CPC Main Group F04D 9/00 Priming; Preventing vapour lock 5 direct subcodes Child Classifications Navigate with arrow keys, Enter to open F04D 9/001 F04D 9/004 F04D 9/007 F04D 9/02 Self-priming pumps F04D 9/04 using priming pumps; using booster pumps to prevent vapour-lock