Bypass valve and pig having a bypass valve

A bypass valve for an inspection and/or cleaning pig for a pipeline through which a medium flows, the bypass valve comprising:

• an inner space which is provided with a flow profile and in which there is arranged a piston which is movable in a longitudinal direction of the bypass valve via a force storage medium in a pressure-dependent manner;
• wherein the piston moves between a first open position of the bypass valve which creates a bypass for the medium, and a second position at higher differential pressure, said second position at least substantially closing the bypass,
• wherein the piston can be further moved from the first position via the second position in the same direction to a third, maximum position at a critical opening pressure which opens the bypass again,
• wherein a flow cross section released in the maximum position is smaller than a flow cross section present in the first position, but is larger than a flow cross section present in the second position of the piston.