Introduction

We use many stainless steel products daily, like knives, appliances, and cookware. Metal hoses and expansion joints are used for construction, plumbing & sanitary purposes. These are also made of stainless steel. 

Stainless steel is an alloy. It contains iron, chromium, and nickel. Initially, chromium reacts with oxygen in the air, forming a layer of chromium oxide on the surface of the metal. When the chromium oxide layer becomes thick, it acts as a shield. It can protect the reliability of the alloy. This layer prevents water and corrosivity from attacking the alloy’s free iron. Sometimes, the oxide layer becomes scratched. It can then repair itself and maintain its corrosion resistance. That’s why it is stainless wire.

Stainless Steel Flexible Hose: An Overview

A stainless steel flexible hose, often referred to as a stainless steel braided hose or simply a flex hose, is a versatile, durable piping product designed to transport liquids and gases. Made from stainless steel, it is known for its strength, corrosion resistance, and flexibility, allowing it to bend and move without cracking or breaking.

Composition and Construction:

The stainless steel flexible hose typically consists of:

• Inner Core: Made of spiral-wound stainless steel, this is the primary conduit for the transported medium (liquid/gas).
• Braided Layers: One or more layers of braiding surround the inner core. This braided mesh, usually stainless steel, gives the hose strength and flexibility. The number of layers often determines the hose’s pressure capacity.
• End Fittings: Depending on the application, various end fittings are attached, like flanges, threaded connectors, or quick couplings.

Key Features:

1. Flexibility: Its main selling point is that this hose can be bent, coiled, and flexed without compromising its structure, making it ideal for tight spaces and dynamic applications.
2. Corrosion Resistance: Stainless steel is inherently resistant to corrosion, making these hoses suitable for various applications, including those where they might be exposed to corrosive elements.
3. High-Temperature Tolerance: These hoses can transport hot fluids or be exposed to hot environments without losing their integrity.
4. Pressure Resistance: The braided design enables the hose to withstand high pressure, especially in hydraulic applications.
5. Longevity: With proper maintenance, these hoses have a long operational lifespan.

Applications:

Stainless steel flexible hoses are used across various industries, including:

• Plumbing: For water supply, especially in areas where vibrations or movements can cause rigid pipes to crack.
• HVAC: In heating, ventilation, and air conditioning systems, these hoses can be used for coolant, refrigerant, or steam transport.
• Industrial: In factories and plants, these hoses transport chemicals, gases, steam, and other fluids under varying conditions.
• Automotive: Used in car exhaust, turbocharger, and fuel lines.
• Marine: Due to their corrosion resistance, they are ideal for saltwater applications on ships and offshore platforms.

Selection Criteria:

When selecting a stainless steel flexible hose:

• Determine the Application: Understand the medium (liquid or gas) you’re transporting, temperature, and pressure.
• Check for Certifications: Ensure the hose meets relevant industry standards.
• Length and Diameter: Ensure the hose’s length and diameter suit your application.
• End Fittings: Ensure compatibility with the systems you’re connecting.
• Braiding: More braided layers usually mean higher pressure tolerance.

In conclusion, stainless steel flexible hoses offer an adaptable and robust solution for various piping needs. Ensure that you choose the right specifications for your application and maintain the hose properly to maximize its lifespan.

Benefits of Choosing Stainless Steel Flexible Hose?

Stainless steel is an excellent substitute for non-metal hoses in specific settings and applications. It can maintain its integrity in moisture or corrosive atmospheres without rusting. It is possible because of an outer oxide layer. Non-metal hoses are unable to provide good resistance to high temperatures. But stainless steel can resist even extreme temperatures. Temperature like -430 up to 1300 degrees Fahrenheit is tolerable for stainless steel. Non-metals like rubber or Teflon will crack at low temperatures and melt at high temperatures.

Sizes For Stainless Steel Flexible Hose:

Stainless steel flexible hoses come in various sizes, commonly ranging from 1/4″ to 12″ in diameter. The length can be customized but is generally available in standard lengths like 10, 25, 50, 100 feet, etc. Here’s a brief breakdown:

• Small Diameter: 1/4″ to 1″ – Used in small, precise applications like medical equipment or sensitive instrumentation.
• Medium Diameter: 1 1/2″ to 4″ – Suitable for most industrial and commercial applications like HVAC systems and medium-pressure fluid transport.
• Large Diameter: 6″ to 12″ – Used in high-flow applications like water supply mains, industrial bulk transfer, etc.

Raw Materials For Stainless Steel Flexible Hose:

While stainless steel is the primary material used for braiding and often the core, flexible hoses can incorporate several other materials based on the application’s specific needs. Some common raw materials include:

• PTFE: Used for the inner lining, PTFE (Polytetrafluoroethylene) offers excellent chemical resistance and is used in hoses meant for corrosive chemicals or high-temperature fluids.
• Rubber: Natural or synthetic rubber may be used as the inner core for hoses designed for specific applications like potable water supply or compressed air transport.
• PVC: Polyvinyl Chloride may be a less expensive inner lining material in less critical applications.
• Silicone Offers high-temperature resistance and flexibility and is often used for hoses that operate in extreme temperatures.
• Zinc and Aluminum: Some hoses feature zinc or aluminum fittings or components to reduce cost or for particular characteristics such as lighter weight.
• Brass/Copper: Often used for end fittings for their excellent conductivity and corrosion resistance.
• Carbon Steel: Sometimes used for end fittings in industrial applications where strength is a priority.

It’s crucial to select a hose with raw materials that are compatible with the fluids or gases being transported to ensure safety and longevity. Always refer to the manufacturer’s guidelines and chemical compatibility charts when making your selection.

Why Stainless Steel Type Hose?

Stainless steel hose has tremendous flexibility. This makes it easy to move around obstacles like trees or shrubs. These hoses have less possibility of bending or twisting. It is static-free. It will not generate static electricity when working with water. Its exterior is smooth and non-toxic and made of seamless pipe. 

The stainless steel hose has a high-temperature-resistant rubber tube. The working temperature can be up to 392 degrees Fahrenheit. This type of steel has outstanding corrosion resistance properties.

The inner diameter ranges from 0.75mm to 10mm. The wall thickness ranges from 0.5mm to 2.0mm.

Stainless steel hose is perfect for different applications. It is best for plumbing improvement, sanitary works, automotive repair, and more. The wire inside the hose makes it hard and durable. It can provide extra flexibility to use in various conditions. It ensures good handling of objects, whatever you put.

We don’t have to replace this hose as often. Stainless steel hose materials can withstand a lot of wear and tear.

Length:

Stainless steel flexible hoses are available in a variety of lengths to cater to different applications. Some standard lengths are:

• Short Lengths: 12 inches to 3 feet – Typically used for applications like connecting appliances in tight spaces or for specific industrial equipment.
• Medium Lengths: 4 feet to 20 feet – Common for commercial applications and certain industrial uses where moderate reach is required.
• Long Lengths: 21 feet to 100 feet or more – Used for extensive applications, including long pipe runs in industrial setups or when connecting equipment located far apart.

Custom lengths can also be ordered based on specific requirements.

Specifications:

The specifications of a stainless steel flexible hose describe its characteristics and define its suitability for different applications. Here’s an overview:

1. Diameter: The hose’s internal diameter, commonly ranging from 1/4″ up to 12″, determines the volume of material (liquid, gas) it can transport.
2. Bending Radius: Specifies the smallest bend radius without kinking or damaging the hose.
3. Material of Construction: While the outer layer is typically made of stainless steel, the inner core can be made from materials like PTFE, rubber, or PVC, depending on the application.
4. End Fittings: These can be made of materials like stainless steel, brass, or carbon steel and can come in various configurations like threaded, flanged, or quick connect.
5. Burst Pressure: Typically several times the working pressure, this indicates the pressure at which the hose might fail.
6. Certifications: Depending on the application, the hose might need to meet specific standards or certifications, like FDA for food applications, SAE standards for automotive uses, etc.

When selecting a stainless steel flexible hose, always ensure its specifications match the requirements of the intended application. This guarantees optimal performance and safety.

Pressure Rating:

1. Low-Pressure Hoses: These can typically handle pressures from atmospheric levels up to about 250 PSI. They are commonly used in domestic and light commercial applications.
2. Medium Pressure Hoses: Designed for 251 PSI to 1,000 PSI pressures. These are used in more robust commercial applications and certain industrial settings.
3. High Pressure Hoses: These are designed for pressures exceeding 1,000 PSI, sometimes even going up to 3,500 PSI or more. Such hoses are used in industrial and specialized applications, including high-pressure cleaning, hydraulic systems, and certain chemical processes.

Temperature Range:

1. Low-Temperature Hoses: These can function effectively in temperatures ranging from -70°F to +250°F. Such hoses are suitable for cold environments or refrigeration applications.
2. Medium-Temperature Hoses: Designed for a range from -30°F to +350°F, these hoses are used in general industrial and commercial applications.
3. High-Temperature Hoses: These hoses can withstand temperatures from -20°F up to +1,000°F or even higher. They are used in applications like steam transfer, hot fluid transport, and certain chemical processes.

However, it’s essential to understand that these are general ranges. Its manufacturer would provide the exact specifications of a particular stainless steel flexible hose based on the design and materials used. Always consult product datasheets or manufacturer guidelines when determining suitability for a specific application.

Features of Stainless steel hose

· High-quality stainless steel is used

· Design is very much simple

· flexibility makes it easy to use and install

· It can ensure long-lasting performance because of corrosion resistance.

· application is vast

· It helps to avoid replacing your entire drainage system

· Easy to install, which makes a hassle-free drainage solution

· Rust & kink resistive. It confirms the free flow of water

· It can be used in both inside and outside settings

· Excellent in liquid and gas transfer applications

· Conditional upon the extremes of temperature;

· Sudden failure does not occur.

· A range of limits exists to prevent superficial abrasion & overbending.

A Guidance for selecting a Proper Stainless Steel Flexible Hose is like below:

The Structure of Stainless Steel Flexible Hose

This hose consists of parallel stainless steel rings. The rings are coated with a stainless steel plate and shaped by hydraulic pressure.

The good thing is Stainless steel flexible hoses have a wide range of temperatures. These are structured by a thin-walled smooth tube. 

Torsion is not suitable for a hose. It must be avoided. The hose is needed to be fitted with cyclical movements. Connectors with or without hex nuts, 3-part connectors, and rotating female connectors are used for stainless steel flexible hoses. Hose service life changes depending upon the severity of the flexing, temperature, and corrosive conditions. Pressure and vibration ratings are also responsible for service life.

The Stainless steel hose is designed to meet several purposes in pipework-

· Absorption or vibration

· Operation under vacuum

· Handling temperature

· Suppression of rigid pipe noise transmitted

· Accommodating the reciprocating and flexing movement

· Operating effectively under high pressures

· Adjust the misalignment

The construction of a Stainless Steel Flexible Hose

The main components of hoses are:

· Corrugated tubing

· Braid

· Braid collars

· End-fittings

These parts are not complex. We can even customize these according to our requirements. Customization helps us to form a variety of configurations. It enables flexible metal hoses to be an optimal solution.

Corrugated Tubing: It’s the principal component of a stainless steel flexible hose. It always plays a value-added feature like corrosion resistance, pressure rating, and flexibility. Corrosion resistance is a matter of selecting the correct alloy. It is essential for the media that is being carried. Using more nickel and other alloying elements in the alloy increases chemical resistance.

Each hose has a specific ability to handle inward pressure. This is called ‘MAWP,’ which means Maximum Allowable Working Pressure. The pressure rating is critical because of the hose assembly. Depending on this, we can decide which type of assembly is proper. Sometimes, a lower pressure rating is used in many standard applications. A higher pressure rating is also used for critical applications. Overall it is a matter of applications.

Another vital issue is flexibility. What do you think about it? It has various meanings to various people. To some, it means the hose’s ability to be twisted into a tight radius. To others, it may refer a high cycle life of the hose. Some others think that a hose will turn without applying spring forces. Flexibility is expressed by ‘MDBR,’ which means Minimum Dynamic Bend Radius. A higher MDBR is acceptable for a lot of applications. A tighter MDBR is also needed.

Braid: The braid is suitable for high-pressure applications. There are several factors that can contribute to the functionality of the braid. The elements are wire diameter, number of wires per carrier, and percentage of braid coverage. We can increase the pressure rating of a hose. For this, we should add additional layers to the braid. The better cycle life of the hose depends on proper braid design. It has an essential effect on the working pressure also. A high percentage of braid coverage helps to ensure that the braid is well-secured on the hose, protecting the assembly from potential deformation. 

Braid Collars: Braid collars assist in joining the inner corrugated hose and the braid together during the cap welding process. This cap weld needs to be perfect. It is the base for subsequent attachment weld. Because of this, all the connection points of the hose can hold together correctly. Along with joining the hose components, the braid collars protect and isolate the corrugations from any movement. Braid collars always ensure the proper distribution of bending stresses. 

End-Fittings: You have many procedures for end fittings. There are many options for selecting the fittings. These help you to allow flexible metal hoses for customized assembling. It indeed depends on applications. Before choosing fittings, we must be sure about the size, alloy, and pressure requirements.

Calculation of Stainless Steel Hose Length

When the minimum bend radius occurs at the offset position, the moving end is free to move “out of line” from the neutral position.

To find the live hose length: 

L = √6(RT) + T2 

Lp = √L2 – T2

When the minimum bend radius occurs at the inline position, the opposite end side of the hose is restricted to use only up and down in line as the hose crosses the neutral position. 

To find the live hose length: 

L = √20(RT) 

Lp = √L2 – T2

Horizontal Movable Pipe System

L = 4R + 1.57T

H1 = 1.43R +0.79T

Vertical Movable Pipe System

L = 4R + T/2

H1 = 1.43R + T/2

L = Live Hose Length (mm) 

R = Least Dynamic Bend Radius for Constant Flexing (mm) 

T = Total Travel (mm) 

H1 = Swing Length of the Loop (mm)

Characteristics of Flexible Metal Hose 

Tolerances: The following length tolerances should be checked when checking the nominal length: 

Dimensions in mm

Nominal Lengths 

up to 500

over 500 up to 1000

over 1000 up to 2000

Tolerances

ISO 10380:2012

Min 495

Max 515

Min 990

Max 1030

Min 1980

Max 2060

Braid: Unbraided hose is suitable for vacuum and low-pressure applications. This hose can give protection against vermin and abrasion. Stainless steel wire braid provides high internal pressure capability for hoses. This braid acts to dampen vibration without significant loss of flexibility. The second layer of the braid may increase the pressure rating. 

Flow Velocity: The flow velocity shouldn’t be more than 150 ft/sec for gas or 75 ft/sec for liquids. When the hose is connected in a twist condition, these flow values should be decreased comparably to the degree of the bend. Sometimes, the flow velocity may exceed these rates. An interlocked metal hose liner is the solution in this case. 

Service Life: Maximum service life can be ensured by proper installation. Incorrect installation may reduce the practical service life of the hose. Incorrect flexing or careless handling also causes premature failure of an assembly. Many external factors are responsible for affecting service life.

Covers: You can use various armor and masks to protect the flexible metal hose from uncommon outside abuse. These are like-

· Silicon Coated Fibreglass Sleeve

· Stainless Steel Interlock Cover

· Bird & Rodent Proofing Braid

· Wire Spring Guard

· Wire Bend Restrictor

· Hose Handling Sling

· Ball Joint Armor

· PVC Covering

· Pigtail

· Whipsock

· Lay-flat

· Rope Lag

· Hose Floats

· Rawhide

Liners: The liner allows a smooth flow rate. It also reduces associated noise. 

Installation Precautions of Stainless Steel Flexible Hose

· Inspect the hose for any apparent damage. You shouldn’t use a damaged hose. Now, the question is how you can identify the damage. Damage includes slices to the cover, kinks, broken braid, and crushing of the hose.

· Ensure proper selection of hose for the specific application. It could be made by inspecting materials, pressures, chemical compatibility & temperature.

· Hose movement should be limited to reduce the resultant torque.

· Axial movement should be excluded.

· Hose pipes should be leak tested.

· Ensure compliance with international standards of hose pipe.

Installation of Stainless Steel Flexible Hose

We shouldn’t use a hose below the most minor bend radius. The bend radius is a measurement of the centerline for the metal hose. This radius is specific for individual products and sizes. In some cases, vacuum and pressure ratings shouldn’t be more than a 2% minimum bend radius. Tight bends can cause kinking in a hose. It may overstress the material & cause damage or failure. If severe angles cannot be avoided, you should use your elbows, which is convenient for changing direction. During installation, we should be careful about twisting the whole assembly. Floating flanges and swivel-type fittings are recommended. These can eliminate improper twisting.

from Advanced Plumbing

Excessive gas or liquid flow through the hose may occur in resonant vibration. It brings rapid failure of the assembly. Pressure drop is an important factor of hose in the piping system. Stainless steel hose produces a greater pressure drop than a rigid hose. Pressure drop is increased by bends and fittings in the hose assembly. Metal hoses carry substances like gaseous, liquid, or solid. We can find out the pressure loss over a certain length of hose. For example, we want to calculate the pressure loss in 85 an 85-foot-long 2″ hose that transfers water. The flow rate should be between 1400 cubic feet per hour. After calculation with the help of the pressure curve, we’ll get pressure loss per foot of the hose, which will be about 3.7 psi. So that the entire pressure drop over the hose length will be 314.5 psi (3.7 x 85). If we transfer gaseous substances instead of water through the hose, then we need to find the ratio of gas and water density. We need to adjust the pressure drop respectively. For example, if we transfer natural gas (density = 0.050 lb/ft3), we can get the pressure drop 3.7 x (0.050/62.4) = 0.0030 psi/ft or 0.255 psi for the entire length of hose (85 x 0.003). Here, the water density is 62.4 lb/ft3.

The term ‘Jacketed Hose’ means hose within a hose. A more giant diameter hose jackets an inner media conveying hose. The hoses are joined at each end. It needs a unique fitting design. As a result, there is no chance to get mixing the media. Steam is often conveyed through the jacket hose. Hot oil or hot water increases the temperature of the fluid moving in the internal hose. Cold products like liquid helium or nitrogen are also used.

Applications of Stainless Steel Flexible Hose

· Heating processes 

· Rail car and tank 

· Truck loading/unloading 

· Marine transfer 

· Flexible connections to vibrating equipment 

· To release pump housing stresses 

· Hazardous material piping system

· Oil & Gas Refineries

· Power Plants

· Steel plants

· Pulp & Paper mills

· Nuclear installations

· Fertilizer industry

· Pharmaceutical industry

· Chemical industry

· Industrial boilers

How to produce a stainless steel flexible hose?

Producing a stainless steel flexible hose involves multiple steps, each designed to ensure the hose is durable, leak-proof, and able to withstand the pressures and stresses it will encounter. Here’s a general overview of the production process:

1. Material Selection:

• Stainless Steel: Typically, grades 304 or 316L are used because of their resistance to corrosion, durability, and strength. The choice often depends on the intended application.
• Inner Tube: Depending on the design, an inner tube of rubber or another material may be used to transport specific media.

2. Tube Formation:

• Helical Coiling: A continuous stainless steel strip is helically wound to produce a flexible, corrugated tube. This corrugation provides the hose with flexibility.
• Annular Coiling: Another method where the stainless steel is formed in continuous annular rings. This design is more resistant to flexing but less flexible.

3. Braiding:

A wire braid is often applied to increase the pressure resistance of the hose and protect the corrugated tube. Machines weave stainless steel wires around the hose in a specific pattern, providing strength.

4. Fittings Attachment:

• Various end fittings are attached to the hose depending on the intended use. Common fittings include flanges, threaded connectors, and quick-release couplings.
• The fittings are usually attached using a combination of welding and crimping to ensure a secure connection.

5. Testing:

• Pressure Testing: Every hose is typically subjected to a hydrostatic pressure test to ensure it doesn’t leak and can withstand its rated pressure.
• Flexibility Testing: The hose might be subjected to repeated flexing to ensure it maintains integrity.

6. Quality Inspection:

• Visual inspection ensures there are no evident defects, irregularities, or damages.
• Advanced methods, like X-ray or ultrasonic testing, can be used to detect any hidden flaws or inconsistencies in the metal.

7. Cleaning:

After manufacturing, the hose is cleaned to remove any residues, ensuring it’s ready for transporting whatever medium it’s designed for.

8. Packaging:

Once cleaned and passed the quality checks, the hose is coiled, tagged, and packaged. Proper packaging ensures the hose remains undamaged during transit.

9. Documentation:

A certificate of compliance or a test certificate is provided detailing the hose’s specifications, materials, and the results of any tests it underwent.

Producing stainless steel flexible hoses requires a blend of the right materials, precise machinery, and skilled workers to ensure a quality product. Proper quality control and assurance protocols are essential, especially since these hoses are often used in critical applications where failures can be costly and dangerous.