Selecting the right hose for an application, whether it’s a brand new hydraulic system you are installing or a replacement for an existing hose that has passed its useful life, requires some careful consideration. Besides issues such as inner diameter, material type, working pressure, surge pressure, and fitting size, the type of hydraulic hose reinforcement used is also critical.
Importance of Hydraulic Hose Reinforcement
Hose reinforcement is the key factor in determining the working pressure of the hose. For example, if a helically-reinforced hose is not used in a suction application, then there is a strong probability that the hose will collapse in upon itself as soon as a vacuum is applied. Even more dangerous would be the failure of a hose that causes a leak of highly pressurized hydraulic fluid. A pressurized leak can cause serious physical harm if it makes contact with the skin, resulting in an injection injury that can even cause death.
Impulse loads often result from shutting a hydraulic machine on or off and are a common cause of hydraulic hose failure. During an impulse load, the pressure within the hoses will experience a surge that can be significantly higher than the working pressure. The type of hydraulic hose reinforcement used will determine how well that hose can handle regular impulse/impact loadings.
The importance of selecting the correct hose for an application cannot be overstated. In order to select the proper hose, you need a good working knowledge of the different types of reinforcements and what their intended use is. The three major types are spiral, braided, and helical wound.
Spiral Reinforced Hoses
As the name implies, a spiral reinforcement consists of a spiral wrap made from wire or a textile material. The spiral is applied at a predetermined angle, and the wires/textile fibers in a layer are all parallel to each other. Multiple layers are used, usually with opposing angles, to provide extra strength. Usually between two and six layers are used, and the wires in a single layer never cross over each other.
Spiral wound hoses are stronger but less flexible than their braided counterparts. The minimum bend radius for these hoses is also larger than braided hoses, primarily because of their added stiffness and the fact that the spirals do not move easily within their layers.
Spiral hoses are used for heavy-duty, off-road hydraulic equipment, such as excavators or earth movers. Because they are stiffer and stronger, these hoses can handle high operating pressures and are not nearly as susceptible to high-impulse loads as braided hoses. When a high-pressure load causes the hose to contract in length and increase in diameter, the spirals do not rub against each because they do not overlap.
Braided Hydraulic Hose Reinforcement
Braided reinforcement is comprised of a wire, synthetic textile, or other material that has been applied around the perimeter of the hose by a high-speed braider. The result is a layer of crisscrossed reinforcement that allows a hose to maintain its flexibility while providing sufficient strength for low and medium-pressure applications. Note that low-pressure hoses have a synthetic textile braid; high pressure hoses usually have a wire braiding. Strength can be increased by adding additional layers of braided material.
Braided hoses have a relatively small minimum-bend radius and do not require much force to bend during routing. While good for flexibility, braided hydraulic hoses can fail when subjected to high-impulse loads. When a hose is suddenly subjected to high pressure, the diameter expands while the length shortens. As a result, the braids, which overlap each other, will rub against each other and cause excessive wear. This will eventually weaken the hose to the point of failure.
Helical Reinforced Hoses
The helical wrap reinforcement is a bit different than the previous two. In this case, a helical coil of monofilament is used to prevent the hose from collapsing when exposed to a vacuum pressure. It is primarily designed for use in suction applications. The helical coil is applied over existing layers of spiral or braided wire/textile.
Helical hoses have better impulse load resistance than plain braided hoses for the same reasons as spiral wound reinforcements do: The individual helixes do not overlap each other, and thus do not initiate wear by rubbing against each other. Helical reinforced hoses are usually found on return lines and suction hoses.
Which Type of Hydraulic Hose Reinforcement Do I Need?
For strength, especially when there is a high probability of impulse loads, the best choice would be a spiral wound reinforced hydraulic hose. If flexibility is key, then a braided hose will suffice. However, in the case of vacuum pressures, neither braided nor spiral reinforced alone can prevent the hose from collapsing on itself. In the case of suction hoses, helical reinforcement is needed.
Hydraulic Repair Facility Servicing All of Your Hydraulic Hose Needs!
Whether you need hoses replaced, maintained, or installed on a brand-new system, MAC Hydraulics has you covered. Our experienced technicians have the right combination of skill and training to handle all of your hydraulic hose maintenance and repair. Fittings, clamps, bend radius, hose type, reinforcement type, and installation are all second nature to our technicians, and they keep the most commonly needed parts on their trucks. They can help you track down the causes of past hose failure and keep them from happening again. Contact MAC Hydraulics today to find out what we can do to keep your hydraulic systems running efficiently with minimum downtime!