Here is everything you want to know about hydraulic lifts.
You will learn:
A hydraulic lift is a device for moving objects using force created by pressure on a liquid inside a cylinder that moves a piston upward. Incompressible oil is pumped into the cylinder, which forces the piston upward. When a valve opens to release the oil, the piston lowers by gravitational force.
The principle for hydraulic lifts is based on Pascal‘s law for generating force or motion, which states that pressure change on an incompressible liquid in a confined space is passed equally throughout the liquid in all directions.
The concept of Pascal‘s law and its application to hydraulics can be seen in the example below, where a small amount of force is applied to an incompressible liquid on the left to create a large amount of force on the right.
Hydraulic systems are used for precision control of large force applications, are economical, and make excellent use of energy resources.
A hydraulic system works by applying force at one point to an incompressible liquid, which sends force to a second point. The process involves two pistons that are connected by an oil filled pipe.
The image below is a representation of the two pistons and how they are connected by a pipe.
The diagram below represents a simple version of the working mechanism of a hydraulic device. The handle on the right moves the incompressible oil, under pressure, from the reservoir to the high pressure chamber in the middle of the diagram. The ram moves up as the oil is pumped in.
The force generated in a hydraulic system depends on the size of the pistons. If the smaller of the two pistons is two inches and the larger piston is six inches, or three times as large, the amount of force created will be nine times greater than the amount of force from the smaller piston. One hundred pounds of force by a small piston will be able to lift 900 pounds.
In this diagram, the piston on the left has a one pound load and an area of one inch. When it moves down ten inches, it is able to move the ten pound load on the piston on the right.
The purposes of hydraulic systems widely vary, but the principles of how hydraulic systems work and their components remain the same for all applications. The most significant part of a hydraulic system is the fluid or liquid. The laws of physics dictate that the pressure on the fluid will remain unchanged as it is transmitted across a hydraulic system. Below is an explanation of each part of a hydraulic system.
Hydraulic Circuits control the flow and pressure of the liquid in the system. The image below shows all of the different parts of a hydraulic circuit.
Hydraulic Pump converts mechanical power into hydraulic energy. Hydraulic pumps create a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line and out to the outlet to the hydraulic system.
Hydraulic Motor is an actuator to convert hydraulic pressure into torque and rotation. It takes the pressure and flow of the hydraulic energy and changes it into rotational mechanical energy, similar to a linear actuator. The pump sends hydraulic energy into the system, where it pushes the hydraulic motor.
Hydraulic Cylinder converts the energy in the hydraulic fluid into force and initiates the pressure in the fluid that is controlled by the hydraulic motor.
Hydraulic Pistons are moved linearly by fluid pressure. Axial designs have a number of pistons arranged in a circular pattern in a rotating housing.
Hydraulic Fluids transfer power in a hydraulic system. Most hydraulic fluids are mineral oil or water. The first hydraulic fluid was water before mineral oil was introduced in the twentieth century. Glycol ether, organophosphate ester, polyalphaolefin, propylene glycol, and silicone oil are used for high temperature applications and fire resistance.
Hydraulic lifts, in their many forms, have become an essential part of several industries from helping patients in and out of bed to specially designed lifts to help people board a bus. The number of uses of hydraulic lifts has been growing rapidly in recent years.
Below are descriptions of a few 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 safely lift people to various heights for work or movement of materials, such as repair of electrical lines, placement of inventory on a shelf, or access to control boxes. In gyms, factories, and entertainment centers, they are used to lift janitorial staff to clean lights and ceilings.
Fork lifts are used for moving materials at construction sites, in warehouses, in factories, and for loading and unloading trucks and airplanes. They are designed to quickly move items from one location to another.
Medical lifts are lifting devices for surgical tables, hospital beds, and monitoring equipment. Hospital beds are a convenient means for moving patients from their rooms to treatment areas. Hydraulics control the height of all parts of the bed to make it more acceptable for hospital staff.
Automotive lifts lift vehicles for repair and inspection. They are the strongest of the different types of hydraulic lifts.
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 also known as elevated work platforms, are similar to lift tables but much larger. They are able to hold groups of workers.
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 raised by a manual hydraulic hand pump and have a release lever to lower the load. They are very sturdy and maintenance free with the ability to lift one ton over six feet.
VRCs, also known as vertical, vertical material, freight, and conveyor lifts, are classified by the American Society of Mechanical Engineers (ASME) as conveyors and related equipment and must comply with ASME B20.1. They are intended for moving materials only and not people. VRCs can be placed almost anywhere inside or outside a building and are designed to move materials of all shapes, sizes, and weights from the floor to mezzanines, balconies, basements, and various levels in a multiple level building.
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 main components of a VRC are a guide column, carriage, and hydraulic actuating mechanism. VRCs can be mechanical or hydraulic with the hydraulic version capable of lifting loads weighing between 3,000 pounds and 6,000 pounds. Hydraulic VRCs are less costly to install than mechanical ones and perfect for lifting applications that are limited to two levels under 25 feet and do not require continuous cycle use.
Configurations
Lift tables have become popular as work surfaces that can be positioned at the exact height necessary to package, assemble, organize, or position items. What makes lift tables different from adjustable tables is their capacity.
A standard lift table is able to lift 2000 to 6000 lbs. and can be lowered to 7 inches or raised to 60 inches with a work space of 24 to 72 inches. They come in a variety of shapes and sizes to fit any application. Below is a description of some of the varieties of lift tables.
Mobile lift tables, or lift carts, are a form of push cart. They are raised by a manual foot pump for light assembly operations.
Rotating hydraulic lift tables are a special type of lift table that have a rotating turntable that is recessed into the surface of the table for positioning a load, which makes the table accessible on four sides. The turntable rests on anti friction bearings such that it can turn easily and effortlessly. When it is not needed, it can be locked in position. Rotating hydraulic lift tables can be low profile hydraulic tables that can be lowered to a few inches off the floor for easy access by a pallet jack or forklift.
As with all hydraulic tables, rotating hydraulic tables are made of highly durable materials capable of lifting close to a ton of products and items. They are designed to perfectly and precisely position a load to prevent workers from having to manually lift materials.
Low profile lift tables have a collapsed height of a few inches allowing the table to be loaded using a hand truck or forklift. Since they do not require a pit or indent in the floor, they can be used on upper floors as well as the main floor. To activate the hydraulic lift of the table, there is a foot switch or push button remote.an operator can use that raises or lowers the table to a comfortable working height.
The purpose of low profile tables is to ergonomically position a load to be worked or unloaded, which lowers worker fatigue, increases productivity, and helps with worker attitude. They offer flexibility and can adapt to the needs of a variety of applications.
Stainless steel lift tables are mainly used in the food and pharmaceutical industries, where there are high standards for hygiene and sanitary conditions. The corrosion and rust resistance of stainless steel makes them easy to clean with solvents and water.
High capacity hydraulic lift tables are heavy duty tools designed to lift loads up to 60 tons with lifting heights of 52 inches up to 92 inches and platforms from 4’ by 6’ up to 10’ by 22’ with customized larger platforms available. They have scissor legs and torque tubes that add stability and exceptional support and prevent load deflection or shift.
The number of scissor legs and hydraulic cylinders vary according to the design of the table and the manufacturer. As with other hydraulic tables, high capacity tables can be activated by a handheld pendant or foot switch with an upper travel limit switch. Possible additional features include tilt tops, powered turntables, V cradles, and corrosion resistant finishes to name a few.
High capacity hydraulic lift tables are the workhorses of lift tables and are designed to withstand the stress and constant use of heavy duty machinery.
Ground entry lift tables have ground level access to the platform due to concerns regarding tripping or being in confined spaces. Access to the platform is by a cut away section in the shape of a "U" or "E", which makes them able to be loaded with an open bottom pallet or skid.
Tilting lift tables are for handling containers with loose parts. The platform lifts to an ergonomic height and tilted toward the operator, which reduces the need for bending and stretching. They are available with tilt angles of up to 90 degrees.
Tandem lift tables combine standard lifting with additional lifts of length or width providing the extra benefit of increased platform size to accommodate larger loads with extra edge and side load capacity.
Multi-stage lift tables stack one pair of scissor arms on top of another with one lift table on top of another, which increases vertical travel but maintains small platform size.
Hydraulic lifts are constructed from steel and have precision accuracy. Their sturdy and durable design has made them popular in a wide variety of industries. Listed below are a few of the industries that rely on hydraulic lifts for their efficiency and ability to supply a great amount of force.
Electro-hydraulics is a common use of hydraulics in industrial applications. The main advantages of hydraulics are its rapid response times and precision. Plastic processing, metal extraction applications, automated production, machine tool industry, paper industries, loaders, crushers, presses, and the textile industry are some of the industrial uses of hydraulics. The image below is a hydraulic press from the plastics industry.
Mobile hydraulics have the advantage of being able to be moved to different conditions and situations. They are especially useful in the construction and building industries where hydraulics are used as cranes, excavators, backhoes, and earth moving equipment. Pictured below is a concrete boom truck using a hydraulic arm to unload concrete.
The automotive industry is the largest user of hydraulics. Production, repair, and internal components on cars all use hydraulics.The image below shows the use of hydraulic automation in the production of trucks.
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.
Components for aircraft have to meet strict standards before being approved for use. Hydraulic pumps and valves meet aircraft regulations and are an essential part of aircraft design and production. Wing adjustments, retraction and extension of landing gear, opening/closing of doors, brakes, and steering are all performed by hydraulics. The image below provides a list of some of the ways hydraulics are used on an aircraft.
Hydraulics are ideal for mining for the same reasons that they are used for other manufacturing operations. Power, controllability, reliability, and serviceability are necessities in mining because of the dangers that are involved. Unlike other manufacturing, mining works on a huge scale requiring massive equipment. The power and force provided by hydraulics fits the conditions.
Hydraulics lifts are heavy duty equipment that can supply a great deal of force. The Occupational Safety and Health Administration (OSHA) and the American National Standards Institute (ANSI) have specific requirements regarding the operation of hydraulic lifts. The first of those requirements is that operators must be an adult, over 18, that have been fully trained in the operation and dangers of the equipment.
Below is a summary of regulations and safety tips regarding hydraulic lifts.
OSHA regulations regarding lifts are generalized to include any form of work that has to be performed on a platform off the ground.
Standard 1926.451 – Safety and Health Regulations for Construction – Though this seems to be directed at construction, it covers the requirements for guardrails and fall protection. The general outline is for scaffolds but has been expanded to apply to lifts.
Standard 1910.29 – Walking-Working Surfaces – This covers fall protection systems and protection from falling objects. It further covers guardrails and railings.
Aerial lifts are defined as mobile elevating work platforms (MEWPs). ANSI A92 requires aerial lifts to be equipped with two types of sensors: one that sounds an alarm and prevents the machine from operating when the load exceeds safety limits, and another that triggers an alarm when the slope level gets too steep and prevents movement of the chassis or work platform.
Gates cannot be chains and must have toe guards. If used for outdoor work, wind speed sensors are required. Platform railings must be at 43.5 in. or greater. If used on uneven ground, tires must be solid or foam filled. Also included in A92 are expanded training requirements.
MH29.1 is revised information regarding how personnel can operate and be raised or lowered using industrial sized scissor lifts. It identifies the differences and similarities between dock lifts, access lifts, and lift tables. MH29.1 includes detailed information regarding the responsibilities of manufacturers, users, owners, and operators with a clearer statement of the requirements for scissor lifts.
B20.1 is a set of safety standards for conveyors and related equipment, under which fall vertical reciprocating conveyors that are designed to operate like an elevator for lifting huge materials between floors in a building. The standards of B20.1 apply to the design, construction, installation, maintenance, inspection, and operation of VRCs in regard to possible hazards and potential dangers. First published in 1947, B20.1 has been edited multiple times over the years to match the ever changing technology of VRCs with the last edits being made in 2021, which cover gates and enclosures.
To be OSHA certified to operate aerial and scissor lift equipment, an operator has to pass an OSHA certified course, which is designed to aid workers on how to safely operate lift equipment. The regulations and stipulations for operating lift equipment legally requires employers to provide certification training.
Training includes:
Below is a sample daily checklist for hydraulic lifts.
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