How to Replace Hydraulic Fittings & Hoses
There are two primary styles of hydraulic fittings: field attachable and crimped. Crimped fittings are sealed with a crimping machine, making them permanent and secure in the hose assembly. Most permanent hose assemblies are performed in the shop with large crimping machines or purchased pre-assembled. Though these assemblies can be performed in the field with portable hydraulic crimpers when installing or repairing a hydraulic hose line, the process can be time-consuming and requires special tools. On the other hand, a two-part reusable field attached field comprised of a socket and nipple can be installed with basic tools.
How to Replace a Hydraulic Fitting in the Field
It is often necessary to replace damaged hydraulic fittings or repair hose in existing assemblies. Utilising reusable hydraulic hose fittings in the field reduces system downtime by avoiding the process of creating a new assembly in the shop or using a portable crimping machine in the field. These field-installable fittings attach to compatible hoses using a wrench, grips or even by hand. Reusable hose fittings are not permanently attached to the hydraulic hose, so they can be disassembled and reassembled if necessary.
Field-attachable, reusable hydraulic fittings are relatively easy to assemble and do not require crimping to the hose. The fitting comprises of two pieces; a collar which slides over the hose end and a stem that is threaded into the collar to create a leak-tight seal. The fitting can be installed by hand and crimped with a handheld crimper, just be sure not to over-crimp which can crack the fitting. As the name implies, these fittings can be reused if you need to replace the hose or move the assembly to another location, simply by unscrewing the collar from the stem and removing the fitting.
To install:
- Place hose end in a vise or rigid clamp
- Put some lubricant on the outside of the hose
- Slide the fitting on and use a wrench to turn it counterclockwise until the fitting bottoms out on the hose
- Slide the stem into the fitting, push down and use a wrench to screw it in clockwise (this inserts the stem into the hose underneath the fitting)
Best Practices for Replacing Hydraulic Fittings
If you suspect a leak because of a loss of pressure, but it is not clear where it’s leaking, take the following steps:
- First, shut off the power source to the hydraulic pump.
- Relieve the pressure once the hydraulic system is turned off.
- You can usually locate a leak by passing a piece of cardboard or micro over the suspected area. Regardless of how confident you are that the pressure has been turned off, never use your hand to identify a leak point. Any built-up pressure can burst through and cause hydraulic injection, which penetrates the skin leading to serious injury and will require immediate medical attention.
Once the system is shut off and relieved of pressure, you can begin the repair. Before repairing the assembly with a new fitting, first confirm the hose has not become brittle or worn. If it is, the hose or entire hose assembly must be replaced. When replacing hydraulic fittings in the field, you must ensure the fitting and hose are clean of dirt or debris that could enter the hydraulic system and cause damage. Then, when repairing and existing assembly, make sure the hose has enough play, or extra hose length to allow room for splicing the hose and installing the new fitting. Whether the section being repaired is from removal of a permanent fitting or spliced into a hose that may have sprung a leak, there must be enough hose to work with. However, if the original hose cut length is not enough to splice in for repair or to replace the permanent fitting, a new hose assembly will need to be installed. Once the repair or hose assembly replacement is complete, test the connection to ensure the seal is secure from any leaks.
When Having to Replace a Hydraulic Hose
Selecting the correct fittings and hoses is based on system requirements, not on hose construction. It's no longer as simple as choosing a four-spiral or two-wire braid hose. In many cases, equipment manufacturers have transitioned to constant pressure (isobaric) hose ratings and hose manufacturers have revolutionised hose construction that reduces weight and provides more flexibility in hoses. Instead of following the same old practices when selecting fittings and hoses, we need to adhere to system requirements for fluid compatibility, temperature and working pressure.
Following the recognised and reliable STAMPED method for selecting hose for specific applications is still the best technique.
Size: Identity what hose ID is required for proper flow. If the ID is too large, it will reduce system performance from pressure loss and excessive heat caused by extreme turbulence in the fluid. If the ID is too small, it can cause an excessive flow rate which will result in internal damage, fluid leaks and even hose burst.
Temperature: The hose must be compatible with the system's minimum and maximum internal fluid and outside ambient temperatures.
Application: The hose assembly must take into consideration where and how it will be used.
Material/Media: The hose tube material, outside cover and fittings must be compatible with the fluid and the ambient temperature and pressure. For instance, EPDM hoses provide excellent resistance to heat and maintain exceptional flexibility in wide temperature variants. It's also a good idea to use special sleeves or protective wrap to keep ice and snow off your hose and hydraulic components.
Pressure: Hose working pressure must be equal to or exceed rated system pressure and consider potential pressure spikes.
Ends: Determine the threads of the receiving fitting or port to establish the appropriate fittings and adapters.
Delivery: Select a hose size that will adequately deliver the requisite fluid volume, not lose pressure, or increase bulk or weight beyond specification. Also, as with all components, consider recording a chain of custody in the event anything needs to be tracked back to its source.
Finally, never use a fitting that appears close enough for the required repair or connection. Make sure the fitting meets specifications for material, the mating hose and system requirements. To ensure safe and leak-free repair, always refer to the equipment manufacturer's instructions for recommended fittings, hoses and installation.
You can purchase Brennan fittings from distributors such as FlowTech. With 40 years of experience, FlowTech is the largest fluid power distributor in the UK and Ireland. They supply fittings to businesses of all sizes and have a dedicated after-sales team to provide support.
A range of Brennan fittings are available on their website: flowtech.co.uk
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