Preparing a Coating Inspection Plan

Report
Determining Conformance to
Steel Profile/Surface Roughness/
Peak Count Requirements
William D. Corbett
KTA-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; Definitions
 Description of Instruments; Verification of Accuracy
 Required Number & Location of Readings
 Reporting
 Conformance to the Specified Surface Profile Range
 Appendix A: Calibration & Verification of Accuracy
 Appendix B: Determining Compliance based on Process
Control Procedure
 Appendix 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 Discs
 S: Sand
 G/S: Grit/Slag
 SH: Shot
• Stencil Code
 Profile 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:
 Fine
 Medium
 Coarse
Depth Micrometers
Instrument sets on
peaks of the profile
while a conicalshaped 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) locations
 Per 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
OK
OK
End of Prepared Area
OK
Nonconforming
Location
6” x 6” (15cm x 15cm)
areas
Nonconforming
Location
OK
OK
OK
Chalk line
demarcating nonconforming area
OK
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 D4417
 Method 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 (reverify 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 remeasurement
• 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)
TABLE B1
PROCESS CONTROL ITEMS
FOR ABRASIVE NOZZLE BLAST CLEANING
1
2
3
4
5
6
7
8
9
10
11
12
Worker performing abrasive blast cleaning
Blast nozzle type
Blast nozzle size
Number of nozzles operating from same compressor
Abrasive manufacturer
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.)
Abrasive size (sieve size)
Air pressure at nozzle
Blast hose length (as a range)
Blast hose diameter
Compressor size (CFM)
Air pressure at compressor
TABLE B2
PROCESS CONTROL ITEMS
FOR POWER TOOL CLEANING (SP 11, SP 15 only)
1
2
3
4
Worker performing power tool cleaning
Power tool type, model and manufacturer
Power tool media manufacturer
Type of media used (e.g. wire brush, coated abrasive disc, abrasive embedded
in matrix, wire bristle, impact tool)
5
6
7
Abrasive media size
Grade of media
Replacement/substitution of consumables (e.g., disc, wire brush, needles,
bristles)
8
Compressor size (CFM) if tool is air-powered
TABLE B3
PROCESS CONTROL ITEMS
FOR CENTRIFUGAL BLAST CLEANING
1
2
3
4
5
6
7
8
9
10
Unit Operator
Blast wheel type
Wheel motor power
Wheel positioning
Control cage movement
Media flow rate
Abrasive manufacturer
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.)
Abrasive size (sieve size)
Configuration, orientation and size of piece being cleaned (if in shop)
Appendix C: Additional
Considerations
• Measuring surfaces prepared in the shop using
centrifugal blast cleaning units
Potential for variability due to wheel alignment
and configuration of item
• Measuring surfaces prepared using portable
centrifugal blast cleaning units
Potential for variability due to uneven distribution
of blast media
Appendix C: Additional
Considerations
• Measuring surface profile exposed by
waterjetting units
Profile 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 required
Use ASTM D4417, Method B only
Appendix C: Precautions
• Determining surface profile on flame cut edges
Removal 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
THE END
William D. Corbett
KTA-Tator, Inc.

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