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Physical Properties, Steam Hose and Hot Air Ducts

Steam has been driving American industry for nearly 300 years. In order to properly harness steam, methods of transferring it needed to be developed. Steam hose, pipes and hot air ducts were in turn made to accommodate this new power source. One of the applications of flex ducting is to move gases from one medium to the next. The pressure and temperature of such gases will vary, thus needing different hoses for different materials. When performing a steam venting, removal or addition from one area to another, it is important to use the appropriate hot air ducts. For example, a steam removal using an incorrect steam hose can be both dangerous and inefficient. The best way to prevent accidents from happening is to understand the nature of steam and the different flexible hoses that help in the process of transferring it.

Basic Chemistry
Steam is the term used to describe H2O in its gaseous phase. Basic chemistry states that matter can take four different forms, often referred to as states. The four states matter can take are solid, liquid, gas, and the lesser known fourth phase of plasma. A change in the state of a molecule is called a physical change, as the chemical composition of the molecule does not alter in any way. For example, when we look at the different phases of the molecule H2O, we have ice when solid, steam when gaseous, and water when liquid.

What is Steam?
In its liquid state, water and its H2O molecules are constantly being joined together and separated. The molecules are constantly in a state of passing their oxygen and hydrogen subparts to neighboring molecules. When the liquid water molecules are heated the bonds connecting them start breaking more rapidly than they can form. As the temperature of the liquid state goes up, some molecules will break free. These free molecules form the gaseous state known as steam. Steam gas forms at 100 °C (212 °F) at standard temperature and pressure. But at the top of high mountains water boils at a lower temperature and pressure.

Wet & Dry Steam
Industrial uses of steam segregate it as two varieties: Dry Steam (also called saturated steam) and Wet Steam. Wet steam applies to steam when a portion of its water molecules have given up their energy and condense to form tiny water droplets. Dry steam applies to steam when all its water molecules remain in the gaseous state. This is not sufficient to change its energy appreciably, but is a sufficient rise in temperature to avoid condensation.

Steam and Industry
Steam played a vital role in the industrial revolution since it was one of the major sources of energy and power. The modernization of the steam engine in the early 18th century led to major breakthroughs such as the invention of the steam locomotive and the steamboat. Innovations such as the steam furnace and steam hammer quickly followed, paving the way for the more modern internal combustion engine.
Steam power has and continues to be an important energy source for industrial applications. Water, itself a valuable resource, when heated to steam in power plants, uses the pressurized steam to drive turbines to produce an electrical current. The thermal energy of steam is thus converted to mechanical energy, which in turn is converted into electricity.

A steam hose can carry a temperature of up to 450° F, with short-term spikes that can go much higher. The temperature of the steam in a steam engine will vary with the pressure of the steam; the higher the pressure, the higher the temperature that the steam headers (pipes) will run at. Since pressure varies between steam engines, temperature will also vary. Those temperatures could be from between 300° to 400° F on up to 700° to 800° F, depending on the actual pressure the boiler is running at.

Construction of Flexible Hoses that Carry Steam
Stainless Steel
"SSti-Flex 1650" Stainless Steel Hose
"SS-Flex 800" Stainless Steel Hose
A stainless steel hose will range in types and depending on the grade of stainless, the steam duct can handle temperatures up to 800° F or 1650° F. Stainless hoses are more rigid than other types of hoses but still maintain their shape when flexed. This greatly reduces installation costs associated with use, since other parts are not needed. Stainless steel hot air ducts are lightweight and bendable, allowing for elbows and turns to be formed easily during installation. Although stainless flexible hoses are not recommended for continuous flexing. The self-supported construction allows for bends to stay in place. Another benefit of a stainless steel steam hose is that it will resist weathering and moisture, making for a steam duct that can handle any industrial environment.

Neoprene and Hypalon Coated Hoses
"Spiral-Lock (Neoprene) 250" High Temperature Duct
"Spiral-Lock (Hypalon) 275" High Temperature Duct
When budgets are limited, a more flexible hose is needed, the application and installation are not permanent, and if temperatures are below 275° F, then Neoprene or Hypalon coated flexible hoses should be considered. These are classic exhaust hoses that are used in industrial steam removal applications because they are durable. Both flex ducting hoses have a metal strip on the outside that acts as a wear-strip and offers excellent resistance to external abrasion. In addition, these two elastomers offer increased chemical resistance to specific compounds and fumes.

Silicone Flex Ducting
"Silico-550 Insulated" Flexible Insulated Duct
"Silico-550 Single Ply" High Temperature Hose
Silicone hoses offer working temperatures of up to 500° F, making these hot air ducts a great option for any high temperature fume exhaust application, such as steam removal. Silicone hoses tend to be less flexible than their Neoprene counterparts, but far more flexible and better at handling flex fatigue than metal flex ducting. Silicone flexible hoses are resistant to many oils and solvents, ozone, water, fungus, and alkalis. In addition, these hoses are offered with insulation if the loss of temperature is a concern during the movement of the gas.

Potential Dangers of Using the Wrong Hose
When it comes to selecting the best steam duct for an application, the most common error that can occur is in the calculation of the temperature maximums. If the temperatures are higher than expected then the hot air ducts will fail and the gas may escape the line. It is always far more cost-effective to purchase a hose that can handle temperature spikes in the line. Other problems occur when the pressure that is applied to the hose exceeds its working pressure. Please check all specifications (hose and equipment) before making a commitment to a product.

When attempting to move either cold/hot materials or low/high pressure substances it is of the utmost importance to make sure that correct hosing is in place for this transfer. Various hoses are made from many different materials to ensure that venting/ducting projects are as safe as possible. While this article specifically highlights what is an acceptable steam duct/steam hose and the proper procedures associated with steam removal, it is always a good idea to seek more information specifically related to your ducting project.