Hydraulic Hose Fittings. How to Find The Right One

Hoses, as well as fittings, come in many different types and materials. Importantly, the material used for the hydraulic hose fitting defines its properties. Most common fittings are made of plastic, steel, stainless steel, or brass.

Plastic fittings generally are considered more resistant to the corrosion but are weaker and less durable. Therefore, they are the least popular choice when it comes to hydraulic applications despite their low price. Due to the high-pressure ratings, metal fittings are a better fit.

Steel fittings come as a mix of iron with some other metals to make them more durable and improve the resistance to the heat. For example, carbon steel fittings made of the mixture of iron and carbon can withstand the temperatures from -65°F to 500°F.

Stainless steel fittings are used when the temperature range required for the job is -425°F to 1200°F. They are an excellent choice for highly corrosive environments. Usually, they are rated up to 10,000 psi. Some of the stainless steel fittings with special designs can be rated up to 20,000 psi. However, the high price makes them less affordable, so other alternatives are usually considered.

Brass fittings are less strong and durable than stainless steel. They can provide a leak-free operation and meet SAE, ISO, DIN, DOT, and JIS standards. Brass fittings temperature range is -65°F to 400°F. They accommodate pressure up to 3000 psi, but lower pressure ranges are usually recommended.

Less commonly used hose end fitting materials

Aluminum fittings are significantly lighter than steel and are corrosion-resistant. Due to their low weight, they are commonly used in the automotive industry.

Types of Hydraulic Hose Fittings

The two main categories include:

• Permanent Crimp Fittings – the most common type of fittings. They require a presence of the crimping machine to attach a hose to a fitting.

• Field Attachable – They are an excellent choice if you do not have access to the crimper provided that your hose is ‘field attachable fitting’ compatible.

Depending on the shape of the hydraulic fitting, they classified into:

• Plugs

• Unions

• Elbows

• Crosses

Six Things to Consider When Picking the Hydraulic Fittings:

1. 1. The Security of the Connection Including Sealing Type

      Be careful if you use NPT (National Pipe Taper) pipe threads fittings. Even though it sounds easy to fix the leak with this type of fitting by tightening the connection, you increase the risk of getting a crack in the fitting. This is more likely to happen with repeated remakes (loosening and re-tightening the fitting).  Use O-rings with the elastomeric seals such as DIN 2353, SAE J1453 to prevent the risk of unexpected leaks and switch to an untapered JIC fitting. If you use elastomeric seals, keep your temperature conditions within the recommended range. Unfortunately, even a single over-temperature event can damage all the seals and cause multiple leaks.

   2. Pressure Rating

      With the modernization of your equipment usually comes higher operating pressure. To address high operating pressure, more and more of our customers prefer to use O-ring seals. They are more resistant to cracks. O-ring seals also prevent the risk of over-torqueing and leakage. In terms of material stainless steel hose fittings have the highest pressure rating.

   3. Vibration

      Vibration affects hydraulic plumbing and can shift the torque and cause fatigue. Remember to inspect areas with high vibration for leaks and damage.

   4. Temperature

      The temperature range for tube fittings is defined by three factors: material, plating, and seal if used. For leak-free operation use O-ring seals if the operating temperature allows you. Check the table below for the temperature range for the most common fitting and seal materials.There are special options available if you need hydraulic hoses and fittings to work under extreme temperature conditions. Contact us to learn more.

   5. Chemical Compatibility and Operating Fluid

      A rule of thumb says that hose inner tube, cover, fittings and O-rings should be chemically compatible with each other. Pay extra caution when selecting a hose for gaseous applications, especially if there is a chance of permeation in order to avoid explosions, fires, and exposition to the toxic fumes. Always check with the manufacturer if the components of your hydraulic system are chemically compatible. Additionally, pay close attention to your seal being compatible with the type of hydraulic fluid used in a system. The Guide for Chemical Resistance Information from Parker can be found here.

   6. Availability

      It all goes great until you need a replacement fitting and the lead time is a couple of weeks, and you need it now. Usually, most NPT and JIC fittings are widely available and have many configurations to choose from. Hence, choose the fittings that are easier to find or stock up if you use any specific fitting with longer lead times.