There’s more to installing a hydraulic hose than tightening metal connections. To maximize the life of the hose and its fittings, you’ll need to take into consideration a variety of factors about the specific application. Broadly, these boil down to:
Routing and clamping
As described in the ParkerStore Hose Installation & Routing Rules video, these considerations can be logically turned into rules to follow for best results.
When hydraulic hose is pressurized, its diameter increases to contain the force of the fluid being transported. Its length therefore decreases—by as much as 4%. That means, for example, that a 3-foot assembly could shorten by as much as two inches! If there isn’t adequate length for slack, fittings will become stressed and cause a leak. Or, worse, the hose could come completely loose. (Note that too much slack can result in hose abrasion, or snagging on nearby components. For help determining how much slack to include, check with your local ParkerStore professional.)
The wire reinforcement built into a hydraulic hose limits its flexibility. How much can you bend a hose before its wire reinforcement begins to kink, going from a smooth arc to a sharp corner? That’s the bend radius you do not want to exceed when installing hose. The Parker hose catalog 4400 contains information to help you determine bend radius. Or, ask your local ParkerStore professional.
A general rule of thumb for hose installation is if the hose needs to bend immediately before the metal fitting, you should keep it straight for at least twice the outside diameter (O.D.). If that’s not possible, use a 90 or 45 degree elbow fitting. This prevents fluid under pressure, traveling at high speeds, from directly impacting the core tube, which can deteriorates the hose and cause premature failure.
Hydraulic hose will naturally experience some movement in use; the ability to do so is what makes flexible hose well-suited for transporting pressurized fluid in dynamic applications. But, this movement should be limited to a single dimensional plane: left to right, or up and down, or forward and back. Any combination of those, resulting in two planes of motion, is called a compound bend. Because the hose ends are fixed and held tight, more than one plane of motion can cause the hose to twist, leading to premature failure. (Note that some applications do require multiple planes of motion; if that’s the case for your application, ask a ParkerStore professional for recommendations on type of hose to use and how to install it properly.)
On the outside surface of hydraulic hose is printed a continuous line of information, called the lay line. If, after installing the hose, the lay line spirals around like the stripe on a candy cane, it means the hose was twisted during installation. That’s not good; the hose is being stressed and can fail prematurely. Loosen the fittings to straighten the hose, and then re-tighten using double wrenching—one wrench to hold and another to tighten.
Abrasion is a primary cause of premature hose failure. When the outside cover of hosing gets worn, it exposes the wire reinforcement, causing that wire to rust when exposed to moisture. To avoid this, clamp each hose individually so it’s held in place (allow for some motion, of course) and can’t rub against another nearby hose or other object. If clamping isn’t an option, ask your local ParkerStore professional for guidance.
Few things are more aggravating than having to take apart adjoining assemblies to access a specific hose that needs maintenance. Avoid this scenario by using different combinations of hose ends and tube fittings, such as short and long straights, or short and long elbows. Taking this step when installing a hose reduces maintenance effort and downtime.
Posted contributed by:
Suzanne Favri, Digital Marketing Specialist
Global Distribution & Sales Services, Parker Hannifin
Related, helpful content for you:
Decoding a Hydraulic Hose Layline
How to Ensure Proper Hose Measurement and Assembly Length Every Time
Working Together: Safety and Maintenance Tips to Ensure Hydraulic Hose Success