Pick the Proper Hose

Making a correct choice requires an understanding of hose components.

By Patrick Werrlein, Swagelok Company

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The right hose keeps your process performing safely and cost effectively. The wrong hose could undermine your operations, put personnel at risk and compromise your bottom-line — sometimes without you being aware of it.

For example, an improperly chosen hose may kink. This permanent buckling disrupts system media flow and creates a rupture threat. However, kinked hoses aren't easily detected and so afflict many plants.

Unfortunately, plants often treat hose selection as an afterthought. So, here, we'll look at the proper approach. You must consider a variety of process requirements — e.g., temperature, pressure, flow, chemical compatibility and drainability. In addition, selecting wisely also requires evaluating hose longevity, maintenance and replacement costs, and other cost-of-ownership factors.

Selection starts with an understanding of the four main parts of a hose (Figure 1):
1. core tube material and construction;
2. reinforcement layers;
3. covers; and
4. end connections.

When choosing a hose, begin with the core tube, which is the hose's innermost layer, the one that contacts the system media.

Answer some basic questions (with the help of product catalogs and your sales and service representative):

• Is the material chemically compatible with the system media? Will it corrode or deteriorate over time?
• Can it tolerate the temperature range of the system media?
• Will the material adequately prevent or limit permeation and absorption? This may not be an issue in your application. If it is, though, understand that permeation and absorption can occur in all materials, even metals; so this question is one of degree.
• Will the core material withstand the cleaning practices for your system —temperature, pressure and any solvents and cleaning agents employed?

Core tubes come in a variety of materials and constructions (summarized in Table 1):

Metal cores (commonly type 316L stainless steel) are a good choice for general needs. They usually are rated for -325°F–850°F (-200°C–454°C), which makes them an especially good choice — sometimes the only choice — for system media at extreme temperatures.

A metal core also makes sense to minimize permeation or absorption. However, it can corrode when contacting highly caustic or acidic media.

Silicone historically has served for sanitary applications. It typically can handle -65°F–500°F (-53°C–315°C) and is flexible.

 Table 1 hose materials
 Table 1. Process requirements as well as cleaning protocols determine the right choice.
 Click table to enlarge.

However, silicone is incompatible with common solvents and has limited chemical compatibility overall. In addition, it is absorptive, which can lead to contamination if fluid absorbed into the tube walls later leaches out into media currently in the system. Removing the absorbed fluid often isn't possible.

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