Why are there different hydraulic hose standards and what do they mean for you and your application? For decades, SAE J517 has published guidelines for 100R1 through 100R12 series hydraulic hoses. These manufacturer-driven SAE standards have been based on design, construction, and pressure ratings to ensure that hydraulic hoses meet minimum construction requirements. SAE established minimum pressure ratings for various hose IDs (inside diameters) and were later revised to also include constant-pressure hoses, such as R13, R15, R17 and R19, which are hoses that maintain pressure ratings within a group regardless of size.
More recently, however, hydraulic system designers began adopting ISO specifications. Many large OEMs switched to ISO standards in their design and manufacturing process to ensure the sale and service of their equipment globally.
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ISO Standard 18752, released in 2006, takes a different approach centered around the design practices of users who typically design hydraulic systems based on performance and pressure requirements. The ISO 18752 Standard has nine pressure classes for maximum working pressure, ranging from 500 to 8,000 psi. Hydraulic hoses meeting ISO 18752 specifications are classified according to their resistance to impulse pressure in four grades: A, B, C, and D. Each grade requires a specific number of impulse cycles at a certain temperature and impulse pressure in order to meet the standard. Additionally, the grade is then classified by the outside diameter (O.D.) of the hose into standard types (AS, BS, CS) or compact types (AC, BC, CC, DC). Compact types have a smaller O.D. and bend radius than the standard types.
Each grade level requires a specific number of impulse cycles the hose must meet at a specified temperature and impulse pressure. The chart below explains, in detail, the ISO 18752 performance specifications.
It is important to note that ISO 18752:2014 does not include requirements for the connection ends. It is limited to the performance of hoses and hose assemblies. The hose assembly maximum working pressure is governed by the lowest maximum working pressure of the components.
Testing for Toughness
The primary concept behind ISO Standard 18752 requires constant pressure performance ratings in each class for different hose sizes. This specification also requires spiral hose to exceed one million pressure impulse cycles according to ISO 18752 hose grade D, type DC. This requirement is the toughest of all grades and classes to achieve, and specifies meeting 248°F temperature and an impulse pressure of 133% of maximum working pressure for at least one million impulse cycles. In this accelerated test, the hose is positioned into a U shape on a test stand, and the fluid is raised to the specified working pressure. Pressure pulses are also applied at an elevated value to stress the spiral wires and end fittings for a minimum number of required cycles.
ISO Benefits to End Customers and Engineers
The ISO 18752 standard makes it easy for end users and engineers to identify what hose should be used on a certain piece of equipment or machinery. Strict testing requirements allow users to know exactly what the hose is rated for and how it should perform while on hydraulic equipment. Hoses tested to higher impulse standards are likely to have a longer hose life, which is why many users are switching to ISO standards. For instance, if you need a hydraulic hose for a severe application presenting many repeated pressure cycles in short time and long continuous service, you would select either the grade C or D hose assemblies. However, this assumption is based on the hose being correctly installed and protected from harsh environments.
An important aspect of ISO standards is that they are accepted worldwide, which means wherever your hose is manufactured or purchased, you know it will be tested to the same standards. Global manufacturing standards are essential for many original equipment manufacturers (OEMs).
Manufacturers Respond to Market Trends
In response to market trends for higher-pressure hoses, Parker developed the GlobalCore family of hoses, which also meets ISO 18752 specifications. GlobalCore includes 387 (3,000 psi), 487 (4,000 psi), 722 (4,000 psi), 787 (5,000 psi), and 797 (6,000) hoses. GlobalCore is a constant working pressure family with color-coded laylines based on pressure rating. Each GlobalCore hose can be ordered in standard, ToughCover, or SuperTough cover to prevent abrasion and extend hose life.
Even though the testing requirements are rigorous for ISO 18752, GlobalCore not only meets the minimum 1 million cycles required in Grade D, Type DC, but has been successfully tested up to 2 million impulse cycles. This is twice the minimum requirement at bend radii, which is even tighter than required by ISO 18752 specification.
To further ensure the longevity of GlobalCore, Parker also tested the hoses under movement. Even though this is not required by SAE or international standards, Parker hoses are flexed while impulse pressure cycles are applied randomly to positively demonstrate superior hose performance and longevity.
Interested in GlobalCore?
The charts below will help you find the GlobalCore equivalent to the SAE or ISO hoses you use today. Find your existing hose/spec in the SAE matrix, then find your comparable hoses using the GlobalCore charts.
Step 1. Identify your existing hose
Step 2. Identify your ISO 18752 equivalent
Step 3. Identify your GlobalCore hose
Step 4. Identify your GlobalCore fitting
Article contributed by Kyri McDonough (top), marketing services manager, and Derek Garceau (bottom), engineering manager at Hose Products Division, Parker Hannifin.
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