Composite CNG cylinders and 70 MPa hydrogen composite tanks – Designing with Statistical Methods, the smart way Fully wrapped composite cylinders, such as CPV's for 70 MPa hydrogen cylinders, compressed natural gas (CNG), breathing apparatus, LPG, and other applications benefit from statistical methods for design and production. Composite cylinder designers face many questions: What is the lower limit “allowable” fiber strength that I should use? How do I know if my cylinders