Abstract: A mathematical procedure is proposed to calculate the inter-lobe clearance between two mating screw rotors in contact state, in which the affect due to the bearing clearance and the imperfections in compressor housing manufacturing can be quantified with a higher accuracy. So the mathematical procedure can be used to quantify eventual rotor interference in screw compressors due to the bearing clearance and the imperfections in compressor housing manufacturing. The results show that the bearing clearances and the imperfections in casing manufacturing change the position of rotor shaft, consequently alter the inter-lobe clearance distribution along the contact line greatly. Some of the positions of rotor shaft minimize the inter-lobe clearance along the contact line which is in the hermetic segment, therefore they cause rotor interference possibly which lead to rotor abrasion or rotor seizing-up.

Key words: Clearance, Interference, Screw compressor