A lay line on a hydraulic hose, much like the sidewall of your car tires, contains a lot of important information. Here’s what you can typically find on a hydraulic hose lay line:

• The manufacturer of the hose, in this case, the manufacture is Aeroquip by Danfoss
• The part number is specific to the hose; in the above example, the part number is GH781
• The hose size will always be known as the dash (-) size. (dash)-6 is the size of the hose. It is important to note that all hose sizes are in sixteenth; for example, the -6 is 6/16 or 3/8; -10 is 10/16 or 5/8. Also, all dash sizes represent the inside diameter (ID). The next reading on the layline is a continuation of the size listed in millimeters (mm), then in American standard units of measurement, and then in Nominal Diameter represented as DN. Nominal denotes non-specificity. It is neither equal to the ID nor the OD.
• The type of hose is listed next. In this case, the manufactured hose, GH781, is a dura-tuff type.
• Certification is the next section of the hose. Certifications on a hydraulic hose layline indicate the standards and specifications the hose meets, including its performance characteristics and compliance with industry regulations.
• Working pressure in BAR and PSI. BAR is the metric unit for measuring pressure; it is precisely 100,000 Pasqual units. to convert BAR to PSI, multiply by 14.50377
• Temperature ratings are next on the layline.

The lay line runs the length of the hose and is used by mechanics and maintenance managers to verify that the right hose is used for their application2. It’s also used as a visual index when routing and tightening the assembly to ensure the hose is not twisted or kinked2.

If you see “No-Skive” printed on some of your hoses, it means the hose and fittings are designed to work without removing (or shaving) part of the hose cover and/or inner tube prior to attaching hose ends2. This speeds up the assembly time of a hose assembly, and there is no additional equipment or clean up needed2.

For more detailed information, you might find these videos helpful: "What’s a Layline? Reading your hydraulic hose"1, "Hydraulic Hose - How To Make an Assembly"4, and "What is a Leyline? How to Read your Hydraulic hose."5.