The minimum bend radius is one of the most important factors when choosing a hydraulic hose because it relates to the length of the hose we should determine and the layout of the hydraulic hose on a machine, ignoring the bend radius may cause some unexpected problems like leakage, shortened lifespan even lead to some risk of injury to human.
What is the bend radius of the hydraulic hose?
When bending a hydraulic hose with a 90° angle, the bend radius of the hydraulic hose is the radius of the circle to which the hose’s inner edge 1/4 arc corresponds. it is also indicated with half of the smallest diameter that a looped hose can achieve. Intuitively, it has something to do with the flexibility of the hydraulic hose.
What determines the bend radius of a hydraulic hose?
The typical hydraulic hoses consist of three layers: inner tube, reinforcement, and outer cover. each layer can add up to the stiffness of the hydraulic hose. moreover, for the same type of hydraulic hose, the bigger the diameter is, the stiffer the hydraulic hose is, so it has a larger bend radius.
When it comes to the materials of hydraulic hoses, hydraulic hoses are generally made of thermoplastic, rubber, and Teflon, as far as the three materials, when the diameter is determined, the bend radius of the hose increase in the sequence: thermoplastic, rubber, and Teflon.
Reinforcement is the most relevant factor to determine the hose bend radius, Textile braid, steel wire braid, and steel wire spiral are the three main reinforcement patterns, textile is more soft and flexible than steel wire, so textile-strengthened hoses are more flexible and have smaller bend radius.
Furthermore, spiral construction hoses are much stiffer than braided ones because of the inherent nature of hydraulic hoses.
As the reinforcement layers increase, the bend radius of the hydraulic hose become bigger.
How to calculate the hose bend radius?
The bend radius of the hose is given once a specific hydraulic hose is made, which is the inherent nature of a hydraulic hose (look at the “what determines the bend radius of the hydraulic hose” part), when you determine the overall length of the hydraulic assembly, don’t neglect the bend length and calculate it with the bend radius formula in the image above；
L — Represent the length of the arc part of the hydraulic hose;
r — Represent the bending radius of the hose given in the hydraulic hose bend radius chart.
The minimum required length of the hose can be got with L plus the length of the straight part.
As the r mentioned above, it is the intrinsic property of a specific hydraulic hose, In the SAE standard, each type of hydraulic hose has its rated bend radius, and it varies in different diameters, the hydraulic hose bend radius chart below illustrates this insight.
The bend radius column shows the minimum bend radius which can be accepted when the hydraulic hose is mounted, a bend radius lower than the rated one may result in a twist or deforming of the hose.
how to avoid disadvantages when determining the minimum bend radius of a hydraulic hose
Ensure the actual hydraulic hose bend radius is above the minimum bend radius, and try to set a room aside for possible requirements when the locations change, tight bent and over-stressed hydraulic hoses may raise some unexpected problems.
Exceeding the minimum bend radius may flatten the hydraulic hose and that will decrease the section area and produce extra resistant power, thus making the hydraulic system less efficient.
It is difficult for deformed hydraulic hoses to restore their original status, and it will fatigue the hoses and reduce their lifespan.
Over-tight hydraulic hose layout violates the principle that bends must take place a certain distance away from the ends and make the connection tenser, in the long run, leakage occurs at this point.
After all, hydraulic hose assembly tends to be not stationary when mounted on the machine, hence, the requirement of the hydraulic hose length is variable, we must make room for the hydraulic hose when considering the bend radius of the hydraulic hose.