When should a hydraulic hose be replaced?

A hydraulic hose must be replaced as soon as any visual defects appear, when the maximum service life as defined by international standards has been reached, or following mechanical damage. Identifying these points in good time prevents unplanned plant downtime, environmental damage caused by oil leaks and safety risks in the workplace. The decision to replace a hose is not based solely on a fixed time period, but depends on specific operational factors and standards.

Key factors affecting the service life of hydraulic hoses

In reality, the degradation of the rubber and the internal pressure-bearing components is determined by the combined effect of several variables:

• Working pressure and pressure spikes: continuous heavy loads and sudden hydraulic shocks (turbulence and pressure spikes) accelerate material fatigue.
• Ambient temperature and fluid: extreme heat or cold, as well as the chemical composition and temperature of the fluid being conveyed, degrade the elastomer.
• Mechanical stress: friction against machine frames or an excessively tight bend radius cause premature wear of the hose jacket.
• Environmental factors: UV radiation, ozone and aggressive substances (such as salt in the maritime sector) accelerate the ageing process of the rubber.

What do international standards say about the service life of hydraulic hoses?

Leading international standards, such as the German DIN 20066, provide clear guidelines for the maximum service life of hose assemblies. In standard industrial applications, a total service life of up to 6 years is recommended. This period comprises up to 2 years’ storage of the loose hose and up to 4 years’ operational use. For specific sectors with increased safety risks or extreme loads, stricter, shorter time limits may apply.

How is it determined whether a hose needs replacing?

The actual condition of a hydraulic hose can only be determined by a targeted on-site inspection. This assessment is carried out through regular visual and functional checks, during which the entire hose assembly is carefully inspected: from the flexible rubber sheath to the critical transition to the hydraulic couplings.
An important aid in this inspection is the so-called layline (the printed production line on the side of the hose). This layline contains vital information such as the manufacturer’s code, the specific standard (for example, EN 853 or EN 856) and the maximum working pressure.

In practice, there are five indicators that directly point to a dangerous weakening of the material.

5 signs that a hydraulic hose needs replacing:

1. Visible steel reinforcement (damaged outer sheath): when the rubber outer sheath has worn away due to abrasion or UV radiation to the extent that the steel braided or spiral layers are visible, corrosion will set in quickly. This weakens the pressure-bearing component.
2. Leakage or ‘sweating’ around the couplings: fluid seeping between the rubber and the hydraulic hose couplings indicates an internal leak or a loosening compression joint. According to the official maintenance guidelines of manufacturers such as Danfoss, ‘sweating’ (the minimal seepage of fluid through the outer jacket) also indicates the onset of structural material degradation and is a direct precursor to a hose rupture.
3. Kinking, twisting or exceeding the bend radius: a twisted or kinked hose leads to localised constriction, heat build-up and premature material fatigue. Installation guidelines from product catalogues show that a hydraulic hose under pressure can expand by up to +2% and contract by up to -4%. A hose that was originally fitted without sufficient slack may become taut under pressure, which can lead to material fatigue.
4. Blisters or soft spots on the outer jacket: blisters on the outer jacket are likely to indicate a tear in the inner hose. The oil is now under high pressure directly against the thin outer layer, posing an immediate risk of bursting.
5. Expired shelf life: the date of manufacture is always printed on the hose’s layline (usually shown as the quarter and year of manufacture, such as 2Q24 or *4Q25*). If the period specified by the DIN standard has been exceeded, or if the layline has become illegible due to external factors such as extreme wear or over-spraying, the hose should be replaced as a precaution.

Why is it incorrect to say that hydraulic hoses need to be replaced after just one or two years?

Applying a standard replacement interval of one or two years is incorrect, as the actual service life depends entirely on the specific application. For example, a hose operating indoors under constant, mild conditions can easily last many years longer than one that is subjected to harsher conditions. In such cases, replacing hoses systematically after one or two years leads to unnecessary expenditure, provided that periodic and expert inspections are carried out.

What are the common mistakes when replacing or repairing hoses?

As soon as an inspection reveals that a hose needs replacing, action must be taken. It is precisely at that moment – when there is intense pressure to get a machine up and running again quickly – that mistakes are often made which can jeopardise safety.

• Emergency repairs to the hose: it is incorrect and dangerous to repair a damaged hose with tape, clamps or by spot-welding it. The extreme forces within the system do not tolerate makeshift solutions.
• Mixing different brands or product ranges: combining hoses from manufacturer A with crimp fittings from manufacturer B is not recommended. In many cases, this also applies within a single manufacturer’s product ranges: the specific tolerances and crimp specifications of, for example, a Danfoss Winner fitting differ from those of the Danfoss Aeroquip ranges. Interchanging these components can compromise structural integrity, preventing the hydraulic hose from functioning properly.
• Ignoring the root cause: simply replacing a faulty hose without addressing the underlying cause (such as an abrasive machine frame or a lack of hydraulic hose protection) will result in the new hose failing just as quickly.

How often should hydraulic hoses be inspected?

The frequency of inspections depends on the operating conditions and the risk class of the installation. In demanding operational environments, such as the earth-moving or maritime sectors, a daily visual check prior to the start of the work shift is recommended. For standard industrial installations, a thorough, documented inspection every 3 to 12 months is sufficient. Consistently maintaining these inspection reports helps to identify wear and tear on the hoses at an early stage.

Can hydraulic couplings be reused when replacing a hose?

Reusing standard crimp couplings is incorrect and poses significant safety risks. During the initial crimping process, the metal sleeve undergoes permanent plastic deformation to seal the hose watertight. Cutting off and re-crimping a used fitting onto a new hose compromises the structural integrity of the metal, which, under high pressure, leads to an immediate risk of rupture or the fitting coming loose. It is therefore advised not to do this. Only specific, purpose-designed screw-type fittings (reusable fittings) may be reused under strict conditions and following a thorough inspection.

How is the length of a hydraulic hose correctly measured when replacing it?

A common mistake when ordering a replacement hose is to measure only the flexible rubber section. International standards stipulate that the total length (Overall Length, or OAL) is the decisive factor. This means that the hose is measured including the fitted couplings. The measurement is taken from the outermost sealing surface of one coupling to the outermost sealing surface of the other coupling. For right-angle couplings, the measurement is taken from the centre of the sealing surface. A correct OAL is crucial to ensure the required slack when the system is pressurised.

Timely maintenance ensures maximum hydraulic reliability

Correctly assessing hydraulic components requires specialist knowledge and a systematic approach. By not relying solely on fixed time intervals, but instead taking into account environmental factors, catalogue specifications, DIN standards and visual indicators, a system remains both safe and cost-effective.

As an official Danfoss distributor, Hydynamic’s specialists provide support in the correct assessment and assembly of high-quality hydraulic hoses and couplings. With an extensive range of genuine Danfoss Aeroquip and Winner components, and expertise in certified hydraulic hose crimping, we ensure minimal downtime and a working environment with maximum safety. Please contact us for tailored advice on replacing hoses or for a reliable supply of bespoke hydraulic hoses.