Guideline Area Classification Drawings
Report
Akzo Ak zo Nob el Eng i n eerin eeri n g b v
doc.no.
2.068.823 A
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1
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2000-11-07
proj.no.
031.154
of
30
encl.
dept
E-DEE
author
P.J.B.H. Peters/cw
direct line
+31 26 366 2243
e-mail
[email protected]
subject
Guideline Area Classification Draw ings
P.O. Box 5136 6802 EC Arnhem Arnhem The Netherlands Phone: Phone: +31 26 366 38 01 Telefax: +31 26 366 58 77 E-mail:
[email protected] [email protected] Internet: Internet: www.AE .akzonobel.com
distr.
CONTENTS 1 2 3 3.1 3.2
General Informatio n Gathering Gathering Obligation to Area Classification Classificati on Classification Classific ation of flammable materials (simplified) Amoun Amo untt in the open ope n air
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Annex Annex no. 1 2 3 4 5 6 7 8 9 10 11
Title Sample form fo rm for fo r the listing of flammable materials. Flowchart Flowchart 1:Obligation to Area Classification Classific ation Flowchart Flowchart 2: Determining Determining the class of the zone Flowchart Flowchart 3: Determining Determining the extent extent of a zone. Basic Basi c example no.1 Gasses heavier than air Basic Basi c example no.2 Gasses lighter than air Basic Basi c example no.3 Gasses Gass es substantial lighter than air. Basic example example no.4 Influence Influence of walls walls on the extents extents of a zone Basic example example no.5 Airlocks and openings openings Mixing room roo m in a coatings factory facto ry Example Example of combined AC report/drawing Example of an AC drawing AE no. A2-1.792.077
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GENERAL This “Manual” provides information on setting up an “Area Classification Drawing” (ACD), as a result of the Hazardous Area Classification Procedure, for plants handling and processing “potentially explosive” liquids gasses and vapors. Comprehensive guidance and information about Area Classification, including a schematic approach to area classification, is given in IEC 79-10. This document should be referred to in all cases where Area Classif ication is required. The manual makes no pretence to completeness and cannot supersede national standards or local provisio ns Akzo Nobel Engineering or the authors cannot be held liable for any damage attributed to use of this manual. Why do you need an Area Classification Drawing? As a result of Counsel Directive 89/655/EEC minimum safety and health requirements for the use of work equipment by workers at work. The Council Directive 89/391/EEC (measures to encourage improvements in the safety and health of workers at work.) requires an employer to draw up an explosion protection document, or set of documents, and to carry out a risk assessment. The •
•
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Area Classification should in general be carried according following diagram:
Collection and collation of both information and property data and amount of the flammable materials. See chapter 2.
Determine if Area Classification is compulsory See chapter 3
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INFORMAT ION GAT HERING Besides the determination of the amount of flammable material present in or outside the building, all flammable materials used in the process and their critical properties, as described below, shall be listed, using a form similar to the one shown at annex 1.
2.1
Flammable materials: A gas, vapor, liquid (or dust), the release of which could form a flammable atmosphere and can be divided into flammable gasses or liquids and liquefied-pressured gasses.
2.2
Flashpoint: The lowest liquid temperature at which, a liquid gives off vapors in a quantity such as to be capable of forming an ignitable vapor/air mixture.
2.3
Ignition temperature: The lowest temperature of a heated surface at which, the ignition of the easiest ignitable vapor/air mixture will occur.
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2.7
Explosiongroup: Explosion protected electrical equipment is divided into 2 groups. Industrial plants, other than mines, are related to Group II. For the types of protection Eex(d) and Eex(i) electrical apparatus of group II is subdivided into gasgroups: IIA, IIB and IIC, depending on the danger level of the gas or vapor atmosphere in which they are operated. Equipment of group IIC is suitable for use in the most dangerous atmospheres. See also table 9.2 for an example of explosion groups.
3
OBLIGATION TO AREA CLASSIFICATION Area Classification shall be carried out whenever flammable materials are present in quantities exceeding the limits in sections 3.2 and 3.3. Flowchart no.1 on annex 2 gives guidance on this subject.
3.1
Classif ication of flammable materials. (Simplified) In this guideline the following classificatio n of flammable liquids is used. Class Limits of Flashpoint
Category
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3.3
Amount inside closed buildings For installations inside closed buildings drawing up an ACD is obliged if the amount of flammable materials exceeds: 5 kg in case of gasses and class 0 liquids; 50 kg for class 1 liquids 500 kg for class 2 and class 3 liquids. -
-
-
4
AREA CLASSIFICATION PROCEDURE Those who have knowledge of the properties of flammable materials, the process and the equipment should carry out the Area Classification Procedure. IEC79-10 describes in detail the way an area classification procedure, based on the source of release methodology should be executed. This manual gives guidance only. This IEC standard refers specifically to gases and vapors but in methodology is broadly applicable to dusts.
4.1
Leakage sour ces
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SECUNDARY GRADE OF RELEASE: This is a release that is not likely to occur in normal operation and which, if it does occur, is likely to do so infrequently and for short periods I.e. < 10 hours per year or < 0.1% of operating time This includes items like flanges and valves that are normally closed but under certain circumstances could leak. Each source of release can be divided into two classes of release rate. SMALL RELEASE RATE: Release < 1 gram per second. SUBSTANTIAL RELEASE RATE: Release > 1 and < 10 gram per second. Note: Release rates > 10 gram per second should normally not occur.
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4.3.1
Types of vent ilati on syst ems. NORMAL VENTILATION: The movement of air caused by the wind and temperature gradients achieves this ventilation. Following situations may occur: OPEN AIR: For outdoor areas, without substantial obstructions, normal ventilation will often be sufficient to ensure dispersal of any explosive atmosphere. An air velocity of at least 0.5 m/s may be assumed. OPEN BUILDING: The ventilation inside this type of building can be regarded as equivalent to that in open air, if the building has open walls for at least 50% of the facade evenly divided over at least 3 walls. And a height of these openings of minimal 2.5 meter, in such a way that at floorlevel and directly under the roof a free flow of air is possible. GENERAL FORCED VENTILATION:
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MEDIUM VENTILATION (Degree VM): The ventilation system of this degree can control the concentration, resulting in a stable situation in which the concentration beyond the zone boundary is below the LEL whilst release is in progress and where the explosive atmosphere does not persist after release has stopped. General Forced Ventilation (4.3.1) must be capable to limit, at a foreseen total release, to keep the average concentration of the gas below 10% of the LEL. For calculations of the execution of this type of ventilation see IEC79-10. HIGH VENTILATION (degree VH) Can reduce the concentration at the source of release instantaneously, resulting in a concentration below the lower explosive limit. This result can generally be applied only to forced local extraction systems. 4.3.3
Availabilit y of vent ilati on Note: The demands for the availability of the ventilation system as described below differ from IEC 79-10.
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4.4
Determining the class of the zones By following the steps of flowchart no. 2 (annex 3) the zone of the concerned area can be determined. As described before, it is possible to control the size of a cloud of vapor or gas and the time for which it persists after release by means of ventilation. However, It should be understood that the effect of ventilation on Area Classification is a complex subject. Although guidance is given below and in flowchart no. 2 (annex 3) and flowchart no. 3 (annex 4), it is necessary to consult International standard IEC 79-10 to obtain the necessary information.
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DETERMINING THE EXT ENT AND BORDERS OF A ZONE The practice of area classification involves knowledge of the behavior of flammable gases Releases from their source and on sound engineering judgement based on experience of the performance of plant equipment under specified conditions. The examples chosen are those which best describe the overall philosophy of area classification and represent guidance only. According to the national or industrial code selected, the shape and extent of the zones may vary. The extent of a zone is mainly determined by: The release rate of the source.(4.1) The condition of the ventilation in the surroundings of the source.(4.3) Possible obstacles and their dimensions. (5.5) •
•
•
The density of the vapor mainly determines the shape and dimension of the zone. Flammable gasses and vapors usually have densities other than air they will tend to accumulate either near the floor or the ceiling of an enclosed area.
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5.5
Walls and obst acles If by the character or the shape of an obstacle the distribution and diluting of the flammable gas is influenced, the shape and dimensions of a zone will be changed. If an obstacle is hindering the flowing of the cloud of gas in such a way that the cloud is staying substantial longer on the spot, the class of the zone might be changed. Obstacles may be: walls, dikes, gutters, ditches, cellars, slopes, roofs etc. Walls and dikes having a height above the proposed zone (see basic example no. 4 annex 8) form a boundary, which will influence a part of the sphere of the cloud of gas. Gastight walls and roofs can, depending on their dimensions, act as a limitation of a classified area. See basic example no.4 (annex 8). If in the walls, the roof or the floor forming the zone boundaries openings, like ventilation holes, piping- or cabletransits are situated, there will be a sphere formed at the outside of the openings with a radius of 1 meter.
5.6
Air locks
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AREA CLASSIFICATION DOCUMENTS
6.1
Area Classification Report A report containing the fundamentals and conclusions of the area classification procedure at least consisting of the following items: - Process description in brief - Plant layout - Location of the plant on the site - List of potential leakage’s sources with grades of release. - Maximum amount of flammable materials in kg - The properties of the process materials relevant for the AC including: - Flashpoint, - Boiling point, - Ignition temperature - Explosive limits, - Gasgroup and Temperature class. - Determining the ventilation conditions.
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ZONE: 0, 1, or 2 for gasses, liquids and vapors GASGROUPING IIA; IIB; OR IIC TEMPERATURE CLASS: T1 .......T6 The preferred area classification symbols are shown in the legends of the basic examples in the annexes of this guideline. - Reference to the elucidating area classification report. See annex 10 for an example of an ACD. A2-1.792.077 For small locations the Area classification report and the related drawing can be combined; as seen on annex no. 9. 7
CONSEQUENCES FROM “ EUROPEAN DIRECTIVES / ATEX” The directive applies to the industrial field and concerns the f ollowing equipment: • Equipment (machines, apparatus, etc.). • Protective systems (discharge devices, explosion suppression devices, etc.). • Components (parts with no autonomous f unction, terminals, etc.).
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7.1
Groups and categories of equipment The directive provides a classification covering the equipment’s intended purpose, the nature of inflammable substances and the degree of presence or duration the explosive atmosphere. This classification is summarized below, with required safety conditions and their correlation with the code of hazardous areas commonly used worldwide. Purpose
Category
Presence or duration
Inflammable
Level of protection
Correlation
of
of explosive
substances
Faults to allow for
with
equipment
atmosphere
hazardous areas Very high level
Continuous presence
1
Long periods Frequent
Gas,
of protection
Zone 0 gas
vapors,
2 types of protection
etc.
mist,
or 2 independent
dust
faults
Zone 20
Rare faults
dust
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Inspection ! Have your electrical installation checked by a third party. Not you’re own personnel; not the company that installed it. Pay special attention to enclosed rooms. Do you use air locks? Are the doors provided with door-checks? Does the airflow have the proper direction that is from the safe to the unsafe area? Are cable openings closed, so that spilled liquid cannot enter other rooms? The same applies to sumps and sewers. Check your ventilation provisions. What is the outcome of a failure of your ventilation system? Alarming and starting the standby system? Complete electrical shut down? Is this in relation with the requirements for the zones concerned? Are there safe procedures for the restart of your production equipment? Putting things right As soon as you have finished your checks you can
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IEC / CENELEC vs. USA PRACTICES
9.1
Area Classification HAZARD:
Contin uous
Primary
Secondary
Zone 0
Zone 1
Zone 2
Zone 0
Zone 1
Zone 2
IEC 60079-10 EN 60079-10 USA NEC art 505 USA NEC art 500
9.2
DIVISION 1
DIVISION 2
Gas / Apparatus classification Representative
IEC / CENELEC
NEC 505
NEC 500
IGNITION ENERGY
Acetylene
GROUP IIC
GROUP IIC
Class I Group A
> 20 µJ
Hydrogen
GROUP IIC
GROUP IIC
Class I Group B
> 20 µJ
Ethylene
GROUP IIB
GROUP IIB
Class I Group C
> 60 µJ
Propane
GROUP IIA
GROUP IIA
Class I Group D
> 180 µJ
Gas
9.3
Selectio
of prot ection of electrical equipment
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APPLICABLE STANDARDS DESCRIPTION AREA CLASSIFICATION INSTALLATION INSPECTION AND MAINTENANCE GENERAL REQUIREMENTS
11
CENELEC
INTERNATIONAL
EN 60079-10 EN 60079-14 EN 60079-17
IEC 79-10 IEC 79-14 IEC 79-17
EN 50.014
IEC 79-17
EXAMPLES OF SOURCES OF RELEASE. Source
Flanged valve Threaded valve
Release grade 4.2 Secondary Secondary
Release rate 4.2 gram/sec 1 1
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Annex 1 Sample form for the listing of flammable materials. Properties of flammable materials -gas/vapor/liquid Materials Flash point Ignition LEL /UEL Temperature Gas °C temperature % class group °C Acetone Acrylontrile Acrylic acid Butanol Ethanol Ethylacetate Ethylacrylate Ethylbenzene Heptane SBP solvents Methanol
-19 -5 54 29 12 -4 9 23 -4 25 10
540 480 375 340 370 427 350 430 215 210 385
2.15/13 3/17 2.4/8 1.4/10 3.3/19 2.1/11.5 1.8/13 1/7.8 1.1/6.7 0.6/8 6.7/36
T1 T1 T2 T2 T2 T1 T2 T1 T3 T3 T1
IIA IIA IIA IIA IIA IIA IIB IIA IIA IIA IIA
Class (flash point)
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