A gas cylinder can carry a familiar approval mark and still be unsuitable for its destination or receiving equipment. Two fittings can also engage for a few turns without forming the specified pressure-tight connection. For buyers, the practical task is to connect three pieces of information: the applicable rules, the identity and records of the package, and the complete interface to the gas system.
Start with three separate checks
A request for an “international standard cylinder” leaves too much open. Specify the destination and use first, then ask for evidence against the requirements that apply to that particular package.
| Layer | Question it answers | Evidence to request |
|---|---|---|
| Regulatory acceptance | Can this package be supplied, transported and used in the intended context? | Applicable regime, approval scope and destination requirements. |
| Construction and inspection | What was this identified package built and checked against? | Exact code or standard, edition, serial identification and relevant inspection records. |
| Connection compatibility | Does the complete interface suit the gas and receiving system? | Inlet and outlet designations, drawings, sealing arrangement, materials and ratings. |
These checks complement one another. A construction standard does not establish every destination approval, and an approval mark does not identify the mating connection.
PED and TPED: the equipment's role matters
The EU Pressure Equipment Directive, PED 2014/68/EU, concerns the design, manufacture and conformity assessment of stationary pressure equipment within its scope. The European Commission identifies a maximum allowable pressure above 0.5 bar as its pressure threshold, subject to the directive's definitions and exclusions.[1]
The Transportable Pressure Equipment Directive, TPED 2010/35/EU, covers defined transportable pressure equipment alongside dangerous-goods transport requirements. It addresses conformity assessment and inspections, and provides for the π mark. Its scope includes specific exclusions, so the label “transportable” alone does not settle applicability.[2]
For purchasing, ask which regime applies to the actual equipment and movement. A CE mark cannot simply replace the assessment and marking required under TPED.
DOT and ASME: distinguish regulation from a construction code
DOT means the US Department of Transportation. In cylinder procurement, the actual DOT specification or special permit matters. PHMSA's manufacturer guidance specifically addresses approval for manufacturing DOT specification and special-permit cylinders outside the United States. A general reference to “DOT approved” needs an identifiable scope and supporting record.[3]
ASME publishes technical codes. Its Boiler and Pressure Vessel Code Section VIII, Division 1 addresses pressure-vessel design, fabrication, inspection, testing and certification within its scope. “ASME” on its own is an incomplete specification: identify the section, division where applicable, edition and relevant records. Compliance with a construction code does not establish permission to transport or operate the vessel everywhere.[4]
PESO, KGS and EAC: check the destination framework
In India, PESO, the Petroleum and Explosives Safety Organisation, administers relevant regulatory processes. Its published framework distinguishes the Gas Cylinders Rules, 2016 from the Static and Mobile Pressure Vessels (Unfired) Rules, 2016. Identify the rules applicable to the equipment, including applicable amendments, rather than treating “PESO” as a construction standard.[5]
In South Korea, the Korea Gas Safety Corporation, KGS, describes an overseas-manufacturer process involving technical review, factory audit and government registration, followed by import inspection. Manufacturer registration and acceptance of a particular imported item are separate checks.[6]
EAC is the Eurasian conformity mark. It indicates conformity under the technical regulations applicable to the product; it is not itself a cylinder-design standard. Read the mark together with the relevant conformity documents, their scope and the equipment identification.[7]
These systems answer different regulatory questions. None should be presented as a universal substitute for the others.
ISO: ask which standard and what it covers
ISO develops international standards, but does not perform certification or issue certificates. Ask for the standard number, edition, certificate issuer and scope whenever certification is claimed.[8]
A management-system certificate concerns the organization and activities in its scope. It does not, by itself, demonstrate that an individual cylinder satisfies a product construction standard. Likewise, a standard addressing a connection has a different purpose from a standard addressing cylinder manufacture. Match each document to the question it can actually answer.
Valve inlet, valve outlet and the complete connection
The valve inlet joins the valve to the cylinder neck. The outlet joins it to downstream equipment, such as a regulator or pigtail. An outlet designation does not identify the neck thread.
Requests for a “DIN valve” or “CGA thread” are therefore incomplete. DIN 477 is a cylinder-valve connection standard; CGA V-1 covers compressed-gas cylinder valve outlet and inlet connections. Retain the exact connection designation and obtain the applicable drawing.[9]
DISS requires the full designation
DISS means Diameter Index Safety System, but the term appears in different gas-connection contexts. CGA V-5 addresses noninterchangeable low-pressure medical-gas connections. CGA V-17 separately addresses the CGA 630/710 series of ultra-high-integrity service connections. Industrial high-purity connections should not all be described as low-pressure medical fittings.[9]
Use the complete numbered designation and the actual manufacturer's specification. A family name alone cannot establish pressure rating or gas suitability. Review the sealing surfaces and components, materials, rated conditions and intended service as well as the threads.
BSP and NPT: a similar size does not establish a match
BSP includes parallel and tapered pipe-thread forms. NPT is a different thread system. The usual BSP profile has a 55° included thread angle, while NPT uses 60°; dimensions and pitches must also be checked. The same nominal size does not establish interchangeability.[10]
Sealing arrangements differ too. Parallel G/BSPP threads under ISO 228-1 use a specified seal outside the threads. ISO 7-1 instead covers pressure-tight thread joints, including tapered external R threads and either tapered internal Rc or parallel internal Rp threads. A parallel internal thread is therefore not automatically a G/BSPP connection. Follow the exact component documentation; do not use partial engagement as a compatibility test or force mismatched fittings together.
An adapter does not resolve an unsuitable pressure rating, material, gas service or approval status. Any proposed connection change needs review against the complete equipment specifications and manufacturer instructions.
A buying checklist for the packaging RFQ
- State the gas, required grade, package type, quantity, destination and transport context.
- Identify whether the package is supplier-owned or customer-owned, with identification and available records for existing equipment.
- Keep working pressure, test pressure and temperature conditions distinct.
- Request the construction standard and edition, applicable approval or conformity documents, and current inspection status.
- Specify the exact valve outlet and receiving connection. Supply a manufacturer's drawing or readable marking photograph; identify a cylinder-neck question explicitly.
See How to Read Gas Cylinder Markings and Labels for the distinction between permanent package identification and gas-content information. Our Packaging, Quality and Safety Documents pages provide related supply context. Include these details in your request for a quotation so the package, destination and receiving system can be considered together.
This guide provides general orientation. Equipment acceptance and connection selection require the current applicable rules, standards and manufacturer instructions for the actual package.
Sources
- [1] European Commission: Pressure Equipment Directive.
- [2] EUR-Lex: TPED 2010/35/EU, consolidated text.
- [3] PHMSA: Cylinder manufacturers.
- [4] ASME: BPVC Section VIII, Division 1.
- [5] PESO: Gas Cylinders Rules and regulatory resources.
- [6] KGS: Overseas manufacturer registration.
- [7] Eurasian Economic Commission: EAC mark provisions.
- [8] ISO: Certification.
- [9] CGA: Valve-connection publications, including V-1, V-5 and V-17.
- [10] Parker: Instrument Pipe and ISO Conversion Fittings, thread comparison.
Scope of this guide
Prepared by SG TRADING L.L.C-FZ. Sources reviewed 23 October 2026. General educational and procurement guidance, not an operating procedure or a determination that a particular item is approved for service. No specific cylinder markings or customer equipment have been decoded or certified in this article.