Thermoplastic hydraulic hose: the difference between R7 and R8

There are various types of thermoplastic hydraulic hoses, including the R7 and the R8. The difference lies in the pressure rating: SAE 100R7 is the standard thermoplastic hydraulic hose and SAE 100R8 is the high-pressure variant within the same family of materials. Both are available in black (conductive) and orange (non-conductive).

What is an R7 hose and what is an R8 hose?

Thermoplastic hydraulic hoses, just like rubber hydraulic hoses, fall within the SAE 100R classification. This classification categorises hoses based on their construction and pressure rating, so the designation alone indicates which category a hose belongs to. Within this series, R7 and R8 are listed separately:

• SAE 100R7: thermoplastic hydraulic hose, available in black (conductive) or orange (non-conductive).
  SAE 100R8: high-pressure thermoplastic hydraulic hose, also available in black (conductive) or orange (non-conductive).

Both types consist of a thermoplastic elastomer inner core, a polyester or aramid fibre reinforcement and a polyurethane (PU) outer jacket. This construction makes the hose lighter than a rubber variant, resistant to corrosion, and recognisable by its smooth plastic outer jacket, in contrast to the woven texture of a rubber hose.

Thermoplastic hoses are often chosen for systems where cleanliness and corrosion resistance are crucial, for example in a maritime environment with exposure to UV radiation and salt water.

The distinction between R7 and R8 lies in the pressure class for which the hose is designed: R8 is the high-pressure variant. To achieve this higher pressure rating, manufacturers typically use heavier reinforcement around the polyester core, such as additional steel or aramid reinforcement. The exact number of layers and the reinforcement used vary by manufacturer and product code, and are specified in the details of the selected product. As with any high-pressure hose, the working pressure, burst pressure and bend radii depend on the diameter, wall thickness and construction.

What should you bear in mind when choosing between R7 and R8?

• System working pressure: check that the working pressure plus the required safety margin complies with the product’s specifications. An R8 designation alone is no guarantee that a specific product can withstand the required pressure.
• Medium and conductivity: choose the black, conductive version where there is a risk of electrostatic charging, for example when transporting fuel. Choose orange where that risk does not apply.
• Diameter and wall thickness: a larger hose diameter generally reduces the permissible working pressure within the same series. Check this for each size, not on the basis of the R-class alone.
• Environmental conditions: temperature fluctuations in the medium and the environment affect the strength of the plastic core and must be assessed against the specifications of the selected product.
• Fittings: the connection type must be suitable for both the hose size and the system requirements; fittings from different product ranges are not necessarily interchangeable.
• Certification: determine in advance whether a certificate is required, as not every product within the R7 or R8 ranges carries the same certification.

Common mistakes or misconceptions regarding R7 and R8 hoses

Confusing class and item number

The designation R7 or R8 refers to the pressure class within the thermoplastic family, but not to the exact technical specifications of a specific hose. These are set out in the product specification for the item number.

Interpreting colour coding as a pressure class

The black and orange versions indicate whether a hose is conductive or non-conductive, not whether it is an R7 or R8 hose. Both classes are available in both colours.

Replacement without reassessment

Replacing a hose from one class with one from another class without reassessing the working pressure, the medium and the environmental conditions undermines the system’s safety margin.

Frequently asked questions about thermoplastic hydraulic hoses

1. Can a worn R7 hose simply be replaced with an R8 hose?

In practice, this often happens, because an R8 hose seems ‘better anyway’. That is not necessarily true: R8 is designed for a higher pressure rating, but that says nothing about the diameter, bend radius or the type of coupling required at that specific point in the system. Replace based on the system requirements, not on the letter R7 or R8 alone.

2. Why does one thermoplastic hose have a black jacket and another an orange one?

This has nothing to do with the pressure rating, but with conductivity. Black is the conductive version and is used where electrostatic charging poses a risk, such as when transporting fuel. Orange is the non-conductive version. Both colours are available in both R7 and R8.

3. Does the R designation automatically determine how much pressure a hose can withstand?

No. The designation indicates the class within the SAE 100R series, but the exact working pressure, burst pressure and bend radius depend on the diameter, wall thickness and construction of the specific product.

Need tailored advice to make the right choice?

The choice between an R7 and an R8 thermoplastic hose directly affects the safety and reliability of a hydraulic system. As an official Danfoss distributor, Hydynamic assists in assessing the correct class and the corresponding part number for a specific application, and also handles the assembly, testing and certification of bespoke hydraulic hoses.

For applications in the offshore and oil & gas sectors, this can be supplied including DNV-certified assembly, usually within one working day. Are you unsure whether to choose a thermoplastic, rubber or polyamide hose?

Then read about the differences between thermoplastic hoses, polyamide 12 and rubber hydraulic hoses. Contact Hydynamic for a tailored assessment of the correct hose class and the matching product.