• 屠呦呦与青蒿素 Tu & Arteannuin
  • 石油化工创新简史 A Petrochemistry History
  • 芳烃-改善人们生活 Aromatics Improving the Quality of Your Life
  • 百折不饶聚氨酯 Polyurethene: the Strength of Flexibility
  • 百变百丽有机硅 Silicone: the Art of Flow
  • 氯 这玩意儿 Chlorine Things


  • 强氧化剂的危害
  • 空气的威力
  • 为什么我打不开那个阀门?
  • 氮气的危险及防范
  • 物料错误混装的危害
  • 管帽和堵头-最后的防线
  • 软管破裂泄漏
  • 蒸气云爆炸
  • 危险物料的储存与运输
  • 沸腾液体膨胀蒸气爆炸(BLEVE)
  • 化学品危害性分类与标识
  • 化学品危害性其它标识方法
  • 化学品燃爆反应危害及防范
  • 化学品失控反应危害与防范-失控聚合-苯乙烯
  • 化学品失控反应危害与防范-失控聚合-丙烯酸及酯
  • 化学品遇水反应危害与防范-硅烷
  • 化学品失控反应危害与防范-失控分解-有机过氧化物
  • 工作场所危害与防范-蒸汽
  • 工作场所危害-登高作业

Steam - The Energy Fluid

Steam provides a means of transporting controllable amounts of energy from a central, automated boiler house, where it can be efficiently and economically generated, to the point of use. Therefore as steam moves around a plant it can equally be considered to be the transport and provision of energy.

For many reasons, steam is one of the most widely used commodities for conveying heat energy. Its use is popular throughout industry for a broad range of tasks from mechanical power production to space heating and process applications.

蒸汽 载能流体



Other methods of distributing energy

The alternatives to steam include water and thermal fluids such as high temperature oil. Each method has its advantages and disadvantages, and will be best suited to certain applications or temperature bands.

Compared to steam, water has a lower potential to carry heat, consequently large amounts of water must be pumped around the system to satisfy process or space heating requirements. However, water is popular for general space heating applications and for low temperature processes (up to 120°C) where some temperature variation can be tolerated.

Thermal fluids, such as mineral oils, may be used where high temperatures (up to 400°C) are required, but where steam cannot be used. An example would include the heating of certain chemicals in batch processes. However thermal fluids are expensive, and need replacing every few years - they are not suited to large systems. They are also very ‘searching’ and high quality connections and joints are essential to avoid leakage.




需要高高温时(上达400),而又不能使用蒸汽的情况下,可以使用热流体,例如矿物油。 常见实例如批量生产工艺中加热某些化学品等。然而,热流体比较昂贵,并且需要每几年更换一次 同时也不适合大型系统。油料“见缝即钻”和必须采用高质量的连接件和接头,以避免泄漏。

The final choice of heating medium depends on achieving a balance between technical, practical and financial factors, which will be different for each user.

Broadly speaking, for commercial heating and ventilation, and industrial systems, steam remains the most practical and economic choice.




At this point it has reached boiling point or its saturation temperature, as it is saturated with heat energy.

If the pressure remains constant, adding more heat does not cause the temperature to rise any further but causes the water to form saturated steam. The temperature of the boiling water and saturated steam within the same system is the same, but the heat energy per unit mass is much greater in the steam.

At atmospheric pressure the saturation temperature is 100°C. However, if the pressure is increased, this will allow the addition of more heat and an increase in temperature without a change of phase.

Therefore, increasing the pressure effectively increases both the enthalpy of water, and the saturation temperature. The relationship between the saturation temperature and the pressure is known as the steam saturation curve.




Water and steam can coexist at any pressure on this curve, both being at the saturation temperature. Steam at a condition above the saturation curve is known as superheated steam:

• Temperature above saturation temperature is called the degree of superheat of the steam.

• Water at a condition below the curve is called sub-saturated water.





If the steam is able to flow from the boiler at the same rate that it is produced, the addition of further heat simply increases the rate of production. If the steam is restrained from leaving the boiler, and the heat input rate is maintained, the energy flowing into the boiler will be greater than the energy flowing out. This excess energy raises the pressure, in turn allowing the saturation temperature to rise, as the temperature of saturated steam correlates to its pressure.

At 100°C, the theoretical internal energy of the saturated liquid is 418.9 kJ/kg while the theoretical internal energy of the saturated vapor is 2506.5 kJ/kg.1  Thus, there is roughly six times more energy in a saturated vapor (steam) than there is in the saturated liquid!


100℃下,饱和液体的理论内能为418.9kJ / kg,而饱和蒸汽的理论内能为2506.5kJ / kg。因此,饱和蒸气(蒸汽)中的能量比饱和液体中的约高六倍!


Superheated Steam

If the saturated steam produced in a boiler is exposed to a surface with a higher temperature, its temperature will increase above the evaporating temperature.

The steam is then described as superheated by the number of temperature degrees through which it has been heated above saturation temperature.

Superheat cannot be imparted to the steam whilst it is still in the presence of water, as any additional heat simply evaporates more water. The saturated steam must be passed through an additional heat exchanger. This may be a second heat exchange stage in the boiler, or a separate superheater unit. The primary heating medium may be either the hot flue gas from the boiler, or may be separately fired.




Superheated steam has its applications in, for example, turbines where the steam is directed by nozzles onto a rotor. This causes the rotor to turn. The energy to make this happen can only have come from the steam, so logically the steam has less energy after it has gone through the turbine rotor. If the steam was at saturation temperature, this loss of energy would cause some of the steam to condense.

superheated steam is not as effective as saturated steam for heat transfer applications. This may seem strange, considering that the rate of heat transfer across a heating surface is directly proportional to the temperature difference across it.


过热蒸汽用于传热不如饱和蒸汽那么有效。这可能看起来难以理解,但想一下通过热表面的 热传导率与该表面的温度差是成正比的。


Why is steam so dangerous?

Because in order to turn water into steam (liquid to gas) it must be heated intensely past the point of boiling, therefore the resulting steam is obviously extremely hot. 

If you are referring to the danger of a catastrophic pressure vessel failure (boiler explosion) the danger comes from a three-pronged issue. Water under pressure will not boil at 212 degrees (100 C). As the pressure goes up, so does the temperature need to get the water to boil.

When a pressure vessel fails, there is the potential for an instantaneous drop in pressure from X pounds per square inches to ZERO psi. But the temperature of the water is (for example 350 degrees F) then without the pressure it will flash boil into steam. This is the theory of why locomotive boiler explosions were so deadly. It was common theory that when the firebox's roof sheet failed and the steam in the boiler evacuated into the firebox, the water flash boiler, instantly raising the pressure to 50 to 100,000psi.




当压力容器破裂时,其潜在危险即是压力从 X psi (/平方英寸) 瞬时下降到 0 psi。但是水温很高(例如180),突然失压,就会闪蒸成蒸汽。这就是为什么机车锅炉爆炸如此致命。通常理论认为,当燃烧室的顶板失效并且锅炉中的蒸汽排入燃烧室时,水在锅炉中闪蒸,可将压力提高到50100,000psi



When the water used to generate steam contains dissolved air, oxygen or carbon dioxide, then these gases end up as contaminants in the steam. At high temperatures of steam both oxygen and carbon dioxide are extremely corrosive.

Carbon dioxide is acidic and therefore attacks metals whereas the oxygen corrodes metals and oxidises rubbers. Corrosion of metals in the presence of both oxygen and acids is forty times faster than with either alone. Boiler water is therefore normally treated not only to remove thehardness” which would cause “furring” of the boiler but also to remove dissolved oxygen and carbon dioxide and to ensure that the steam is not only not acidic but even slightly alkaline. Boiler water treatment is a specialized subject to be covered in lengthy technical sheets but correct steam generation is important.




Like all rubber products steam hoses have a finite life and are subject to gradual deterioration with use.

Rubber steam hoses are oxidized and attacked by high temperature oxygen and acidic CO2 within Corrosive Steam.

Water or moisture residing on surface and texture of inner wall of rubber steam hoses will be heated up by steam passing by and expands into vapour bubbles and break, which will crack the surface of inner wall of rubber steam hoses.

Steam hoses are mostly used at chemical and petrochemical plants. These factories and plants have aggressive atmospheres with substances such as chlorine and salt. Also, industrial hoses for steam are being dragged and used by workers in a dynamic, rough way.

These effects may result in a “popcorning” finish of rubber steam hoses sooner or later.








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