We use many stainless steel products daily, like knives, appliances, and cookware. For construction, plumbing & sanitary purpose, metal hoses and expansion joints are used. 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 also. That’s why it is stainless wire.

Benefits of Choosing Stainless Steel?

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.

Why Stainless Steel Type Hose is the Best?

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 also.

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.

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 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 stainless steel plate and shaped from 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 rating 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 increase 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)

What are the Main 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 & causes 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 occurs 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 feet long 2" hose which 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 hose 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 the density of gas and the density of water. 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 entire length of hose (85 x 0.003). Here the water density is 62.4 lb/ft3.

There is a term ‘Jacketed Hose’ which means hose within a hose. An inner media conveying hose is jacketed by a more giant diameter 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