Tolerances in Length of Hydraulic Hose Assemblies
Unless specified by your customer, hydraulic hose assemblies are measured from end to end. The only exception being assemblies with O-ring face seal end connections, in which they are measure from seat to seat. Make sure when measuring these assemblies that you pull back the nut to reveal the seat to achieve a proper length. If the end on the assembly is a 90- or 45-degree fitting, make sure the measurement cuts through the center of the angle. When you’re screwing into a port using a 45- or 90-degree fitting, you can come up short or long if you don’t measure through the center line. Considering jump sizes, the nuts on your end connections can be larger or smaller, so you need to make sure you are consistent. Please see the image below for a visual reference.
Hydraulic Hose Length Tolerance
NAHAD lists the tolerance, determined by length, as shown below:
Tolerances for a hose up through 12 inches (304.8 mm) = 1/8″
A hose measuring 12 through 18 inces (304.8 through 457.2 mm) = 3/16″
A hose length of 18 through 36 inches (457.2 through 914.4 mm) = 1/4″
A hose assembly longer than 36 inches (914.4 mm) = 1% of the overall length
TCH Quick Tip
When building a hydraulic hose, it’s easy to cut the hose, insert the ends and measure to the length we’re looking for. For example, we cut and inserted ends to achieve a hose that was precisely twenty-six inches long, which grew nearly half an inch after crimping.
We measured a hose end-to-end at precisely 26 inches, using Danfoss’ H43020-100, 1-1/4-inch hose, along with their 4S-style 1-1/4-inch male JIC and male NPT end connections. After crimping, the hose assembly measured at just under 26.5 inches, nearly one-half of an inch in length.
When you crimp the ends on, the hose is going to grow, and this is something you need to keep in mind with assemblies, especially when the OAL is critical.
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