DESIGN, APPROVAL AND TESTING OF FABER'S CYLINDERS
Faber’s cylinders comply with the most stringent specifications set down by International Bodies and Local Authorities. All over the world Faber is well known for the comprehensive range of safety and standard approvals of its cylinders. A list of Faber’s Approvals is available. Following you will find an introduction to the design, the approval and the production tests undertaken for Faber’s cylinders.
1. The design of Faber’s cylinders uses not only specified calculation formulae but also finite element analysis (FEA). The calculated data are then verified/confirmed experimentally, using a number of techniques which include strain-gauge measurements.
2. After veryfing the chemical, physical, mechanical characteristics and, where necessary, its stress-corrosion resistance; the candidate materials (steels, fibres, resins, etc.) are all carefully selected depending on the eventual use conditions of the proposed cylinder.
3. Faber also undertakes a fracture mechanics analysis of the steel, which allows us to define the maximum permissible defect size in the cylinders, in order to enable us:
- to establish the non-destructive tests limits which should be undertaken in the production line
- to guarantee the cylinder’s fatigue life
- to demonstrate that a leak precedes the hypothetical burst of the cylinder (LBB)
4. The cylinder’s surface protection is considered to be a function of the various environmental conditions of use and of the various corrosion agents which the cylinder may come into contact with
Prototype design tests and analyses are undertaken by an independent organization such as a Notified Body/Independent Inspection Agency, for every new cylinder design at Faber, in order to gain the necessary approvals. All the test work necessary to gain the approvals, as stipulated in the relevant specification, is conducted at Faber using our own equipment and facilities. Such tests include, apart from the conventional mechanical test and fatigue/burst testing, advanced tests on full scale cylinders such as environmental testing, extreme temperature tests, flawed burst tests, bonfire/high velocity impact tests (gunfire), gaseous pressure cycling test etc. Additionally a number of material tests such as Sulphide Stress Cracking (SSC), compatibility and fatigue crack growth propagation under gaseous hydrogen up to 1100 bar are performed.
Apart from the prototype test regime regular tests have to be performed to satisfy the requirements of the standards/regulations. Often referred to as batch/production tests, these comprise:
1. Mechanical tests: strenght (yield and tensile), elongation, Charpy impact, toughness, stress-cracking
2. Chemical analysis on prototype cylinders (check of safety performance)
During production depending on the nature of the standard being applied, cylinders are subjected to:
1. Hardness test
2. Ultrasonic examination (for detection of imperfections and wall thickness measurement)
3. Hydraulic test (proof or volumetric expansion) test
4. Leak test on the base of tube spun cylinders
5. Check of the critical dimensions and of the neck threads
6. Check of the stamp markings
7. Check of the specified internal and external surface finishing
8. Flawed cylinder burst-test
UPDATED: JANUARY 2021