Static protective FIBC classification

Antistatic

The word antistatic, in the most literal sense, means against static (electricity). It is often used in this sense to describe materials and products that provide protection against electrostatic hazards. However, antistatic is also used to refer to products that are intermediate between conductive and insulating. For example, in the ISO 20345/6/7 standards for footwear, antistatic footwear is specified has having a resistance higher than conductive footwear, but lower than electrically insulating footwear. Another use of the word antistatic is to describe a material that is not conductive, or low resistance, but nevertheless has some mechanism that resists electrostatic charging or dissipates charge other than by conduction.

In the IEC Technical Committee No. 101 (IEC/TC 101), the committee responsible for international standards in electrostatics, consideration was given to standardising the definition of antistatic. Given the many different uses and interpretations of the word, it was concluded that agreement on a single definition would be difficult, if not impossible, and that any definition that could be agreed would only add another to the many that are already in common use. To avoid any confusion in the standards it develops, IEC/TC 101 decided that antistatic is a deprecated word, meaning that antistatic is not used in any standard document to describe products or materials. Instead, terms that are related to measurable parameters or new unambiguous classification terms are used.

Standard classification for static protective FIBC

When it came to developing a standard for FIBC, it was fortunate that some prominent industry experts had already suggested a new way of classifying static protective FIBC. In a paper written by Maurer et al in 1987*, three types of FIBC were proposed: Types A, B, and C. Type A FIBC are bulk bags without any static protection. Type B FIBC are bulk bags made from materials with a low breakdown voltage to avoid propagating brush discharges, and Type C FIBC are conductive bags that protect against electrostatic hazards by conducting electrostatic charge to ground.

*Maurer B, Glor M, Lüttgens G, Post L, 1987 “Hazards associated with propagating brush discharges on flexible intermediate bulk containers, compounds and coated materials”, Inst. Phys. Conf. Ser. No. 85, pp. 217 – 222, IOP Publishing, Bristol.

The first standard to use this classification system was a European (CENELEC) Technical Report CLC/TR 50404:2003. By the time this standard was being developed, the safety record established by CROHMIQ® static protective FIBC had proven that it is possible for FIBC to be fully protected against electrostatic hazards without the need for a connection to ground. For this reason, CLC/TR 50404 extended the classification system proposed by Maurer et al to include Type D to describe FIBC that provide full static protection without the requirement for grounding. The four-type classification system is now used in IEC 61340-4-4, IEC TS 60079-32-1, NFPA 77, NFPA 652, NFPA 654, JNIOSH TR No. 42 and TRGS 727.

An important aspect of the four-type classification system is that it provides an unambiguous method of referring to static protective FIBC. Although the actual terms are not descriptive of electrostatic properties, all of the aforementioned standards clearly describe the requirements and safe use applications for each of the types, including convenient summary tables, an example of which can be viewed at FIBC Classification Type A, B, C, D.

Avoiding confusion

Although the standard classification system for FIBC has been widely adopted in national and international standards, and is also widely used within the FIBC industry, there is still some confusion, and misuse in some cases.

The ubiquitous use of antistatic still continues. It is not unreasonable to use antistatic in its literal sense to refer to all types of static protective FIBC. But it does create a problem if by referring to Type B, Type C, and Type D as antistatic, it is interpreted as meaning they are all equivalent, which is definitely not the case. Each type is distinct from the others, both in terms of the materials used for construction and the intended safe use applications.

The descriptions and summary tables in the standards are intended to provide FIBC users with clear instructions about the applications for which the different types of FIBC are safe to use. To ensure the safety of workers and factories handling products in bulk bags, it is important to follow these instructions. The summary tables do contain terminology related to explosive atmospheres that perhaps is not always known or understood. The article Explosive Atmospheres explains the terminology related to explosive atmospheres.

Companies selecting or specifying FIBC, or receiving products packaged in FIBC should not just ask for or accept antistatic bulk bags, but should demand the specific type of FIBC appropriate for the intended application. The table below is a simplified guide to selecting the safe type of FIBC for different applications.

Guide for Selecting Type of FIBC by Application