Hydraulic systems use liquid under pressure to perform work. Designing and building a hydraulic system requires some mechanical knowledge and specialised components, but the results can allow a machine to do jobs it would be difficult to do otherwise.
1Understand how a hydraulic system works. There are basically four elements to the system, as well as possibly many smaller associated components for specialised purposes. Here are the basic four and a brief description of each.
- Fluid Reservoir. This is a tank or other container that holds the fluid to supply the rest of the system.
- Fluid Circuit. These are the pipes or hoses which transfer the fluid from one element of the system to another.
- Hydraulic Pump. This device pushes hydraulic fluid through the circuit and provides the energy for the system to do its job.
- Hydraulic motor or cylinder. This is the component that causes something to move, driven by the power of the hydraulic pump.
- Subcomponents that manipulate or regulate the fluid as it does its job include various valves which allow excess fluid to bypass the hydraulic motor or cylinder, control valves or valve spools, regulators, accumulators, pressure switches, and pressure gauges.
2Determine what type of power source your hydraulic system will require. This can be an electric motor, and internal combustion engine, steam, wind, or water power. The main requirement is that the means for supplying the system with energy is that it is available and can generate sufficient torque for the purpose it is intended.
3Look at some simple, everyday hydraulic systems to help you become familiar with their function. A hydraulic jack can allow a small person to lift 20 tons of weight or more. A power steering system on a car can reduce the force required to steer it considerably, and a hydraulic log splitter can force a steel wedge through even the toughest wood.
4Plan your hydraulic system project with the design parameters you will require. You will need to decide what type of power you will use for generating pressure for the system to do the work, what type of control valves, if any, what type of pump you will use, and what type of tubing you will pipe/plumb your system with. You will have to choose a power delivery system to accomplish the task you are building your system for, an example would be using a hydraulic cylinder to split a log, or lift a heavy weight.
5Determine the amount of work your system will do to allow you to size the components correctly. A large capacity system will need a pump rated at a high volume, measured in volume per minute, such as GPM, or gallons per minute, and pressure, measure in weight per unit of area, such as PSI, or pounds per square inch. This being said, and typical hydraulic pump may deliver 0.65 GPM at 2200 PSI. The same applies to the hydraulic engine or cylinder you will use to drive, or operate your machine. An example is a cylinder that lifts a set of forks on a forklift. It requires "X" gallons of oil at "Y" pressure to lift "___" pounds, "___" feet in the air.
6Choose the appropriate container for your hydraulic fluid reservoir. A steel or plastic tank that can have leak proof fittings attached to it to connect hoses or pipes will work. Remember, the reservoir is not pressurized when the system is operational, but you will need to vent it if you pipe excess fluid directly back to it through a bypass valve or other device.
7Pick a suitable material to plumb up your hydraulic circuit. Reinforced rubber hoses with o-ring seals or flared fittings may be the easiest to route on your machine, but high-tensile steel tubing is more durable and requires less maintenance over time.
8Find a suitable valve system for your task. A simple On/Off fluid valve will function as a control valve if it is rated for the operating pressure of your system, but for complicated functions, you will be better off with a variable flow valve spool, which can regulate the flow, and in some instances, the direction of flow in a hydraulic circuit.
9Select the type of and capacity of your hydraulic pump. There are essentially two types of hydraulic pumps, a generator type, which forces oil between two or more meshed gears in a sealed housing, or a roller type, which operates with a number of cylindrical rollers configured around a cam in a sealed housing. They each have advantages and disadvantages, so choosing one that performs to your machine's requirements is up to you.
10Pair up a suitable motor to your pump. Pumps may operate off of a direct-drive shaft, a reduction gear drive, a chain and sprocket drive, or a belt drive. Obviously each is more suitable in specific applications, and the choice depends on individual design criteria.
11Hook up your power application component. For simply moving an arm or lever on a machine, a hydraulic cylinder is your most likely choice. This device is a steel tube with a piston/rod assembly inside of it, sealed to prevent oil from escaping. There are a number of types of cylinders in many different sizes, so again, selection depends on the specific design requirements of the project. Another device that uses the hydraulic power supplied by the pump is a hydraulic motor, seen used on winches and ground drive wheels on some types of aerial equipment, as well as manufacturing equipment like metal forming rollers.
12Build a support frame that will position each component in a position where it will perform it's task. This can be done on a flat surface, a metal framework, or even in multiple framed, remote function elements. An example would be having a pump, reservoir, and valve assembly on one platform, and having the hydraulic cylinder and support assembly in another location, as is found on hydraulic elevators in 2 to 4 story (or even higher) buildings.
13Fill the system with the hydraulic fluid you choose, bleed the air out of it, then pressurize it to check for leaks. Now it should be ready to operate it to assess the function of the components. Without specific design criteria and engineering, it is likely you will need to tweak the finished product to optimize its operation.
- Look at common applications of hydraulic power in the everyday world. Automotive brakes, some automotive transmission clutches, hydraulic jacks, and the Jaws of Life used by emergency responders are hydraulically operated, and looking at them will give you an idea of how a hydraulic system works.
- Do not under design the power supply side of your system. Using too small of a motor to drive a pump may result in immediate failure. A large backhoe or forklift uses as much as 100 horsepower or more to operate a single cylinder under a heavy load.
- Be aware that there are non-toxic, environmentally friendly, and non-flammable hydraulic oils available in the industry.
- To prevent this make sure the pressure is released slowly under control before making any repairs, alterations or even a routine check.
- Hydraulic oil often operates under extreme pressure, and can become very hot, so use caution when opening the hydraulic system for maintenance or repair.
- In addition, the pressurized oil as any liquid or gas under pressure can be injected into your body through the skin. In particular, pressurized oil when injected causes great damage to cellular structures of the human body, it literally destroys the cells and does not stop until completely removed.
Things You'll Need
- Hydraulic oil or other fluid
- Hydraulic pump with motor to drive it
- Hydraulic hoses with compatible fittings or steel tubing
- Hydraulic motor or cylinder to do the work
- Control valves, bypass valves, and pressure regulators
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