IAEA 2007 PLIM(IAEA-CN-155/046) Relational equation between elongation and indent data based on ageing time of CSP and CR cable jacket 2007. 10. 16 KEPRI Jong-Seog Kim HL5JAA@kepri.re.kr 1/20
Why Condition Monitoring? Plant cables have 30~ 40 years life After 30~40 years, what do I have to do? Replace all of the plant cable because the lifetime is expired? IEEE383 suggests several methods for life extension Reduce conservatism after temperature monitoring of plant cable) Condition monitoring of actual aging degradation OIT, FT-IR, indenter and ultrasonic is used for non-destructive evaluation Indent methodology is one of condition monitoring programs 2/20
1. Introduction break-elongation elongation test according to ASTM D412 has been widely used for the life evaluation of cable it is not easy to apply this method to the cable of operating NPP Dumbbell specimen from plant cable is needed for break-elongation test One of alternatives is indenting test which non destructively measures the aging of cable jacket Relational equation is needed to use Indent data instead of Break- elongation data Need comparison of two data since indent method is not a standard method We decided to develop relational equation between elongation and indenting CSP and CR cable jacket is used for relational equation between elongation and indenting 3/20
2. Test Method(1/5) Accelerated aging Electric ovens shown on Fig. 1 was used for accelerated aging of cables Dumbbell specimens for elongation test and 100mm long cables for indenting test were prepared Accelerated aging during 48hours, 72hours, 96hours, 168hours and 164hours at the each temperature of 116, 126, 136 and 146 Air cooled for 24 hours after finishing the accelerated aging Break-elongation elongation test Destructive aging evaluation method which measures the elongation length after elongates aged dumbbell specimens until they are broken Dumbbell specimens in accordance with ASTM D412 Die C dimension Speed of 500±50mm/min during break-elongation test Used specially designed machine which can elongate 5 cable specimens at one time as shown on Fig. 2 4/20
2. Test Method(2/5) 1 body plate of upper specimen grips 2 upper specimen grip 3 lower specimen grip 4 load cell Fig 2. Cable elongation tester Computer screen of Break-elongation test Fig. 1 electric Heating Chamber 5/20
2. Test Method(3/5) Indenting test Indenting test is non destructive aging evaluation method which measures the hardness of cable by pressing a cable surface with steel probe at the vertical direction Portable cable indenter as shown on Fig.3 was used for this test Composed of cable clamp assembly, probe, load cell assembly, PDA, replaceable Li-Ion Battery 2mm round and 0.56mm edge of truncated con type probe was used for indenting Pressing load was limited to 0.5kg f to protect damage of cable jacket Indenting depth didn t go over 0.7mm for every cable specimens Fig.4 shows deviation-speed curve for various type of probes 0.56mm flat edge probe and moving speed of 0.031 mm/sec were chosen for best accuracy Fig. 5 shows detail of indent probe. 6/20
2. Test Method(4/5) Fig. 3 Portable cable indenter Internal part of indenter 7/20
2. Test Method(5/5) 0.56con mean cone type probe of 0.56mm flat edge, 2.0ball mean ball type probe of 2.0mm ball edge. Fig. 4 Deviations of modulus according to the probe types and speeds Fig. 5 Truncated cone type probe 8/20
3. Test Result Break-elongation for aging time of CSP cables Indent modulus for aging time of CSP cables Break-elongation for aging time of CR cables Indent modulus for aging time of CR cables 9/20
4. Relation between Elongation and Modulus(1/3) Elongation - modulus for CSP cables(116 ) Elongation - modulus for CR cables(116 ) Elongation - modulus for CSP cables(146 ) Elongation - modulus for CR cables(146 ) 10/20
4. Relation between Elongation and Indent depth(2/3) Elongation & indent depth for CSP cables(116 ) Elongation & indent depth for CR cables(116 ) 11/20
4. Relation between Elongation and Indent depth(3/3) Relation between elongation and indent modulus Aging rate in elongation test is break-elongation rate which comes from length of aged specimen divided by that of un-aged specimen Indent modulus is a value which comes from the indent load divided by depth Elongation rate and indent modulus have reverse linear relationship Relation between elongation and indent depth Elongation length is elongation length at break point Indent depth is the value at the designated indent load Elongation length and indent depth have proportional linear relationship 12/20
5. Relational Equation between Elongation-Indent(1/2) e/ e= 3.9E 6( P/ d ) 0 t 2.5 2.57 e= 310( h t ) Fig. 9 Relation between elongation & modulus for CSP Fig. 11 Relation between elongation & indent depth for CSP e/ e= 2.2E6( P/ d ) 0 t 2.14 ee = 5 2 0 ( h t ) 1.9 6 Fig. 10 Relation between elongation-modulus for CR Fig 12 Relation between elongation-indent depth for CR 13/20
5. Relational Equation between Elongation-Indent(2/2) Elongation and indent data have proportional relation Fig. 9 and Fig. 10 show relationship between elongation rate and indent modulus for CSP and CR cables aged at 116, 126, 136 and 146 during 48, 72, 77, 88, 93, 94, 96, 168, 264, 312 hours Fig. 11 and Fig. 12 show relationship between elongation length and indent depth for CSP and CR cables Relational equations between elongation and indent are described as equation (1) ~ (4) (1) Elongation-indent modulus for CSP cable : (2) Elongation-indent modulus for CR cable : (3) Elongation-indent depth for CSP cable : (4) Elongation-indent depth for CR cable : e/ e= 3.9E6( P/ d ) 0 e / e = 2.2E6( P / d ) 0 2.57 e= 310( h t ) 1.96 e= 520( h t ) t t 2.5 2.14 14/20
6. Review of Relational Equation Analyzed deviation between actual data and equation data Deviation of indent modulus and indent depth for CSP and CR cables are described on table 1 14.6% average deviation for CSP cable and 10% average deviation for CR cable at the equation of elongation rate and indent modulus is observed 9.2% average deviation for CSP cable and 7.9% average deviation for CR cable at the equation of elongation length and indent depth are observed Equation for indent depth and elongation length had better accuracy than that of indent modulus and elongation rate Table 1 Deviation of elongation corresponding to modulus and indent depth CSP Cable CR Cable Deviations of Indent Modulus Related 18.87mm(14.6%) 12.97mm(10%) Deviations of Indent Depth Related 11.84mm(9.2%) 9.87mm(7.9%) 15/20
7. Comparison of Activation energy(1/2) Activation energy (ev) at 50% break-elongation rate(%) and indent modulus rate(%) Activation energy by elongation - modulus for CSP Activation energy by elongation - modulus for CR 16/20
7. Comparison of Activation energy(2/2) Instead of selecting a data at 50% break-elongation elongation rate for the calculation of activation energy, we compared activation energies of every 5% 5 decrement for break-elongation elongation rates and every 5% increment for indenter modulus For the CSP cable jacket 0.885ev at 50% break-elongation rate were showed 0.962 ~ 0.945ev at indenter modulus increasing rate of 15% ~ 25% Indenter modulus showed 1.08 times value of break-elongation For the CR cable jacket 0.793ev at 50% break-elongation rate were showed 0.8 ~ 0.809ev were showed at modulus increasing rate of 30% ~ 40% Indenter modulus showed 1.01 times value of break-elongation 17/20
Relational equations between elongation and indent were obtained Coefficients in the equation were different according to the material type Good convergence was observed when indent depth was used as equation factor instead of indenting modulus 8. Conclusion It was verified that elongation data can be delivered by indent data if we had enough amount of experiment result for various material type Activation energy can be calculated by using indent methodology if cable is composed of relative hard material like CR cable jacket Indent methodology will be useful to evaluate the aging condition of plant used cable without destructing the operating cables 18/20
9. Lessons learned and future plan Lessons learned during life extension of used cables in Kori-1 1 NPP Natural ageing of 30 years was not severe than expected Radiation ageing does not give severe damage to electric insulation resistance(ir) ) of cable if DBA does not follow it Actual ohm heat of power cable was not severe as they did during g EQ test Ageing of plant cable will not be severe if it is not heated continuously (Polymer material has recovering character during rest time depend on material type) Future plan of cable condition monitoring New project will be started for non-destructive cable aging diagnosis(2008. 4 ~ 2010. 6) Have a plan of developing automatic indenting mini robot during this project 19/20
Thank you!!! 20/20