Determining Conformance to Steel Profile/Surface Roughness/ Peak Count Requirements

William D. CorbettKTA-Tator, Inc.

Webinar Content• Review of industry

standards• Review of

instrumentation and measurement acquisition procedures

• Content of Proposed SSPC Standard

Learning Objectives/Outcomes

• Completion of this webinar will enable the participant to describe: The industry standards for surface profile, surface roughness and

peak count measurement The instruments used to measure surface profile/ roughness and to

quantify peak count The proposed content of the SSPC standard, “Procedure for

Determining Conformance to Steel Profile/Surface Roughness/Peak Count Requirements”

Industry Standards for Surface Profile, Surface Roughness and Peak Count Measurement

• ASME B46.1, Surface Texture (Surface Roughness, Waviness and Lay)

• ASTM D4417, Standard Test Methods for Measurement of Surface Profile of Blast Cleaned Steel

• ASTM D7127, Standard Test Methods for Measurement of Surface Roughness of Abrasive Blast Cleaned Metal Surfaces Using a Portable Stylus Instrument

Industry Standards for Surface Profile, Surface Roughness and Peak Count Measurement, continued• ISO 4287, Geometrical Product Specifications (GPS) - Surface

Texture: Profile Method - Terms, Definitions and Surface Texture Parameters

• ISO 8503, Preparation of steel substrates before application of paints and related products - Surface roughness characteristics of blast-cleaned steel substrates Part 4: Method for the calibration of ISO surface profile comparators

and for the determination of surface profile - Stylus instrument procedure

Part 5: Replica tape method for determination of the surface profile

• NACE SP0287, Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces

Proposed SSPC Standard

• Procedure for Determining Conformance to Steel Profile/Surface Roughness/Peak Count Requirements

• Draft #6b (May 21, 2012) in SSPC Standards Review Committee (SRC)

• After SRC approval, SSPC Board must approve• Timeline for approval is unknown at this time

Content of Proposed SSPC Standard

Scope; Description; Referenced Standards; DefinitionsDescription of Instruments; Verification of AccuracyRequired Number & Location of ReadingsReportingConformance to the Specified Surface Profile RangeAppendix A: Calibration & Verification of AccuracyAppendix B: Determining Compliance based on Process

Control ProcedureAppendix C: Additional Considerations when Measuring

Surface Profile

Instrumentation and Measurement Acquisition Procedures• Visual Comparators• Depth Micrometers• Replica Tape• Stylus Instruments

Visual Comparators• ASTM D4417, Method A

5-10 X illuminated magnifier

Comparator Disc

Visual Comparators

• Three Comparator DiscsS: SandG/S: Grit/SlagSH: Shot

• Stencil CodeProfile depth (2)Abrasive Type (Sand)Year reference (1970)

Visual Comparators

• Select Disc• Attach Disc to

Comparator• Examine Surface• Select Segment(s)

ISO Visual Comparators

• Grit or Shot prepared surfaces

• Used with 5-10X magnifier

• Surface roughness “graded” as:FineMediumCoarse

Depth MicrometersInstrument

sets on peaks of the profile while a conical-shaped point projects into the valleys

Digital models store and upload data for analysis (“paperless”)

Replica Tape• Used in conjunction

with a spring-loaded micrometer (analog or digital)

• Compressible foam attached to 2 mils of polyester film (Mylar®)

• Digital version of micrometer can upload data (USB)

Replica Tape

Using HT Replica Tape• Obtain measurement with X-Coarse replica tape

If reading is 0.8-1.5 mils (red zone), record the measurement using Coarse tape

If reading is 2.6-4.5 mils (blue zone), record the measurement using X-Coarse tape

If reading is between 1.5-2.5 mils using X-Coarse, obtain a second reading (same location) with the Coarse tape

If the reading with the Coarse tape is also within 1.5-2.5 mils inclusive, average the two values

Portable Stylus Instruments (ASTM D7127)• Retractable arm with diamond

point stylus• Arm is automatically retracted• Rt: The distance between the highest peak

and the lowest valley within any given evaluation length

• Rmax: The greatest distance between the highest peak and lowest valley for any of the five sampling lengths that comprise an evaluation length

• Pc: The number of peak/valley pairs, per unit of evaluation length, extending outside a “deadband” centered around the mean line over the sampling length

Frequency of Surface Profile Measurements

• No. of readings indicated in ASTM standards• No. of locations not indicated in ASTM

standards• No. of locations may be indicated by the

project specification• Proposed SSPC Standard provides no. of

locations to characterize the surface Primary purpose of this webinar

Number of Readings (to determine location average)• Based on Test Method (unless otherwise specified)• ASTM D4417

“Sufficient” number of readings for Method A (visual comparator)

10 readings per “location” for Method B (depth micrometer)

3 readings per “location” for Method C (replica tape)

• ASTM D7127 (portable stylus instrument)5 traces per “location”

Number of Locations (to characterize the surface)

• Minimum of three 6” x 6” (15cm x 15cm) locationsPer surface preparation “apparatus”Per work shift or 12-hour period (whichever is shorter)

• Optional method (Non-mandatory Appendix B)Based on changes in process between acceptance of jobsite

standard & completion of production surface preparation

Surface Preparation “Apparatus”• Individual Blast Pot

(multiple nozzles) [1]

• Individual abrasive recycling/blast cleaning units (multiple pots) [2]

• Individual centrifugal units (stationary or mobile) [3]

• Individual power tool [4]

1 2

3

4

Reporting• Report:

Range of Location Averages (lowest location average & highest location average)

Surface Profile Measurement (per “apparatus”)

• Example (based on replica tape):Location 1: 4.5, 4.8, 4.1 mils; (4.5) Location 2: 4.0, 5.0, 3.8 mils; (4.3)Location 3: 3.5, 4.1, 4.8 mils; (4.1)Range: 4.1-4.5 mils; Average 4.3 mils

Conformance to the Specified Surface Profile Range• The average of the “location averages” must

fall within the specified surface profile range• Location averages and average surface profile

measurements outside of the specified range are not acceptable

• The magnitude of the non-conforming surface profile measurement areas must be determined, marked and recorded

Non-conforming Location

OK

OK

OK OKNon-conforming Location

OK

OK

OK

End of P

repared A

rea

6” x 6” (15cm x 15cm) areas

Chalk line demarcating non-conforming area

Appendix A: Calibration & Verification of Accuracy (shop/field)• Calibration of instruments (applies to ASTM

D4417 methods B&C; ASTM D7127)• Calibration by manufacturer or approved

laboratory only• Recalibration per manufacturer’s

recommended interval (typically annual)• Obtain a dated Certificate of Traceability

Appendix A: Calibration & Verification of Accuracy (shop/field)• ASTM D4417

Method A (visual comparator): visual for damage

Microscopic examination in a laboratory to confirm depth of valley relative to corresponding peak (if necessary)

Appendix A: Calibration & Verification of Accuracy (shop/field)

• ASTM D4417Method B (depth

micrometer)• Zero set (float glass plate)

beginning & end of shift• Verify accuracy using

shim with cut-out/hole on float glass plate

• Verify cone tip condition using 10x magnifier

• Tips are replaceable (re-verify accuracy upon replacement)

Appendix A: Calibration & Verification of Accuracy (shop/field)• ASTM D4417

Method C (replica tape)• Select appropriate tape• Coarse (0.8-2.5 mils)• X-Coarse (1.5-4.5 mils)• X-Coarse Plus (4-5 mils)• Recheck if in “overlap

area” of 1.5-2.5 mils• Verify accuracy of

micrometer using traceable shims

Appendix A: Calibration & Verification of Accuracy (shop/field)• ASTM D7127 (portable

stylus instrument)Set gage parameters

(sampling & evaluation length, deadband & filter) per Standard

Verify accuracy using standard (provided with gage) prior to each use

Appendix B: Determining Compliance Based on Process Control Procedure• Based on establishing a process control prior to

production blast or power tool cleaning• Within 15 minutes after start of surface preparation,

prepare sample area (min 2’ x 2’)• Measure surface profile. If surface profile conforms,

document process control items

Appendix B: Determining Compliance Based on Process Control Procedure• A change in process during production requires re-

measurement• Denote time of the change & location of surfaces prepared

prior to the change• Obtain two measurements at random locations

One in an area prepared prior to the change in process One in an area prepared after the change in process

• Document: Locations of tests; test method(s); test results; conformance to specification

• The magnitude of the non-conforming surface profile measurement areas must be determined, marked and recorded (as described earlier)

1 Worker performing abrasive blast cleaning 2 Blast nozzle type 3 Blast nozzle size 4 Number of nozzles operating from same compressor5 Abrasive manufacturer 6 Abrasive type, hardness and physical shape (e.g., steel grit, steel shot, or

ratio of mix, or type of mineral abrasive, such as garnet, coal slag, etc.)7 Abrasive size (sieve size)8 Air pressure at nozzle 9 Blast hose length (as a range)10 Blast hose diameter 11 Compressor size (CFM)12 Air pressure at compressor

TABLE B1 PROCESS CONTROL ITEMS

FOR ABRASIVE NOZZLE BLAST CLEANING

1 Worker performing power tool cleaning2 Power tool type, model and manufacturer3 Power tool media manufacturer4 Type of media used (e.g. wire brush, coated abrasive disc, abrasive embedded

in matrix, wire bristle, impact tool)

5 Abrasive media size6 Grade of media7 Replacement/substitution of consumables (e.g., disc, wire brush, needles,

bristles)

8 Compressor size (CFM) if tool is air-powered

TABLE B2PROCESS CONTROL ITEMS

FOR POWER TOOL CLEANING (SP 11, SP 15 only)

1 Unit Operator2 Blast wheel type3 Wheel motor power4 Wheel positioning5 Control cage movement6 Media flow rate7 Abrasive manufacturer8 Abrasive type and physical shape (e.g., steel grit, steel shot, or ratio of

mix, or type of mineral abrasive, such as garnet, coal slag, etc.)9 Abrasive size (sieve size)10 Configuration, orientation and size of piece being cleaned (if in shop)

TABLE B3PROCESS CONTROL ITEMS

FOR CENTRIFUGAL BLAST CLEANING

Appendix C: Additional Considerations• Measuring surfaces prepared in the shop using

centrifugal blast cleaning unitsPotential for variability due to wheel alignment

and configuration of item• Measuring surfaces prepared using portable

centrifugal blast cleaning unitsPotential for variability due to uneven distribution

of blast media

Appendix C: Additional Considerations• Measuring surface profile exposed by

waterjetting unitsProfile may vary considerably. Additional

measurement locations may be required• Measuring surfaces prepared using power

tools (SSPC-SP11; SP15)Consider productive life of cleaning media;

Additional measurement locations may be requiredUse ASTM D4417, Method B only

Appendix C: Precautions

• Determining surface profile on flame cut edgesRemoval of carburization (hardening) may be

required prior to blast cleaning• Effect of existing surface profile on newly

generated surface profile– Existing profile beneath coating may exceed

specified profile for maintenance painting. Prepare test area prior to production work

• Pitted steel: Measure in non-pitted areas

Summary• During this webinar, we have described :

The industry standards for surface profile, surface roughness and peak count measurement

The instruments used to measure surface profile/ roughness and to quantify peak count

The proposed content of the SSPC standard, “Procedure for Determining Conformance to Steel Profile/Surface Roughness/Peak Count Requirements”

Determining Conformance to Steel Profile/Surface Roughness/ Peak Count Requirements

William D. CorbettKTA-Tator, Inc.

THE END