SSPC PA 17-2012 Procedure for Determining Conformance to Steel Profile Surface Roughness Peak Count Requirements.pdf

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1、SSPC-PA 17September 25, 2012Editorial Revision May 15, 20151SSPC: The Society for Protective CoatingsProcedure for Determining Conformance to Steel Profile/Surface Roughness/Peak Count Requirements 1. ScopeThis standard describes a procedure suitable for shop or field use for determining compliance

2、with specified profile ranges on a steel substrate using Methods A (visual compar-ator), B (depth micrometer) and C (replica tape) as described in ASTM D 4417, and the portable stylus instrument method used to determine surface roughness and peak count as described in ASTM D 7127. 2. Description The

3、 standard includes brief generic descriptions of the instruments used by each Method, procedures for verification of accuracy for each type of instrument, and requirements for evaluating the preparation process, obtaining surface profile readings, obtaining surface roughness and peak count read-ings

4、, and determining if the profile of an evaluated area is within the specified range. 3. Referenced Standards3.1 The latest issue, revision, or amendment of the refer-enced standards in effect on the date of invitation to bid shall govern, unless otherwise specified.3.2 If there is a conflict between

5、 the requirements of any of the cited referenced standards and this standard, the require-ments of this standard shall prevail.3.3 American Society for Mechanical Engineers Standard1ASME B46.1 Surface Texture (Surface Roughness, Waviness and Lay)3.4 ASTM International Standard2D 4417 Standard Test M

6、ethods for Field Measurement of Surface Profile of Blast Cleaned SteelD 7127 Standard Test Method for Measure-ment of Surface Roughness of Abrasive Blast Cleaned Metal Surfaces Using a Portable Stylus Instrument1 American Society for Mechanical Engineers standards are available online from http:/www

7、.asme.org.2 ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959. For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standards volume infor-mation, refer to the standards Document Su

8、mmary page on the ASTM website.3.5 International Organization for Standardization (ISO) Standard3ISO 4287 Geometrical Product Specifications (GPS) Surface Texture: Profile MethodTerms, Definitions and Surface Texture Parameters4. DefinitionsAccuracy: The degree of conformity of a measured or calcula

9、ted value to some recognized standard or specified value. This concept involves the systematic error of an opera-tion, which is seldom negligible.Adjustment: The physical act of aligning a gages read-ings to match those of a known sample (removal of bias), in order to improve the accuracy of the gag

10、e on a specific surface or within a specific portion of the gages measurement range. Calibration: To check and adjust measurement equip-ment to a measurement standard. The controlled documented process of measuring traceable calibration standards and verifying that the results are within the stated

11、accuracy of the equipment. Calibrations and any resulting adjustments to the measurement equipment are typically performed by the equip-ment manufacturer or by a qualified laboratory in a controlled environment using a documented process. The standards used in the calibration are such that the combi

12、ned uncertainties of the resultant measurement are less than the stated accuracy of the equipment.Deadband: That distance above and below the mean line that a continuous Trace line must cross in both directions (up and down) to count as a single peak. Depth Micrometer: A surface profile gage consist

13、ing of a dial or digital gage and a stylus that protrudes from the base of the gage into the valleys of a blasted steel surface. The extent of protrusion provides a measure of the profile. Its use is described in ASTM D 4417.Evaluation Length: A sequence of five consecutive sampling lengths.Gage/Gau

14、ge: an instrument for measuring quantity, or an instrument for testing.Location Average: The average of a series of instrument readings within a 15 x 15 cm (or 6 x 6 inch) area on the profiled steel surface.Mean Line: A line defining the statistical average height of the profile in an evaluation len

15、gth.Measurement: The single average of multiple location averages obtained, in accordance with ASTM D 4417 or ASTM 3 ISO standards are available online from http:/www.ansi.org or http:/www iso.org.SSPC-PA 17September 25, 2012Editorial Revision May 15, 20152D 7127, “in a sufficient number of location

16、s to characterize the prepared surface,” and reported as the surface profile. Peak Count (Pc): (sometimes referred to as peak density) The number of peak/valley pairs, per unit of evaluation length, extending outside a “deadband” centered around the mean line over the sampling length.Replica Tape: A

17、 layer of crushable plastic microfoam coated onto an incompressible polyester substrate of highly uniform thickness. Different grades of replica tape are available for different ranges of profile height. The tape is compressed against the surface to produce an impression of the surface profile; then

18、, the impression in the tape is measured with a micrometer. The use of replica tape is described in ASTM D 4417.Rmax: The greatest distance between the highest peak and lowest valley for any of the five sampling lengths that comprise an evaluation lengthRt: The distance between the highest peak and

19、the lowest valley within any given evaluation length.Sampling Length: The nominal distance parallel to the surface being assessed within which a single value of a surface parameter is determined.Shim: A flat strip of plastic, metal, or other material of known uniform thickness used to verify the acc

20、uracy of a micrometer. Structure: A unit composed of one or more connected steel members comprising a bridge, tank, ship, etc. It is possible for a single steel shape (beam, angle, tee, pipe, channel, etc.) to be considered a structure, if it is painted in a shop.Surface Profile: The textured surfac

21、e that results from abrasive blast cleaning, commercial grade power tool cleaning or power tool cleaning to bare metal. For steel, surface profile is an instrument reading of the peak-to-valley height of the surface, often expressed as an average of multiple individual instrument readings, and typic

22、ally ranges from less than 25 m up to 127 m (1 mil up to 5 mils). A statement of the measure-ment method used should accompany both specifications and records of profile.Surface Profile Reading: A single instrument reading. When using a stylus-type device, each “sampling length” provides one reading

23、 containing two parameters (Rt and Pc). When using replica tape, each replica provides one reading. When using a depth micrometer, each placement of the probe provides one reading.Surface Roughness: The combined characteristics of surface profile (height) and peak count or density for a surface. Ver

24、ification of Accuracy: Obtaining readings on a refer-ence standard prior to gage use for the purpose of determining the ability of the gage to produce reliable values compared to the combined gage manufacturers stated accuracy and the stated accuracy of the reference standard.5. Description of Instr

25、uments5.1 Visual Profile Comparator (ASTM D 4417 Method A): A set of discs, coupons, or areas prepared to various identified surface profile depths using a designated abrasive type (typically grit/slag, shot, sand). The profile comparator is used for comparison by touch or by visual examination, wit

26、h or without magnification of 5 to 10 power.5.2 Depth Micrometer (ASTM D 4417 Method B): An instrument used to measure surface profile by measuring the depth of a “single valley” (in relation to the height of the surrounding peaks) using a pointed, cone-shaped probe. 5.3 Replica Tape (ASTM D 4417 Me

27、thod C): Replica tape (see definition in Section 4) is used to form a negative impression of the profile that is then measured with a spring micrometer. Spring micrometers with a measurement accuracy of at least 5 m (tenths of a mil 0.0001 in) specifically designed for measuring replica tape are req

28、uired. It is important that the spring micrometer has the anvil size, parallelism and spring loading that is specified for the replica tape application.5.4 Portable Stylus Instrument (ASTM D 7127): A portable electronic instrument for determining surface rough-ness (Rt and Rmax) in compliance with I

29、SO 4287, and Pc in compliance with ASME B46.1. 6. Verification of Accuracy Prior to determining compliance with specified profile range, the instrument used to obtain the required readings and averages shall be checked for accuracy in accordance with the written instructions provided by its manufact

30、urer. Appendix A2.1 and subsections contain suggested procedures for verifying the accuracy of the various instruments if the manu-facturer provides no instructions. An instrument that fails to provide accurate readings shall not be used.7. Required Number and Location of Readings7.1 Number of Locat

31、ions Used to Characterize the Surface: Unless otherwise specified, select a minimum of three 15 x 15 cm (or three 6 x 6 inch) locations in which to take readings for each specific surface preparation apparatus used during each work shift or twelve-hour period, whichever is shorter. For the purpose o

32、f this standard, “apparatus” is defined as an individual blast pot (which may supply multiple nozzles), individual self-contained abrasive recycling/blast cleaning units (which may contain multiple pots), individual stationary or mobile centrifugal cleaning unit, or individual power tool. An optiona

33、l method for specifying required number of locations based on process changes between acceptance of a field job standard and completion of production work is provided in Nonmandatory Appendix B. 7.2 Number of Readings to Determine Location Average: Unless otherwise specified, the number of read-ings

34、 to determine the average profile at each location on steel substrates shall be the number required by the Test Method specified from ASTM D44174or, if the portable stylus instru-4 Visual comparators used for ASTM D 4417 Method A represent surfaces prepared by abra-sive blast cleaning and are inappr

35、opriate for comparison with power tool cleaned surfaces. The replica tape used for ASTM D 4417 Method C cannot accurately measure the profile produced by some types of power tool cleaning media. A test area prepared at the job site can be used to assess the suitability of media and profile measureme

36、nt method for a project prior to full-scale production.SSPC-PA 17September 25, 2012Editorial Revision May 15, 20153ment is specified, the number required by ASTM D 7127 (see Note 11.1). The average of the readings at each location shall be the “location average.”8. ReportingReport the range of locat

37、ion averages (lowest loca-tion average and highest location average), and the profile measurement (see Definitions) for each surface preparation apparatus.9. Conformance to the Specified Surface Profile Range9.1 Surface Profile: The average of readings obtained at each location (“location average”)

38、shall be within the speci-fied profile range. 9.2 Non-Conforming Surface Profile: STEP 1: Determine location averages at regular intervals in four equally spaced directions radiating outward from the non-compliant 15 x 15 cm (or 6 x 6 inch) location. If there is no space to take readings in a given

39、direction, then no readings need to be taken. Determine additional location averages in each direction until two consecutive location averages are compliant in each direction or until there is no space to take additional measurements in that direction. Determine a single location average on repeatin

40、g structural units or elements of structural units until location averages on two consecutive units (or elements) in each direction are compliant or until there are no more units or elements to test. STEP 2: Acceptable location averages are as defined by the specification for minimum and maximum val

41、ues. Use removable chalk or other specified marking material to identify the extent of the non-conforming surface profile.STEP 3: Record the extent of the nonconformity using readily identifiable structural members or permanent structural details. 10. AccuracyTo qualify under this standard, the inst

42、ruments employed for ASTM D 4417 Methods B and C must have accuracy of +/-10% or better. 11. Notes11.1 Four different methods for measuring surface profile are referenced in Section 5 of the standard. It is important to consider the type and interpretation of the data provided by each method when sp

43、ecifying the profile measurement method for a given project.12. Disclaimer12.1 While every precaution is taken to ensure that all information furnished in SSPC standards and specifications is as accurate, complete, and useful as possible, SSPC cannot assume responsibility nor incur any obligation re

44、sulting from the use of any materials, coatings or methods specified therein, or of the specification or standard itself.12.2 This standard does not attempt to address prob-lems concerning safety associated with its use. The user of this standard, as well as the user of all products or practices des

45、cribed herein, is responsible for instituting appropriate health and safety practices and for ensuring compliance with all governmental regulations.NONMANDATORY APPENDIX A: Calibration and Verification of Accuracy A1 Calibration: Instruments used for ASTM D 4417 measurement Methods B, C, and ASTM D

46、7127 are cali-brated by the manufacturer or a qualified lab that may issue a Certificate of Calibration or other documentation showing traceability to a national metrology institution. There is no standard time interval for re-calibration. Calibration intervals are usually established based upon exp

47、erience and the work environment. A one-year calibration interval is a typical starting point suggested by equipment manufacturers. Recalibration of the comparator used for Method A is not practical, so regular replacement of the comparator depending on its visual condi-tion is recommended. Calibrat

48、ion and verification for Method C applies to the spring micrometer only.A2 Verification of Accuracy A2.1 Visual Comparator (ASTM D 4417 Method A): The comparator should be inspected visually for damage prior to each field use. Use of the portable stylus instrument, as described in ASTM D 7127, is an

49、other option for evaluating the condition of the comparator. Verification of the reference profiles is normally performed on the master profile used by the manufacturer to form the comparators used in the field. The laboratory method requires visual inspection using a microscope to determine the depth of the valley relative to the nearest peak. Details of these assessments are provided with the comparator. A2.2 Depth Micrometer (“Fine Pointed Probe” per ASTM D 4417 Method B): Verification of “zero setting” of a depth micrometer requires placing the gage probe onto the supplied