Qualification of the Inclined Fuel Transfer Machine Chain Based on Fatigue and Break Load Test

Abstract

Certain surface defects of significant depth with maximum linear indication of 20mm at the weld area have been observed during Liquid Penetrant Inspection (LPI) of the Inclined Fuel Transfer Machine (IFTM) welded chain. The same has been subjected to fatigue and break load testing to ascertain its structural integrity under service conditions. Two specimens have been subjected for testing to get repeatable experimental observations. Both the specimens tested for the required number of fatigue cycles (97000 cycles as per ASME, Mandatory Appendix 6) towards the structural integrity demonstration. At the end of fatigue testing, the maximum linear indication of the surface defect of the weld area increased from 20mm to 25mm without any loss of integrity. Individual links of both the chains were able to articulate freely after completing the fatigue test. After completing the required fatigue cycle both the specimens were subjected to break load testing. The lowest break load obtained from both the specimen was 27.1t and the respective collapse load obtained as per the ASME double slope method was 22 t. The above results indicated that, IFTM chain assembly qualifies for the safety with very high margins. Also, these experimental results give confidence that, collapse load obtained by the ASME double slope method is having a very high margin (∼ 18%) with the actual break load. Finite element analysis has also been performed before conducting the experiment to understand the overall stress distribution of the chain under load condition and also to identify the critical location. The critical location predicted by FE analysis was in good agreement with the experimental results.