coating specifications

The Use of Shall, Should and May in Coating Specifications and Standards

coating specifications coating standards

When reviewing reference standards, a single word can make the difference between a requirement that is mandatory, versus one that is recommended or optional.  The same is true of specifications, although in that case, most if not all requirements should be written as being mandatory.   The words shall, should, and may are the focus of this article as used in SSPC/NACE standards.  The examples below are from the 2007 version of SSPC-SP10/NACE No. 2 Near-White Metal Blast Cleaning.  The words have been underlined and shown in italics for emphasis.

Shall – Shall is used to designate a mandatory requirement.

Examples of Shall:

3.1 The latest issue, revision, or amendment of the docu­ments listed in Paragraph 3.3 in effect on the date of invitation to bid shall govern unless otherwise specified.

3.2 If there is a conflict between the requirements of any of the documents listed in Paragraph 3.3 and this standard, the requirements of this standard shall prevail.

4.1 Before blast cleaning, visible deposits of oil, grease, or other contaminants shall be removed in accordance with SSPC-SP 1 or other agreed-upon methods.

Should – Should is used for requirements that are considered good and are recommended, but are not absolutely mandatory.

Examples of Should:

4.2 Before blast cleaning, surface imperfections such as sharp fins, sharp edges, weld spatter, or burning slag should be removed from the surface to the extent required by the procurement documents (project specification). Additional information on surface imperfections is in Paragraph A4 of Appendix A.

4.3 If reference photographs or comparators are specified to supplement the written standard, the condition of the steel prior to blast cleaning should be determined before blasting commences. Additional information on reference photographs and comparators is in Paragraph A3 of Appendix A.

8.3 The procurement documents (project specification) should establish the responsibility for inspection and for any required affidavit certifying compliance with the specification.
May – May is used to for requirements that are optional.

Examples of May:

5.3 Other methods of surface preparation (such as wet abrasive blast cleaning) may be used to achieve a near-white metal blast cleaned surface by mutual agreement between those responsible for establishing the requirements and those responsible for performing the work. Information on the use of inhibitors to prevent the formation of rust immediately after wet abrasive blast cleaning is in Paragraph A5 of Appendix A.

7.2.2 Moisture separators, oil separators, traps, or other equipment may be necessary to achieve clean, dry air.

Combinations of Shall and MayFollowing are a few examples where shall and may are used together in the standard.

Examples of Shall and May combined:

2.1 Near-White Metal Blast Cleaned Surface: A near-white metal blast cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter. Random staining shall be limited to no more than 5 percent of each unit area of surface (approximately 5,800 mm2 [9.0 in.2] (i.e., a square 76 mm x 76 mm [3.0 in. x 3.0 in.]), and may consist of light shadows, slight streaks, or minor discolorations caused by stains of rust, stains of mill scale, or stains of previously applied coating.

2.1.2 SSPC-VIS 1 may be specified to supplement the written definition. In any dispute, the written definition set forth in this standard shall take precedence over reference photographs and comparators.  Additional information on reference photographs and comparators is in Paragraph A3 of Appendix A.

5.1 Clean, dry compressed air shall be used for nozzle blasting.  Moisture separators, oil separators, traps, or other equipment may be necessary to achieve this requirement.

6.4 Any limitations on the use of specific abrasives, the quantity of contaminants, or the degree of allowable embed­ment shall be included in the procurement documents (project specification) covering the work, because abrasive embedment and abrasives containing contaminants may not be accept­able for some service requirements. Additional information on abrasive selection is in Paragraph A6 of Appendix A.

7.2.1 The presence of toxic metals in the abrasives or coating being removed may place restrictions on the methods of cleaning permitted. The chosen method shall comply with all applicable regulations.

When reviewing standards or writing specifications, the words must be selected with the intention clearly in mind.  “Must” is the same as “shall” and is another option in those cases when “shall” isn’t appropriate for the sentence structure.

ken trimber kta Ken Trimber KTA

 

 

 

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