A Practical Guide to Hydraulic Hose Media Compatibility

Hydraulic hoses, as important components for power transmission, are used in various industries. However, when selecting a hydraulic hose, in addition to considering the quality and dimensions of the hose itself, the hydraulic hose media compatibility with the conveyed medium and the external environment should also be considered.

Medium compatibility refers to the suitability of the chemical and physical interactions between the inner layer material of a hydraulic hose and the fluid being conveyed. Medium compatibility is a two-way concept, considering both the effect of the medium on the hose and whether the hose material will contaminate the medium. Hydraulic hose media compatibility is crucial for selecting the appropriate hydraulic hose for a specific fluid, as incompatible combinations can lead to hose bulging, leakage, and contamination of the conveyed medium, further impacting system performance and potentially causing serious personal injury and system failure.

Factors Affecting Hydraulic Hose Media Compatibility

In hydraulic systems, the suitability of a hydraulic hose for a particular medium depends on more than just the “medium itself.” Even the same fluid can have different effects on the hydraulic hose under different operating conditions. A comprehensive approach considering multiple factors is necessary.

Hydraulic Hose Media Compatibility

1. Chemical Composition of the Medium

The chemical composition of the conveyed medium and the hose material are key factors in determining compatibility. Different types of liquids have significantly different effects on rubber materials, and the specific chemical composition of the medium will have different impacts on the hose.

2. Inner Tube Material of the Hose

Hoses made of different materials have different resistance to the conveyed medium. The inner tube material determines its applicable range. Specific factors to consider include oil resistance, chemical resistance, temperature resistance, and permeability.

3. Operating Temperature

Temperature accelerates hose aging. The temperature of the conveyed medium or the operating environment also affects the hose’s compatibility and service life.

4. Operating Pressure

Pressure affects the structural strength of the hose and the interaction between the medium and the inner tube. High pressure accelerates the penetration of the medium.

5. Flow Rate of the Medium

The flow rate and flow pattern of the medium in the hose also affect its compatibility with the hose. High flow rates increase friction and generate heat. Systems operating continuously for extended periods require higher demands on medium compatibility.

6. External Environment

The external environment also affects the compatibility of hydraulic hoses. For example, ultraviolet radiation, ozone, humid environments, high-pressure pulses, or frequent bending can all affect the hose structure and, consequently, its compatibility with the conveyed medium.

Common Hydraulic Hose Media

The following content represents common applications in the industry.  Whether a specific application is suitable still needs to be confirmed based on the hose structure, inner rubber material, and actual working conditions. If you are unsure, please contact our hydraulic experts.

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1. Hydraulic Fluids:

Mineral-based hydraulic fluids: the most common type of hydraulic fluid

Synthetic hydraulic fluids: (esters, polyalphaolefins, polyethylene glycols, etc.)

Vegetable oil-based (rapeseed oil, soybean oil)

2. Lubricants: engine oil, gear oil, grease
3. Gases: air, inert gases (nitrogen, etc.), some process gases
4. Water: cold water, hot water, seawater, fresh water
5. Chemicals: acids, bases, solvents, additives, etc.
6. Special Fluids: refrigerants, food-grade liquids, pharmaceutical raw materials, high-temperature heat transfer oils, etc.

Hydraulic fluid

Hydraulic Hose Fluid Compatibility

The fluid conveying capacity of a hydraulic hose is primarily determined by its inner layer material. The image below shows several common inner rubber materials for hydraulic hoses and the fluids they are suitable for.

How to confirm the compatibility of the fluid medium with the hydraulic hose?

1. Identify the accurate information of the fluid medium and the hose.

Read the markings on the hose, which usually indicate the manufacturer’s name, hose series, size, and rated pressure.  You can use this information to find more details about the hose or contact the hydraulic hose manufacturer to check the hydraulic hose media compatibility.

The fluid medium will also have specifications regarding additive types and content. Read these carefully and match them with the hose specifications.

2. Sample testing (essential for critical applications)

72-hour immersion test (ASTM D471)

Volume expansion < 30%, hardness change < 15 points

No cracks, bubbles, or stickiness in appearance

3. System-level verification

Small-scale trial, regularly check for performance changes, inspect the appearance of the hose for signs of swelling, cracking, hardening, or stickiness. Check the connectors for signs of loosening, leakage, or bursting. Address any problems immediately to prevent small problems from becoming major issues.

Summary

There is no “one-size-fits-all” solution for hydraulic hoses. Understanding hydraulic hose media compatibility and thoroughly communicating actual operating conditions during the selection phase are crucial prerequisites for ensuring system safety and extending hose service life.

FAQ

1. Can hydraulic hoses be used for diesel fuel?

Some hydraulic hoses can be used, but it is not recommended for long-term use.

Hydraulic hoses can usually withstand the structural strength required for diesel fuel transfer, but diesel fuel has strong permeability, which may adversely affect the rubber inner lining of standard hydraulic hoses, leading to expansion, softening, or premature aging.

2. Can hydraulic hoses be used for gasoline?

Hydraulic hoses are not recommended for transporting gasoline. Gasoline is highly volatile and incompatible with the inner lining materials of hydraulic hoses, easily causing leaks with long-term use.

3. Can hydraulic hoses be used for propane?

Hydraulic hoses are not recommended for transporting propane. Propane is a flammable gas, requiring extremely high sealing performance from the hose material. Specialized gas hoses should be used for propane transfer.

4. Can I use a hydraulic hose to transport compressed air?

Hydraulic hoses can usually withstand the pressure of compressed air, but air is a compressible medium. If the hose ruptures, the energy released is far greater than that of a liquid, posing a higher safety risk.

5. Can hydraulic hoses be used as LPG hoses?

No. Liquefied petroleum gas systems must use specialized LPG hoses.

6. Are hydraulic hoses compatible with brake fluid?

Hydraulic hoses are not compatible with brake fluid. Brake systems should use hoses specifically designed for brake fluid, not ordinary hydraulic hoses.

7. What is the resistance of various materials to different types of media?