Fracture mechanics analysis of NGV fuel cylinders. Part 1. Steel cylinders. Topical report, August 1989-February 1993. [NGV (Natural Gas Vehicles)]

Technical Report · Mon Feb 01 00:00:00 EST 1993

OSTI ID:6550218

Connolly, M P; Hudak, S J; Roy, S

Compressed natural gas (CNG) cylinders for natural gas vehicles (NGVs) are subject to a combination of pressure cycles, associated with periodic refueling, and a potentially corrosive CNG environment. Under these conditions it has been shown that the life of the cylinder is governed by the corrosion-fatigue crack growth of internal flaws such as voids, pits or folds that may be present after manufacture. For NGV applications, these cylinders are required to operate for at least 15 years and the report, through a detailed fracture mechanics analysis, describes approaches to achieving the desired life. The analysis shows that a 15 year cylinder life can be obtained by using quality control to ensure that no initial defects greater than 0.045 in. X 0.090 in. exist after manufacture. Alternatively, gas drying can be used at the distribution stations to reduce the detrimental effects of the remaining CNG impurities, and thereby, produce long cylinder lives. The analysis also considers the role of in-service inspection/retest and shows that in-service NDE has little advantage, either technically or economically, for ensuring the fitness-for-service of steel NGV cylinders. The analysis also shows that hydrostatic testing of cylinders, either at manufacture or in service, is ineffective for detecting fatigue cracks and therefore should not be implemented as part of a fitness-for-service plan for NGV fuel cylinders. The issue of cylinder geometry was also considered and the analysis shows that improperly designed flat-bottomed CNG cylinders can result in premature fatigue failures originating at the inner wall in the transition region between the cylinder end and sidewall.

• Research Organization: Southwest Research Inst., San Antonio, TX (United States). Dept. of Materials and Mechanics
• OSTI ID: 6550218
• Report Number(s): PB-93-165835/XAB; SWRI-06-1566-2; CNN: GRI-5086-252-1440
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
36 MATERIALS SCIENCE
GAS CYLINDERS
FRACTURE MECHANICS
SERVICE LIFE
CORROSION FATIGUE
CRACK PROPAGATION
FAILURE MODE ANALYSIS
IN-SERVICE INSPECTION
NATURAL GAS
QUALITY CONTROL
STRESS CORROSION
CHEMICAL REACTIONS
CONTAINERS
CONTROL
CORROSION
ENERGY SOURCES
FATIGUE
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
INSPECTION
LIFETIME
MECHANICAL PROPERTIES
MECHANICS
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
032000* - Natural Gas- Transport
Handling
& Storage
360103 - Metals & Alloys- Mechanical Properties
360105 - Metals & Alloys- Corrosion & Erosion