Hydraulic hoses move pressurized fluid to and from hydraulic system components. Designed to be flexible and durable, all hose assemblies eventually wear down from constant pressure and need replacement.
Hose assemblies that suddenly fail can cause employee injury, property damage, expensive cleanup, wasted production, unscheduled downtime and increased material and labor costs. With these consequences in mind, most fluid power experts recommend replacing hose assemblies before they fail.
Well-constructed, modern hose assemblies make it hard to know when they are ready for replacement. Sometimes there are clear signs that one will soon fail, but in many cases, the signs are hard to see. In this article we discuss:
- The factors that contribute to hose assembly wear-and-tear
- How to tell it’s time to replace hose assemblies – before they fail
- How to replace hydraulic hose assemblies.
How Long do Hydraulic Hose Assemblies Last?
Manufacturers provide estimates on how long their hose assemblies will last, but outside factors come into play and can reduce the lifespan of a hydraulic hose assembly.
Hydraulic hose assemblies can last about 10 years from the date of manufacture. However, factors such as the temperature and pressure level of the fluid running through hydraulic hose assemblies can affect their lifespan. Manufacturers cannot predict how long hydraulic hose assemblies will last—no one can without knowing the specifics about where and how the hose assembly is used.
5 Factors That Wear Down Hydraulic Hose Assemblies
Factor #1: Pressure
Hydraulic hose assemblies have maximum rated working pressures. If the system pressure exceeds this point, the hose assembly may suffer permanent damage and/or fail. For this reason, hose assemblies rated for a few hundred psi over the system’s maximum working pressure will last longer. Installing quick acting pressure-relief valves can also help minimize the risk of pressure spikes, which create damage over time within the hose assembly and can shorten it’s useful life.
Factor #2: Temperature
Typical rubber hose assemblies are designed for operating temperatures between -40° F to 212° F. Certain other materials can provide safe performance up to 250°, even 300° F. PTFE-tubed hose assemblies can safely be used up to 450° F. Hydraulic fluids or ambient conditions outside of this range can lead to premature failure. Higher temperatures can lead to the hose assembly becoming hard, brittle and cracked, while lower temperatures result in the hose assembly becoming cracked without losing its softness or flexibility. The cooler the hose assembly fluid, the longer the hose assembly will resist degradation. When possible, hose assemblies should be shielded from heat sources such as engine manifolds.
Factor #3: Size
Hydraulic hose assemblies differ in size depending on the needs of a system. It is important to be aware of the limitations of the hose assemblies and avoid exceeding their operating capacities. Excessive velocity will damage the inner surfaces of the tube and tube debris could damage hose assembly components. High flowrate can cause friction and raise the temperature of the hydraulic fluid. Manufacturers often provide a simple nomograph to guide safely sizing the hose assemblies for hydraulic system’s pressure.
Factor # 4: Application
Each hose assembly is designated for a specific set of system functions and duty cycles. However, even when used properly, they can suffer damage from environmental factors related to their application, such as rubbing against other equipment or other hose assemblies or when they are used in vertical installations, which add stress not present in horizontal configurations.
Factor #5: Fluid
When selecting a hydraulic hose assembly for a system, make sure its construction materials are right for the hydraulic system fluid. The Material Safety Data Sheet (MSDS) for the fluid and the hose assembly manufacturer’s compatibility listings will help find the right match. Using incompatible materials can damage the assembly and hurt system performance. Some fluids can damage the tube and lead to failure, so you must make sure of compatibility with the hose assembly.
Signs Signaling a Need for Hydraulic Hose Assembly Replacement
While it is often hard to tell whether a hose assembly needs replacement, there are some signs that indicate it has reached the end of its life. For example, if any of the following conditions are present, it signals the need for replacement:
- Crushed or distorted hose assemblies
- Fluid leakage (within the hose assembly length or at the fitting end)
- Exposed wire reinforcement
- Significant surface damage (beyond scuffs and small nicks)
- Kinks (an indication of incorrect routing)
- Twisted hoses (another indication of incorrect routing)
- Hardened or blistered cover as well as any signs of the cover softening significantly which may signal a fluid compatibility problem
- Corroded fittings (white oxidation is normally, acceptable while red rust warrants replacement)
How to Replace a Hydraulic Hose Assembly
When a hose assembly exhibits any of the conditions above, it’s time to replace it. Here are the steps to take to replace a worn hydraulic hose assembly.
Step #1: Identify the Issue
Identify the issue. Verify the damaged hose assembly before removing and replacing it. Take care assessing the situation to ensure that the repair actually addresses the problem. With this information in hand, buy a replacement that will provide the same or a better performance rating.
Step #2: Assess the Situation
Determine which system components must be removed to replace the problem hose assembly.
Step #3: Prepare the System
Address any components connected to and around the hose assembly to ensure they do not hinder the replacement process. This step includes relieving pressure to avoid fluid leaks, lowering pieces to the ground to prevent them from falling and removing parts to allow for an obstructed view.
Step #4: Loosen the Fittings
Once the hydraulic assembly is ready for hose assembly replacement, loosen the fittings as required that attach the hose assembly to the machine. If replacing multiple assemblies, it is helpful to mark or color code the ends of each to ensure proper connections are maintained.
Step #5: Remove the Hose Assembly
When the fittings are loosened, remove the hose assembly and pour any residual fluid into a waste container.
Step #6: Seal the Fittings
Before installing the replacement, seal the fittings with a designated fitting plug or lint-free rag to avoid further leakage.
Step #7: Install the New Hose Assembly
Install the replacement using the proper techniques and reassemble the rest of the system. Use the double wrenching technique to prevent hose assembly twist. Refer to manufacturer’s recommendations for details and any applicable torque recommendations. Consider tagging the hose assembly.
Step #8: Check the New Installation
Check the now-installed hose assembly. Make sure the installation is proper in routing and connection.
Step #9: Test the System
After replacing the hose assembly and reassembling the system, test the system to verify there are no leaks or performance issues.
All hydraulic hose assemblies will eventually fail. Preventing their failure from affecting equipment or facility operations requires careful monitoring and staying ahead of the curve, as described in this article. If you see the signs described here, it might be necessary to bring in expert hose assembly vendors for help finding the right replacement and creating a replacement schedule.
Steve Downey is an Adjunct Fluid Power Instructor at Henry Ford Community College and Macomb Community College. He has worked in the Fluid Power Industry for 30 years in both Industrial and Mobile Hydraulics. Steve Holds 11 International Fluid Power Society certifications.