Inclined separator (1, 14, 15, 16, 17) for separating oil well substances, the separator (1, 14, 15, 16,17) comprising: - an elongated outer, closed tubular section (20, 85) and an elongated, inner tubular section (21, 80) arranged inside the elongated outer tubular section (20, 85), where both the elongated outer, closed tubular section (20, 85) and the elongated, inner tubular section (21, 80) are inclined either upwards or downwards relative to horizontal, - where the elongated, inner tubular section (21, 80) is closed in one end by an end cap, working as a slug breaker, and open in another end for connection to a tube feed section (10, 23) via a conical expansion between the tube feed section (10, 23) and the inner tube section (21, 80), - and where oil well substances are introduced into the open end of the inner tubular section (21, 80) via the tube feed section (23, 10) passing through the outer tubular section (20, 85) and into the inner tubular section (10, 23), - and where the inner tubular section (21, 80) comprises multiple slots (22, 81, 90) arranged in a longitudinal direction of the inner tubular section (21, 80) in a circumferential manner, - where the inclination of the separator (1, 14, 15, 16, 17) facilitates separation of the oil well substances into lower density substances and higher density substances, - where the lower density substances by buoyancy drift upward through the slots (22, 81, 90) and exit via an upper outlet (3, 86) in the outer tubular section (20, 85) and higher density substances sink downward through the slots (22, 81, 90) and by gravitation exit via a lower outlet (2, 84) in the outer tubular section (20, 85), when the direction of flow in the inner tubular section (21, 80) is either upwards or downwards. - an elongated outer, closed tubular section (20, 85) and an elongated, inner tubular section (21, 80) arranged inside the elongated outer tubular section (20, 85), where both the elongated outer, closed tubular section (20, 85) and the elongated, inner tubular section (21, 80) are inclined either upwards or downwards relative to horizontal, - where the elongated, inner tubular section (21, 80) is closed in one end by an end cap, working as a slug breaker, and open in another end for connection to a tube feed section (10, 23) via a conical expansion between the tube feed section (10, 23) and the inner tube section (21, 80), - and where oil well substances are introduced into the open end of the inner tubular section (21, 80) via the tube feed section (23, 10) passing through the outer tubular section (20, 85) and into the inner tubular section (10, 23), - and where the inner tubular section (21, 80) comprises multiple slots (22, 81, 90) arranged in a longitudinal direction of the inner tubular section (21, 80) in a circumferential manner, - where the inclination of the separator (1, 14, 15, 16, 17) facilitates separation of the oil well substances into lower density substances and higher density substances, - where the lower density substances by buoyancy drift upward through the slots (22, 81, 90) and exit via an upper outlet (3, 86) in the outer tubular section (20, 85) and higher density substances sink downward through the slots (22, 81, 90) and by gravitation exit via a lower outlet (2, 84) in the outer tubular section (20, 85), when the direction of flow in the inner tubular section (21, 80) is either upwards or downwards.