ASME Code Case 2229 provides minimum requirements for designing and constructing flat ribbon wound layered pressure vessel. The authorhas worked in this field for more than 10 years and describes the design philosophy of the fiat ribbon wound layered pressure vessel through four parts: strength calculation, fatigue strength, engineering design, and nozzle reinforcements. A new joint construction between ribbon wound shell and hemispherical head thinner than shell and comments on the Code Case are also given.