Cruas Nuclear Solves Erosion Problems

Cruas Nuclear Generating Station recently had to replace its moisture separator and reheater drain valves with one CCI globe valve. It was due to process conditions that the existing valve was experiencing erosion, requiring body replacement every ten years. Cruas also had to replace the valve trim every five years, since it was severely eroded as well.

Body erosion can be a typical problem in severe service control valve applications, oftentimes caused by the usage of incorrect technology. Other problems include premature trim as well as poor shutoff capability, i.e. leakage through the valve when closed, poor control and/or poor dynamic response. Such inferior performance can cost the plant revenue due to wasted energy and lost power production. Having the correct technology for the use of severe service valves is a must if such losses are to be eliminated.

In the case of Cruas, they combated their erosion problems by replacing their problem with a CCI DRAG® 100D globe valve, similar to the one installed in 1991. This valve is 3- x 3-in (76- x 76-mm), with design pressures up to 1100 psig (76 BarG), and temperatures up to 296 F (147 C). With a mass flow rate of 240,000 lbm/hr (109 mt/hour), this valve also has a differential pressure of 1090 psig (75 BarG). The design of the DRAG® 100D is specialized in that it’s custom-designed to provide years of uninterrupted service, made possible with the DRAG® velocity control design. It can also provide for the elimination of leakage and unwanted trim erosion with tight shutoff. Such superior service has been proven with the installed CCI valves that have been in service since 1990. Upon recent dismounting, an inspection confirmed that there was no damage to the main or pilot plug. There was also no erosion to the disk stack, thus Cruas did not have to perform costly maintenance of any kind to this valve.

Published in SOLUTIONS Fall 2001