SLIDE 1
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2 ¡
- 1. Current standards
- 2. Material aspects
§ Cement § Purity of glass § Molding and toughening
- 3. Type and sample tests
§ Residual strength test § Steep front wave § RIV
- 4. Recommendations
Necessary check points & testing for quality screening of - - PowerPoint PPT Presentation
Necessary check points & testing for quality screening of - - PowerPoint PPT Presentation
Necessary check points & testing for quality screening of insulators J.M. GEORGE INMR 2017 Barcelona, Spain 1 Summary 1. Current standards 2. Material aspects Cement Purity of glass Molding and toughening 3. Type and
SLIDE 2
SLIDE 3
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- 1. Current standards
- 2. Material aspects
§ Cement § Purity of glass § Molding and toughening
- 3. Type and sample tests
§ Residual strength test § Steep front wave § RIV
- 4. Recommendations
Summary
SLIDE 4
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Type tests
SLIDE 5
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Sample and routine tests
SLIDE 6
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- 1. Current standards
- 2. Material aspects
§ Cement § Purity of glass § Molding and toughening
- 3. Type and sample tests
§ Residual strength test § Steep front wave § RIV
- 4. Recommendations
Summary
SLIDE 7
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Typical chemistries of cements. Mortars which are being used with these cements mixed with other additives have approximately 40% of CaO for Portland and at least 30% of Al2O3 for Aluminous cement assemblies
Cement
SLIDE 8
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Cold cured aluminous cement generates unstable hydrates while the conversion is done during the curing process if it takes place in hot water
Conversion process
SLIDE 9
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Purity of glass
Impurities in glass have different origins among which but not only particles from the refractories of the furnace. Numerous other origins have been identified by Sediver in extensive research which started in the early 1980s
SLIDE 10
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Toughening is a precise operation in the process. « More is better » is a wrong statement leading to improper toughening
Toughening and moulding of glass
SLIDE 11
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- 1. Current standards
- 2. Material aspects
§ Cement § Purity of glass § Molding and toughening
- 3. Type and sample tests
§ Residual strength test § Steep front wave § RIV
- 4. Recommendations
Summary
SLIDE 12
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Residual strength test is a critical evaluation process. It needs to be done with thermal preconditioning cycles having a hot temperature around 85°C. This will help pointing out low performance of cold cured aluminous cement
Residual strenght test
SLIDE 13
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Steep front wave test
CSA type test protocol includes a thermo-mechanical preconditionong prior to steep front test
SLIDE 14
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Some manufacturers apply coatings on the cement to improve artifically their RIV performance. After several hours in an environment where dry band arcing exist the performance is severely degraded.
RIV
Before and after 20h at 10g/l of salt fog: the RIV coating is gone and RIV performance is degraded.
SLIDE 15
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Very low quality cap contact on the dielectric can lead to corona and generate corrosion
Cap gap
Flock application at the base of the cap is the preffered solution Low quality insulators are using a plastic ring at the base of the cap which typically will be destroyed
- vr time and service conditions
new After some time in service conditions
SLIDE 16
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- 1. Current standards
- 2. Material aspects
§ Cement § Purity of glass § Molding and toughening
- 3. Type and sample tests
§ Residual strength test § Steep front wave § RIV
- 4. Recommendations
Summary
SLIDE 17
17 ¡