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SSPC-PA 17 September 25, 2012 Editorial Revision November 1, 2012
D 7127, “in a sufcient number of locations to characterize the used for comparison by touch or by visual examina prepared surface,” and reported as the surface prole. without magnication of 5 to 10 power. Peak Count (Pc): (sometimes referred to as peak density) 5.2 Depth Micrometer (ASTM D 4417 Meth The number of peak/valley pairs, per unit of evaluation length, instrument used to measure surface prole by extending outside a “deadband” centered around the mean the depth of a “single valley” (in relation to the h line over the sampling length. surrounding peaks) using a pointed, cone-shaped Replica Tape: A layer of crushable plastic microfoam coated onto an incompressible polyester substrate of highly 5.3 Replica Tape (ASTM D 4417 Method C uniform thickness. Different grades of replica tape are available tape (see denition in Section 4) is used to form for different ranges of prole height. The tape is compressed impression of the prole that is then measured w against the surface to produce an impression of the surface micrometer. Spring micrometers with a measureme prole; then, the impression in the tape is measured with a of at least 5 µm (tenths of a mil [0.0001 in]) specical micrometer. The use of replica tape is described in ASTM D for measuring replica tape are required. It is impor 4417. spring micrometer has the anvil size, parallelism Rmax: The greatest distance between the highest peak loading that is specied for the replica tape applica and lowest valley for any of the ve sampling lengths that comprise an evaluation length 5.4 Portable Stylus Instrument (ASTM D Rt: The distance between the highest peak and the lowest portable electronic instrument for determining sur valley within any given evaluation length. ness (Rt and Rmax) in compliance with ISO 4287 Sampling Length: The nominal distance parallel to compliance with ASME B46.1. the surface being assessed within which a single value of a surface parameter is determined. 6. Verication of Accuracy Shim: A at strip of plastic, metal, or other material of known uniform thickness used to verify the accuracy of a Prior to determining compliance with spec micrometer. range, the instrument used to obtain the required re Structure: A unit composed of one or more connected averages shall be checked for accuracy in acco steel members comprising a bridge, tank, ship, etc.You're It is possible Readingthe a Preview written instructions provided by its manufacture for a single steel shape (beam, angle, tee, pipe, channel, etc.) A2.1 and subsections contain suggested proc Unlock full access with a free trial. to be considered a structure, if it is painted in a shop. verifying the accuracy of the various instruments i Surface Prole: The textured surface that results from facturer provides no instructions. An instrument abrasive blast cleaning, commercial grade power tool cleaning Download With Free Trial provide accurate readings shall not be used. or power tool cleaning to bare metal. For steel, surface prole is an instrument reading of the peak-to-valley height of the 7. Required Number and Location of Read surface, often expressed as an average of multiple individual instrument readings, and typically ranges from less than 25 µm 7.1 Number of Locations Used to Chara up to 127 µm (1 mil up to 5 mils). A statement of the measure Surface: For each specic surface preparation ment method used should accompany both s pecications and used during each work shift or twelve-hour period records of prole. Sign up to vote on this title is shorter, select a minimum of three 15 x 15 cm (o Surface Prole Reading: A single instrument reading. 6 inch) locations to take readings. For the Usefulin which useful Not When using a stylus-type device, each “sampling length” this standard, “apparatus” is dened as an individu provides one reading containing two parameters (Rt and Pc). (which may supply multiple nozzles), individual se When using replica tape, each replica provides one reading.
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Septemb Editorial Revision Novem
instrument is specied, 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. Reporting Report the range of location averages (lowest loca tion average and highest location average), and the prole measurement (see Denitions) for each surface preparation apparatus.
9. Conformance to the Specied Surface Prole Range 9.1 Surface Prole: The average of readings obtained at each location (“location average”) shall be within the speci ed prole range. 9.2 Non-Conforming Surface Prole:
12. Disclaimer
12.1 While every precaution is taken to ens information furnished in SSPC standards and spec as accurate, complete, and useful as possible, SS assume responsibility nor incur any obligation res the use of any materials, coatings or methods speci or of the specication or standard itself.
12.2 This standard does not attempt to add lems concerning safety associated with its use. T this standard, as well as the user of all products described herein, is responsible for instituting health and safety practices and for ensuring comp all governmental regulations.
NONMANDATORY APPENDIX A: Calibra Verication of Accuracy
A1 Calibration: Instruments used for AST STEP 1: Determine location averages at measurement Methods B, C, and ASTM D 712 regular intervals in four equally spaced brated by the manufacturer or a qualied lab that directions radiating outward from the a Certicate of Calibration or other documentati non-compliant 15 x 15 cm (or 6 x 6 inch) traceability to a national metrology institution. T location. If there is no space to take standard time interval for re-calibration. Calibratio readings in a given direction, then no readings need to be taken. Determine are usually established based upon experience a additional location averages in each You're Readingenvironment. a Preview A one-year calibration interval is a typ direction until two consecutive location point suggested by equipment manufacturers. Rec averages are compliant in each direction the acomparator Unlock full access with free trial. used for Method A is not practical or until there is no space to take additional replacement of the comparator depending on its v measurements in that direction. Determine tion is recommended. Calibration and verication fo a single location average on repeating Download With Free Trial applies to the spring micrometer only. structural units or elements of structural units until location averages on two A2 Verication of Accuracy consecutive units (or elements) in each direction are compliant or until there are no A2.1 Visual Comparator (ASTM D 4417 M more units or elements to test. STEP 2: Acceptable location averages are as The comparator should be inspected visually for da dened by the specication for minimum to each eld use. Use of the portable stylus ins Sign up to vote on this title and maximum values. Use removable described in ASTM D 7127, is another option for chalk or other specied marking material Useful Not useful the condition of the comparator. Verication of th to identify the extent of the non-conforming proles is normally performed on the master pro surface prole. the manufacturer to form the comparators used STEP 3: Record the extent of the nonconformity
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SSPC-PA 17 September 25, 2012 Editorial Revision November 1, 2012
Shims, which may be supplied by the gage manufacturer or purchased separately, are used to verify gage accuracy. Most shims for use with prole gages have a hole cut in the center to allow the cone-shaped metal tip to pass through to a glass slide below. The value displayed by the gage is compared to the stated thickness value of the shim to verify that the gage can measure known thicknesses accurately. The condition of the cone-shaped tip should be veried by visual inspection with a 10X magnier before use. Tips are usually made of tungsten carbide, which can be chipped by impact. The visual inspection should ensure that the tip is not chipped or cracked. Verify the accuracy of the micrometer after replacement of the tip.
accuracy of a portable stylus instrument then requ of a surface roughness standard containing a kno roughness and peak count. The gage manufactu supplies the surface roughness standard. To prev tion of readings with an inaccurate instrument, the should be checked against the surface roughne prior to each use. If the portable stylus instrument is suspected of giving erroneous readings during the its accuracy should be rechecked. If readings do with the surface roughness standard, all readings the last accuracy check are suspect. In the event damage, wear, high usage, or after an established portable stylus instrument shall be rechecked for a
NONMANDATORY APPENDIX B: De A2.3 Replica Tape (ASTM D 4417 Method C): The primary prole measurement range for replica tape is 20 to Compliance Based on Process Control P 115 µm (0.8 to 4.5 mils). Begin by selecting an appropriate (Nonmandatory unless specied) grade of replica tape based on the target prole. For a target This process is based on several process co prole between 20 to 64 µm (0.8 and 2.5 mils), select “Coarse” dures identied prior to beginning work. A change i grade. For a target prole between 38 and 115 µm (1.5 and process control procedures during production wo 4.5 mils) select “X-Coarse” grade. (Use of “Coarse Minus” verication of continued conformance with speci grade, less than 20 µm or less than 0.8 mil, or “X-Coarse Plus” prole. grade, greater than 115 µm or greater than 4.5 mil, should be restricted to checking measurements at the lower or upper B1 Development of Process Control Proced ends of the primary range.) Prepare the micrometer thickness 15 minutes after the start of surface preparatio gage: clean the contact surfaces and adjust the zero point project, the contractor shall prepare a representa to read –51 micrometers, or –2.0 mils, the thickness the You'reofReading a Preview area for testing to determine compliance with pro incompressible substrate. (Pre-setting the gage in this way ments. automatically subtracts the thickness of the incompressible Unlock full access with a freeUnless trial. otherwise specied, the sample measure at minimum 61 cm x 61 cm (2 x 2 ft). Af plastic substrate from all subsequent readings.) Afx the lm area has been determined to comply with the req to the proled surface. Firmly compress the replica lm against Download With FreeforTrial range the project, the items listed in Tables B1, the surface to be measured with a suitably rounded rubbing below shall be identied and documented. tool, applying sufcient pressure to fully compress the lm and produce a replica with a uniform “pebble-grain” appearance. Remove the replica and place it between the contact surfaces of the micrometer thickness gage. If the gage reading obtained using either Coarse or X-Coarse grade is inside the 38 to 64 µm (1.5 to 2.5 mil) “overlap” window, take a second reading with the OTHER grade. If both readings are in the 38 to 64 µm (1.5 to 2.5 mil) range, record the average as the observed prole. Readings made with either grade that are outside this range – i.e.,
B2 Number of Readings and Measurement
B2.1 Number of Readings Required: Unles specied, the number of readings to determine Sign up to vote on this title measurement of abrasive blast cleaned substrates Usefulby the Not useful Test number required Method specied fro 5 4417 or the number required by ASTM D 7127 if t stylus instrument is specied (see Note 11.1). Th
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TABLE B1 PROCESS CONTROL ITEMS FOR ABRASIVE NOZZLE BLAST CLEANING 1
Worker performing abrasive blast cleaning
2
Blast nozzle type
3
Blast nozzle size
4
Number of nozzles operating from same compressor
5
7
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)
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
6
TABLE B2 PROCESS CONTROL ITEMS FOR POWER TOOL CLEANING (SP 11, SP 15 only) 1
Worker performing power tool cleaning
2
Power tool type, model and manufacturer
3
Power tool media manufacturer
5
You're Reading Preview Type of media used (e.g. wire brush, coated abrasive disc, a abrasive embedded in matrix wire bristle impact tool) Unlock full access with a free trial. Abrasive media size
6
Grade of media
7
Download Withbrush, Freeneedles, Trial bristles) Replacement/substitution of consumables (e.g., disc, wire
8
Compressor size (CFM) if tool is air-powered
4
TABLE B3 PROCESS CONTROL ITEMS FOR CENTRIFUGAL BLAST CLEANING Sign up to vote on this title 1
Unit Operator
2
Blast wheel type
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SSPC-PA 17 September 25, 2012 Editorial Revision November 1, 2012
shall be obtained on a representative vertical or horizontal surface. When measuring, the inspector shall document the location and results of the individual readings, the test method used, and whether the measurement conformed to contract requirements. A change in any of the items or personnel listed in Tables B1, B2, or B3 (as applicable) between acceptance of the test area and the end of surface preparation shall require verication that the prole remains in compliance with project requirements (see Appendix B3).
STEP 3: Record the extent of the noncon using readily identiable structur members or permanent structura
NONMANDATORY APPENDIX C: Additiona erations When Measuring Surface Prole
C2.1 Determining Surface Prole/Peak Surfaces Shop-Prepared Using Stationary C Blast Cleaning Units: A centrifugal blast m comprised of one or more spinning wheels that thr B3 Additional Requirements for Process Changes blast media at a conveyed part that moves parallel machine. Various parameters, including dwell tim B3.1 If there is a change to any of the items listed in of travel, can affect the degree of cleaning and Tables B1, B2, or B3 (as applicable) during surface prepara achieved. A key parameter that can affect the unifo tion, the time that the change took place and the location of blast prole depth is the positioning of the adjusta the surfaces or the identity of the pieces prepared before the Improperly aligned wheels may not achieve a un change shall be identied. prole because some areas could be partially or missed. In some cases the blast media may strike B3.2 Unless otherwise specied in the contract docuat an oblique angle resulting in a lesser prole dep ments, two measurements shall be taken at randomly to account for the potential variability in the surf selected locations on the prepared surface(s) of the struc the prole should be measured at representative u ture (or on a minimum of two of the prepared pieces) upon tions. For example, U-shaped sheet piles have thr completion of surface preparation. One measurement oriented surfaces on each side. Each of the thre shall be taken on the structure’s surface(s) prepared (or on should be evaluated for compliance to the spe one of the pieces prepared) before the process change. prole separately. The values should not be avera The second measurement shall be taken on the prepared one surface is non-compliant, the machine should surface(s) of the structure (or on one of the pieces prepared) You're Readingand a Preview the piece reblasted and checked for complian after the process change. The location of the tests, the surface. The procedure should be repeated until th test methods used, the test results and whether the results Unlock full access with a free trial. prole is achieved. Caution should be exercised in conformed to contract requirements shall be documented. as steel surfaces can be compromised by over blas failures in the grain structure of the steel Free Trial once during Withsurface B3.3 If the process changes more than Download surface preparation, an additional measurement per the above procedure each time the process changes shall be taken. B4 Non-Conforming Surface Prole: 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 direction, then no
C2.2 Determining Surface Prole on Surfac Using Portable Centrifugal Blast Cleaning Units centrifugal blast machine uses one or more spinn that throw abrasive blast media at a surface a machine is moved parallel to the surface. Various p Sign up to vote on this title including dwell time and rate of travel, can affect th cleaning blast prole achieved. Useful useful A key parame and Not affect the uniformity of the blast prole depth is the of blast media across the width of the c leaned surfa
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C2.4 Determining Surface Prole on Surfaces Cleaned to SSPC-SP 15 or SSPC-SP 11: When power tool cleaning to SSPC-SP 15 or SSPC-SP 11, the designed service life of the cleaning media may end before the specied or default minimum surface prole required is achieved. The frequency of determining additional location averages of prole or surface roughness and peak count should be increased to reect the productive life of the media being used. The designed service life of the power tool cleaning media used should be considered when specifying the frequency for determining compliance. C2.5 Precautions Regarding Determination of Surface Prole C2.5.1 Determination of Surface Prole on Flame Cut Edges: When steel is cut using oxy-acetylene torches, the heat that is generated during the cutting process hardens the cut edge. This is known as carburization or case-hardening (surface hardening) of the steel. Subsequent abrasive blast cleaning of these surfaces will typically yield a shallower surface prole depth due to the increased hardness of the surface. Removal of the hardened surface using grinders prior to abrasive blast cleaning will typically resolve the problem. Surface prole readings and location averages should be obtained in these areas to verify compliance with project requirements.
C2.5.2 Effect of Existing Surface Prole Generated Surface Prole: Steel surfaces w coating that must be removed may already have surface prole. During surface preparation, the n prole combined with the existing surface prole m the specied maximum surface prole for m operations. A representative area of the structure evaluated to determine the surface prole yield bef tion abrasive blast cleaning begins so that adjustm abrasive, equipment or other factors (or the projec tion requirements) can be made.
C2.5.3 Determining Surface Prole on Pi Surface prole readings taken on pitted areas of ste false high values (even with visual techniques). Su readings should be obtained from non-pitted area steel surfaces contain pits. If the steel is 100% p panel should be created to evaluate the surface
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