Attention to detail is critical when selecting hydraulic hose. Several important considerations that must be addressed when choosing hydraulic hose are:

  1. Correct size — both ID and length
  2. Adequate rated working pressure
  3. Tube stock to accommodate the hydraulic fluid
  4. Cover stock to resist the environment
  5. Reinforcement to withstand crushing, pinching, extreme suction, and other forms of abuse
  6. End connections, recommended for the hose, that are compatible with the fluid and ambient environment
  7. Temperature of the material conveyed and cleaning temperature used on hose.

Select the right size

Most hydraulic hose is built to conform to Society of Automotive Engineers (SAE) requirements for size, tolerances, construction and minimum performance characteristics of each major hose type. SAE standard J517 provides general, dimensional and performance specifications for the 100R hose series, which are the most common hoses used in hydraulic systems, Table 1.

Some manufacturers have developed hose products that far exceed the performance and construction requirements of the SAE specifications. These include higher pressure and temperature capability, greater flexibility, and bend radii down to one-half that of SAE standards.

Table 1: Descriptions of SAE 100R series hose
SAE 100R1 series
Description
100R1
Steel wire reinforced, rubber covered hydraulic hose (one wire braid)
Type A - Thick cover (skive type)
Type AT - Thin cover (no-skive type)
100R2
High pressure, steel wire reinforced, rubber covered hydraulic hose (two wire braid)
Type A - Thick cover (skive type)
Type AT - Thin cover (no-skive type)
100R3
Double fiber braid (non-metallic), rubber covered hydraulic hose
100R4
Wire inserted hydraulic suction hose
100R5
Single wire braid, textile covered hydraulic hose
100R6
Single fiber braid (non-metallic), rubber covered hydraulic hose
100R7
Thermoplastic hydraulic hose
Black
Orange - non-conductive
100R8
High pressure thermoplastic hydraulic hose
Black
Orange - non-conductive
100R9
High pressure, four-spiral steel wire reinforced, rubber covered hydraulic hose
Type A - Thick cover (skive type)
Type AT - Thin cover (no-skive type)
100R10
Heavy duty, four-spiral steel wire reinforced, rubber covered hydraulic hose
Type A - Thick cover (skive type)
Type AT - Thin cover (no-skive type)
100R11
Heavy duty, Six-spiral steel wire reinforced, rubber covered hydraulic
100R12
Heavy duty, high impulse, four-spiral wire reinforced, rubber covered hydraulic hose
100R13
Heavy duty, high impulse, multiple-spiral wire reinforced, rubber covered hydraulic hose
100R14
Polytetrafluorethylene (PTFE)-lined hydraulic hose, single-stainless steel braid
Type A - Reinforced with a one braid of 303XX series stainless steel
Type B - Same as Type A; includes electrically conductive inner tube
100R15
Heavy duty, high impulse, multiple-spiral wire reinforced, rubber
100R16
Compact high pressure, one- and two-wire reinforced rubber covered hydraulic hosecovered hydraulic hose
100R17
Compact 21 MPa maximum operating pressure, one- and two-steel wire reinforced rubber covered hydraulic hose with smaller bend radius
100R19
Compact 27.5 MPa maximum operating pressure, one- and two-steel wire reinforced rubber covered hydraulic hose with smaller bend radius
1The number designation following the letter R does not identify the number of reinforcement layers, but rather the specific requirements of a type of hose.

When selecting a hose assembly, carefully measure the distance between the two ports of the components. Too long a hose can lead to it being severed or pinched by moving components of equipment. If the hose is too short, pressure contraction may cause it to stretch, leading to shorter service life. (Hose length can change +2%to -4% from fluid pressure cycles.) So allow for possible shortening of the hose during operation by making the hose lengths slightly longer than the actual distance between the two connections.

Hose OD is important when hose routing clamps are used, or when hoses are routed through bulkheads. Check individual hose specification tables for outer diameters in suppliers' catalogs.

Pressure capabilities

Most important in the hose selection process is knowing system pressure, including pressure spikes. Hose working pressure must always be considered greater than or equal to the maximum system pressure because pressure spikes that exceed the published working pressure will shorten hose life. When equipment has been modified to perform special operations, it is not uncommon for unanticipated spikes in hydraulic pressure to occur. As a general rule, apply a generous margin of safety when choosing hose to transmit pressurized hydraulic fluid. Typically, for dynamic hydraulic applications, the minimum burst pressure rating is four times that of the maximum working pressure rating.

It also is important to account for pressure drop that occurs between the inlet of a hydraulic hose and the outlet. The following conditions can affect the amount of pressure drop:

Friction — Fluid rubbing against the inner surface of the hose assembly creates friction. Higher friction increases pressure drop through the hose, as does higher fluid velocity.

Viscosity — If a fluid's viscosity is not correctly matched to the operating temperature range of the hydraulic system, maximum performance and component life will not be achieved.

Fluid temperature — Higher temperatures tend to reduce viscosity of hydraulic fluid. This lower pressure drop through the hose, but can degrade the lubricity of the fluid.

Couplings and adapters — Any change in bore or change in direction (such as with 45° or 90° elbows) can increase the amount of pressure drop.

Hose ID — For a given flow rate, the smaller the hose ID, the higher the fluid velocity. Likewise, for a given hose ID, a higher flow rate increases fluid velocity. As noted above, higher velocities result in greater pressure drop. Therefore, you can minimize pressure drop by specifying a hose with the largest ID that is practical.

Managing pressure drop is important when designing a hydraulic hose assembly that requires a specific output pressure to run equipment efficiently. This means the input pressure to the hose assembly must be equal to the output, plus the amount of pressure drop. For example, if a system requires 4000 psi, and you calculate pressure drop through a hose assembly to be 150 psi, fluid pressure entering the assembly would have to be 4150 psi.

Help in determining pressure drop is available from representatives of hose and coupling manufacturers. Be prepared to describe the type of application, fluid type and viscosity, fluid and ambient temperature, fluid flow rate, hose size and length, routing requirements, government and industry standards being met, and the number and type of fittings.