This specification covers flanged and welding end steel valves for pipeline service in the following types. Gate valves: egular double-disc@ rising-stem Regular double-disc@ non-rising-stem Conduit@ rising-stem Conduit@ non-rising-stem Plug valves: Short pattern Regular Venturi Round-port@ full-bore Swing check valves: Regular Full-opening NOTE: The valve sketches herein are illustrative of some of the stipulations of this specification. Although these sketches are based upon designs now available@ they are to be construed neither as sponsoring such designs in whole or in part nor as discriminating against others that may be offered in the future as adequate for the services defined herein-provided@ however@ that they comply with the general requirements herein. Also@ the choice of materials for certain valve parts is optional with the purchaser. Therefore@ the purchaser should state all his requirements at the time of purchase@ with the understanding that@ it not otherwise specified on the order@ the manufacturer may supply any commercial variation meeting the requirements of this specification; and further@ that no one manufacturer is prepared to furnish valves in all applicable variations. In all cases@ therefore@ it must be the responsibility of all cases@ therefore@ it must be the responsibility of the purchaser to insure that any valves ordered in accordance with the general requirements herein@ will operate satisfactorily under the particular service conditions for which the valves are required. Nothing contained in this specification is to be construed as granting any right@ by implication or otherwise@ for manufacture@ sale@ or use in connection with any method@ apparatus@ or product covered by letters-patent@ nor as insuring anyone against liability for infringement of letters-patent. This specification is for the convenience of purchasers and manufacturers in ordering and producing valves. It is not intended to inhibit purchasers and producers from purchasing and producing valves meeting specifications other than those contained herein; nor is it intended in any way to inhibit purchasers from purchasing valves from companies not authorized to use the API monogram@