The manufacturing tolerance is the level of deviation from the values guaranteed in the acceptance test that is permitted and which occurs as a result of imprecision when manufacturing the hydraulic pump components. It includes profile defects, surface factors and assembly differences, as well as all factors arising from differences between the prototype version and subsequent reproductions (e.g. the series).
The manufacturing tolerance affects the pump operating data (e.g flow rate, head) and is determined by the pump production method. It must be taken into account, for example, when carrying out a characteristic curve comparison between the catalogue values (possibly also guaranteed values) and the measurement results for a real pump. Measurement errors may even occur when tests are merely repeated without making any changes to the pump.
Acceptance standard DIN EN ISO 9906 for centrifugal pumps does not refer to the manufacturing tolerance specifically. However, it is taken into account as part of the tolerance factors in the form of a certain allowance for measurement uncertainty.