When specifying hydraulic hose, you need to fully analyze the application first and foremost. The application determines how your hose assembly is going to be used, which has a direct impact on hose selection.
Every manufacturer offers hoses based on specific applications such as for suction and return, phosphate ester, low temperature, transportation, marine, refrigerant, and oil and gas. However, when it comes to hydraulic hose in general, certain aspects of a hose could be preferred due to the application requirements. Click here for hydraulic hose suggestions based on certain applications.
For instance, if you have a tight bend radius requirement for the application, you typically need a hose that has half the radius of bending or more. Hoses with a half bend radius not only allow you to fit a hose into a tighter space, but they have a high bend rate. Bend rate refers to the general flexibility and the fatigue, how many times the hose can bend through an arc without failing early. As you may know, with any kind of steel braided wire, even rubber, the more you flex it back and forth, the quicker it will fatigue. Parker’s Hose Products Division offers a full line of hydraulic hoses designed for one-half SAE bend radius such as the 787 and 797.
There are also external conditions you need to consider for the application. Is there risk of abrasion? Most hose has a neoprene outside, but if you have hoses that will inevitably rub against materials, against machinery, against the jib or boom, any application where it can rub back and forth, a high abrasion carcass is a good way to go. Hydraulic hoses tend to fail by rubbing on the outside until they wear through the outer wall into the braiding. Eventually, they wear enough that the hose can no longer contain pressure. This is when you get a hose burst. So, for applications where hoses will encounter rubbing or abrasive surfaces, consider choices that offer enhanced cover options such as Tough and Super Tough. Utilizing a Tough Cover or Super Tough Cover simplifies an assembly by eliminating the need for any additional protective sleeving.
Specific environment conditions such as ultraviolet rays, ozone, sea water, chemical agents and other aggressive elements can degenerate the hose prematurely. You need to determine if there is something caustic in the environment that can cause fluid to permeate through the outer carcass of the hose and perhaps rust, corrode or breakdown the layers of spiral or winding around the reinforcement. You may need a hose with synthetic material that will not rust and is non-reactive against the ambient conditions.
The temperature requirement for the application is another environmental factor to consider. Manufacturers design hoses for specific operating temperature ranges, and there are versions that operate at temperatures as low as -70°F and as high as +302°F. It is important to remember that some media can increase or decrease the effects of temperature on the hose and the maximum rated temperature of a hose is specific to the media.
When identifying all aspects of the application, you must consider the chemical compatibility requirements of the hose inner tube, cover, fittings and O-rings. For instance, you might have an unusual fluid that requires a specific rubber compound. Usually mineral-based hydraulic fluid is compatible with most types of hose. The majority of hydraulic hose has a nitrile interior with a neoprene outside, but it is important to consider the chemical compatibility requirements of the application when selecting a hose. Each manufacturer should have a document regarding chemical resistance for each of the hydraulic hose and fittings they manufacture. Click here to reference Parker's media guidelines in regards to chemical resistance.
Consider the surrounding environment of the application. The image at the top of this article displays an electrical boom truck. You can imagine that any opportunity to conduct electricity back through the machine or to an individual needs to be reduced for this type of application, and the hydraulic hose used should be constructed of a synthetic material that is non-conductive.
Finally, when selecting your hose, if your application requires all equipment to meet certain regulatory standards such as SAE, ISO, USCG, EN/DIN, ABS, MSHA, DNV, Lloyd’s Register, etc, then it is important that the hydraulic hose assemblies within the equipment also meet these standards.
Article contributed by Kyri McDonough, marketing services manager at Hose Products Division, Parker Hannifin.
Other related topics on hydraulic hose, hose application, and selection criteria:
The Love-Hate Relationship Between Hydraulic Hose and Chemical Compatibility
Decoding a Hydraulic Hose Layline
Five Most Important Factors You Need to Consider for Hydraulic Fittings
Hydraulic Hose 101: Fast Facts
Successful Hydraulic Hose Assembly Starts Here
Going to Extremes: A Closer Look at Hydraulic Hoses