Overview
ISO 22991:2004 - Gas cylinders: Transportable refillable welded steel cylinders for liquefied petroleum gas (LPG) - Design and construction - defines minimum requirements for the design, materials, construction, testing and manufacture of transportable, refillable welded steel LPG cylinders of water capacity up to and including 150 L, intended for service at ambient temperatures. The document supports safe, consistent production and type approval of LPG cylinders used in commercial and consumer applications.
Key topics and requirements
- Scope and applicability
- Covers welded steel, transportable and refillable LPG cylinders (≤150 L water capacity) exposed to ambient temperatures.
- Materials
- Shell and end-pressing materials shall conform to ISO 4978 or an equivalent specification.
- Chemical limits in the standard (cast analysis) include: C ≤ 0.22%, Si ≤ 0.45%, Mn ≤ 1.60%, P ≤ 0.025%, S ≤ 0.020%, and P+S ≤ 0.040%. Micro-alloying limits for niobium, titanium and vanadium are specified.
- Traceability: manufacturers must keep ladle analyses and mechanical property certificates and maintain material identification.
- Design and calculation
- Prescribes calculation methods for minimum wall thickness of cylindrical shells and ends based on yield stress, calculation pressure (Pc), geometry and shape factors.
- Calculation pressure: 15 bar for commercial butane-only cylinders; 30 bar for other LPG cylinders.
- Factors such as the weld stress-reduction factor J (J = 0.9 for longitudinal-weld cylinders; J = 1.0 for seamless-type) and shape factor C for end geometry are used.
- Construction and welding
- Welding procedure and welder qualification requirements (references to ISO welding standards).
- Requirements for workmanship, tolerances, heat treatment, valve protection and closure of openings.
- Testing and acceptance
- Mechanical tests, tensile and bend tests, burst (hydraulic) tests, pressure tests, radiographic and macroscopic examination, visual weld inspection, and pressure cycling (fatigue) tests.
- Batch testing, failure handling, type approval, marking and certification requirements are included.
Applications and users
- Cylinder manufacturers and fabricators designing and producing welded steel LPG cylinders.
- Certification and approval bodies performing type approval, batch testing and conformity assessment.
- Design engineers, safety/compliance officers, testing laboratories, and regulators responsible for pressure-vessel safety and LPG distribution.
- Buyers and specifiers seeking internationally harmonized requirements for safe, refillable LPG containers.
Related standards
Normative and referenced standards include ISO 4978 (materials), ISO 13769 (stamp marking), ISO 10920 / ISO 11116 (valve threads), and welding and NDT standards such as ISO 9606-1, ISO 1106, ISO 17637 and ISO 5817.
Keywords: ISO 22991:2004, LPG cylinders, welded steel cylinders, transportable refillable, cylinder design, cylinder testing, pressure calculations, manufacturing standards.