Are field-attachable fittings truly reusable?

Hydraulic hose fittings are essential components in countless stationary and mobile machines. The parts are critical links in fluid-power systems, designed to ensure safe and reliable operations and prevent equipment shutdowns, catastrophic failures and danger to nearby personnel.

And in the hydraulics world, there are generally two types of hose fittings — permanent and reusable or field-attachable. Permanent crimp fittings mechanically interlock to hose by means of a crimping or swaging machine and are designed to form a durable, leak-proof connection. A crimp fitting cannot be removed and reinstalled.

Reusable fittings, as the name implies, are designed to be used multiple times. These hydraulic fittings can be disassembled and reassembled so that modifications or repairs can be made to the hydraulic system without replacing the entire hose assembly.

Given that these fittings may be considered for reuse, they can make for an economical choice in applications where field repairs are necessary or frequent changes are anticipated. And the relatively simple design facilitates quick disassembly and reinstallation, saving both time and labor costs.

However, one major drawback is their general unsuitability for high-pressure applications. The absence of a mechanical lock typical in crimp fittings reduces their overall pressure tolerance. Reusable fittings tend to be limited to low-to-medium pressure applications up to around 3,000 psi.

Therefore, these fitting are generally preferred when adaptability and flexibility are more critical than high-pressure performance. These include prototyping hydraulic systems that are still being tested and require frequent modifications. In high-speed industrial production and assembly operations, downtime can be costly. Where pressure requirements are moderate field-attachable fittings offer the ability to make quick or emergency repairs right at a machine.

In less critical mobile systems like agricultural sprayers or other low-pressure hydraulic machinery, the fitting’s on-site repair ability is also an advantage, especially in remote or rural areas where new components or crimpers may not be readily available.

But are field-attachable fittings truly reusable?

Many experts agree that, in a perfect world, it’s always preferred to opt for new fittings when a user reassembles the connections. But, thanks to improvements over the years in terms of better materials, designs and manufacturing processes, hydraulic fittings that are in good working order can sometimes be reused.

According to John Joyce of Brennan Industries, several factors come into play when considering whether hydraulic fittings can be reused. The most crucial is the condition of the fitting. A fitting may appear in good condition, but it must be inspected before reuse.

Visually check for anything sketchy. Look for any signs of concern, such as:
• Wear or damage on the fitting, such as cracks or deformations.
• Nicks or scratches to any sealing surface.
• Corrosion, rust, or material deterioration that can weaken the metal and compromise the fitting’s integrity.
• Physical abuse such as dents or any distortion to the shape of the fitting.
• Fitting nose collapse.

If there are any signs of damage, the fitting should be replaced to ensure the safety and reliability of the hydraulic system. In addition, it’s best to replace O-rings or seals regardless of how they may look.

And many industry representatives do not recommend reassembling tapered thread pipe fittings and JIC 37° flare fittings. Pipe fitting connections rely on deformation of the sealing threads to obtain a seal, and they can wear out or deform with repeated assembly and disassembly.

JIC 37° flare fittings use a cone and flare connection to seal. The connection causes a slight deformation of the metal surfaces to obtain a seal. Excessive torque can permanently distort the interfaces and lead to an insufficient seal.

Again, best practice is always to replace a fitting with new parts. But if the fitting is found to be in good condition, and the user opts for reuse, here a few additional tips. First, plan to reassemble the assembly with new hose — not the existing worn or damaged hose. Confirm that the hose and fitting are compatible in terms of material, size, and pressure ratings.

Before reuse the fittings must be thoroughly cleaned, as any dirt or debris could potentially enter the hydraulic system and cause damage. Ensure you are following the proper procedures for reassembly. Never mix fittings from different manufacturers or use “similar looking” parts, and follow the guidelines provided by the equipment manufacturer.

After reassembly, look for any signs of improper installation, such as misalignment or visible gaps. And finally, test the new connection to ensure the seal is tight. If there are any leaks, replace the assembly immediately.

In the end, be critical and always err on the side of caution. If you have any doubts — if you question the viability of the fitting in any way — it is always best to replace the fitting to avoid potential risks.