Steam is a gas formed when water converts from liquid to gaseous state. Wet steam is a mixture of liquid water and steam. Wet steam contains liquid droplets that have not changed its phase. Dry steam must be used for heating applications for better product quality. Dryness fraction of steam should be as high as 97-98%.

Wet Steam

Dryness fraction of steam is weight of steam to weight of steam & moisture present along with steam and it is used to quantify the amount of water present in the steam. Dryness fraction of steam is important as it has the direct impact on the total amount of transferable energy present within the steam, which directly affects heating efficiency and product quality.


  • SCALING AND CORROSION – If water present in the boiler contains any impurities, as water evaporates it leaves back the impurities within the drum. These impurities form an insulating layer in the boiler that is called scale. These impurities present in boiler along with moisture droplets damage the steam systems by corroding it and also the impurities present in water droplets leads to scale formation.
  • EQUIPMENT DAMAGE – Wet steam can cause damage to process equipment and other accessories. It is advisable to use dry steam as wet steam can cause severe losses and unavoidable damage.
  • WATER HAMMER- Wet steam can enhance the chances of water hammer. Water hammer can result due to the presence of both steam and condensate in piping. To minimize the presence of condensate in piping we need to avoid wet steam.
  • REDUCED EFFICIENCY – Presence of water in steam can lead to reduced heat transfer & reduced efficiency. As we know thermal conductivity of water is much lower than of steam. This will result in less heat transfer & uneven product heating.
  • EROSION OF PIPING & CRITICAL equipment- Wet steam can also cause erosion of equipment such as turbine blades, piping etc. It is highly recommended to take some preventive measures such as using steam traps, steam separators to remove entrained condensate.

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