AIDGC PRESENTATION MARCH 2006 HAZARDOUS AREAS STANDARDS & CLASSIFICATION Jeff Strath Principal Engineer Paterson Flood Engineers Pty Ltd www.pfe.com.au
INTRODUCTION This presentation provides an overview of the processes typically used to classify hazardous areas in Australia. Special attention is paid to the types of situations frequently encountered when storing and handling dangerous goods. A number of other standards, in addition to the usual hazardous areas standards, are presented in this document. The following key themes are explored: Classification Why, What and How Combustible Liquids consideration of various standards Installation Issues
CLASSIFICATION - WHY Classification is the key tool used to identify areas of a facility which may contain an explosive atmosphere. Once an area has been classified as Hazardous, special precautions for equipment can be implemented to prevent ignition of an explosive atmosphere. Classification is the onus of the occupier of the site. Where a material is known to be explosive (have a flammable vapour), the area must be classified to meet the requirements of the Electrical Safety Act, which requires compliance with AS/NZS 3000 for most sites. The Workplace Health & Safety Act should also be considered. Additionally the Dangerous Goods Safety Management Regulation requires the occupier of a premises to ensure that ignition sources in a hazardous area are eliminated or controlled to an acceptable level of risk.
CLASSIFICATION - WHAT There are three categories of materials that require classification: Flammable Liquids (eg. Petroleum, Ethanol, MIBC) Flammable Gases (eg. Methane, Hydrogen) Combustible Dusts (eg. Flour, Coal) Recent Incidents have included: Flour (Food Manufacturing) Sugar (Raw Material Processing) Hydrogen (Food Manufacturing) Xanthates - Carbon Disulphide gas (Minerals Processing) Blood Meal (Raw Material Processing) Explosions and Fires are happening.
A typical process followed may be: CLASSIFICATION - HOW Step Description 1 Assemble a classification team & prepare a project execution plan. 2 Identify input data. 3 Identify any special circumstances and legislation. 4 Identify sources of release & grades of release. 5 Define ventilation. 6 Define zones. 7 Prepare area classification schedules. 8 Prepare area classification drawings. 9 Prepare area classification report. 10 Review documents within the classification team. The importance of understanding the properties of the hazardous materials should also be recognised. In particular the properties such as the temperature class and apparatus group must be identified, not just the Zone.
CLASSIFICATION
CLASSIFICATION THE TEAM Title Process Engineer Electrical/Instrumentation Engineer (s) Project Manager Competent Person (s) / Industry Expert (s) Owner (Persons having legal ownership of the facility) Operations Representative Maintenance Representative Function Defines the process and operating implications Reviews the Electrical and Instrumentation implications of the area classification on the equipment and installation Defines the cost implications of the area classification Assists in ensuring the relevant standards and procedures are followed in performing the area classification Person who is defined in AS/NZS 2381.1 as being responsible for providing the area classification to the electrical contractor Aids in defining the operation of equipment and the implications of the area classification Aids in defining the maintenance of equipment and the implications of the area classification The skills required for a person to be considered competent in performing a hazardous area classification are described by AS/NZS 4761. A least one person who can demonstrate competency is required to be involved in preparation of the classification documentation.
CLASSIFICATION STANDARDS The Standards which detail the methods for classification of Hazardous areas are changing. The current key standards are: Flammable Liquids & Gases AS/NZS 60079.10:2004 - Electrical apparatus for explosive gas atmospheres - Part 10: Classification of hazardous areas Combustible Dusts AS/NZS 61241.10:2005 - Electrical apparatus for use in the presence of combustible dust. - Part 10 Classification of areas where combustible dusts are or may be present. These Standards are generally in line with the IEC classification standards and supersede Standards AS/NZS 2430.1 and AS/NZS 2430.2
CLASSIFICATION STANDARDS For flammable liquids, gases and vapours, more detailed classification examples are provided in the AS/NZS 2430 series of standards as follows; AS/NZS 2430.3 Examples of area classification.1 - General - Vehicle workshops, Vehicle parking, fuel dispensing stations.2 and aircraft hangars.3 - Flammable liquids.4 - Flammable gases.5 - Refineries and major processing plants - Laboratories, including fume cupboards and flammable.6 medical agents.7 - Landfill gas, sewage treatment and sewage pumping plants.8 - Surface coatings and adhesives.9 - Miscellaneous
CLASSIFICATION VENTILATION Ventilation is a key issue in the dispersion of explosive gas atmospheres. The ventilation must be assessed when determining the hazardous area classification. It is acceptable for the ventilation to be inadequate, however this usually leads to a more onerous classification (eg Zone 1 rather than Zone 2). AS 1940 requires a minimum level of ventilation when dealing with package stores, either natural or mechanical. But the minimum level of ventilation required by AS 1940 does not equate to adequate ventilation for hazardous area classification.
CLASSIFICATION VENTILATION For hazardous area classification, the level of ventilation is assessed using the following terms; Degree of Ventilation There are three degrees of ventilation recognised as described in AS/NZS 60079.10 Appendix B4 as follows: High, Medium & Low. The degree of ventilation is typically calculated using formula detailed in AS/NZS 60079.10. Availability of Ventilation There are three levels of ventilation availability described by AS/NZS 60079.10 as follows: Good, Fair & Poor. By assessing the combination of the degree and availability of ventilation, it can be determined if the ventilation is adequate or inadequate to dilute and remove the explosive atmosphere.
CLASSIFICATION SOURCES & ZONES Grade of Release Continuous Releases continuously Primary Releases occasionally during normal operation Secondary Not expected to release in normal operation Typical Zone Liquids, Gases and Vapours Zone 0 Zone 1 Zone 2 Typical Zone Dusts Zone 20 Zone 21 Zone 22 Recent Changes to Dust area classification Standards include the treatment of dust layers as a source of release rather than directly leading to a Zone application.
CLASSIFICATION DG STORES Many Dangerous Goods Stores include storage of flammable liquids. Often decanting operations are also conducted in the storage area. There is no minimum quantity of flammable liquids which require hazardous area classification, however the examples provided in the AS/NZS 2430 Standards are not representative for quantities up to; 100L in closed containers 25L for decanting purposes 5L in open containers for occasional use 1L in an open container for continuous use For these smaller quantities, first principles in accordance with AS/NZS 60079.10 must be used. Consequently, a classification is required for all dangerous goods stores containing flammable liquids, including package storage, storage cabinets and minor stores.
CLASSIFICATION DG STORES In general, dangerous goods stores require a Zone 2 classification where the packages remain closed and a Zone 1 classification with additional Zone 2 classification if packages are opened for decanting. This introduces the need for special precautions for electrical equipment (Explosion protected electrical equipment). This is often an issue in larger storages where electric forklift trucks are used. AS 1940 has strict requirements/permit systems to allow the use of non-explosion protected electrical forklifts. Similarly for forklift trucks with internal combustion engines, AS 1940 has strict requirements/permit system to allow their use. Where a store is classified as Zone 1, a daily hot work permit system is required for the use of forklifts.
CLASSIFICATION LABS Classification of Laboratories which handle flammable liquids is often overlooked by the owner/occupier. In Queensland, this may result in a breach of the Electrical Safety Act, which could result in a improvement notice or protection notice from the Electrical Safety Office and possible disconnection of supply. Very small quantities of flammable liquids may lead to an explosive atmosphere depending on the room size, ventilation and processes being conducted in the laboratory (eg heating of flammable liquids). In general, the classification of a laboratory results in a Zone 2 classification up to a height of 0.3m above floor level, for the entire floor (AS/NZS 2430.3.6 clause 5.2.3). Other areas where flammable liquids are handled (eg a designated decanting area on a bench or a minor storage area) also require classification in accordance with the principles described by AS/NZS 60079.10.
CLASSIFICATION LABS Classification of laboratory benches will often lead to difficulties from an electrical safety perspective. In particular, it is common for power outlets and PC s to be located on laboratory benches. Many of the problems can be overcome through the use of procedures (eg designated decanting areas). Conducting processes such as decanting in fume cupboards is often the best solution to reduce the classified areas within the general laboratory area. Fume cupboards complying with AS/NZS 2243.8 (specifically the air change rate and face velocity) are classified as non-hazardous (AS/NZS 2430.3.6 clause 5.2.1). Fume cupboards not complying are classified Zone 1 internally and Zone 2 externally for a distance of 0.6m from the opening extending down to ground level (AS/NZS 2430.3.6 clause 5.2.2).
COMBUSTIBLE LIQUIDS A debate continues within parts of the engineering community, regarding whether combustible liquids give rise to a classified hazardous area, thus requiring explosion protected electrical equipment. Events such as the HMAS Westralia fire and the two fires at Olympic Dam are examples of fires involving combustible liquids resulting in damage, injury and fatality. To classify or not to classify? Classifying an area as hazardous, due to the presence of a combustible liquid, is generally more expensive in electrical materials, and will lead to a requirement for competency in the relevant workforce. Failure to classify could lead to property damage, injury or even death. Over-classification could lead to a waste of funds better spent elsewhere.
COMBUSTIBLE LIQUIDS - STANDARDS The following clauses are drawn from a number of Australian and International Standards (which are referenced in the AS2430 series of standards). AS/NZS60079.10 Notes that flammable mists can be generated from combustible liquids. No guidance is given. NOTE in Clause 1 of AS/NZS 2430. 3.3 - Combustible liquids that are stored, handled or processed at a temperature greater than T FP - 6 o C (where T FP = Flash Point of the liquid) should be considered as flammable liquids (NB read the MSDS s for each product!). American Petroleum Institute - RP505 (1997) - This document denotes the internal area of a combustible liquid storage tank as Zone 1 and a 0.5m radius around a vent as Zone 2. The area surrounding the vents is classified to allow for the possibility that the surface of the liquid might be heated above its flash point by the ambient.
COMBUSTIBLE LIQUIDS - STANDARDS Institute of Petroleum - Model Code of Safe Practice Part 15, (2002) (very) abbreviated where materials are released under pressure forming mist or spray, a flammable liquid can be ignited at temperatures far below the flashpoint. There is little knowledge on the formation of flammable mists and the appropriate extents of associated hazardous areas....further research is needed. (referring to a paper on the subject) porous spray guards can be used around flanges and known potential leakage points, causing the material to coalesce back to a liquid below its flashpoint, rendering it non-hazardous To clarify the position pending further research, it is suggested that, where a fluid is more than 5 C below its flashpoint, and at atmospheric pressure or under only a few metres head in a storage tank, it can be treated as non-hazardous; where it is pumped and under pressure, it should be regarded as generating a hazardous area because of the possibility of a mist or spray formation from a small hole or a flange leak.
COMBUSTIBLE LIQUIDS - A WAY FORWARD There does not appear to be an easy right or wrong answer with regard to combustible liquids and hazardous area classification (certainly there is confusion between standards!). The correct answer will depend on the details of the actual installation and equipment involved. The use of Risk Management techniques is a positive way of moving forward sensibly and safely. AS/NZS2381.1 (section 1.10) reinforces the Risk Management concept when it refers to conditions of control and elimination of the hazard, being a way of preventing the simultaneous occurrence of an explosive atmosphere and a source of ignition.
INSTALLATION ISSUES Electrical equipment in hazardous areas must be Explosion Protected Electrical Equipment, to prevent a dangerous ignition of an explosive atmosphere. AS/NZS 2381.1. describes the use of these techniques and the requirements for electrical installations There are also significant documentation requirements including the preparation of a Hazardous Area Verification Dossier for each site. Installation of Fire systems, exhaust fan / ventilation systems and other services often do not consider the hazardous area requirements.
INSTALLATION ISSUES Electrical equipment is required to be certified under the AUS Ex, ANZ Ex, or IEC Ex, not Atex, if it is to be used in Australia. Where equipment with a suitable certification is not available, Atex certified equipment may be used only provided a Conformity Assessment Document (CAD) is produced and accepted by the legal owner of the installation as providing sufficient information to ensure the installation will be safe. In Queensland, the installation and CAD must also be accepted by the Accredited Auditor prior to energisation. The validity/completeness of some CAD have recently been brought into question by Auditors. However prescriptive requirements of a CAD are not available. The owner should ensure they are both technically and legally satisfied by the contents of a CAD before accepting it.
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