Hydraulic Hoses 101

With hydraulic hoses just a few years shy of being a century old, here is a Hydraulic Hoses 101 lesson exploring what they are made of, their types, and a memorable method for how to select the right hose for your needs.

Playing anything but a minor role in the design of hydraulic systems, a hydraulic hose is an essential part of your hydraulic system. It is responsible for transporting the fluid that transforms and creates mechanical energy. You could say it is the vein that transports the lifeblood through your machine.

Everything from choosing the right hydraulic hose type and the perfect fit for your machine, then, is incredibly important. In fact, a hose that is sized too small or too large can lead to damage, clogs, hose failure, and a delayed hydraulic system.

If you are in the market for a new hydraulic hose, here is a quick rundown of what you need to know that will help you make the best choice.

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Parts of a Hydraulic Hose

The job of a hydraulic hose sounds easy enough but, in reality, it has to bear enormous pressure, as well as high temperatures. For this reason, the hose is made of an inner tube, a reinforcement layer, and a protective outer layer.

The inner tube is what actually carries the hydraulic fluid. It is usually made of one of the following compounds: synthetic rubber, thermoplastics, and PTFE (or Teflon). It needs to be somewhat flexible as hoses have to be compatible with the hydraulic fluid they are carrying, and because the hoses are usually positioned in tight spaces and woven throughout a hydraulic power system.

The reinforcement layer of the hose does exactly what its name describes: It is the strength that handles and absorbs any movement caused by the hydraulic fluid through the inner tube. It is made from either single or multiple braided wire, yarn, or spiral-wound wire.

The protective outer layer of the hose acts as a cover and is often made of a variety of synthetic rubber materials. The type of outer layer you choose should be based on the environment the hydraulic hose will be in. Neoprene is one popular synthetic cover material that remains flexible across a wide range of temperatures (from –40°C to 100°C).

Types of Hydraulic Hoses

Hydraulic hoses are varied and many! Generally speaking, there are several categories based on their uses:

• Reinforced hoses – materials include wire helix, textile braid, and wire braid, among others
• Coiled hoses – a great choice if you need elastic and flexible qualities
• Convoluted / corrugated hoses – the flexibility afforded by the spiral convolutions in these hoses allows for both compression and elongation

Another hydraulic hose worth knowing about is the SAE hose (which stands for Society of Automotive Engineers), the most popular and a standard in the hydraulics industry. There are 16 SAE hose styles that exist within the 100R series.

How to Choose Your Hydraulic Hose

While the inside diameter and working pressure ratings are the typical go-to considerations for choosing a new hydraulic hose, the outer diameter and hose weight – among others we will discuss – are critical, too, especially depending on the machine the hose will be used in.

The industry standard followed by professionals when choosing a hydraulic hose is to use the S.T.A.M.P.E.D method, an acronym for considering size, temperature, application, media, pressure, ends, and delivery.

Size

The size of your hydraulic hose is based on its inside diameter, also known as the Dash Size, which measures from the two furthest points on the inner surface of the tube. Most North American hoses are measured in inches of I.D., and Dash Size is simply the I.D. divided into 1/16” increments (with the exception of SAE 100R5, 100R14, and a few other hoses).

Temperature

When it comes to temperatures that will affect the hose, keep in-mind ambient and media temperatures. The primary differences are that the ambient temperature is any environmental factor affecting the outside of the hose (usually ranging from a maximum of 200° to 400°F), while the media temperature is the internal temperature or, specifically, the temperature of what is flowing through the hose.

Application

Simply put, application represents how your hydraulic hose system will be used. With all of the measurements and ratings, it is equally important to think about the hose in-context for your machine and industry.

Media

As previously mentioned in regards to media temperature, the media is the type of hydraulic fluid that will be flowing through the hose. You can reference a chemical compatibility chart to determine which hose materials are best for transporting which media.

Pressure

The working pressure (WP) rating is also a factor that is related to both the size and the materials of a hydraulic hose, along with burst pressure. Essentially, you should size your hose according to both the minimum and maximum pressures the hose can safely withstand; the burst pressure rating of a hydraulic hose is typically four times the working pressure rating, or greater.

Ends

When you think of ends, think of fittings or couplings; each hydraulic hose has a connector type, which have specific characteristics (sizes, materials, and applications) along with limitations. These must be compatible with the hose you select. Generally, these fall into two categories: permanent and field-attachable.

Delivery

From a logistics standpoint, what good does the perfect hydraulic hose do if it is not delivered on-time? Is it unique, and is it available? Make sure you select the right manufacturer when you order your hose!

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