What to consider when replacing your industrial hoses

Properly specified industrial hoses allow plants to achieve safe and effective fluid system operation. Choosing an incorrect hose can do the opposite, affecting processes, placing personnel in potential danger, and making a significant impact on profit margins. However, these issues often do not present themselves until they have reached the point of no return. That is why it is critical to reconsider specifications when replacing hoses. If a hose failed faster than expected for the application, do not replace it with the same hose. You can surely find one that provides a longer service life, while also increasing safety and reliability.

A reliable fluid system component provider can advise you on making the best hose choices.

To choose the right hose, engineers must look beyond the purchase price to understand the hose’s potential effect on system operation. It is important to consider application variables like temperature, chemical compatibility and drainability, as well as pressure and flow requirements to ensure the hose will be compatible. A hose’s past performance history is also a helpful resource to understand how it has held up to the rigors of its primary application.

Of the multitude of variables to consider for a hose’s construction, the core tube — an industrial hose’s innermost layer — is among the most critical features that enables compatibility with a process and system media. This article will highlight various hose core materials and constructions and share how to choose the optimal replacement hoses for specific applications.

What to consider before choosing a core tube material

You should consider several questions before choosing a core tube material for your hoses, including:
Is the core material chemically compatible with the system media? Will it corrode or deteriorate over time?
Can the core material tolerate the temperature range of the system media?
Will the core tube material prevent or limit permeation and absorption? (Depending on your application, permeation and/or absorption may not be an issue.)
Will the core material withstand your system’s cleaning practices? This includes temperature, pressure and material compatibility with any solvents and cleaning agents.

You can find this information from myriad sources, including product catalogs and manufacturer support teams.

Core tube categories

When it comes to choosing replacements for your industrial hoses, it is important to understand the strengths and weaknesses of each core type. Finding the core type that is most appropriate for your specific application will ensure proper functioning and life span. As a guide for selecting the right construction for your application, here is a helpful review of the most common hose core types:

Metal

Pros: For general fluid system needs, metal cores (Figure 1) — most commonly 316L stainless steel — remain the standard. Intended to be used at temperatures between 325°F to 850°F (163°C to 454°C), metal core tubes are the ideal core for extreme temperature applications. Flexible metal tubing is also excellent at preventing the permeation or absorption of the transmitted media.

Cons: Metal core tubes have been known to corrode when transporting highly caustic or acidic media. They are also likely to suffer fatigue failure in applications that involve repetitive movements and vibrations.

Silicone

Pros: Their flexibility and cleanliness make silicone cores an affordable option for sanitary applications. Under normal circumstances, silicone can be used at temperatures ranging from 65°F to 500°F (18°C to 260°C).

Cons: The main drawback to silicone hose cores is that they are prone to contamination because they are significantly absorptive. Any fluid they absorb can leech back into future fluids passing through the same hose, thus contaminating that fluid. While steam cleaning is frequently used to sterilize silicone, it does not always remove the absorbed fluid and can easily destroy a silicone core.

Silicone also possesses limited chemical compatibility and cannot be used with many common solvents. Lastly, premature failure can result if silicone cores are used at high temperatures, which cause the hose to weaken structurally and disintegrate over time.

Fluoropolymer

Pros: Frequently used as a silicone substitute in sanitary applications, fluoropolymer cores (Figure 2) are becoming more common. Three commonly used fluoropolymers are PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane), and FEP (fluorinated ethylene propylene), which can be used at temperatures ranging from 65°F to 450°F (18°C to 232°C).

Fluoropolymer cores mirror metal cores in their low absorption rates, and they do not age, are nonstick, and are easy to clean. They can undergo repetitive steam cleaning without degrading, and they remain the most chemically inert cores on the market.

In addition, new technologies allow fluoropolymer cores to be nearly as flexible as silicone, and bonding technology provides additional flexibility through the use of a fiberglass braid. As a glue-free bonding process, the possibility of contamination from glue seeping into the core walls is eliminated.

Cons: Static sparking, caused by fluid passing through a hose, is more common in fluoropolymer core tubes. Such sparking can damage the hose and present safety hazards for system operators. The problem can be addressed by adding a carbon black-filled fluoropolymer hose core, which allows electricity to move through the hose to the end connection and dissipate safely.

In addition, while fluoropolymers have low absorption rates, they are more absorptive than metal cores. Therefore, if permeation will cause problems for the process, metal cores should be considered instead.

Thermoplastic (Nylon)

Pros: Hydraulic applications often call for thermoplastic (nylon) core tubes (Figure 3) because they can handle high pressures and temperatures ranging from 40°F to 200°F (4°C to 93°C). Considered superb general purpose hoses that do not carry the expense of other technologies, thermoplastic hose cores accommodate pressure impulses more effectively than metal or fluoropolymer core hoses.

Cons: Media can permeate nylon hoses more easily because they are soft and porous. Plus, thermoplastic hose cores cannot handle high-temperature applications in comparison to other materials.

Rubber

Pros:Similar to thermoplastic hoses, rubber core hoses (Figure 4) are economical and have a similar temperature profile. They can be crushed without being damaged permanently and are constructed with little or no special equipment. With diameters of more than 2 inches, they are able to be made larger than any of the other materials discussed here.

Cons: Rubber cores cannot be used in high-pressure applications and tend to degrade more quickly than other materials.

Core tube wall construction

In addition to deciding which tube core makes the most sense for your application, it is also critical to recognize whether the hose’s walls should be smooth (rigid) or have convolutions (which provide flexibility to the core). Several factors will determine what type you choose, including how much flexibility, pressure, flow and drainability you need.

Smooth-bore

Pros: As the name implies, smooth-bore cores (Figure 5) have no ridges inside. They are available in all core materials except metal. If precise flow control or excellent drainability is essential to your application, then smooth-bore cores are the preferred choice.

Cons: Smooth-bore cores are more susceptible to kinking, specifically as diameters grow. Kinking can often be mitigated by adding reinforcement layers.

Convoluted

Pros: Convoluted core tubes are designed to bend without kinking, using folded walls. Typically, only metal and fluoropolymer cores have these walls.

There are two types of convoluted cores — helical (Figure 6, top) and annular (Figure 6, bottom). Typically used in fluoropolymer cores, the helical design features one convolution that spirals down the length of the hose, improving downstream flow for excellent drainability and flexibility. Annular designs, found primarily in metal cores, are made up of a series of connected rings with deep convolutions for maximum flexibility.

Cons: In addition to being more expensive than other hose core options, metal flexible tubing is not effective in situations where it will be subject to repetitive motion or vibration because it will often fail from fatigue after repeated use.

Finding the right core

Choosing the right industrial hoses for your applications can be challenging, but with these considerations in mind, it will be easier to find a reliable fluid system component provider to advise you on your choices. Together, you can consider every variable before making an ideal choice.

Editor's note: An original version of this article appeared on the Swagelok Reference Point blog at bit.ly/2OK7XfS.