Isobaric　energy　recovery　devices　(ERDs)　are　developing　rapidly　and　playing　a　significant　role　in　reducing　specific　energy　consumption　(SEC)　of　seawater　reverse　osmosis　(SWRO)　desalination　systems.　However,　leakage,　abrasion　and　large　pressure　loss　are　still　big　challenges　and　remain　big　problems　unsolved　among　the　present　ERDs.　In　this　paper,　a　novel　isobaric　ERD　based　on　so-called　fully-rotary　valves　(FRVs)　is　developed　to　resolve　these　problems.　The　key　fully-rotary　valve　energy　recovery　device　(FRV-ERD)　consists　of　only　two　FRVs　and　pipelines.　The　performance　of　the　FRV-ERD　is　tested　by　means　of　an　ERD　performance　test　system.　The　hydraulic　performance　of　the　device　is　tested　under　laboratory　conditions　with　the　test　pressure　about　3.0　MPa.　Experiments　show　that　the　operation　of　the　FRV-ERD　is　stable　and　the　pressure　fluctuations　of　high　pressure　streams　are　small.　The　leakage　is　not　detected　and　therefore　excellent　seal　performance　is　proved　through　tests　as　well.　The　measured　pressure　loss　is　low　and　the　energy　recovery　efficiency　is　as　high　as　98.47%　which　is　among　the　best　of　the　reported　values.　(C)　2016　Elsevier　B.V.　All　rights　reserved.