In: Chemistry
What problems would you foresee in naming equipment in a process that had a unit number of 10 (for example, pumps starting with P-11, P-12, etc.)?
By having a unit number with only 2 digits (10, 20, 30, etc.), the maximum number of equipment items within an equipment class is 9. For example, pump 11 in unit 20 would become P-31, which could be in conflict with the first pump of unit 30. By numbering units in the hundreds (200, 300, etc.), the maximum number of items in an equipment class is 99 so there will never be a conflict of this type.
Numbering units with two digits allows 9 items/class; hundreds prevents conflicts with 99 items/class.