A. Spiral steel pipe deviation: During the production process, it is often difficult to achieve the nominal size requirements, resulting in actual sizes that are often larger or smaller than the nominal sizes. Therefore, the standard specifies an allowable difference between actual sizes and nominal sizes. A positive difference is called a positive deviation, while a negative difference is called a negative deviation.
B. Spiral steel pipe tolerance: The sum of the absolute values of the specified positive and negative deviation values in the standard is called tolerance, also known as 'tolerance zone'.
Deviation has directionality, represented as 'positive' or 'negative'; tolerance does not have directionality. Therefore, referring to deviation values as 'positive tolerance' or 'negative tolerance' is incorrect. | 
