A constant cost of operating any type of hydraulic equipment is the purchase of replacement fluid. And this cost can really add up over time. Although the integrity of hydraulic seals can sometimes be to blame for leakage, the reliability of any hydraulic system is due to more than one factor.
The Downtime Downside
A lot of leaky hydraulic equipment goes unrepaired because of the large amount of downtime that’s usually required for fixing. As a result, oftentimes leakage is allowed to continue until the cost of replacement oil becomes enough of a cost to justify the cost of repair and downtime. However, there are several ways to rid a system of leaks so that little to no downtime needs to occur.
Get Rid of Vibration
Vibration not only causes fatigue in a hydraulic system, but also affects connector torque and stresses conductors. Vibration that’s become so prevalent that it’s obvious requires immediate attention. Eliminating vibration may involve eliminating its ‘bridges’ via the installation of rubber mounting blocks or hoses. Vibration bridges can include the valves, hydraulic power unit and reservoir. Sufficient clamps should also be present and able to support conductors like tubes and pipes adequately.
Ensuring that reliable connectors are used is another way to eliminate leaks. When choosing connectors for high-pressure hydraulic systems, avoid those connectors that provide eventual leak paths such as BSPT and NPT connectors. These connectors, when tightened or loosened become deformed, and the more they tightened or loosened, the higher the potential for leaks becomes.
High seal reliability is available in several forms, including BSPP, SAE 4-bolt flanges, ORFS and UN O-rings. These all incorporate an elastomeric seal, and can be used to replace pipe-thread connectors.
A word on the JIC-37 flare: this relies on a seal that’s metal to metal, which will not always offer a permanent or leak-free seal. However, the installation of a conical washer between the flare and nose of the joint can eliminate leakage.
Keep Temperatures Low
Keeping the hydraulic system cool is critical where hydraulic connectors with elastomeric seals are being used. Temperatures below 85°C will extend the life of most seal compounds. Even a single event that surpasses temperature limits can be enough to damage all of the seals in a system and cause leaks, rendering the entire system unreliable.
Ensuring that reliable connectors are used is not enough; they must also be tightened correctly and to the correct tightness. Incorrect torque is responsible for a large number of leaks in compression-type tube fittings and 37 degree flare joints. In the latter, too little torque will cause seat contact to be inadequate. Too much torque will cause connector and tube damage. Inadequate or excessive crush on the ferrule is the result of incorrect torque on compression joints. Regardless of the type of connector, consulting the manufacturer’s recommendations for torque and then applying them is always recommended.
Change the Design
Although this may need to take place during the design stages of your hydraulic system, another way to prevent leaks would simply be to eliminate or significantly reduce the number of connectors. This can be done by using cartridge valves, manifolds and stack valves. These integrated hydraulic circuits can replace line-mounted valves and greatly simplify plumbing as well as reduce potential leakage points.
Although it can take time to find the offending leaky seal/s, identify the magnitude of the leak and then repair it, the end result will be far less costly than simply replacing the oil over time until this no longer suffices, as it will save your entire hydraulic system.