Third Party Inspection for Generator - Procedure

The Third Party Inspection for Generator article provides a sample procedure  /instruction for generator testing and generator inspection in manufacturing shop. 

You may also need review generator inspection and test plan. 

This content guides you through all the necessary stages in the production of the electric generators, including the material, final inspection, preservation and packing, and dispatch to site.

You need to take this point into account: this article is written for a typical electric generator and might not be detailed for special cases.

All electric generator inspection and generator testing is done 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 a electric generator that is under the construction process is:

  • Design code and Standard
  • Purchase order specification
  • Purchaser's standards
  • Approved drawings

Your applicable codes and standards may be based on 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 upon in the Pre-Inspection meeting, which is held several weeks before the actual commencement of the inspection work. The parties that participate in this meeting are the manufacturer, purchaser and third party inspection agency representatives.

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

Third Party Inspection for Generator - Material Inspection

The first actual inspection work in the electric generator is the raw materials inspection.

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

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

The review includes checks on:

  • Maker’s name and location
  • Certificate number, grade
  • Batch number
  • Chemical composition
  • Cast or Heat number (for metal parts)
  • Heat treatment condition
  • Surface finish 
  • Structural observations, notable defects

Ancillary e.g. instruments, meters and etc. 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 the materials marking. It is also necessary to check these with the electric generator drawing datasheet, material list and other specifications as appropriate.

Visual inspection for surface finish and probable defects is done and dimensional compliance with specification need to be controlled, as well.

When the third party inspector carries out the material inspection, then provides the inspection visit report (IVR), the report contains the 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 Generator - Construction

When the electric generator raw material inspection is carried out, and the results were satisfactory or non-conformities were closed by remedial action, then the electric generator manufacturer will start fabrication.

The third party inspector checks the following points on the electric generator, based on the inspection and test plan (ITP), which has already been agreed upon between the purchaser and the electric generator manufacturer.

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

This depends in the inspection budget, which purchasers assign for inspection. Much more inspection will have a much larger cost and less risk, and conversely, less inspection will have less cost but more risks.

The third party inspector checks the following items in the electric generator casing inspection process:

Third Party Inspection for Generator - General Arrangement Check

The third party inspector checks that all layout, instruments, controls, terminal boxes, etc., are correctly rated and are correctly located, with specified labeling. The inspection is carried out in accordance of approved drawings.

Third Party Inspection for Generator - Armature and Field Windings Resistance Test

Generator Armature and field Windings Resistance Test is done before running test. Each phase winding of stator and rotor is tested by Kelvin Double Bridge instrument.

It is necessary the measured values to be corrected by using appropriate formula to obtain the resistance values in specified temperature.

Third Party Inspection for Generator - Armature and Field Windings Insulation Resistance Test

Generator armature and field windings insulation resistance test are done before and after dielectric test. Each phase winding of stator and rotor is tested by 1000 V megger (for stator winding) and 500 V megger (for rotor winding). Reading of the insulation resistance is taken one minute after voltage application.

The test would be acceptable if the measured values are more than specified values. The Temperature of winding and ambient, and humidity are recorded at the same time.

Third Party Inspection for Generator - High Voltage tests of Armature and Field Windings

Insulation resistance is measured before and after high voltage test. Each phase winding is tested one by one. Other two phase windings are grounded during testing. The Test voltage would be 2E + 1000 (V) when E is the rated voltage and test duration is 1.0 min. The test would be acceptable when each phase winding endures the specified conditions.

Third Party Inspection for Generator - Dynamic Balance Test

The generator dynamic balance test is done after completion of assembly. Vibration of each bearing shaft is measured for specified range of speeds. The test is done in rated gas pressure and test would be acceptable if the measured value is less than specified value. The measured vibration value in critical speed also needs to be less than specified value.

Third Party Inspection for Generator - Open Circuit Saturation Curve Test

The test is done in running condition and in rated speed and in rated gas pressure.

Readings for the saturation curve is always taken with only increasing excitation up to 20% over voltage, and next taken with only decreasing excitation. It is necessary balance of voltage to be controlled at the rated voltage; the phase sequence also is checked.

The test would be acceptable if the field current at rated voltage is 1 + 0.1 x designed value.

Third Party Inspection for Generator - Three Phase Short Circuit Saturation Curve Test

The test is done in rated speed and in the rated gas pressure condition. Reading for the short circuit characteristic curve is usually taken up to rated current. The phase balance is checked at the rated current. 

The test is acceptable if the field current at rated armature current is (1 + or minus 0.1) x designed value.

Third Party Inspection for Generator - Telephone Harmonic Factor (THF) Test

The telephone harmonic factor of the line-to-line terminal voltage shall be measured with a harmonic analyser during core loss heat run test.The test would be acceptable if the THF is less than < 1.5%

Third Party Inspection for Generator - Temperature Rise Test

Each temperature rise at rated load is circulated from two heats run test that is core loss heat run test and copper loss heat run test at following Measuring points:

  • Stator coil temperature (Armature winding temperature)
  • Room temperature
  • Stator core temperature
  • Rotor coil temperature (Field winding temperature)
  • Stator frame temperature
  • Bearing oil inlet/outlet temperature
  • Cooling water inlet/outlet temperature of gas cooler
  • Seal oil temperature

The test conditions for core loss heat run test are:

  • Rated speed
  • Rated gas pressure
  • Rated voltage
  • Open circuit (no load)

The test conditions for copper loss heat run test are:

  • Rated speed
  • Rated gas pressure
  • Rated current
  • Three phase short circuit

This condition is kept until each temperature rise becomes saturated. The test would be acceptable if the temperature rise is on the specified value.

Third Party Inspection for Generator - Segregated Losses Test

Mechanical loss is measured in rated speed and rated gas pressure. Core loss test conditions are in rated speed, during no load saturation characteristic test and under the rated voltage. Copper loss test conditions are in rated speed, during three phase short circuit test and under the rated current. The test would be acceptable if the measured values are in the range of designed values.

Third Party Inspection for Generator - Calculation of Efficiency

Efficiency calculation is made at rated output and other outputs which are mentioned on the specification. The result would be satisfactory if calculated value to be in the range of specified value. It is necessary the third party inspector review the manufacture calculation sheet. 

Third Party Inspection for Generator - Sudden Three Phase Short Circuit Test

The test is done in the rated speed and rated gas pressure. The generator generator output terminal is shorted suddenly. The test would be acceptable if the obtained value to be in specified design value.

Third Party Inspection for Generator - Noise Level Test

The test is done in the rated speed, rated gas pressure and rated voltage at no load. The sound pressure level is measured at 1 meter from the surface of generator. This measurement is performed using some temporary covers at coupling and testing slip ring at shop. The test would be acceptable if the obtained value to be in specified design value.

Third Party Inspection for Generator - Reporting

The third party inspector provides an Inspection Visit Report (IVR) after each visit, as well as a final report summarizing the activities carried out during the electric generator production in accordance with the contract requirements and circulated within the time limits specified in the contract.

Third Party Inspection afor Generator - Release Note

When required by the contract or purchase order, a release note is issued by the third party inspection agency and given to the manufacturer when the electric generators have been accepted. 

Third Party Inspection for Generator - Packing, Marking and Shipping

The following points are checked by the third party inspector for packing inspection:

  • 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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