Third Party Inspection for Electrical Insulator - Procedure

The Third Party Inspection for Electrical Insulator article is a sample procedure for electrical insulator testing and electrical insulator inspection in the manufacturing shop.

You may need to review this article in conjunctions of following article:

Inspection and Test Plan for Electrical Insulator

This content guides you about all necessary stages in the production of the Electrical Insulators from the examination of raw material to the final inspection, preservation and packing to despatch to site.

You need to take this point in account this article is written for a typical Electrical Insulator and might not be detail for special cases.

This content may be useful for second party inspectors, Electrical Insulator manufacture quality control personnel, engineering companies and purchasers as well.

All Electrical Insulator inspections and tests are carried out against the approved drawings, purchase order specifications, purchasers or company standards, and within the practices and rules of the country, state or province and any government decrees, laws, ordinance or regulation as may apply.

The applicable codes and specifications for the Electrical Insulator which is under construction process are:

Design code
Purchase order specification
Purchaser's standards
Approved drawings

The applicable codes and standard may be based any international standards. This content is general and can be useful for all recognized standards.

Required Documents for Third Party Inspector Review

The list of documents normally is agreed in the Pre Inspection meeting which is hold several weeks before actual commencement of inspection work. The parties which are participated in this meeting are manufacture, purchaser and third party inspection agency representatives.

This already explained in the Inspection and Test Plan for Electrical Insulator article.

These are the list of documents which are normally agreed to be presented to the inspector:

Electrical Insulator Purchase Order or Contract
Electrical Insulator Manufacture Quality Control Plan
Electrical Insulator Inspection and Test Plan
Electrical Insulator Data Sheet
Electrical Insulator Approved Drawings, (arrangements, schematics, wiring, single line)
Electrical Insulator Material Test Reports
Electrical Insulator Calibration Certificates for Test Equipment
Electrical Insulator Special Procedures
Electrical Insulator Special Qualifications
Electrical Insulator Preparation and Painting Procedure
Electrical Insulator Preservation, Packing and Shipping Procedure
Electrical Insulator Packing List

Third Party Inspection for Electrical Insulator -Material Inspection

The first actual inspection work in the Electrical Insulator is raw materials inspection.

The original or authenticated copies of mill certificates of material normally are available at manufacturer's premises.

The third party inspector examines these certificates for compliance with specifications and where appropriate, drawings.

The review includes checks on:

Maker’s name and location
Certificate number, grade
Batch number
Chemical composition
Cast number (for metal parts)

Ancillary items may be supported by test certification, or by certificates of conformity. It is necessary the content of certification to be appropriate to the required scope of the items.

Then the inspector witnesses the materials identification on the certificates against materials marking. It is also necessary to check with Electrical Insulator drawing datasheet, material list and other specification as appropriate.

When the third party inspector carried out the material inspection, then provides inspection visit report (IVR), the report contains following items:

Confirmation of satisfactory document review
Record of the endorsement of certification reviewed/witnessed
Record of all non-conformities
Record of any tests witnessed and the result

Third Party Inspection for Electrical Insulator - Construction

When Electrical Insulator raw material inspection carried out and results was satisfactory or non-conformities closed by remedial action, then Electrical Insulator manufacture will start construction.

The third party Inspector checks following points on Electrical Insulator based on the inspection and test plan (ITP) which is already agreed between purchaser and Electrical Insulator manufacture.

The inspection scope is determined in the ITP, some purchasers prefer to have stringent control and assign the TPI inspector in more “hold or witness points” for inspection and test activities and some others prefer lesser “hold or witness points” and assign TPI much more in the “review document”.

This depend to the inspection budget which purchasers assign for inspection, much more inspection will have much more costs and less risks and conversely less more inspection will have less costs but more risks.

For more detail review Inspection and Test Plan for Electrical Insulator article. There is draft ITP in this article which I believe it is the best practice for Electrical Insulator inspection.

The third party inspector checks following items in Electrical Insulator construction process in accordance of approved drawings and applicable standards:

Plating and thickness measurement
Outline dimensions and interface dimensions

If third party inspector is not in the hold or witness point in the ITP for this test, then will review Electrical Insulator manufacture quality control test report in his/her coming visit or in final inspection day.

Third Party Inspection for Electrical Insulator General Arrangement

The third party inspector checks all parts are appropriate to correctly assemble to the required layout in accordance approved drawings.

Similarly If third party inspector is not in the hold or witness point in the ITP for this test, then will review Electrical Insulator manufacture quality control test report in his/her coming visit or in final inspection day.

Third Party Inspection for Electrical Insulator Dry Lighting Impulse Withstand Voltage Test

The Electrical Insulator is taken under condition specified in IEC and the impulse generator is adjusted to 1.2/50 wave. Impulse of both positive and negative are used.

There are two common test procedures one with withstand procedure with 15 impulse and the other one with withstand calculated from the 50% flashover level.

The Electrical Insulator would pass the test if is not damaged by these tests, but slight marks on the surface of the insulating parts would be acceptable.

Depending to the ITP the third party inspection for Electrical Insulator either witnesses the test or will review the Induction Motor manufacture quality control test report in the coming visit or in the final inspection day.

Third Party Inspection for Electrical Insulator Wet Switching Impulse withstand Voltage Test

The Electrical Insulator is taken under condition specified in IEC, and the impulse generator is adjusted to 250/2500 impulse. Impulse of both positive and negative are used.

Similarly there are two test procedures. Withstand value is calculated from the 50% flashover level.

The Electrical Insulator would pass the test if it is not damaged by these tests, but slight marks on the surface of the insulating parts would be acceptable.

Third Party Inspection for Electrical Insulator Wet Power Frequency Withstand Voltage Test

The insulation is taken under the conditions specified in IEC, and the characteristic of the artificial rain is as per the requirement in the IEC clause.

The Electrical Insulator is subjected to test voltage in the specified wet power frequency withstand voltage. The test result would be satisfactory if no flashover or puncture happen during the test.

Third Party Inspection for Electrical Insulator Verification of the Locking System

This test is done only in Electrical Insulators with ball and socket couplings. The third party inspector checks following points:

Locking devices conform to the requirement of IEC Pub.372.
Verification of locking.
Position of the locking device.
Operation test is done by proper device.

The Electrical Insulator would pass the test if obtained values of the load F remain between F minimum and F maximum for the three operations.

Third Party Inspection for Electrical Insulator Verification of Dimension

The dimensions are checked in accordance with the relevant drawings.

Third Party Inspection for Electrical Insulator Temperature Cycle Test

The test is performed in accordance with IEC Pub.383 Clause 26 and Electrical Insulator would pass the test if withstand without cracking, puncture or mechanical breakage.

Third Party Inspection for Electrical Insulator Electromechanical Failing Load Test

This test is applied to type B string Electrical Insulator units only. The string Electrical Insulator units are subjected individually to a power frequency voltage and to a tensile load applied simultaneously between the metal parts.

The Electrical Insulator passes the test if the specified electromechanical failing load is reached without puncture or mechanical failure.

Third Party Inspection for Electrical Insulator Mechanical Failing Load Test

This test is applied to type A string Electrical Insulator units and rigid Electrical Insulators only. The string Electrical Insulator units are subjected individually to a tensile load applied between the metal parts.

Pin Electrical Insulator is subjected to a mechanical load applied perpendicularly to the axis of the Electrical Insulator in the plane of the conductor, and it is applied by means of wire rope.

The Electrical Insulator passes the test if the specified mechanical load is reached without mechanical failure.

Third Party Inspection for Electrical Insulator Thermal Shock Test

This test is applied for toughened glass and it is performed in accordance with IEC Pub.383 Clause 29.

The Electrical Insulator would pass the test if withstand without breakage of the glass.

Third Party Inspection for Electrical Insulator Puncture Test

This test is applied for type B Electrical Insulator only. The Electrical Insulator is completely immersed in a tank containing a suitable insulating medium and the specified puncture voltage is applied.

The Electrical Insulator would pass the test if no puncture occurs below the specified puncture voltage.

Depending to the ITP the third party inspector either witnesses the test or will review the Induction Motor manufacture quality control test report in the coming visit or in the final inspection day.

Third Party Inspection for Electrical Insulator Porosity Test

A ceramic fragment from the Electrical Insulators is immersed in a 1% alcohol solution of fuchsin under the following condition.

Pressure – 15 x 10 N/m

Duration – 12 hours

The Electrical Insulator would pass the test if there is no sign of dye penetration.

Depending to the ITP the third party inspector either witnesses the test or will review the Induction Motor manufacture quality control test report in the coming visit or in the final inspection day.

Third Party Inspection for Electrical Insulator Galvanising Test

First the Electrical Insulator coating appearance is checked and its mass is determined by magnetic test.

The test would be acceptable if coating is continuous, as uniform and smooth as possible, and the obtained values of mass of zinc coating is above the minimum acceptable value in the requirements.

Depending to the ITP the third party inspector either witnesses the test or will review the Induction Motor manufacture quality control test report in the coming visit or in the final inspection day.

Reporting:

Third party inspector provides Inspection Visit Report (IVR) after each visit as well as a final report summarising the activities carried out during the Electrical Insulator production in accordance with the contract requirements and circulated within the time limits specified in the contract.

The report is in the format required by the client and clearly indicates final acceptance or rejection of the Electrical Insulator.

Release Note:

When required by the contract or purchase order a release note is issued by third party agency and given to the manufacturer when the Electrical Insulators have been finally accepted.

Electrical Insulator Packing, Marking and Shipping:

The following points are checked by third party inspector:

Verify that the packing materials conform to specifications and accepted practice for the mode of transport.
Verify protection against humidity, abrasion, distortion and other damage.
Verify shipping marks to marking instructions and record.
Verify handling marks.

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