Steam is often viewed as a pure vapor—but in reality, it can carry unwanted contaminants that jeopardize system performance and reliability. Even in well-designed boiler systems, dissolved and suspended solids in boiler water can be entrained in the steam and carried downstream. This phenomenon, known as carryover, can lead to significant operational challenges, including corrosion, scale buildup, and reduced efficiency in critical components like turbines, superheaters, valves, and process equipment.
Understanding Carryover and Its Causes
Carryover is the unintended transfer of boiler water impurities into the steam phase. These impurities, if not properly controlled, can deposit on internal surfaces of downstream equipment, leading to:
- Equipment damage
- Reduced thermal efficiency
- Costly downtime
- Poor process and product quality
Carryover typically arises from two root causes:
- Mechanical causes, such as poor boiler design or malfunctioning separators
- Chemical causes, often due to imbalanced water chemistry or overconcentration of solids
Even high-efficiency steam generators equipped with modern separation equipment can deliver 20–50 parts per billion (ppb) of impurities under normal operating conditions. Mechanical issues or chemical imbalances can push these levels significantly higher.
Why Monitoring Matters
Accurate and proactive monitoring of steam purity is essential to identify and mitigate carryover before it escalates. By selecting the right monitoring tools, facilities can maintain system integrity, improve equipment life, and avoid unplanned shutdowns. Two common methods are used based on the required steam purity level:
1. Sodium Ion Analysis: Precision for High-Purity Systems
Best for: High-pressure applications, including systems with steam turbines.Sodium ion analyzers use ion-selective electrodes—similar to pH probes—to measure sodium concentrations in condensed steam with remarkable sensitivity. They can detect sodium levels as low as 0.1 ppb, making them ideal for applications where even minimal carryover poses a risk.
Benefits:
- High precision for detecting slight carryover (<1 ppm sodium)
- Useful in protecting sensitive equipment like turbines
Limitations:
- Higher initial investment
- Fixed monitoring ranges (0–1 ppm, 1–10 ppm, 10–100 ppm)
- Slower response time
- Requires frequent maintenance and calibration
While highly accurate, sodium ion analyzers are generally reserved for specialized applications where minimal carryover can have significant consequences.
2. Low-Level Conductivity Monitoring: Cost-Effective and Reliable
Best for: Conventional steam systems where gross carryover is a primary concern.
Low-level conductivity monitors provide a broader, more accessible solution. By establishing a baseline conductivity and monitoring for deviations, operators can quickly identify changes in steam purity.
Advantages:
- Fast response time
- Lower cost
- Minimal maintenance requirements
- Broad monitoring range
This method offers a practical approach to ensure steam quality across a wide range of industrial and commercial applications. It supports early detection of carryover events, helping teams take corrective action before serious damage occurs.
Choosing the Right Method for Your Facility
At Watertech of America, Inc., we believe that steam quality is a key driver of system reliability and operational efficiency. Our technical experts partner with customers to assess boiler performance and recommend tailored monitoring strategies based on system pressure, critical equipment, and purity requirements.
Whether your operation demands pinpoint accuracy or a broader, cost-effective solution, Watertech provides the expertise, equipment, and service to safeguard your steam system from the risks of carryover.
Ready to improve your steam system performance?
Let’s start with a site evaluation. A Watertech Technical Engineer will assess your current monitoring approach and recommend a strategy designed to protect your assets and maximize uptime.
