Around 740,000 tank containers transport bulk liquids, powders and gases around the world on a daily basis. Many of these substances are highly toxic and potentially dangerous, yet without them many of the things we take for granted could not be manufactured.
So, making sure that moving these products is done as safely and securely as possible is paramount. A group of materials little known by the public plays a crucial role in ensuring this high degree of safety. Yet this group is itself is now under scrutiny.
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a class of several thousand synthetic chemicals widely used in everyday products, such as clothing, carpets, fabrics for furniture, adhesives, paper packaging for food, and non-stick cookware.
In tank containers, one particular PFAS – polytetrafluoroethylene (PTFE) – is used to make sealing elements around a tank container’s potential weak points, like valves and access hatches.
PFAS materials are widely used because of their proven properties of chemical resistance, temperature range, durability, shrinkage and vibration resistance, and cutting and machining qualities.
Because of these exceptional properties, the operational safety and leak tightness record of the tank container remains excellent.
However, PFAS are also sometimes known as ‘forever chemicals’ because they do not easily break down, but accumulate in the environment and in human bodies.
Consequently, as long as PFAS continue to be released into the environment, humans and other animal species will be exposed to ever greater concentrations. Even if all releases of PFAS stopped now, they will still be present in the environment for generations to come, potentially contaminating groundwater and drinking water.
Certain PFAS are known to have toxic effects, and can even harm the development of foetuses. Several PFAS are believed to be carcinogenic in humans, while some are also suspected of interfering with the human endocrine system.
Consequently, there is growing pressure to restrict the manufacture and use of PFAS. A group of European countries – Germany, Netherlands, Norway, Sweden, and Denmark – originally proposed a joint restriction on PFAS under REACH, the EU regulation covering the production and use of chemical substances.
A consultation process on further restrictions of PFAS is now being conducted by the European Chemicals Agency (ECHA), which implements EU chemicals regulations.
But such is the concern in the tank container sector, that the industry trade group ITCO – the International Tank Container Organization – recently submitted a case study setting out reasons why regulators should designate PFAS sealing elements in tank containers as “materials of essential use”.
The study points out that tank containers are already highly regulated, primarily through the International Maritime Organization’s International Dangerous Goods Code.
Materials used for sealing elements must provide a range of technical properties that ensure they function as reliable and safe containment means for liquids and liquefied gases.
Importantly, PFAS substances used in tank sealing elements are in solid form which poses far less risk than other forms being scrutinised by ECHA. These solid materials do not shred or degrade to particles as is the case with some other industries, such as food packaging, clothing, and fire-fighting foams.
Waste from used sealing elements is disposed of at licensed industrial waste sites, while new material from manufacturing cut-offs and drilling are recycled. Initiatives to develop recycling of used materials are in progress in the Netherlands, and ITCO is actively encouraging more such efforts.
But the point is that solid PFAS-based sealing elements pose minimal risk to the environment.
ITCO emphasises that currently alternative materials do not provide the crucial performance range achieved by existing specified solid state PFAS sealing elements.
Some of the non-PFAS alternatives researched – which include UHMW-PE, PVC-U, polypropylene, elastomeric compounds, and natural rubber – could be economically beneficial, but the operational cost resulting from the risk of leakage would exceed any saving by a long way.
For example, a fibrous material might be used as a gasket to seal the face between two flanges, but the material cannot be used in the manufacture of an ‘O’ ring. In addition to being less reliable as a sealing gasket, fibrous material might become saturated with the dangerous substance transported in the tank, a toxic chemical, say. The gasket would then need to be handled by personnel undertaking maintenance, so adding a health and safety issue along with an additional environmental disposal risk.
Furthermore, other materials are technically unsuitable in many required applications and therefore cannot be considered as feasible alternatives.
But even if a suitable alternative is found soon – which is unlikely – it would likely take a long time before it could be introduced into the market.
All valves and equipment must undergo rigorous testing processes which are witnessed and signed off by an authorised industry inspector, acting for the relevant governmental administration. This type-approval testing can take months to carry out and must be repeated if subsequently there is a variance in design or materials.
So, a widespread restriction on PFAS would require: first, finding technically suitable alternatives as detailed above; and, second, manufacturing and testing these alternatives and then re-applying for industry approval.
However, the life expectancy of a tank container often exceeds 20 years and there are thousands of valve designs still in use around the world. To re-approve all this equipment would take many years and cost a small fortune. Some valve designs might not even achieve re-approval using non-PFAS alternatives. And achieving approval does not mean they will necessarily satisfy the customer’s end needs.
The consequent disruption to global supply chains would be severe, and the economic impact will be felt by consumers as a result of increased shipping timeframes and cost.
In addition, some chemicals might no longer be transportable until there are viable alternative sealing materials. The risk of leakage, risk to life and risk to the environment will increase with the restriction of PFAS materials, ITCO explains.
Hopefully, ECHA will take on board ITCO’s arguments and designates PFAS substances as essential materials so that the tank container industry can continue to transport everyday chemicals and the like efficiently and safely.