Here is everything you want to know about hydraulic lifts.
You will learn:
A hydraulic lift is a device used to move objects by applying force created through pressure on a liquid within a cylinder, which in turn moves a piston upward. Incompressible oil is pumped into the cylinder, causing the piston to rise. When a valve opens to release the oil, the piston descends due to gravitational force.
The principle behind hydraulic lifts is based on Pascal’s Law, which states that any change in pressure applied to an incompressible liquid in a confined space is transmitted uniformly throughout the liquid in all directions.
Pascal’s Law and its application to hydraulics can be illustrated by the example below, where a small amount of force applied to an incompressible liquid on one side results in a larger force on the opposite side.
Hydraulic systems offer precise control for high-force applications, are cost-effective, and efficiently utilize energy resources.
A hydraulic system operates by exerting force on an incompressible liquid at one point, which then transfers this force to a second point. The system consists of two pistons connected through a pipe filled with oil.
The image below illustrates the two pistons and their connection via a pipe.
The diagram below depicts a basic hydraulic device mechanism. The handle on the right pumps incompressible oil from the reservoir into the high-pressure chamber in the center. As the oil is pumped in, the ram rises.
The force produced in a hydraulic system is related to the size of the pistons. If the smaller piston measures two inches and the larger piston measures six inches, which is three times larger, the force generated will be nine times greater than that of the smaller piston. Therefore, a small piston applying 100 pounds of force can lift 900 pounds with the larger piston.
In this diagram, the piston on the left has a one-pound load and an area of one square inch. As it moves downward by ten inches, it is capable of lifting a ten-pound load on the piston on the right.
Hydraulic systems serve a wide range of purposes, but their fundamental principles and components remain consistent across different applications. The most crucial element of a hydraulic system is the fluid or liquid. According to the laws of physics, the pressure applied to the fluid remains constant as it is transmitted throughout the system. Below is a detailed explanation of each component of a hydraulic system.
Hydraulic circuits manage the flow and pressure of the liquid within the system. The image below illustrates the various components of a hydraulic circuit.
A hydraulic pump converts mechanical power into hydraulic energy. It creates a vacuum at the pump inlet, drawing liquid from the reservoir into the inlet line and then delivering it to the hydraulic system through the outlet.
A hydraulic motor is an actuator that converts hydraulic pressure into torque and rotational motion. It transforms the pressure and flow of hydraulic energy into rotational mechanical energy, much like a linear actuator converts hydraulic energy into linear movement. The pump delivers hydraulic energy to the motor, which then uses it to generate rotational force.
A hydraulic cylinder converts the energy from hydraulic fluid into force. It generates pressure within the fluid, which is regulated by the hydraulic motor.
Hydraulic pistons move linearly due to fluid pressure. In axial designs, multiple pistons are arranged in a circular pattern within a rotating housing.
Hydraulic fluids transfer power within a hydraulic system. While most hydraulic fluids are either mineral oil or water, water was the original hydraulic fluid before mineral oil was introduced in the twentieth century. For applications requiring high temperature resistance or fire safety, fluids such as glycol ether, organophosphate esters, polyalphaolefins, propylene glycol, and silicone oil are used.
Hydraulic lifts, in their various forms, have become indispensable in numerous industries, from assisting patients with mobility to enabling accessibility for boarding buses. The applications of hydraulic lifts have expanded significantly in recent years.
Below are descriptions of several types of hydraulic lifts.
Table lifts are used to move items from the floor to a workable level. Transportation companies use them to lift materials onto a truck bed or warehouse floor.
Personnel lifts are designed to safely elevate individuals to various heights for tasks such as repairing electrical lines, placing inventory on shelves, or accessing control panels. They are commonly used in gyms, factories, and entertainment venues to lift staff for cleaning lights and ceilings.
Forklifts are employed to transport materials at construction sites, warehouses, and factories, as well as for loading and unloading trucks and airplanes. They are designed to efficiently move items from one location to another.
Medical lifts are used to adjust surgical tables, hospital beds, and monitoring equipment. Hospital beds equipped with hydraulic systems facilitate patient transport from rooms to treatment areas, allowing staff to easily adjust the bed’s height for improved accessibility and comfort.
Automotive lifts are used to raise vehicles for repair and inspection. They are among the most robust types of hydraulic lifts, designed to handle the heavy weight of cars and trucks.
Post car lifts are a variation of automotive lifts. The vehicle to be repaired is suspended between two posts with hydraulic drives that have four arms. They are designed to lift any type of vehicle.
Platform lifts, or elevated work platforms, are larger versions of lift tables designed to support groups of workers. They provide a spacious and stable platform for various tasks at height.
Pallet lifts are used for material handling and shipping. They function like a forklift and are able to lift pallets from ground level to load trucks, place on shelves, or move supplies to production lines.
Hand-pumped lifts are operated with a manual hydraulic hand pump and feature a release lever for lowering the load. They are highly durable, require minimal maintenance, and can lift up to one ton to a height of over six feet.
Recognizing that each industrial application is unique and demands tailored engineering, hydraulic lift manufacturers provide custom-designed lifts to address specialized, unconventional, and innovative requirements. Every aspect of a hydraulic lift can be engineered, redesigned, and configured to suit specific conditions or environments. Adjustable factors include:
Every hydraulic lift manufacturer employs a team of engineers skilled in adapting their lifts to meet diverse industrial and manufacturing requirements. As new innovations and conditions emerge, it is crucial for hydraulic lifts to be flexible, allowing for modifications, adjustments, and redesigns to accommodate evolving industrial needs.
Vertical Reciprocating Conveyors (VRCs), also known as vertical material lifts, freight lifts, and conveyor lifts, are classified by the American Society of Mechanical Engineers (ASME) as conveyors and related equipment, adhering to ASME B20.1 standards. Designed solely for moving materials, VRCs are not intended for carrying people. They can be installed in various locations both inside and outside buildings, efficiently transporting materials of all shapes, sizes, and weights between floors, mezzanines, balconies, basements, and different levels of multi-story buildings.
VRCs offer more placement options than elevators and do not require separate machine rooms or feet of pit depth, making them space efficient. They feature structural supports and enclosed carriages that keep loads from falling, offering a safer and more efficient alternative to forklifts or scissor lifts.
The primary components of a VRC include the guide column, carriage, and hydraulic actuating mechanism. VRCs can be either mechanical or hydraulic, with hydraulic versions capable of lifting loads between 3,000 and 6,000 pounds. Hydraulic VRCs are more cost-effective to install than mechanical ones and are ideal for applications involving two levels and a height of up to 25 feet, without the need for continuous cycle operation.
Lift tables have gained popularity as work surfaces that can be adjusted to the precise height needed for tasks such as packaging, assembly, organization, or positioning items. Unlike adjustable tables, lift tables are distinguished by their higher lifting capacities.
A standard lift table can handle loads ranging from 2,000 to 6,000 pounds and can be adjusted from as low as 7 inches to as high as 60 inches, with a workspace that typically ranges from 24 to 72 inches. Available in various shapes and sizes to suit different applications, lift tables offer versatile solutions for many industrial needs. Below is a description of some of the different types of lift tables.
Mobile lift tables, also known as lift carts, are a type of push cart that can be raised using a manual foot pump. They are commonly used for light assembly operations and offer the convenience of mobility.
Rotating hydraulic lift tables are specialized lift tables featuring a turntable recessed into the surface, allowing access to a load from all four sides. The turntable operates on anti-friction bearings, enabling smooth and effortless rotation. When not in use, it can be locked in place. These lift tables often have a low profile, allowing them to be lowered to just a few inches off the floor for easy access with a pallet jack or forklift.
Like all hydraulic tables, rotating hydraulic lift tables are constructed from highly durable materials and are capable of lifting nearly a ton of products. They are designed to precisely position loads, reducing the need for manual lifting by workers and enhancing operational efficiency.
Low-profile lift tables have a collapsed height of just a few inches, allowing them to be loaded with a hand truck or forklift. Because they do not require a pit or floor indentation, they are suitable for use on upper floors as well as the main floor. The hydraulic lift is activated via a foot switch or push-button remote, enabling operators to raise or lower the table to an optimal working height.
Low-profile tables are designed to ergonomically position loads for easy handling or unloading, reducing worker fatigue, boosting productivity, and improving overall worker satisfaction. Their flexibility makes them adaptable to a wide range of applications.
Stainless steel lift tables are commonly utilized in the food and pharmaceutical industries due to their adherence to strict hygiene and sanitary requirements. Their resistance to corrosion and rust allows for easy cleaning with solvents and water, making them ideal for maintaining high standards of cleanliness.
High-capacity hydraulic lift tables are heavy-duty tools capable of lifting loads up to 60 tons, with lifting heights ranging from 52 to 92 inches. They feature platforms varying from 4' by 6' to 10' by 22', with options for custom larger platforms. Equipped with scissor legs and torque tubes, these tables provide exceptional stability and support, minimizing load deflection and shifting.
The number of scissor legs and hydraulic cylinders can vary based on the table's design and manufacturer. Like other hydraulic tables, high-capacity models can be operated using a handheld pendant or foot switch, and often include an upper travel limit switch. Additional features may include tilt tops, powered turntables, V-cradles, and corrosion-resistant finishes, among others.
High-capacity hydraulic lift tables are built to endure the rigorous demands and continuous use of heavy-duty machinery, making them the robust workhorses of the lift table category.
Ground entry lift tables are designed with ground-level access to the platform to address concerns about tripping hazards and space constraints. They feature a cut-out section in the shape of a "U" or "E," allowing for easy loading with open-bottom pallets or skids.
Tilting lift tables are designed for handling containers with loose parts. They raise to an ergonomic height and tilt toward the operator, reducing the need for bending and stretching. These tables can be adjusted to tilt up to 90 degrees, enhancing accessibility and ease of use.
Tandem lift tables integrate standard lifting functions with additional lifts to extend the length or width of the platform. This design provides the added benefit of increased platform size, allowing for the accommodation of larger loads and enhanced edge and side load capacity.
Multi-stage lift tables use stacked pairs of scissor arms, with one lift table mounted on top of another. This configuration allows for increased vertical travel while maintaining a compact platform size.
Hydraulic lifts are built from steel and offer precise accuracy, making them both sturdy and durable. Their robust design has led to their widespread use across various industries. Below are a few industries that depend on hydraulic lifts for their efficiency and powerful performance.
Electro-hydraulics is a widely used application of hydraulic technology in various industrial settings. Key advantages of hydraulics include rapid response times and high precision. Hydraulic systems are employed in a range of industries, including plastic processing, metal extraction, automated production, machine tools, paper manufacturing, loaders, crushers, presses, and textiles. The image below showcases a hydraulic press used in the plastics industry.
Mobile hydraulics offer the flexibility to adapt to various conditions and scenarios. They are particularly valuable in the construction and building industries, where they are utilized in cranes, excavators, backhoes, and earth-moving equipment. The image below shows a concrete boom truck equipped with a hydraulic arm for unloading concrete.
The automotive industry is the largest consumer of hydraulic technology. Hydraulics are extensively used in production, repair, and various internal components of vehicles. The image below illustrates the application of hydraulic automation in truck manufacturing.
Marine hydraulics deliver linear and rotary force and torque rapidly and efficiently. The three types of marine hydraulic systems are open, closed, and semi-closed. They are used for cranes, mooring and anchor winches, stabilizers, steering, thrusters, propellers, and platforms.
Aircraft components must adhere to stringent standards before they are approved for use. Hydraulic pumps and valves are crucial in meeting these regulations and play a vital role in aircraft design and production. Hydraulics are used for various functions, including wing adjustments, landing gear retraction and extension, door operations, brakes, and steering. The image below highlights some of the key applications of hydraulics in aircraft.
Hydraulics are well-suited for mining due to their power, controllability, reliability, and ease of maintenance—qualities that are essential in this high-risk environment. Mining operations, which involve large-scale equipment and operations, benefit from the significant power and force provided by hydraulic systems, making them an ideal choice for handling the demanding conditions of the industry.
Hydraulic lifts are robust pieces of equipment designed to exert significant force. Both the Occupational Safety and Health Administration (OSHA) and the American National Standards Institute (ANSI) set stringent guidelines for their use. A fundamental requirement is that operators must be at least 18 years old and have undergone thorough training on the safe operation and potential risks associated with hydraulic lifts.
Below is a summary of the key regulations and safety tips for operating hydraulic lifts.
OSHA regulations for lifts broadly apply to any work performed on elevated platforms.
Standard 1926.451 – Safety and Health Regulations for Construction – Although primarily focused on construction, this standard outlines requirements for guardrails and fall protection. Originally designed for scaffolds, it has been extended to include lift systems as well.
Standard 1910.29 – Walking-Working Surfaces – This standard addresses fall protection systems and measures to prevent falling objects, including specifications for guardrails and railings.
Aerial lifts are classified as mobile elevating work platforms (MEWPs). According to ANSI A92, these lifts must be equipped with two types of sensors: one that sounds an alarm and prevents operation when the load exceeds safety limits, and another that triggers an alarm and halts movement if the slope becomes too steep.
Gates on aerial lifts must be equipped with toe guards and cannot be chains. For outdoor use, wind speed sensors are mandatory. Platform railings must be at least 43.5 inches high. When operating on uneven ground, the tires must be solid or foam-filled. Additionally, ANSI A92 includes expanded training requirements for operators.
MH29.1 provides updated guidelines for operating and using industrial-sized scissor lifts for personnel. It outlines the distinctions and similarities between dock lifts, access lifts, and lift tables. This standard includes comprehensive details on the responsibilities of manufacturers, users, owners, and operators, along with a clearer explanation of the requirements for scissor lifts.
B20.1 sets the safety standards for conveyors and related equipment, including vertical reciprocating conveyors (VRCs), which function similarly to elevators for transporting large materials between floors in a building. These standards cover the design, construction, installation, maintenance, inspection, and operation of VRCs, addressing potential hazards and risks. Initially published in 1947, B20.1 has been updated several times to reflect advancements in technology, with the latest revisions in 2021 focusing on gates and enclosures.
To be OSHA certified for operating aerial and scissor lift equipment, an operator must complete an OSHA-approved training course. This course is designed to teach workers how to safely operate lift equipment. Regulations mandate that employers must provide certification training to ensure legal compliance.
The training includes:
Here below is a sample daily checklist for hydraulic lifts.
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