Downhole tractor comprising two or more hydrualic supply lines

A downhole tractor having at least one hydraulic drive section, the downhole tractor comprising:

• a first hydraulic supply line (200, 200-1) for actuating at least one hydraulic cylinder (160) for actuating at least one tractor arm and a second hydraulic supply line (300, 300-1) for driving at least one hydraulic motor (170) for rotating at least one tractor wheel;
• and
• a hydraulic power pack (100) configured for supplying hydraulic fluid to the hydraulic supply lines (200, 200-1, 300, 300-1), wherein the hydraulic power pack (100) comprises a pressure-setting valve (115) provided between the first hydraulic supply line (200, 200-1) and the second hydraulic supply line (300, 300-1), the pressure-setting valve (115) being configured to hold a preset pressure on an input side of the pressure-setting valve (115) and supply the hydraulic fluid to the first hydraulic supply line (200, 200-1) and, at the same time, for feeding excess hydraulic fluid in the first hydraulic supply line (200, 200-1) to the second hydraulic supply line (300, 300-1) to increase the speed of the downhole tractor, the first hydraulic supply line (200, 200-1) being at a higher pressure than the second hydraulic supply line (300, 300-1).