The definition of a hydraulic hose is that it handles liquid pressure or flow between components. Components include valves, tools and actuators. Hydraulic hoses are not minor parts, you need to select the correct type and grade of hose for its intended use and it must be correctly installed.

The Anatomy of a Hose:

Parts

A hydraulic hose consists of at least three parts, and inner tube that carries the fluid, a reinforcement layer and a protective outer layer.

  • The inner tube needs to be compatible with the fluid it is carrying and requires some flexibility.
  • The reinforcement layer consists of one or more sheaths of fabric, braided wire or spiral-wound wire. A wire braided hose is comprised of crossing and woven high tensile steel wires overlapping one another to reinforce the tube underneath, these are a one or two fabric braid. A spiral wound hose is made of a one or two wire or sometimes even a four or six wire braid of helically wrapped high-tensile wire that exhibits exemplary strength, making the hose strong but also rigid. A spiral hose is usually much stronger and can withstand higher pressures.
  • The outer layer is often resistant to weather and oil, and abrasion-resistant, depending upon the type of use the hose is designed for.

Construction

These hoses are often constructed of multiple materials. The most common materials are fluoropolymers and silicone, elastomers, metal, and thermoplastics. Composite or laminated materials are also common.

  • Rubber and elastomeric hydraulic hose is a strong choice when you need flexibility.
  • Fluoropolymer hose has a durable flex life and has excellent corrosion and chemical resistance, and it can handle high temperatures.
  • Thermoplastic hydraulic hose has a tight bend radius and has superior resistance to kinks.
  • Metal hoses handle high temperatures and high flow materials well. They can also handle high pressures. Metal hoses can be flexible or stiff.

* Note that flexible hoses are easier to install, and route compared to rigid tubing. The flexibility reduces noise and vibrations and reduces pressure surges while allowing for movement between the parts.

Bend Radius

The bend radius is how much you can bend a hose without damaging the inner tube. This is important when choosing a hose and determining its layout. Subjecting a hose to a bend radius smaller than is recommended places excessive stress on it and severely reduces the ability of the hose to withstand pressure, thereby reducing the hose life. Hoses are designed to bend. All bending affects hose life to some degree.

Working Pressure

When selecting the right hose for your application, you must stick to the working pressure ratings, this is the maximum pressure a hose will support safely. Smaller diameter hoses usually have a higher working pressure rating. While paying attention to the working pressure be sure to also adhere to the burst pressure, which is the minimum amount of pressure that will burst the hose.

Layline

The layline (or writing along the hose) runs the length of the hose with information to assist in the re-ordering of an existing hose. The writing identifies the manufacturer, part number, hose I.D, industry standards, approvals, fitting icon, cover type, bend radius, pressure, temperature and where it was made. Hoses marked with No-Skive means the hose and fittings are designed to work without removing or shaving the hose cover prior to attaching hose ends.

Choosing Your Hose

To help with choosing the proper hose use the acronym STAMPED. This will help reduce the chance of a failure, damage or injury that may occur if a hose or fitting is used improperly. These simple questions can greatly reduce the chance of a problem and help increase the useful life.

To get the most life out of a hydraulic hose choose the correct size and type to extend its working life. It is recommended not to mix hose manufactures and fitting manufacturers when building a hose assemble. Remember, even the most durable hydraulic hoses have a life span.

SIZE:

  • What is the inside diameter (I.D.) of the hose required?
  • Is the outside diameter (O.D.) critical?
  • How long of a length is required?
  • Is the exact overall length including fittings critical?

TEMPERATURE:

  • What is the temperature of the product being conveyed?
  • What temperatures will the outside cover be subject to?

* Temperatures have a considerable impact on the working pressure of a hose. As the temperature goes up the working pressure goes down. Never operate a hose to it’s highest recommended working pressure while is at or near its maximum temperature range.

APPLICATION:

  • Where will the hose be used and installed?
  • Will the hose be subject to flexing, dragging or chemicals and oils?
  • If the hose is replacing an old hose, what is the reason for replacement?
  • Does the hose have to be statically conductive or meet FDA, ULC, CGA, US, Coast Guard, or other regulations?

MATERIAL:

  • What is the substance or material being conveyed through the hose?
  • If it is a chemical, what is the concentration?
  • If it is material is wet or dry?
  • Are they sharp or abrasive?

PRESSURE:

  • Is it a pressure or vacuum application?
  • What is the maximum working pressure?
  • Are there any pressure surges?

ENDS:

  • What type of end is required to connect the hose to the system?
  • What type of fitting and clamping system is required?

* The type of fittings and clamps must take into consideration the size, application, and pressure of the material being conveyed. The greatest cause of hose failure is typically the hose and fitting connection.

DELIVERY:

  • When is the hose required by?
  • How much time is required to properly install the system?
  • Does it need to be tested and certified before use?

* Once a hose assembly has been put into service, it is recommended that a full inspection and testing be done on a regular basis. All hose assemblies should be treated as potential hazards and any worn-out or missing parts should be replaced immediately.