Flexible Hoses Part 1: Understanding the Basics

How well do you know your flexible hoses? Do the terms &#;permeation,&#; &#;post-sintered&#; or &#;bend radius&#; have meaning or do they seem more like unintelligible industry jargon? If it&#;s the latter, you&#;re not alone! Bottom line, it&#;s easy to order the wrong hose.

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Ratermann is here to help. Below we&#;ve got the basics you need to understand hose terminology, and more importantly, choose the correct hose for your application.

Why flexible hoses?

Let&#;s start with the &#;why&#; behind flexible hoses. Flexible hoses are a staple in the cryogenic and compressed gas industry for the transfer of gases and liquids, and they&#;ve come a long way in terms of safety and durability. Flexible hoses are THE answer to the biggest problems created by rigid hoses: cracking and leaking. 

Ratermann has an exhaustive selection of flexible hoses for cryogenic and compressed gas applications from high pressure to CO2 to tube trailers. Whether you&#;re working with liquified nitrogen, oxygen or argon or compressed gases like oxygen, helium and hydrogen, we have a hose in-stock for your application. And if an off-the-shelf hose doesn't fit the bill, we can create a custom solution.

Most common flexible hose materials:
There are several choices to consider when choosing a hose: stainless steel, PTFE (polytetrafluoroethylene) and composite materials are among the most common. These are chosen for their ability to withstand extreme temperatures, high pressures and corrosive environments. The hose material you choose will depend on your application. (Stay tuned for Flexible Hoses Part 2, where we&#;ll deep dive into hose materials and applications.)

Important hose terms:
There are a number of terms that pop up when talking about flexible hoses for cryogenic and compressed gases. Here&#;s a brief glossary of some of the most common terms, phrases and acronyms you&#;ll see:

Adapters: Refers to accessories to reduce or enlarge the size of a connection or hose line, used to bridge a hose assembly.

Adiabatic Compression: This refers to the heat generated by compressing air that remains in the compressed air.

Armor Casing: Armor casing can easily be installed over a braided hose to prevent kinking and whipping in the event of a hose burst. It also protects the hose exterior from incidental damage.

Bend Radius: The minimum distance a hose can be bent without causing damage.

Braiding: A stainless steel braid that encases the inner core and gives the hose its strength to hold pressure. A high pressure hose can have from one (3,000 PSI) to four braids (5,000 PSI) depending on pressure requirements.

Burst Pressure: Maximum pressure before a hose will rupture. Make sure the average working pressure of the hose is well above the required maximum pressure of your application.

CCB: Clean, Capped & Bagged - meaning that a hose is cleaned and ready for oxygen service.

CGA: The Compressed Gas Association is a trade association for the industrial and medical gas supply industry, and publishes standards and practices to codify industry practices.

Diffusion/Effusion: Diffusion occurs when gas molecules disperse throughout a container. Effusion occurs when a gas passes through a small opening, often described as a pinhole. Hoses that effuse gases can also diffuse gases. Diffusion can introduce contaminants that could affect the high purity gas stream. If this is a concern, consider using an all-metal hose.

FNPT: Female national pipe threads.

MAWP: Maximum Allowable Working Pressure is the maximum pressure for which the hose assembly is designed.

Molecular Size: The size of molecules that a hose can effectively contain or prevent from passing through. For example, hydrogen and helium have the smallest molecular weight, and thus present a higher risk of permeation loss.

Permeation: How gas molecules pass through the pores of a hose. If permeation is a concern, consider using an all-metal hose. Make certain the flow rate is below the suggested threshold level. Alternative options are ETFE or PTFE post sintered hoses, which reduce effusion by around 75 percent.

Post Sintered: A process used to enhance the properties of a material by improving strength, density, etc. Essentially, heating or &#;baking&#; a material to a temperature just below its melting point, causing it to fuse into a solid mass.

Swivel Fittings: Fittings that allow the coupling and hose connection to rotate, preventing kinking and excessive bending.

Velocity or SCFH: The amount of flow a hose is rated for, as standard cubic feet per hour (SCFH).

Choosing a hose? Ask these questions.

As we mentioned earlier, it&#;s all too easy to order the wrong hose &#; either because of a misunderstanding of hose terminology or of how important it is to match the hose with your application. To prevent wasting time and money, ask these questions when selecting a hose:

• What is the application? Do you need a hose for high pressure gas or cryogenic liquids?
• What is the maximum pressure in your application?
• What is the flow rate (SCFH)?
• What length is needed? Standard lengths are in-stock and ready to ship, custom lengths can be ordered. It&#;s also a good idea to give yourself extra length, just in case.
• What type of end fittings do you need? The most common are ¼&#; female NPT.
• Do you need armor to protect the hose from kinking and reducing whip?
• Do you need CCB for oxygen service?
• Do you need swivels, tethers, or other special options?

Ratermann has the hoses you need in-stock and ready to ship!

Shop our extensive hose collection or check out our Hose Builder tool to build the right hose for your application!

Xinshun are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

It's fast, it's flexible, and can come with a wide variety of end connections

"When you go to vacuum in the airlock and you take the hose off the front of your space suit, there's a little bit of water in there, and you can see that sublimate and ice crystals form and fly away. My thought at that moment was, 'Oh, we are not kidding at vacuum here; we are really in space"

- From Kathleen Hallisey Rubins, a NASA astronautet

Flexible hose may be one of the most under-used components in power plant, refineries, and other general industrial and manufacturing environments. Many technicians and engineers don&#;t realize how far hose technology has come. Now, with the latest advances, you can use hose in many places historically limited to tubing or pipe.

The principal benefit of hose is easy installation and easy replacement of adjoining components like valves. It&#;s just a lot easier to work with hose than with rigid tubing or hard pipe because there is no bending, welding, or fitting. As a result, you will save a lot on your labor costs. Installing it takes a matter of seconds &#; minutes at most.

Hose is especially appropriate for short connections between movable parts, parts in high vibration, or parts that need to be frequently connected and disconnected.

In power plants, refineries, and other general industrial and manufacturing environments, that makes hose an excellent choice for:

• Compressed and instrument air applications
• Connections to compressors, pumps, or other devices that cause vibration
• Connections to pneumatic actuators on large control valves
• Chemical tote offloading equipment
• Hydraulic and lube oil applications subject to vibration
• Pressurized gas delivery from tanks and cylinders
• Sample analysis systems that draw fluid from process lines
• Natural gas, diesel, or liquid fuel handling applications

What's in a Hose?

Typically, hoses consist of a core, reinforcement, covers, and end connections (Figure 1). Core materials may be metal, fluoropolymer, thermoplastic, or rubber. Many power plant applications employ stainless steel cores, which offer corrosion resistance and high-temperature compatibility &#; up to 850˚F (454˚C).

Reinforcement layers &#; often stainless steel woven braid &#; improve pressure containment and flexibility. With stainless steel braid, hoses available from Swagelok can manage pressures up to psig. Stainless steel braided reinforcement layers also prevent easy cutting &#; whether accidental or purposeful.

In semiconductor fabs, a silicone cover and insulation is often added in high-temperature applications to greatly reduce the likelihood of burns on contact.

Hoses can be fitted to a wide range of end connections, including tube adapters, tube fittings, VCR metal gasket face seal fittings, VCO O-ring face seal fittings, swivel fittings, NPT pipe threads, pre-swaged nuts and ferrules, tube butt welds, flanges, Kwik-Clamps, cam and groove, tube stubs, and more.

When Should You Use Hose?

There are many places where hose pays for itself very quickly.

Connections Requiring Complex Tube Bending: Tube bending is not difficult, but it does require some tools and training. If you don't have them, it may be advisable to go with hose. Sometimes a replacement part does not have the same dimensions as the original, and the original section of tubing or pipe does not quite align with the new connections. You can sidestep frustration with hose.

Applications with Severe Vibration: Hose can manage vibration stress better than tubing, especially under high pressure. Frequent vibration may stress tubing to the point of fracturing. A run of hose can dampen vibration between the source and the rest of the tubing assembly. All you need is an end connection that can handle vibration. For example, Swagelok tube fittings are designed not to leak with vibration.

Temporary Connections: Hose is an excellent choice for water sampling, chemical sampling for analysis, or for offloading chemicals from totes. It bypasses alignment issues associated with rigid pipe or tubing, and it can attach with a cam-lock or quick-connect (Figure 2).

Moving Parts: The pneumatic actuators on some large control valves move up and down and therefore require a flexible connection to the compressed air source. An example would be control valves for oxygen fuel dampers. There are many other such applications in a power plant or refinery.

Parts Requiring Frequent Replacement or Servicing: When connected with Swagelok tube fittings, hose can be disassembled and reassembled with the turn of a wrench. Gas turbine inspections, for examplel require frequent assembly and reassembly of components, and hose makes this easier. If the hoses need to be changed out, it's a relatively simple process. You don't have to worry about an alignment issue.

Get it quickly

Swagelok hose is available in custom lengths up to 100 feet, in diameters 2 inches and under, and with a wide variety of end connections.Standard sizes and end connections ship within 24 hours.

With the proper selection of material options, hoses are completely dependable in a wide range of pressures and temperatures.

Just ask

Swagelok Northern California has a great deal of exposure to all aspects of fluid system design and engineering. Whether you have a simple question or a complex challenge, we're glad to hear from you. 

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