SWAS means Steam and Water Cycle Analysis, Today in power plants, high pressure boilers and steam turbines are under constant attack from erosive and corrosive elements such as Silica, Sodium, Dissolved Oxygen, Calcium, Chloride and Phosphates. Without accurate measurement and monitoring, the plant may suffer heavy mechanical damages that can be caused due to imbalance of turbines, reduced efficiency, deposition on turbine blades, corrosion of steam pipe work and so on. The SWAS sampling system shall obtain samples from steam and water pipelines which shall be adequately conditioned and flow through water analyzers for continuous analysis and provide parallel facility for grab sampling.
The key to plant safety in today’s environment is on-line analysis of steam and water at different points in the power plant steam cycle, some of most important analysis are;
- pH
Analysis of pH helps detect changes that impact the effectiveness of closing and potential corrosion of the boiler tubes. - Conductivity
Provides an indication of total dissolved solids and susceptibility to scaling. - Dissolved oxygen
Monitoring of dissolved oxygen level helps to keep the corrosion in check as, dissolved oxygen analysis help to monitor the efficiency of the deaerator. - Silica
Silica volatizes in steam and it is carried into the turbine. Although the silica deposits are not corrosive, but they severely reduce the efficiency. - Hydrazine
It works as an oxygen scavenger, destroying traces of dissolved oxygen. Hydrazine is also passivating agent and produces a protective oxide coating on metal tube wall.
Steam Sample Points and Analysis Locations in Power Plants
Steam and Water Analysis System (SWAS) are designed for continuous monitoring and control of water and steam purity in the boiler plant cycle and at other important analysis points.
The analyser outputs signals shall be used for continuous monitoring of various parameters like analysis of pH, Specific Conductivity, Cation Conductivity, Degassed Conductivity, Sodium, Silica, Dissolved Oxygen, Phosphate, Chlorides, TOC etc.
In the steam boiler cycle of power plants we find the following locations for monitoring and control the steam and water samples;
- Demi Water
- Feedwater
- Condensate
- Boiler Water
- LP Drum Water
- LP/IP/HP Steam
- Life Steam
- Saturated Steam
- Superheated Steam
- Reheated Steam
- Main Steam
- Feedwater