Presented are test results of gas separators for submersible pumps MN-GSB5. designed by "Borets" plant, and MN-GSL5. designed by State Oil&Gas Academy and Lebedyanskiy Machine Works, which have been conducted on model gas liquid mixtures at the stand in Russian State Oil&Gas University under I.M.Gubkin. It is stated, that efficient operating range of gas separator MN-GSB5 of "Borets" plant is much less, than that of gas separator MN-GSL5, manufactured by Lebedyanskiy Machine Works. Assumption is made, that authors of gas separator design, manufactured by "Borets" plant, failed to implement successfully super-cavitation principle, utilization of which is the basis of free gas separation technology, protected by patenet RF # 2027912.