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