A.02.10 Statement of Work PWS (07-16-21).pdf

SECTION 48 13 13.07 26

TURBINE GUIDE BEARING MACHINING

1/2020

PART 1 GENERAL

1.1 GENERAL INFORMATION

1.1.1 Description of Work

This section governs the machining of 3 turbine guide bearings for Chief Joseph Dam. These bearing belong to the family of units orignally manufactured by Newport News (Units 5-14). Only 1 bearing at the time will be made available to the Contractor for all required work. The scope of work also includes shipping between the project site and the Contractor's workshop.

The bearings were rehabbed by Alstom Power 10 years ago and have been in service ever since. The bores of the bearings are currently at the limit of the minimum bore diameter tolerances; this is causing them to run hot when the units are operated at their normal rating.

The purpose of this service contract is to perform a skim cut on the babbitt lining material of all three bearings and open the clearance between the bearing and the turbine shaft. Existing bearing bore dimensions are shown in the bearing drawings that have been included with this contract. The target bore diameter for all three bearings is between 41.002 inches and 41.004 inches.

1.1.2 Description of Turbine Guide Bearings

a. The turbine guide bearings are a cast iron tapered shell type that are fitted into a bearing housing. The bearing nominal bore is 41 inches, addditional bearing dimensions and tolerances are shown on the reference drawings. The babbitt is of a tin base material.

b. Dimensions, fits and estimated weights are based on original design drawings and these specifications.

1.2 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by basic designation only.

ASME INTERNATIONAL (ASME)

ASME BPVC SEC V (2019) Boiler and Pressure Vessel Code;

Section V, Nondestructive Examination

ASTM INTERNATIONAL (ASTM)

ASTM B23 (2014) Standard Specification for White

Metal Bearing Alloys (Known Commercially as "Babbitt Metal")

ASTM E114 (2015) Standard Practice for Ultrasonic Pulse-Echo Straight-Beam Examination by the Contact Method

ASTM E165 (2018) Standard Practice for Liquid Penetrant Examination for General Industry

AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING (ASNT)

ASNT SNT-TC-1A (2016) Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing

AMERICAN WELDING SOCIETY (AWS)

AWS D1.1/D1.1M (2018) Structural Welding Code - Steel

INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE)

IEEE 1095 (2012) Guide for Installation of Vertical Generators and Generator/Motors for Hydroelectric Applications

1.3 SUBMITTALS

Government approval is required for submittals with a "G" designation;

submittals not having a "G" designation are for information only. When used, the acronym following the "G" designation identifies the office that will review the submittal for the Government. The acronym "HDC" identifies the reviewing office as the Hydroelectric Design Center. The following shall be submitted in accordance with SECTION 01 33 00 SUBMITTAL PROCEDURES.

SD-01 Pre-Work Submittals

Turbine Guide Bearing Machining Procedure; G, HDC

Submit 14 calendar days in advance of machining, Paragraph 3.1

Turbine Guide Bearing Machining Schedule; G, HDC Submit 10 calendar days in advance of refurbishment, Paragraph 3.2.1.

SD-07 Certificates

Notice of Turbine Guide Bearing Finished Inspection; G, HDC

Submit 14 calendar days in advance of inspections, Paragraph 3.2.2.

Qualifications of Nondestructive Testing Personnel; G, HDC

Submit 14 calendar days in advance of inspections, Paragraph 3.3.

SD-09 Manufacturer's Field Reports

Turbine Guide Bearing As Found Inspection Report; G, HDC

Submit 5 calendar days following inspections," Paragraph 3.1 As Found Inspection.

Turbine Guide Bearing Finished Inspection Report; G, HDC

Submit 7 calendar days following inspections and prior to shipment, Paragraph 3.2.2.

1.4 SHIPMENT

Contractor shall be responsible for all related costs to ship the bearings between Chief Joseph dam and the contractor's shop. The Contractor shall pick up all parts from the project site no later than 60 days after award.

The address of the project location is "Chief Joseph Dam, Highway 17 and Pearl Hill Road, Bridgeport, WA 98813-1120". Each bearing will be shipped fully assembled. The estimated shipping weight is 6000 pounds including the shipping crate. The dimensions of the shipping crate are 72 inches wide by 72 inches long by 48 inches high. The following shipping requirements apply:

a. The Government will visually inspect the condition of each bearing prior to shipment from Chief Joseph dam. Any existing damage will be recorded by the Government prior to shipment. The Contractor shall either accept the content of the Government condition report, or shall supply a representative to inspect the bearing prior to shipment.

b. The Government will package the bearings in shipping containers at the project site and prepare them for shipment. The Government will load all of the containers onto the Contractor provided truck. The Contractor shall provide 48 hours advance notice to the Government when the truck is scheduled to arrive on project.

c. The Contractor shall provide round trip shipment for each of the bearings between the project and the contractor's workshop. Pick up and delivery at the project site shall be between the hours of 0730 and 1530, Monday through Thursday, excluding Federal holidays.

d. Prior to return shipment, coat bearings with a suitable preservative and package all contents for long term storage. Cover all inlets and outles to exclude dirt, water, etc.

e. Bearings shall be prepared for shipment in a manner to protect them from damage during shipment. The Contractor shall be responsible for and make good at no extra cost to the Government damage resulting from improper preparation, as well as for damage occurring during shipping.

f. If steel banding is used, it shall have adequate protection so that it does not harm the bearing.

h. All packaging materials provided by the Contractor shall become the property of the Government.

i. The Government will unload the bearings and related parts from the Contractor provided truck, after return shipment. The Contractor shall provide 48 hours advance notice to the Government when the truck is scheduled to arrive on Project.

PART 2 PRODUCTS

NOT USED

PART 3 EXECUTION

3.1 AS FOUND INSPECTION

Clean each bearing as required to perform the following inspections. Ensure that the flange bolts located at the top of the bearing are fully torqued to 330 ft-lbs prior to taking measurements. These flange bolts are the only bolts securing both halves together. The bearing is a tapered fit at the bottom, therefore the bottom will need to be pulled together with either a strap or metal banding. The bearing shall be pulled together in such a manner that it doesn't cause any damage. Prior to performing any work, each bearing shall be NDT inspected by the Ultrasonic Test Method (UT) as detailed below. The results of the NDT inspection shall be submitted as part of the Turbine Guide Bearing As Found Inspection Report.

As found inspection of the turbine guide bearing shall at a minimum consist of the following:

a. The entire bearing shall be visually inspected. The inspection report shall include comments regarding any damage, irregular or unacceptable surface condition or deterioration.

b. Measure and record the Babbitt surface finish.

c. Measure the babbitt bore diameter at three elevations top, middle and bottom. Take four measurements on 45-degree increments per elevation.

d. Using feeler gauges, measure the O.D. and I.D. gap at the bearing split lines along the lines entire length. Record any gap

0.001 inch or larger listing width, length and approximate depth.

The results of the measurements and inspection shall be submitted to the Government prior to the beginning of any work and shall be taken into account when preparing the Turbine Guide Bearing Machining Procedure. The tolerances for decimals shall be to the nearest 0.001 inch.

3.2 TURBINE GUIDE BEARING MACHINING

3.2.1 General Machining Requirements

Workmanship shall be of the highest grade and in accordance with the best modern standard practice. Machining consists of performing a skim cut on the bore of the bearings in order to open up the inside diameter (ID). New bore diameter shall range between 41.002 inches and 41.004 inches. Final ID dimensions will be confirmed after as-found inspections. Contractor shall assume up to a .010 inch cut on the bore of each bearing. The existing bore diameter of each bearing included in this contract is shown on table 1 of reference drawing 1-16101-003 sheet 2 of 3. General requirements are listed below:

a. Any changes to the bearings by the Contractor that deviate from contract requirements shall require the Contractor to submit a brief description of the changes. The Contractor shall not perform any work until receiving written approval from the Government.

b. A proposed Turbine Guide Bearing Machining Schedule, i.e. dates and times, shall be submitted a minimum of 10 calendar days in advance of the beginning of the work. The schedule shall be updated and revised as required. The Government will use this schedule for witnessing the machining process and will notify the Contractor in advance if the process will be witnessed.

c. Bearings shall be machined fully assembled and in one setup on the machining turntable. The setup on the turntable shall be such that the bore of the bearing is fully vertical.

d. The rotation of the machining table shall be clockwise which is opposite to the direction of rotation of the generating unit.

e. The requirements for the finish machined babbitt bore are as follows:

(1) Babbitt inner diameter: 41.002 inches to 41.004 inches.

Existing inner diameter for all bearings is shown on drawing 1-16101-003 sheet 2 of 3 table #1.

(2) Babbitt surface runout: max 0.001 inch TIR. Applies for the complete bearing over one revolution of the machining table over any and all elevations.

(3) Perpendicularity: Perpendicular to the horizontal flange mounting surface to within 0.002 inch.

(4) Concentricity: Concentric with the machined spigot fit OD(s) to within 0.002 inches T.I.R

(5) Surface finish: maximum 32 microinch, free of chatter and abnormal tool marks.

f. Finish dimensions and runout checks shall be made while the bearings are still on the machining table.

g. Oil supply grooves, temperature probe holes, radii at the bearing edges and other details existing on the original bearings (or as shown on the drawings) shall be preserved.

h. All non-Babbitted surfaces and holes shall be thoroughly cleaned.

i. Following the completion of the work, the Contractor shall protect the bearings from damage and corrosion with appropriate coatings and packaging.

3.2.2 Inspection of Finished Generator Guide Bearings

Final inspection will be witnessed by the Government at the refurbishment location. Final acceptance will be made upon safe delivery to the project location. Any materials or workmanship not complying with the provisions of these specifications will be cause for rejection. Corrections shall be made at the expense of the Contractor, and are subject to approval.

Measurements may be repeated at the project site to ensure that workmanship conforms to contract requirements. Following the completion of all machining work, each bearing shall be subjected to NDT inspection by the Ultrasonic Test Method (UT) as detailed below. The results of the NDT inspection shall be submitted as part of the Turbine Guide Bearing Finished Inspection Report. Additional inspection requirement are as follows:

a. The Contractor shall submit Notice of Turbine Guide Bearing Finished Inspections to the Government. All inspections may be witnessed by the Government at its discretion.

b. The finished guide bearing shall be inspected while on the machining turntable for the purpose of verifying the requirements (diameter, runout, surface finish) listed in Paragraph 3.2.1.

c. Measure the babbitt bore diameter at three elevations top, middle and bottom. Take four measurements on 45-degree increments per elevation.

d. Measure and record the Babbitt surface finish, and the surface finish for any other contractor machined surfaces.

e. Using feeler gauges, measure the O.D. and I.D. gap at the bearing split lines along the lines entire length. Record any gap 0.001 inch or larger listing width, length and approximate depth.

f. All measurements shall be taken with calibrated instruments accurate to the nearest 0.001 inch, unless otherwise indicated.

Calibration certification for all equipment shall be furnished with the report of findings.

g. All data shall be recorded on the Contractor supplied inspection sheets which shall be provided to the Government inspector prior to departure from the Contractor's facilities.

h. Turbine Guide Bearing Finished Inspection Report shall be submitted prior to shipment and shipment shall not be made until authorized by the Government.

3.3 NONDESTRUCTIVE TESTING (NDT)

The metallurgical bonding of the babbitt shall be examined using the Ultrasonic Test Method (UT). Qualifications of Nondestructive Testing Personnel shall be prepared and submitted at least 15 calendar days prior to their performance of work. Testing personnel shall be NDT ASNT RP SNT-TC-1A Level 2 qualified with three (3) years of current experience. The results of the inspection shall be included in the turbine guide bearing finished inspection report. Report shall indicate whether there is a lack of bonding between the babbitt material and the base metal. The testing will be witnessed with Government personnel unless waived.

3.3.1 Babbitt Ultrasonic (UT) Testing

The Pulse-Echo Method of UT inspection shall be employed. UT examination shall be performed in accordance with the applicable portions of ASTM E 114 or of Article 5 of the ASME Boiler and Pressure Vessel Code Section V. The entire babbitt surface of each bearing shall be scanned, overlapping scan paths by at least 20 percent of the effective transducer width. Scanning rates shall not exceed 3 inches per second. Unbonded babbitt areas will result in an increase in the size of the reflection or indications of multiple reflections at the interface of the babbitt and base metal.

Babbitted areas located over anchoring dovetail grooves will be excluded from UT inspection. All unbonded babbitted areas shall be carefully scanned to determine their size and configuration. The outside edges of all unbonded areas shall be marked on the surface of the babbitt and recorded on inspection sheets. UT equipment shall conform to the following:

a. Search Unit

(1) All testing of the babbitt bond shall be performed with a 2.25 MHz or 5 MHz longitudinal wave crystal.

(2) Transducer diameter shall be 0.25 inch.

(3) Transducer gloves or delay lines shall be made of Lucite or other materials with similar sonic properties.

b. Couplants used for testing shall be either lightweight oil or glycerin, the viscosity of which is no more than SAE 30 oil.

c. Reference Block

(1) A reference block shall consist of a soundly babbitted steel block with a scanning surface and babbitt thickness representative of the bearing being tested. The block shall be used to set the sensitivity of the instrument. A reference block with artificially unbonded areas shall be provided for comparison of indications for areas showing bond and lack of bond.

(2) Test sensitivity shall be such that the babbitt-to-base material interface is readily identified on the CRT. Details of sensitivity calibration and determination of bonded and unbounded areas shall be defined in the UT procedure.

(3) Reference blocks shall be kept available for frequent reference during actual testing.

3.3.2 Procedure

The entire babbitt surface of each bearing half shell shall be scanned, overlapping scan paths by at least 20 percent of the effective transducer width. Scanning rates shall not exceed 3 inches per second. Unbonded babbitt areas will result in an increase in the size of the reflection or indications of multiple reflections at the interface of the babbitt and base metal. Babbitted areas located over anchoring dovetail grooves will be excluded from UT inspection.

All unbonded babbitted areas shall be carefully scanned to determine their size and configuration. The outside edges of all unbonded areas shall be marked on the surface of the Babbitt and recorded on inspection sheets.

3.3.3 Acceptance Standards

Babbitt bond acceptance criteria is defined below:

a. Perimeter and Holes. Zone defined as bond surface area within 1 inch from any edge or hole having an exposed bond line. The maximum dimension of any individual unbonded area shall be less than 1/2 inch, with acceptable unbonded areas located no closer than two inches apart.

The total unbonded area in the perimeter zone shall be no larger than 5% of the total zonal area as examined by the UT method.

b. Corners. Zone defined as bond surface area within 1 inch from any corner having an exposed bond line. Corners shall have no unbonded areas as examined by the UT method.

c. Remainder of Shell. Zone defined as bond surface area other than perimeters, holes, corners and dovetails. The maximum area for any individual unbonded area shall be less than 1 sq. inch or 3 percent of the total zonal area, whichever is less. Acceptable unbonded areas shall be located no closer than 2 inches apart. The total unbonded area shall be no larger than 5 percent of the total zonal area as examined by the UT method.

e. Additional Requirements. Visual (VT) acceptance standards. The babbitt surface shall have no visible porosity, blow holes, shrinkage or cracks. The exposed bond line shall have no visible disbonding.

3.3.4 NDT Inspection Report

A babbitt bond NDT inspection report shall be submitted as part of both the as found inspection report and the finished inspection report. The report shall include a complete description of the UT procedures used, equipment used, a mapping of the areas tested, shell/pad number, and interpretation of results. The report shall specifically address areas of lack of bond between the babbitt and the shell/pad and their accumulated total surface area relative to the area allowed for the zone.

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