Introduction
Standardisation is a living process. Often yesterday’s development is today’s operation, based upon tomorrow’s standard.

Formulating a standard at a national level is a relatively easy task, unimpeded by any language barriers or local procedures. However, for over half a century efforts have been underway to unite gas cylinder manufacturing and operations under a global umbrella. In the early days efforts at the International Standardisation Organisation (ISO) were thwarted by various nations, each with what it considered to be a worthy cause. Sometimes the reasons for the lack of an agreement were embedded in a nation’s belief in their long held (but considered by others to be outmoded) practices, while other nations attempted to achieve a technologically advanced product from a global standard. Occasionally, poor communications also contributed to the overall slow progress. As you can imagine, such opposing objectives bred an atmosphere of distrust and compromises were difficult to achieve.

It took several decades to break down these barriers and for confidences to be built. But once a hardcore of experts got truly underway, standards began to flow under the auspices of a technical committee, ISO TC58 (Gas Cylinders).

The result is that there are currently well over 50 standards within its repertoire, with many of the documents assisting gas cylinder manufacturers and users alike. Of greater interest is the importance given by some competent authorities (governmental bodies) to these standards both by incorporating them at national levels, while also agreeing to their international use. There are still however some glaring exceptions with major nations such as S. Korea, Japan, the US, and Canada yet to incorporate certain basic standards into their national legislation.

Cylinder manufacturing
It has only been around a decade since ISO 9809 Part 1 was first published, under the auspices of ISO TC58/SC3 (Cylinder Design). This is the work-horse seamless steel cylinder in the industrial gases business, for high pressure applications, being manufactured today.

Remarkably, already several million cylinders have been made in Europe, Asia and the Americas, to this standard and are in safe service worldwide. Its popularity has been enhanced by the road and rail transport agencies (ADR/RID) referencing this as an approved standard.

The standard drew upon worldwide expertise and, though less prescriptive than other regional standards, uses an advanced design concept (Lamé-von Mises) which results in efficient, light-weight cylinders. The safety aspects of this thin walled cylinder design, are tempered with the requirements of a stringent minimum burst pressure requirement and every cylinder having a mandatory ultrasonic examination at the time of manufacture, in addition to all earlier tried and tested requirements.

Interestingly, ISO 4706 for welded steel cylinders has been around for over 20 years and has been widely manufactured and used for liquid petroleum gases (LPG) for cooking and heating applications, particularly in South Africa. In fact, this family of cylinders are the most common in the cylinder world.

One standard, ISO 11439, intended for manufacturing cylinders for storing fuel gases (CNG) on-board vehicles, has really caught the imagination of users worldwide. Its usefulness has been highlighted by some legislators incorporating an earlier draft of this standard in some vital legislation, which has led to some difficulties currently being addressed.

Cylinder operations
In some ways ISO standards have been more useful to gas cylinder users than to manufacturers. This is because standards published through ISO TC58/SC4 (cylinder operations) are intended to be applied not only to ISO manufactured cylinders, but also to cylinders in the gas companies’ fleets made to other standards. The latter does not need the consent of the local authority or governmental body, though in many cases this is a formality; the standard emanating from ISO is often more relevant to current operations, environmentally responsible and modern compared to the national counterpart. In the periodic inspection and testing standards for example, a stringent non-destructive test in the form of ultrasonic examination, may be substituted in place of the sometimes unreliable and outmoded hydraulic pressure test. Apart from a entire suite of periodic inspection and test standards such as ISO 6406 (for seamless steel) and ISO 10461 (for seamless AA), ISO has published standards for precautions to be taken for all types of cylinder filling operations and for times when cylinders are to be converted from one gas to another.

Overlapping Interests
Some vital standards of use to manufacturers, users and legislators have also been published.

These include the “stampmarking” standard (ISO 13769) and the ISO 11119 series which gives guidance on the chemical compatibility of gases with the cylinder/valve materials. In some ways these cross-discipline standards have been some of the most time-consuming ones to publish, though their value is enormous. For example, all users of cylinders now expect to find key characteristics pertinent to a particular cylinder at prescribed locations on the cylinder (usually the shoulder area), using agreed abbreviations and all in the English language. While ISO 11119-1 cites hundreds of gas/cylinder-valve compatibility combinations, of probably greatest value is the data for hydrogen and embrittling gases in steel cylinders (see Fig. 1).

The importance of this group of gases (in view of its potential use as a motor vehicle, clean-fuel gas) has prompted the recent publications of ISO 11119-4 specifically dealing with test methods for hydrogen. Though a thorough absence of standardisation here has meant some conflicting data has resulted. ISO TC58 is currently tackling this issue with a view to reviewing ISO 11119-4 and this is a perfect example of “standardisation being a living process”.

Usefulness of ISO standards
Who values ISO standards? The list is long and the answers are varied depending on the motives.

The principal benefits are:
Cylinder manufacturers are discovering that ISO standards are a useful tool in reducing their wide range of designs thus eliminating duplications with the numerous national standards previously employed.

Developing countries, in the absence of relevant standards of their own, adopt ISO standards as national standards thus enhancing local safety. This is to be viewed in the light of an ever-decreasing number of experts available in a given nation in an ever-specialising subject area, as more efficient gas cylinders are constantly demanded (see Fig 2).

Global industrial gas suppliers enjoy a major cost benefit by specifying a common ISO standard across many of their operating companies when ordering gas cylinders. Furthermore, the operational standards are being applied, sometimes as part of their requirements, by gas companies across their regions globally.

ISO standards are increasingly being recognised at United Nations to support the “Transport of Dangerous Goods” regulations. Apart from achieving global harmonisation, such an approval ensures a safe and equal platform for all who adopt these standards.

The future is ISO
Enormous investment is made by individual organisations in providing experts to participate in ISO work. Starting with the laborious stages of drafting documents in working groups, through a series of voting phases, which are always interspersed with extensive comments and re-drafting at various stages, the overall effort expended is a testament to the high value placed on the finished product.

In the last few years the working of ISO TC58 has fallen into an efficient pattern. Earlier published standards are being constantly reviewed and modernised, whenever possible. An ever-increasing number of nations are actively participating with China, India, South Africa and Australia among others attending committees previously populated mainly by European, American and Japanese delegates. Notable hurdles have still to be overcome such as the mutual recognition of inspection bodies. But with ever-growing trust between nations and ease of communications, the future is bright for gas cylinder standards’ harmonisation through the support of ISO throughout our world.