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Hose is an important part of a hydraulic system. Hydraulic hose provides a basic means for transporting fluid from one component to another. The flexibility of hose enables components to be positioned in the most efficient or convenient places, because the hose has the ability to bend around corners, through tight spaces, or across long distances.

Hose fittings have an impact on the overall efficiency and safety of a hydraulic system. A typical hydraulic hose consists of mainly three parts: an inner tube that carries the fluid, a reinforcement layer, and a protective outer layer. The inner tube must have some flexibility and needs to be compatible with the type of fluid it will carry. Commonly used compounds for making inner tubes include synthetic rubber, thermoplastics, and PTFE. The reinforcement layer consists of one or more sheaths of braided wire, spiral-wound wire, or textile yarn. To protect these inner layers of the hose from the ambient conditions, an outer synthetic rubber cover is extruded around the reinforcement. The outer layer is often weather, oil, or abrasion-resistant, depending upon the type of environment the hose is designed for.

Proper sizing and use of the correct type of hose will extend the life of a hose assembly, but there are many different factors that affect a hose?s lifespan.

Market and technology trends
India is already home to the major global players in this sector and more are trying to set base here in what is promising to be a stable growth market. The entry of many global players has helped to raise the bar for performance.

According to Rajesh C Bhandari, Managing Director, Gates India, the market for hydraulic applications has been growing and the trend has been towards high performance hose and fittings. He says, ?Though there has been a de-growth in the major segment of new construction and earthmoving equipment in the last two years, there are sure signs of the end markets getting back on the growth track. The current market size for hydraulic hoses is about Rs 500 crore.?

The technology in hose and fittings has been steadily moving towards high flexibility and compact design with longer flex impulse life going to a million cycles and beyond. Bhandari elaborates, ?Hose and fittings are engineered together for reliable leak-free performance. The hoses are manufactured using different types of synthetic rubbers depending on the application and reinforced with specialized high tensile steel wire or textile yarn. The fittings are usually manufactured with low carbon steel and finished with environment-friendly and highly corrosion-resistant trivalent zinc plating. A range of hydraulic hoses are available to operate up to 420 bar working pressure, temperature up to 150?C. There are specialized hose cover designs - MegaTuff and XtraTuff to operate in extremely abrasive operating conditions. The hoses are also designed with a low minimum bend radius tighter than what is specified in the SAE and EN standards, resulting in savings in new platforms and ease of installation on existing machines. We also work with our customers to reduce pressure drop in the system.?

Future outlook
Like many other sectors of the economy, 2014 was a stagnant year. But according to Bhandari, the markets are expected to be on the growth mode from 2015 on the back of many infrastructure projects announced by the Government and the ?Make in India? initiative.

Selecting the proper hose
The first step in achieving a safe hydraulic system is selecting correct components that meet the user?s needs. There are seven recommended steps the system designer should follow during the hose and coupling selection process. The seven steps are coded with the acronym STAMPED, which stands for Size, Temperature, Application, Materials, Pressure, Ends, and Delivery.

Proper hose selection is critical to a safe hydraulic system. Thus the simple rule of thumb for proper hose selection is ?STAMPED?.

Size: The inside diameter of the hose must be adequate to keep pressure loss to minimum and avoid damage to the hose due to heat generation created by excessive turbulence.

Temperature: The hose selected must be capable of withstanding the minimum and maximum temperature of the system. Do not expose hose to internal or external temperatures exceeding the recommended limits. An increase of 10?C above the maximum recommended temperature may reduce the hose life by half. Also, hose will crack if flexed at temperatures below the minimum recommended.

Application: Select the proper hose for the application. Determine where, or how, the assembly is to be used.

Material: Hose selection must assure compatibility of the hose tube, cover, reinforcement, couplings, o-rings, etc., with the fluid used. Many hoses are compatible with one type of fluid or another, but often times not all fluids. Pressure: It is essential in the hose selection process to know the system pressure, including pressure spikes. Published working pressure must be equal to or, greater than the system pressure. Pressure spikes greater than the published working pressure will shorten hose life or lead to hose ruptures.

Ends: Connecting ends of coupling must be correctly identified.

Delivery: How much fluid must go through the hose will determine the size of hose that must be used. Under sizing a hose leads to increased pressure loss, while over sizing the hose adds unnecessary cost, weight and bulk.