The experimental evaluation of the power criterion for the metal fracture of the reserve and the long operated drill pipes was carried out. The conditions under which, during tripping operations, the failure of explored drill pipes, containing external or internal transverse annular cracks are possible. An interrelation between the depth of critical external or internal transverse annular cracks in drill pipes with the weight of the drilling string is considered, taking into account the influence of dynamic loads during tripping operations. It is shown that internal transverse annular cracks in lowering operating drilling strings at depths of more than 1400 m are more dangerous than external ones, while at depths up to 1400 m, external cross-sectional circular cracks are more dangerous.