He was a brother of ship-owner Anton Fredrik Klaveness (1903–1981),[1] brother-in-law of Johan H. Andresen,[2] nephew of Johan Karsten Rasmussen,[3] and grandnephew of ship-owner and politician Henrik Klaveness.
[5] Klaveness finished his secondary education in 1931 and took one year of officer's training before moving to Switzerland.
From 1939, he spent his career as chief executive officer of the major shipping corporation A. F. Klaveness & Co.[1] He chaired Selco from 1956 to 1965, Skipsassuranseforeningen Unitas and Robergmyrene.
He was a board member of Høyanger, Norsk Aluminium Compani and Nordisk Aluminiumindustri from 1958 to 1967.
He was a supervisory council member of Årdal og Sunndal Verk[1] and the Norwegian America Line (deputy).