When ordering a replacement hydraulic hose assembly, a lot rides on getting the decision right, so what information do you need before sourcing the replacement? We find that a replacement hydraulic hose assembly is easiest to specify accurately when the failed hose is treated as evidence, not as the whole specification. By this, we mean that the removed – presumably faulty – assembly tells you the bore, end style, length and routing history you will need to replicate, but it’s also important to look for physical evidence that shows why the last hose did not survive duty. Before ordering a Gates hydraulic hose assembly or any other part, the information worth capturing is the data that determines whether the new hose will carry the required flow, tolerate the pressure cycle, fit the machine envelope and connect without twist or side load. Read on to find out more.
Capture The Duty Data Behind The Removed Hose
System pressure is the first design constraint in any fluid power system, but the service condition of hydraulic hose fittings is always broader than the gauge value written on a machine plate. The replacement therefore needs to be checked against maximum working pressure, variable pressure spikes, impulse frequency, fluid temperature, ambient temperature and the movement cycle of the hose. Burst pressure is a test and design reference; it is not a working allowance for a circuit that sees repeated pressure cycling.
The hose bore also needs to be confirmed rather than inferred from the outside diameter. Flow velocity follows , so a small reduction in internal diameter can produce a large increase in velocity because the area changes with the square of bore. The consequence usually appears as pressure loss and heat. As a quick sense check, a 10 bar pressure drop at 40 L/min represents roughly 0.67 kW of hydraulic power being turned into heat, before any wider cooling or oil-life effects are considered.
Record Pressure Class, Bend Radius And Routing
An accurate Gates hydraulic hose selection depends on construction as well as pressure rating. Wire braid, spiral reinforcement, cover type, abrasion resistance, flexibility and minimum bend radius will affect whether the assembly is suitable for the installed route. A hose that fits when a system is static might not if articulation pulls it below the minimum bend radius, rubs the cover against steelwork, or places the reinforcement in torsion.
The overall length should also be recorded with the fitting geometry in mind. Cut length, live length and bend allowance are not interchangeable. A 90-degree swept elbow, compact elbow or straight stem changes how the hose leaves the port, where the bend begins and whether the hose has enough free length to move without loading the crimped end. This is the reason that coupling-end burst problems are often linked to insufficient assembly length, excessive bending and the need to accommodate hose movement under pressure.
Identify The Fittings As Part Of The Assembly
Hydraulic hose fittings should be identified by thread, sealing face, stem type, nut type, angle, drop length and orientation. The difference between a fitting that screws in and a fitting that seals correctly is often found at the cone, O-ring, bonded seal or seat face. To avoid misidentification, product photos should show both the male and female sides, the sealing surface, any adaptor stack and the hose route after the fitting leaves the port.
Compatibility between hose and fitting is part of the pressure boundary. Gates hose fittings and Gates hydraulic hose fittings are not generic ends to be mixed by appearance; the selected hose family, coupling series, stem insertion, ferrule and crimp diameter have to match the approved assembly data, which is why part numbers, layline details and removed assemblies are valuable when ordering.
Order The Correct Hose Assembly First Time
At Hydrastar, we supply a wide range of Gates hydraulic hose, Gates hose fittings and related hydraulic hose fittings for replacement assemblies. If you are uncertain what part you need, please send us the hose layline, end-fitting photos, machine details, pressure information, measured length and failure evidence so the replacement can be specified from the duty as well as the removed part.
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