How to properly install hydraulic hose fittings: step-by-step crimping guide?

A proper fitting for hydraulic hoses involves selecting the right fitting and hose and preparing the hose's end with care, inserting the hose in the proper depth, and then crimping to the manufacturer's recommended diameter by using a crimping machine that is calibrated. If you skip any step, you risk blowoffs, leaks, or even hose rupture under pressure.

Hydraulic hose assemblies are the main arteries of any power fluid system. A crimped fitting that isn't properly crimped won't only leak; it could blow away completely under pressure, resulting in the possibility of causing serious injuries or even fire. Crimping is typically viewed as a standard shop job instead of a precise process.

This guide covers every phase of hydraulic fitting installation, starting with hose selection and measurement through final inspection with the care that high-pressure systems need.

The importance of the method used to crimp?

Hydraulic hose fittings are connected to hoses using two main methods: reusable fittings (screwed or pulled onto the hose by hand) or fittings that are crimped (permanently attached to the hose with a crimping device). Crimped assemblies are the most popular in hydraulics for mobile and industrial applications due to their highest resistance to pull-off and leak integrity, as well as pressure rating stability.

The crimp process operates by deforming the plastic ferrule (sleeve) of the fitting that is placed around the outer wire braid or spiral, and securing the pipe between the ferrule and the stem of the fitting. If done correctly, the hose will be more durable than the hose. Incorrectly done -- over-crimped, under-crimped or using the wrong die the hose assembly will be an unplanned failure.

Materials and tools you'll require

Before beginning, collect the following information:

• Hydraulic crimping machines (bench and portable) using the right die set
• Manufacturer's chart of crimp specifications (or digital crimping application)
• Vernier caliper or digital gauge
• A cutting device for hoses or a sharp rotating blade (not hacksaw)
• Skiving tool (if required by the hose type)
• Ruler or depth gauge
• Plugs and end caps for the hose
• Safety gloves and glasses
• Pens, paint or markers that are permanent

Step 1: Choose the correct fitting and hose combination.

Hydraulic fittings and hoses cannot be interchangeable between different manufacturers without confirmation. Each hose comes with a distinct fitting model that is designed to meet its wall construction, and tolerances for diameter.

Important parameters to confirm:

• Pressure rating and hose ID must be in line with or exceed the system's working pressure
• Hose series (e.g., SAE 100R1, 100R2, 100R15, EN 853, EN 856)—determines fitting compatibility
• The fitting series must match the hose's diameter range as specified in the Crimp chart
• End connection type: JIC, BSP, NPT, ORFS, SAE straight thread or the metric

The use of the Parker fitting on the Gates hose, as an example, could be a possibility; however, only in the event that the crimp specifications specifically cover the combination. Don't assume that a brand is compatible without verifying the crimp specifications.

Step 2. Cut the hose in squares

A square, clean cut in the hose is vital to making sure that the hose is properly fitted with the correct in the insertion and for ensuring an airtight seal.

Utilize an cut-off hose machine equipped with an abrasive wheel sharp enough or cold-cut blade. If you are cutting by hand employ a sharp rotary cutting tool as well as a mitre block to keep an angle of 90 degrees. Avoid hacksaws as they cut wire braid leaving metal particles inside the hose, and seldom result in a squared end.

After cutting:

• Examine the cut for frayed wires, pinched tubes within the inner tube.
• Blower out any debris using dry, clean compressed air.
• Stop the end of the pipe immediately to stop contamination

Step 3: Skim the hose (if necessary)

Skiving refers to the process of removing the rubber cover off the hose's end generally 25-40 millimeters dependent on the design of the fitting. Certain fittings have it while other don't.

Fittings that are non-skive (also known as"no-skive" or "push-type) are made to cut into the cover's outer layer during assembly making the process easier and reducing the possibility of a mis-skiving.

Fittings that require skives include a ferrule that rests directly on wire braid. By leaving the cover in place can cause an under-crimp situation even if the machine has been properly set, as the cover can add an unexpected amount of thickness to the ferrule.

Make sure you read the assembly instructions in detail. If you require skiving you should use a skiving tool or a bench-mounted skiver, not cutting. Inconsistent hand-skiving is a frequent cause of problems with assembly.

Step 4: Make a mark and determine the depth of the insertion

Before putting the fitting in, find the minimum depth of insertion - the length of the hose that has to be within the ferrule for fitting to be a valid fitting. The details are in the fit data sheets.

Note this depth onto the hose OD with a paint pen or a permanent marker. The mark must be placed in a precise distance from the cutting end that is equal to the depth of insertion. The mark serves as a verification line after assembly: it should appear from the ferrule's mouth (or close to it, within the tolerance). When the marking disappears completely within the ferrule, it means the hose wasn't inserted sufficiently far. If it's not the ferrule, it wasn't placed enough.

Step 5. Lubricate and then insert the fitting.

Apply a thin layer made of fluid from hydraulics or hose manufacturer's recommended lubricant for the stem of the fitting. This helps reduce the resistance to insertion and helps protect the tube from folding back in the course of the assembly.

Place the fitting stem in the hose's end using an firmly, rotative motion. Press until the hose sits completely against the shoulder of the fitting, and you will notice a distinct resistance once it reaches its bottom. Verify using your depth mark.

For larger sizes of hose (1" ID or more) make use of the bench vise as well as a fitting tool for insertion. Making an attempt to push a large-bore hose into the fitting by hand could result in an insufficient insertion and a torn inner tube.

Step 6: Choose the appropriate die and determine the crimp diameter.

It is the single most important procedure. The Crimp diameter (also known as the target OD or the finished crimp diameter) is the diameter outside of the ferrule following crimping. It is set by the fitting and hose manufacturer within +-0.1 millimeters in the majority of instances.

Find the specification for crimp using the manufacturer's chart, indexed by:

• Hose series and sizes (e.g. 100R2AT or 1/2" ID)
• Series of Fitting
• Material for Ferrule (steel or stainless)

Choose which die that best matches the ferrule's OD of the fitting ferrule. The machine stop is set to reach the desired crimp diameter. If your machine has micrometer adjustments, perform an experiment crimping on a scrap piece of assembly and then measure the result prior to making production assemblies.

Common die-selection errors:

• Making use of the previous job's die without confirming
• The term "nominal hose size" is often confused with die size
• Utilizing dies that are worn beyond the manufacturer's tolerance (check using an gauge ring)

Step 7. Crimp the assembly

Insert the hose inside the crimper, ensuring that it has the ferrule in the die. In the majority of bench crimpers, the hose must be parallel to the die's axis to prevent the off-axis load that causes the appearance of an oval-shaped crimp.

Make sure to activate the machine. The dies must close completely and easily. If the machine fails to close after full closing it could be because the die is incorrect or the machine might require hydraulic pressure adjustmentdon't press it.

After the cycle has finished Remove the assembly with care. Do not turn the assembly while the crimping process as this could cause corrosion to the ferrule's surface and cause an inconsistent OD.

Step 8. Measure the measurement and examine the crimp.

After crimping, take a measurement of the ferrule's diameter using the vernier caliper in three locations around the circumference - sides, top as well as 45°. All measurements must be within the tolerance for crimp diameter.

Checklist for visual inspection:

• No splits or cracks in the ferrule
• A mark indicating the depth of the hose appears at or within tolerances at the ferrule's mouth
• There is no visible inner tube extrusion at the stem at the stem's end
• Ferrule surface that is free of deep gouges and die marks that indicate a wrong die dimension
• Body is in good condition and threads in good condition.

When any measurements are outside within tolerances, then the entire assembly should be re-cut and rebuilt. It is not being re-crimped. Re-crimping an assembly that is not in compliance with the specifications can produce unpredictability and is not an accepted repair procedure.

Step 9: Test the pressure prior to use

A complete hose assembly must be tested for pressure prior to installation in use, preferably for safety-critical circuits or high-pressure systems.

The standard practice is testing the pressure at 1.5x the working pressure with a minimum hold duration of 30-60 seconds, observing to check for leaking, fitting movement and hose bulge. Utilize a test bench for hydraulics using a gauge that is calibrateddo not make use of compressed air when test of hydraulic components.

Cap and label the tested assembly with the hose ID and fitting type, as well as the working pressure and the date of assembly.

Crimping mistakes that are common to avoid

How can I make crimps on hydraulic fittings on my own without having a machine?

No. Bench vises and hand tools are not able to produce consistent measured crimp diameters or crimp sizes and are not appropriate to be used in any applications. A crimping machine calibrated to the specifications is required.

What can I tell whether a fitting is not properly crimped?

Take a measurement of the ferrule's OD using the help of a caliper. If it's higher than the maximum diameter of crimp specified in the crimp diagram, the assembly is over-crimped and should be cut off and rebuilt.

Are different brand names of hoses and fittings mix?

Only if the crimp specification specifically covers the cross-brand combo. If you are unsure, use the same fittings and hoses from the same manufacturer.

When should dies used for crimping be examined?

Check the surface of the die for pitting, wear, and dimensional precision at each maintenance interval for the machine - usually every 500-1,000 cycles, or as per the manufacturer's recommendations. Replace worn dies immediately.

What's the shelf time for an hose that has been crimped?

Most manufacturers stipulate a maximum shelf life of 2 years for unused but assembled the hoses that are stored in dry, clean and UV-protected environments. Review the storage guidelines specific to the compound.