UAMA B74的适用范围。22-1991（R2014）仅限于9“x 1/4”27型便携式砂轮，其破裂方式可能导致操作员看不到裂纹。如果9“x 1/4”车轮通过了试验，则同样设计的7“x 1/4”车轮也被视为通过了试验，因为9“x 1/4”车轮上的试验条件比7“x 1/4”车轮上的试验条件要严重得多。

The scope of UAMA B74.22-1991 (R2014) is limited to 9" x 1/4" Type 27 portable grinding wheels that can be cracked in such a manner that the crack is not visible to the operator. If the 9" x 1/4" wheel passes the test then 7" x 1/4" wheels of the same design are also considered to have passed since the test conditions on a 9" x 1/4" wheel are much more severe than on a 7" x 1/4" wheel.