Abstract: A single anchor leg mooring (SALM) installation which enables replacement of a product distribution unit (PDU) without removal of the upper buoyancy structure, including a plurality of arms that can extend around the PDU to connect the buoyancy structure lying above the PDU with a lower structure that lies below the PDU and extends to the sea floor. The transference of oil or other cargo can continue during the replacement of a malfunctioning PDU, by providing a pair of PDUs and a pair of valves for bypassing one of them which is to be removed.