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Hydraulic Hoses: Buying the Right Size Hose

Hydraulic hoses are some essential parts of many hydraulic systems. When replacing hoses and hydraulic assemblies, you should consider several things, and the most critical part of hose selection is getting the correct size. If it is a little too small, pressure may compromise the structure and integrity of the hose. If you buy a hose too large, it may not fit hydraulic hose couplings, and it has a good chance of leaking and not delivering the correct pressure to hydraulic components. Here are some useful tips to help you achieve the correct size of hoses.

Finding the Inside Diameter

The most important thing to remember when sizing hoses is the inside diameter or the I.D. You can’t tell the I.D. by just looking at the hose’s outside diameter. Some hoses are thicker and have more layers than others, and sizing must be exact.

The most important thing to remember when sizing hoses is the inside diameter.

The Importance of Laylines

The best way to determine the inside diameter is to check the hydraulic hose layline. The layline is the line across the middle of the hose with all those numbers, letters, and other information. It runs the entire hose length and repeats itself. Every character on the line gives you information about the hose. Typical information includes the manufacturer, part number, size, pressure ratings, industry-standard rating, and a date code that tells you when the hose was manufactured.

What Do Dashes Mean on the Layline?

You may see a number like “-5”. The dash denotes one-sixteenth of an inch, so -5 is a 5/16 inch hose, and “-8” is one-half inch I.D. Some hoses may have sizes like “5/8” or “1/2” printed, but the industry standard uses dashes. Yet, some manufacturers may have their own codes, so take your own measurements if you are unsure.

What if You Can’t Read the Layline?

If the hose is old, its layline could be worn, and you cannot read the information. If this is the case, remove the hose and cut it. Measure the inside diameter. Do not guess because you need an exact fit for hydraulic hose fittings and hydraulic hose couplings.

Hydraulic Assembly Length

It is usually better to have hydraulic hoses a little bit too long than too short. However, too long of a hose can get in the way with equipment, potentially causing a space problem. Measuring the length of a hose includes hydraulic hose fittings. For example:

  • Male threads – measure from the thread ends.
  • Angled fittings – measure from the center of sealing surfaces.
  • Flanged and female threads – take measurements starting at the sealing surface of the fittings.

Cut Length and Cut-off Length

Cut length and overall length are not the same. Overall length (OAL) is the actual length of the assembly from end to end. If the hose has an angled hydraulic hose fitting, measure from the center of its sealing surfaces for OAL. To find the cut length, you can figure out the cut-off lengths and subtract them from the OAL. To determine the cut-off length, measure from the end of the fitting to the end of the fitting collar. Subtract these two measurements from the OAL. You can also measure from fitting collar end to fitting collar end to get the cut-off length.

Things to Remember

Hose size is determined by inside diameter. You can find this number on the layline or cut the hose and measure the I.D. Overall, hose length is the distance from fitting end to fitting end. Cut length is from the fitting collar end to fitting collar end. When you need assistance, contact your hydraulic hose supplier. They can help you with hoses, couplings, hydraulic assemblies, and hydraulic hose accessories. 

If your hoses need replacing, a member of our team would be more than happy to assist at a time and place that suits you. You can contact us here, or alternatively connect with us on social media.

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