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bulletin - The National Board of Boiler and Pressure Vessel Inspectors

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Stamp<br />

Maintenance By<br />

John Hoh, Assistant Director <strong>of</strong> Inspections<br />

AApproximately 3,000 boiler <strong>and</strong> pressure vessel manufacturers around the world have received the <strong>National</strong> <strong>Board</strong><br />

“NB” symbol stamp for use on those items registered with the <strong>National</strong> <strong>Board</strong>. While the m<strong>and</strong>atory effective date for the<br />

stamp was January 1, 2003, many manufacturers began using the stamp as soon as they received it. This provided well<br />

over one year <strong>of</strong> feedback from manufacturers. Of the total number <strong>of</strong> stamps in use, three reported problems concerned<br />

the same issue, maintenance <strong>of</strong> the stamp.<br />

Any struck tool such as the “NB” stamp can exhibit deformation or “mushrooming” at the point where it is struck by the<br />

hammer. While this is normal, the user <strong>of</strong> the tool should inspect the struck end for small cracks, especially around the<br />

perimeter <strong>of</strong> the “mushroom.” <strong>The</strong>se cracks develop as the steel deforms. If not removed, the cracks can cause the stamp<br />

to split down its length (as shown in these photographs). <strong>The</strong> cracks are easily removed by light grinding or by using a<br />

h<strong>and</strong> file. This simple maintenance will greatly extend the life <strong>of</strong> the stamp. ❖<br />

NATIONAL BOARD BULLETIN/FALL 2003<br />

FEATURE<br />

21

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