Prevent attemperator overspray damage with FLEXIM flow measurement

Attemperation is a critical process related to steam generation for steam turbines. It is achieved by spraying liquid water into a steam flow which lowers the temperature of the steam by means of evaporation of the water. Typically, fleet spray water lines operate with a block valve and temperature control valve combination. It is critical that the attemperator is providing the intended cooling effect, however, it is equally as important that water is not sprayed into the attemperator piping when it is not required. Wear on the block valve can lead to leak-by – which has detrimental effects on the attemperator, internal liner, steam piping, turbines, valves and surrounding components.

The FLEXIM flowmeter on the attemperator spray block valve is an ideal solution because it provides valuable information for monitoring, control, optimization, troubleshooting, and safety considerations of the attemperator spray system. It enables operators to maintain efficient operation, diagnose problems, and ensure the safe functioning of the system.

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Case Study

Combined-cycle power stations are characterized by relatively high energy efficiency and are capable of operating flexibly. As a result, CCP stations are helping to drive the energy transition. However, this flexible mode of operation can present challenges for operators.

At a large U.S. power producer, several cracks had been discovered on the HP attemperator spray lines, due to the attemperator spray water block valves developing undetected leak-by. The leak-by led to severe quenching of the steam pipe which eventually caused thermal fatigue cracking. The existing DP flow transmitters were unable to detect the leak-by, particularly when the fluid flows were low, as they are designed for relatively high flow under normal operation. In addition, when these plants are operating in low load conditions and during start-up and shutdown, the potential of tube stress is higher. This, in turn, means the risk of long-term damage is higher which is extremely costly for the plant.

Site engineers began to look for a solution that would determine when these block valves were starting to degrade. FLEXIM’s FLUXUS F601 ultrasonic flowmeters were installed on the HP and RH attemperator spray lines to evaluate flow detection effectiveness. The FLUXUS F601 flowmeter proved to have many advantages for this application. FLUXUS is able to capture the entire flow range and even leaks. It can replace the established DP flowmeter for process control purposes, providing reliable and continuous leakage detection. It is non-invasive which means it can be retrofitted easily without any process interruption, pipework, or subsequent inspection and documentation. There is no pressure loss and, therefore, no energy reduction. The non-invasive flowmeter does not come into any contact with the pressurized hot spray water which means there is no maintenance required. As a result, operating expenses are almost zero.

Since the installation of FLEXIM technology, the site engineers are now able to detect attemperator spray block valve leak-by and take corrective action to quickly repair these important service valves. Thanks to FLEXIM’s flowmeters, this US company can mitigate damage to their HRSG pressure parts ensuring lower replacement cost, more reliable unit operation, and avoiding unplanned downtime at all costs.

RH Attemperator Spray Line

FLEXIM Installed

The client is extremely satisfied with FLEXIM’s technology for spray water valve monitoring. They decided to equip their RH and HP spray water lines with permanent devices to continuously measure the flow for process control and monitor leakage. They are now moving towards installing FLEXIM technology on their entire CCGT fleet. Once again, FLEXIM has proven to be the ideal solution.