to choose from. Hydraulic lift companies have their information on their websites, online directories, and consumer review sites. With so much information, consumers can choose the company that will meet their needs.
The basic component of a hydraulic lift platform is the drive system. This system is made up of the cylinder on which the ram slides and the ram on which the capsule or carrying platform is placed. Other components of the system include:
- Lift Reservoir
- A reservoir holds the hydraulic system fluid, transfers heat, allows contaminants to settle at the bottom, and ensures that moisture and air are released from the system.
- Lift Pump
- The function of the pump is to convert mechanical energy from the hydraulic power unit into hydraulic energy. The movement of the transmission fluid achieves this. Lift manufacturers use different types of pumps, including gear pumps, piston, and vane types. Each of these pump types comes with different variants to meet the needs of specific applications, such as the displacement vane pump and the bent axis piston pump. Pumps, whether hydraulic pallet lift or hydraulic elevator, follow the same principle; they displace hydraulic fluid against a load or pressure.
- Hydraulic Lift Valves
- Valves control fluid flow. They are made of spools that can be controlled electrically, manually, mechanically, pneumatically, or hydraulically.
- Hydraulic Lift Actuators
- Actuators reverse hydraulic energy back to mechanical energy. This can be done either through a hydraulic cylinder, which transmits hydraulic energy to linear motion and work or through a hydraulic motor that converts the hydraulic energy into rotary motion and then works. Like hydraulic pumps, there are different types of hydraulic actuators designed for different applications.
Lubricated Components of Hydraulic Systems
It is costly to replace the key components of a hydraulic system. Valves and pumps are considered key components, which should be maintained and kept lubricated. Different configurations for hydraulic pumps are lubricated individually.
- Vane Pumps
- There are different variants of vane pumps from different lift manufacturers. However, they all operate the same. Each vane pump comes with a drive shaft and a slotted rotor. Vanes are placed in rotor slots and they follow the inner surface of the cam rings as the rotor turns. The inner surface of the cam rings and the vanes are in contact and as such, they are subject to wear. Continued wear makes the vane move out of their slots. In short, vane pumps produce a steady flow of hydraulic fluid but at a high cost. They may not be ideal in high-pressure lifting equipment where it is not easy to control contaminants. They will operate at normal viscosity between 14 and 160 cSt.
- Piston Pumps
- Piston pumps are offered in fixed and variable displacement designs. They are the most common pumps, offering versatility and ruggedness. They can operate at high pressures, above 6000 psi. Compared to vane pumps, they are more efficient and produce less noise. Even better, they resist wear and tear better than other pumps. They operate on normal fluid viscosity between 10 and 160 cSt. They are the ones commonly used on car lift and hydraulic pallet lift systems.
- Gear Pumps
- Gear pumps are either internal or external. There are different variants of each gear pump type, but all of them work by carrying fluid between the gear teeth. Though these pumps are less efficient compared to vane and piston pumps, they are more resistant to contamination. Internal gear pumps produce up to 3500 psi and come with a wide viscosity range up to 2200 cSt. Generally, the pumps are quiet. Their efficiency is not affected by viscosity.
- External gear pumps, on the other hand, can handle pressures up to 3500 psi. They are less expensive and deliver a mid-pressure and mid-volume displacement. Their viscosity range is capped at 300 cSt.
Hydraulic Lift Applications
Hydraulic lifts are commonly used for loading and placing work objects in position. However, they are also used to transport personnel when required. Hydraulic lifts used in a given situation will be dictated by the type of platform, mounting style, and construction material. Common lift styles include dock lifts, auto lifts or vehicle lifts, forklifts, table lifts, and pallet lifts.
Both table lifts and positioners position work equipment or work material. They ensure that the material to be worked on is placed in an ergonomically stable access location. A truck or vehicle lift is offered with an attachment and can be mounted on the rear side of a vehicle. Truck lifts are used to lift objects to the bed of a truck. These lifts are commonly used by companies that transport heavy machinery by road.
A dock lift is similar to an auto lift. However, these are different in that they are mounted on docks. Dock lifts position material, objects, or personnel for the purposes of loading. Personnel lifts move workers up, down, or across to the work area. This is done when it is more practical to move the workers to the work area than moving the work area to the workers. When the work area is large or when the area is located high in a building and cannot be moved, workers are moved to the workspace.
Pallet lifts and forklifts are common in docks. They are used to lift material from the ground and load them on cars or other modes of transport. Besides docks, forklifts are used in warehouses and other storage spaces. They are used as mobile lifts that transport goods for short distances before loading them into other trucks. The trucks can load, unload, store, and act as working spaces.
Another form of hydraulic lifting equipment is the tilt table. This is like a hollow bin that raises and lowers the working space and tilts it at an angle to make the working space more ergonomic.
Maintaining Hydraulic Lift Systems
A hydraulic platform lift, like other machinery, requires regular maintenance. Note that, even when the system is shut down completely, hydraulic lifts are still under high pressure and can cause serious injury. The fluid can puncture the human skin if not properly handled. Care should be taken, not only during maintenance and use but also during manufacture.
A hydraulic lift table or platform should be considered when designing a lift for a given task. However, the hydraulic lift fluid should be a priority. Different lifts operate with different viscosities; the fluid in a hydraulic scissor lift may not work well in a hydraulic lift cart. When choosing a fluid, say for a hydraulic car lift, the viscosity, the viscosity index- change of viscosity with temperature- oxidation stability- resistance to degradation caused by a reaction between the chemical and oxygen- and the fluid's ability to reduce wear are considered.