Water droplets (moisture) traveling at steam velocities erode valve seats and fittings leading to leaks. Install moisture separators to maintain dryness of steam.

Wet steam is steam containing a degree of water, and is a concern as it reduces plant productivity and product quality, and causes damage to most equipment. Water droplets traveling at high steam velocities will erode valve seats and fittings, a condition known as wiredrawing. The water droplets will also increase the amount of corrosion.

While careful drainage and trapping can remove most of the water droplets, it will not remove the water droplets suspended in the steam. To remove these suspended water droplets, moisture separators are installed in the steam pipelines.

As a general rule, provided the velocities in the pipework are within reasonable limits, separators will be same as the line size.

* Moisture separators are especially effective and a must for coil type (NIBR) boiler which by design have a dryness fraction of 80% against 98% for shell type boilers.