Selecting the proper hose for a hydraulic assembly is critical to ensure that it meets the requirements for that specific application. One of the first steps in selecting the proper hose is to identify the type of reinforcement that is needed. The reinforcement is the strength of all hydraulic hoses; it determines the working pressure of the hose. Within the hydraulic hose industry, you will commonly see three types of reinforcement:
It is important to note that there are hoses that have a reinforcement that is a combination of fiber and wire, or multiple layers of wire braids or spiral layers but typically there are one or the other. Watch this video to see the differences.
Hose reinforcement has a direct correlation to the working pressure rating of a hydraulic hose. Pressure capacity is the defining criteria for hydraulic hose and pressure dictates how it is constructed. The type of reinforcement as well as the number of layers; 1-wire hose, 2-wire, 4-wire, etc., generally indicates pressure capacity. As you increase the number of layers, the pressure rating increases.
Hose reinforcement also impacts the flexibility of a hydraulic hose. Although hydraulic hoses are usually fairly stationary and don’t move around very much, hoses used on a piece of equipment that has a flexible joint, like a backhoe, must be flexible. Furthermore, the flexibility of hose enables components to be positioned in the most efficient or convenient places due to its ability to bend around corners, through tight spaces, or across long distances. Braided and spiral hoses definitely differ in terms of flexibility along with other differentiating factors.
Braided construction has a crisscross wire arrangement. This ends up looking like a braid when it’s all done. Braided constructions allow for increased flexibility of the hydraulic hose. Several layers of wire braid can make the hose stronger while keeping the reinforcement material untangled and maintaining a constant pitch (i.e. the inclination and the thread count per unit length). "Medium-pressure hoses" typically feature one- and two-wire braided construction. These hoses are frequently found on construction equipment, heavy-duty trucks, and fleet vehicle applications. In general, braided hose is selected for its flexibility, however, this type of hose is also more susceptible to failure under high-impulse applications.
The majority of "low-pressure braided hoses" have a textile reinforcement. In applications with typical operating pressures below 300 psi, the use of fiber braid allows for maximum flexibility. Hoses with textile reinforcement are commonly used to transmit petroleum-based fluids, diesel fuel, hot lubricating oil, air, ethylene glycol anti-freeze and water.
Below is an image of one of Parker Hose Product’s braiding machines.
At one time in the industry, two-wire braided hose was most commonly used in many applications. But the advent of larger, off-road specialty equipment drove the creation of spiral hose, which is very well suited for applications where extremely high impulse pressure is encountered.
Spiral hose construction consists of either textile or wire reinforcement. Each ply is laid at a specified angle for maximum dimensional stability. Instead of crisscrossing, wires remain parallel as they wrap around the circumference of the hose. Even though spiral reinforcement results in a stronger hose; there is an increased minimum bend radius and less flexibility due to the stiffness of the wire reinforcement in most cases. Spiral wire construction was designed to handle the high impulse applications such as construction equipment, heavy-duty trucks and fleet vehicle applications.
Below is an image of one of Parker Hose Product’s spiral hose machines.
Usually the more layers of wire, the stronger the hose, which means higher pressures can be achieved. Multi-layer spiral hoses, such as four- or six-wire construction, are used in a wide variety of applications from lawn tractors to earth movers. The demand for durable, high-performance spiral hydraulic hoses is continually growing, especially in applications where service life is critical.
Helical wire construction is used in addition to layers of fiber spiral or fiber braid hose reinforcements. Helical reinforced hoses are designed with maximum flexibility and vacuum handling in mind. The use of a helical reinforcement construction prevents collapse under vacuum. Helical wire reinforcement can be found in low pressure suction and return line hoses.
If you are in need of a hydraulic hose but don’t know which is best for your application, contact a local hose distributor. Provide them with all the details of your application in order for them to fully understand what you need. You can also download Parker’s HoseFinder to go through the STAMP process, which enables you to identify hoses based on your specific application.
From one- and two-wire braided, and up to six-wire spiral hose construction, and with a variety of cover options to protect from abrasive situations, Parker’s hydraulic hoses cover the pressure and media requirements for most hydraulic applications.
Article contributed by Kyri McDonough, marketing services manager at Hose Products Division, Parker Hannifin.
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