Hydraulic hoses are a vital component of high-pressure fluid power systems. These flexible hoses connect various hydraulic system components and offer excellent pressure resistance and flexibility. They are available in a variety of materials—such as PTFE, rubber, and thermoplastics—all of which ensure the hose remains flexible.
Beyond flexibility, hydraulic hoses offer many other advantages, making them an ideal choice for complete system piping.
Compared to hydraulic pipe, hydraulic hoses are not only less expensive and lighter, but also more shock-resistant. This contributes to improved system stability. Furthermore, hydraulic hose assemblies are easier to assemble than hydraulic pipe; they can be assembled using a crimping machine. Additionally, hydraulic hoses have an outer layer of rubber or fiber material, making them less prone to rusting than hydraulic hoses (unless they are made of stainless steel), which typically require painting to prevent rusting.
How Hydraulic Hoses Are Built - Hydraulic Hose Construction
The construction and materials of hydraulic hoses depend on the application and operating conditions. The various application parameters required when selecting a hose are size, temperature, fluid type, and pressure, to name a few. Depending on these criteria, the choice of hose construction will change to suit the conditions.
The majority of hydraulic machines do not use special hoses. Typically, standard wire-braid reinforced hydraulic hoses, such as the 100R1 (single-wire braid) and 100R2 (double-wire braid) types. For applications requiring extremely high pressure ratings or involving special fluids, hose models such as 100R12 or 100R15 are typically selected. Hydraulic hoses can withstand pressure ranges from 1,000 to 6,000 psi or even higher. All hydraulic hoses are manufactured in accordance with North American or international standards to ensure that their construction and quality meet or exceed relevant specifications.
Hydraulic hoses' three-layer construction
Hydraulic hoses are built with a three-layer structure: an inner tube, a reinforcement layer, and an outer cover.
Inner tube
The material of a hydraulic hose's inner tube is determined by the type of hydraulic fluid. For example, nitrile rubber is suited for petroleum-based hydraulic fluids but is incompatible with synthetic hydraulic fluids (such as phosphate ester-based fluids). When conveying synthetic hydraulic fluids, use materials with higher corrosion resistance—such as a fluoroelastomer or PTFE inner tube.
The materials used for the inner tube and outer cover also influence the optimal operating temperature.
The general hose construction is suitable for a temperature range of -40 to 202°F (-40 to 94°C). This type of hose generally consists of an inner tube made of nitrile rubber and an outer layer of chloroprene rubber.
However, lower-temperature environments require the use of specially formulated polymer rubber. Cold-resistant polymer rubber must possess high ductility to prevent cracking and hose failure.
Reinforcemence layer
The core characteristic of a hydraulic hose is its pressure resistance, which depends primarily on the reinforcement layer.
The reinforcement layer is created by tightly winding steel wire or fabric around the inner tube wall using spiraling and braiding machines; the subsequent extrusion of the outer rubber layer completes the hose.
Steel wire is the most commonly used material for the reinforcement layer of hoses; there are two braiding methods: braiding and spiral.
Braiding refers to the alternating weaving of vertical steel wires in opposite directions on the pipe wall. Braided steel wire hoses come in single-layer and double-layer, with double-layer braided hoses usually separated by a layer of rubber.
The most common types of hydraulic hoses are SAE 100R1 and 100R2 braided hoses, which are single-wire and double-wire hoses. Braided hoses are the most commonly used type of hydraulic hose, and are available in a variety of sizes and pressure ratings.
It should be noted that the increased inner diameter will reduce the rated pressure of the hose. Furthermore, the working pressure of the hose is one-quarter of its burst pressure, its safety factor is 4:1.
Braided hoses are strong and flexible; most manufacturers produce highly flexible braided hoses with a bending radius that is only half that of standard braided hoses.
There are two types of spirally wound hydraulic hoses. Helically coiled hose is a slightly reinforced type of hose used to improve pressure resistance, but it is limited to suction lines with very low or no pressure, and sometimes also used in return lines with low pressure peaks.
Tightly spiral hydraulic hoses are used in ultra-high-pressure systems. This hose is made of four layers of high-strength steel wire, with each layer of wire perpendicular to the others. Four-layer spiral wound hydraulic hoses have extremely high strength and are often used in high-pressure, large-diameter hose assemblies.
Four-layer spiral wound hydraulic hoses have extremely high strength and are commonly used in high-pressure, large-diameter hose assemblies. This four-layer steel wire hose can withstand pressures up to 5000 psi at a diameter of 2 inches, but sometimes a six-layer steel wire hose is used to meet more stringent requirements. The disadvantage of four-layer and six-layer steel wire hoses is their poor flexibility. Due to their rigid multi-layer structure, four-layer steel wire 100R12 hoses have greater stiffness; however, advancements in materials and manufacturing processes have enabled major hose manufacturers to significantly reduce their bending radius.
Outer Cover
The hydraulic hose outer cover is primarily for protecting the hose and its reinforcing layer from the environment. The outer cover material is usually nitrile rubber, but chemical compatibility is required in highly corrosive environments.
The outer layer material has more types than the inner layer material and can be made of neoprene rubber, polyvinyl chloride, nitrile rubber, or even woven fabrics.
On the other hand, excessively high ambient or operating temperatures can cause the hose's inner tube and outer layers to soften, leading to premature hose failure.
While most hydraulic systems (and hydraulic fluids) do not operate at extreme temperatures, there are times when it is necessary to prevent localized high temperatures. For example, in steel mills where temperatures can reach 400°F (about 204°C), Teflon hoses with a stainless steel outer layer should be used in such high-temperature environments. The disadvantages of Teflon hoses are their relatively poor flexibility and large bending radius. However, they are resistant to high temperatures and corrosion.
Another common issue with hydraulic hoses is abrasion of the outer layer; therefore, special attention should be paid to the material and construction of the outer cover.
In high-abrasion environments—such as construction sites—you should select hoses featuring specialized construction and abrasion-resistant outer layers (and use hose protective sleeves) to prevent wear.
That covers how hydraulic hoses are built—including the inner tube, reinforcement layer, and outer cover—as well as their various types, advantages, and disadvantages. Whether you work in construction, agriculture, manufacturing, or any other industry that relies on hydraulic power, this information will help you understand how these hoses operate and how to make the right choice.
FAQ
How to Choose the Right Hydraulic Hose?
When selecting a hose, factors such as size, temperature, fluid type, pressure, and application details need to be considered.
How to properly assemble the hydraulic hose?
Proper assembly techniques, including accurate hose measurements, proper fitting of connectors, and thorough pressure testing, help prevent leaks and system failures.
How to Properly Store Hoses
Most hydraulic hoses should be stored in a cool, dry place, away from direct sunlight and contact with chemicals. Additionally, sharp bends or kinks should be avoided during storage and handling to prevent structural damage.
Sinopulse is a manufacturer and supplier of hydraulic hoses and fittings. Our experts are available to answer any questions you may have about selecting the right hydraulic hoses and fittings for your application.