Failure Analysis and Salvaging of Bellow-Sealed Sodium Valve
- PDF / 1,470,750 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 99 Downloads / 169 Views
TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis and Salvaging of Bellow-Sealed Sodium Valve S. C. S. P. Kumar Krovvidi . P. Madankumar . S. Chandramouli . S. I. Sundarraj . B. K. Sreedhar . R. Mythili . P. Parameswaran . B. K. Nashine . S. Raghupathy . A. K. Bhaduri
Submitted: 30 June 2020 ASM International 2020
Abstract Valves with conventional gland packing seals are not suitable in high-temperature sodium systems. Bellow-sealed valves are used in sodium systems in which bellows are used as primary leak tight barrier. Bellows are made up of very thin gauge material, and hence, most of the failures in the bellow-sealed valves are due to failure of the bellows. The cost of the bellows is typically \ 20% of overall cost of the valve. This paper discusses the failure analysis of the bellows in a failed bellow-sealed sodium valve and reconditioning of the same by replacing the failed bellow with new and improved bellows. Initially, sticking sodium from the internal surfaces of the valve was cleaned using alcohol. Subsequently, the failed bellows were disassembled from the valve and a detailed failure analysis was carried out. New and improved bellows were designed initially as per Expansion Joint Manufacturer’s Association (EJMA). The geometry arrived as per EJMA was further analyzed using visco-plastic constitutive model to obtain the creep–fatigue life of the bellows. The inputs from the failure analysis were considered while evolving the new and improved design of the bellows. The bellows were tested and qualified at high temperature and installed in the bellow-sealed valve. Integral testing of the valve was carried out using pressure hold testing and helium leak testing. The valve was reconditioned for further use in sodium services.
S. C. S. P. Kumar Krovvidi (&) P. Madankumar S. Chandramouli S. I. Sundarraj B. K. Sreedhar R. Mythili P. Parameswaran B. K. Nashine S. Raghupathy A. K. Bhaduri Indira Gandhi Centre for Atomic Research, Kalpakkam 60312, India e-mail: [email protected]
Keywords Bellows Bellow-sealed valves Sodium systems Failure analysis EJMA Finite element analysis High-temperature testing
Introduction In sodium systems, conventional gland packing-sealed valves are not suitable for primary sealing due to high temperature and high chemical reactivity of sodium. Bellow-sealed valves are used in sodium systems [1] in which metallic bellows are used as primary leak tight barriers to prevent the leakage of sodium from the space between the bonnet and the actuating stem. Figure 1 shows the schematic of a bellow-sealed sodium valve, and Fig. 2 gives the bellow-sealed sodium valve used in sodium systems [2, 3]. The important parts of the bellow-sealed valve consist of valve body, bonnet, stem, bellows and actuating mechanism. The valve body houses the seat and the valve body is welded to the sodium piping. The bottom end of the stem consists of the plug. The stem passes through the bonnet and is connected to the actuating system through a coupler. Bellows are welded
Data Loading...
