In many hydraulics systems, inflexible or rigid pipes or tubes are used to transfer energy-generating liquid between different components to form a complete hydraulic circuit. Pipes and tubes can be rigid in order to bridge small amounts of space in a controlled manner. For instance, in a hydraulic circuit contained within a small casing, there is no extra room for piping, so the connections must be rigid and contained within the casing. Some hydraulic circuits have much more liberal space accommodations or even require connection flexibility to facilitate faster replacement or range of motion operations. For example, many construction machines have external, flexible hydraulic hose connections so the tools are free to move.
A number of standards exist for hydraulic hose production and use. Standards govern industry connection specifications and hose material, as well as guide installation operations.
Basic Hydraulic Hose Construction
The basic hydraulic hose construction involves three layers. These layers help maintain a consistent and reliable flow of liquid while protecting the overall assembly from breaking down as a result of wear or abrasion.
Types of Hydraulic Hose Construction
Due to the variety of hydraulic hose applications and the range of chemicals and pressures they will be subjected to, there are likewise a number of hydraulic hose constructions.
Hydraulic Hose Compatibility: Liquids
There are three main kinds of liquid that will pass through a hydraulic hose. These include:
· Petroleum oil
· Synthetic oil
· Liquid with a high-water content
Most hydraulic hoses are capable of transporting petroleum oil and liquids with high-water contents, but synthetic oils require dedicated hose materials. Compatibility ratings are generally available from the manufacturer or from resource literature.
Hydraulic Hose Compatibility: Temperature
Hydraulic hoses are exposed to two temperature concerns: internal liquid temperature and external working temperature. As a result, hoses are rated for performance in terms of both temperatures, with a maximum and minimum functioning temperature rating. Exceeding these ratings can result in severely reduced working life or even failure, so it is pertinent to use a hose that is properly rated to both the liquid temperature and the environment temperature.
Hydraulic Hose Compatibility: Pressure
Hydraulic hoses are designed to withstand both an external and an internal pressure minimum and maximum. Exceeding either of these ratings can severely curtail hose performance. Pressure ratings or recommendations for a specific type of hose are generally available from the manufacturer.
With the above considerations about hose performance, it is also important to understand other application necessities for hydraulic hoses. Because pipes and tubes are generally more rigid, they can handle higher temperature or internal pressure in a given application. However, this increased rigidity makes them much more difficult to use in a moving operation. For instance, a construction digger requires a hydraulic system to operate a digging tool, but the freedom of movement needed to operate the tool can place limitations on hydraulic connections. A hydraulic pipe can allow torque, flexibility and elasticity in tool arm movement that is unavailable with tubes or pipes.
Additionally, some hydraulic systems can benefit from combinations of pipes, tubes and hoses. Large vehicles like airplanes require hydraulics systems to operate wing movements and landing gear, but the complexity of vehicle geometry necessitates variation in the hydraulics system.
A general rule used for hydraulic hose installation is to match the hosing to the machine contour. This means that a hose should follow machine geometry as much as possible. If a hose is hanging off of a tool, it can snag or puncture because of the tool’s wider movement radius. By matching the hose to the tool or machinery, an operator does not have to consider extra obstacles when using the equipment.
Choosing a Hydraulic Hose
Hydraulic hose users have a number of temperature, size and pressure factors to consider when choosing a hose for an application. There is a helpful acronym to track all of these considerations—STAMPED.
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