Explosion Protection. Electrical Apparatus and Systems for Chemical Plants Oil and Gas Industry Coal Mining

531 Pages·2002·29.52 MB·English

by  Heinrich Groh (Auth.)

Preface
Explosion protection, the prevention of ignition sources in areas endangered
by combustible gases, vapours, mist or dusts in combination with the oxygen
content of air, has been a main objective in engineering and physics for many
years. Starting with Sir Humphrey Davy's lamp in 1815 and, ninety years
later, Beyling's essential research in the field of flame transmission, consider-
able work has been done and produced safe as well as economic and reliable
motor drives, process control and monitoring equipment, electric power con-
trol apparatus and lighting installations in hazardous zones. The focus of this
book is on electrical apparatus and systems in hazardous areas in chemical
plants, oil and gas industry and underground coal mining. The book intends
to present a survey of this field, a snapshot demonstrating the 'state of the
art'.
The inspiration for this book was a series of courses on 'Explosion Protec-
tion' given in chemical plants and the enthusiastic response to these courses,
as well as the progress made in protection techniques, for example in pres-
surization, in more recent times.
This book is intended for engineers, scientists, plant safety personnel and
for students in the field of electrical engineering to give an introduction to
the basic principles of explosion protection and the relevant protection
techniques.
The book is organized into three parts (Chapters 1-5, 6-8, 9-12) and a bib-
liography followed by an extensive index. The first chapter gives an intro-
duction into basic physics - the determination of ignition temperatures and
energies, of the maximum experimental safe gap and other safety related
data, and summarizes these values into tables and diagrams. Chapter 2 deals
with the classification of hazardous areas into 'zones' according to national
and international standards or directives. In addition, a survey of standards
for zones 0, 2 and 20-22 as well as for Ml-equipment closes this chapter. In
Chapter 3, national and international standardization for zone I and approval
procedures are described, including European Harmonization, the 'New
Approach'-ATEX 100a-Directive- and the IECEx-Scheme. Chapter 4 pres-
ents the grouping and classification of combustible substances according to
their safety related data, e.g. ignition temperature and maximum experi-
mental safe gap. Chapter 5 closes the first part with marking requirements
according to international standards or directives and deals with selection
aspects related to explosion protected apparatus.
Part two - as the main part of the book - starts with Chapter .6 Here,
detailed descriptions of the different types of explosion protection are given,
combined with illustrations of today's explosion protected apparatus.
Chapter 7 deals with modern contents of 'pressurization'. According to those,
x Preface
an internal release of combustible substances can be handled in a safe way by
dilution, and a draft standard for 'manned' pressurized enclosures has been
published for voting. Closing the second part, Chapter 8 describes type test-
ing procedures for 'flameproof enclosure, d' or 'intrinsic safety, i', accompa-
nied by a description of partial discharge measurements, a highly efficient
test method for monitoring the quality of insulation materials in electrical
apparatus.
In the final part of the book, focal points are financial considerations
(Chapter 9), inspection, maintenance and repair of explosion protected
apparatus (Chapter 10), apparatus for installation in zone 0 and in zone 2
(Chapter )11 and cable protection systems, especially for underground instal-
lations in coal mines (Chapter 12).
The creation of such a work is impossible without competent help. ,oS first
of all, I am indebted to Dipl.-Ing. Michael Hagen, Product Manager
Instrumentation, .R STAHL Schaltger~ite GmbH, Waldenburg, Germany, for
his sterling work as a co-author, namely his comprehensive representation of
intrinsically safe electrical apparatus and systems. I have translated his part
into English, and I must apologize for any stylistic incongruities and unclear-
ness which may result therefrom.
Michael Hagen and I myself are greatly obliged to various companies,
institutions and firms for providing very instructive photos and detailed
diagrams.
I gratefully acknowledge the support of my publishers, Elsevier, in prepar-
ing this book, especially for the help in improving the style of my English!
A special expression of thanks is addressed to Dr Arnulf Krais, expert-
Verlag GmbH, Renningen-Malmsheim, Germany, for his important part in
launching this book project.
Heinrich Groh
L~inen Germany
September 2003
stnemegdelwonkcA
The authors are greatly obliged to companies, institutions and firms for very
instructive photos and diagrams.
The following figures are by courtesy :fo
erugiF ,ynapmoC ,noitutitsni firm
332.6 BA Allen Bradley
Milwaukee, Wisconsin/USA
6.25, 6.124, 6.125, 6.126, 6.127, BBA Automation Products GmbH
6.128, 6.129 Frankfurt / Germany
96.6 BBA Calor Emag Mittelspannung GmbH
Ratingen/Germany
6.26, 6.27, 6.33 BBA Industrie AG
Birr / Switzerland
9.5, 6.9 ALSTOM Power Conversion GmbH
Essen/Germany
6.7, 6.174 Auergesellschaft GmbH
Berlin/Germany
6.103(a), )b( BARTEC Sicherheits-Schaltanlagen GmbH
6.104(a), )b( Menden/Germany
6.37, 6.38, 6.70, 6.75, 6.120, BARTEC Componenten und Systeme GmbH
6.178, 6.179 Bad Mergentheim/Germany
6.20(a)-(d), 6.23, 6.24, Becker Machaczek GmbH
6.170(h)-(j), 6.173, 6.176(a), Friedrichsthal / Germany
(b), 9.11, 9.12, 9.13(a), )b(
781.6 BERNT GmbH, D~isseldorf/Germany and
Drexelbrook Engineering Co., Horsham,
Pennsylvania/USA
531.6 Bieler + Lang GmbH
Achern/Germany
6.122, 6.123 Bopp & Reuther Messtechnik GmbH
Mannheim/Germany and
Josef Heinrichs GmbH & Co.
Messtechnik KG
K61n/Germany
)deunitnoc(
xii stnemegdelwonkcA
erugiF ,ynapmoC ,noitutitsni firm
6.91, 6.93, 6.94, 6.95, 6.96 BREUER-MOTOREN GmbH & Co. KG
Bochum/Germany
6.97 BROOK CROMPTON
Huddersfield/UK
6.109, 6.110, 111.6 BRUSH Transformers Ltd
Loughborough, Leicestershire/UK
6.53(a)-(c), 6.61, 6.62, CEAG Sicherheitstechnik GmbH
6.65, 6.112 Soest/Germany
6.138, 6.139 DMT Deutsche Montan Technologie GmbH
Essen/Germany
6.133, 6.134, 6.175 Dr/iger Sicherheitstechnik GmbH
Liibeck/Germany
6.189, 6.190 ECOM Rolf Nied GmbH
Assamstadt / Germany
6.3, 6.136, 6.137 Eickhoff Bergbautechnik GmbH
Bochum/Germany
6.118,6.119 ELMESS-Thermosystemtechnik GmbH & Co.
Uelzen/Germany
6.202 Emerson Process Management
Baar / Switzerland
6.177, 11.3, 11.4 Endress + Hauser Conducta GmbH & Co.
Gerlingen / Germany
6.188 ESCAPELINE Ltd
Luton, Bedfordshire/UK
6.28, 6.29 Federal Mogul RPB Ltd
Shoreham-by-Sea / UK
6.243, 6.244 Fieldbus Int. AS
Oslo/Norway
6.99 ITT Flygt Pumpen GmbH
Langenhagen / Germany
6.170(a)-(g), 6.171(a), (b), FHF Funke + Huster Fernsig
6.172 Bergbautechnik GmbH
Velbert/Germany
6.41, 6.42, 6.43, 6.44, ,.pA-.1E Elektro-Apparate Gothe & Co.
6.49, 6.74 GmbH
M/ilheim a. d. R./Germany
1.1, 1.2, 1.3(a)-(c), 1.4, 5.1 Dr. Heinrich Groh VDE
1.6, 1.7, 1.8, 1.9, 1.10(a)-(c), Konstruktions-und Planungsb/iro,
1.11, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, L/inen/Germany
)deunitnoc(
stnemegdelwonkcA xiii
erugiF ,ynapmoC institution, firm
3.1(a), 3.1(b), 3.2, 4.1, 4.2,
4.3(a), (b), 5.1, 6.9, 6.11, 6.12,
6.13, 6.14, 6.15, 6.16, 6.17, 6.21,
6.22, 6.40(a)-(d), 6.56, 6.57,
6.58, 6.59, 6.76, 6.77, 6.78, 6.79,
6.82(a)-(c), 6.145, 6.146, 6.147,
6.148, 6.149, 6.150, 6.151, 6.152,
6.153(a), (b), 6.154(a), (b), 6.155,
6.156, 6.157, 6.158(a), (b),
6.159(a), (b), 6.160, 6.161, 6.162,
6.163, 6.164, 6.165, 6.166, 6.167,
6.168, 6.191, 6.194, 6.195, 6.237,
7.1, 7.2(a), (b), 8.1, 8.3, 8.4,
8.5(a), (b), 8.6, 8.7, 8.9,
8.10, 8.12, 9.1, 9.2, 9.3, 9.4, 9.8,
9.10, 10.1, 12.1, 12.2(a), (b),
12.3(a)-(d), 12.4(a), (b), 12.5,
12.6, 12.7, 12.8, 12.9, 12.10,
12.11, 12.12
8.8 Haefely Test AG
Basel / Switzerland
6.4, 6.66, 6.67, 6.68 HAGEN Batterie AG
Soest/Germany
6.18,6.19 H + R Hansen & Reinders GmbH & Co. KG
Gelsenkirchen / Germany
6.208, 6.209 HART Communication Foundation
Austin, Texas/USA
6.98 HUBNER Elektromaschinen AG
Berlin/Germany
6.140, 6.141 ISV Industrie Steck-Vorrichtungen GmbH
Willst~itt-Sand/Germany and MARI~CHAL
Saint-Maurice/France
6.85(a), (b) Leumann & Uhlmann AG
Muttenz / Switzerland
6.86, 6.87, 6.88, 6.89, 6.90, LOHER GmbH
6.92 Ruhstor f / Germany
6.36 MAGNET-SCHULTZ GmbH & Co. KG
Memmingen / Germany
6.130, 6.131, 6.132 MAIHAK AG
Hamburg/Germany
6.64(b) OSRAM GmbH
MLinchen/Germany
)deunitnoc(
xiv stnemegdelwonkcA
erugiF ,ynapmoC ,noitutitsni firm
6.8, 6.117, 1.11 .F H. PAPENMEIER GmbH & Co. KG
11.2(a), )b( Schwerte / Germany
6.180, 6.181, 6.182, 6.183, Pepperl + Fuchs GmbH
6.184, 6.185, 6.196, 6.207, Mannheim/Germany
612.6
6.50, 6.51, 6.52 EMIL .A PETERS GmbH & Co. KG
Iserlohn / Germany
611.6 Otto Pfannenberg Elektro-
Spezialger~itebau GmbH
Hamburg/Germany
,45.6 55.6 RERETSIFP Kontaktsysteme GmbH & .oC GK
Winterb ach / Germany
6.39, 6.46 PHOENIX Contact GmbH & Co.
Blomberg/Germany
6.226, 6.234, 6.235, ,632.6 BTP Physikalisch-Technische Bundesanstalt
31.8 Braunschweig and Berlin/Germany
6.213, 6.214 PROFIBUS Nutzerorganisation
Karlsruhe / Germany
6.81, 6.105(a), (b), 6.106 PROMOS-Electronic GmbH
6.107, 6.108(a), (b), 6.142 Marl/Germany
6.6 VEM Sachsenwerk GmbH
Dresden/Germany
2.8 Maschinenbau SCHOLZ GmbH & .oC GK
Coesfeld/Germany
6.63, 6.64(a), 6.113, ,411.6 Adolf Schuch GmbH
511.6 Worms/Germany
6.30, 6.60 Siemens AG Large Drives Div.
Berlin/Germany
691.6 Siemens AG
Karlsruhe / Germany
6.35, 7.9 Spillingwerk GmbH
Hamburg/Germany
6.10, 6.71, 6.72, 6.73, 6.80, .R STAHL Schaltger~ite GmbH
6.83, 6.84, 6.100, 6.101, 6.102, Waldenburg/Germany
6.121, 6.169, 6.192, 6.193,
6.196, 6.197, 6.198, 6.199,
6.200, 6.203, 6.204, 6.205,
6.206, 6.210, 6.211, 6.212,
6.215, 6.217, 6.218, 6.219,
6.220, 6.221, 6.222,
)deunitnoc(
stnemegdelwonkcA
xv
erugiF ,ynapmoC institution, firm
6.223, 6.224, 6.225,
6.227(a)-(c), 6.228, 6.229,
6.230, 6.231, 6.232,
6.239, 6.241, 6.242, 6.245,
6.246, 8.11, 11.5, 11.6
6.1, 6.2, 6.31, 6.32, 6.34 Oivind Hagen, STATOIL
Stavanger/Norway
5.6 Maschinenfabrik SULZER BURCKHARDT
AG
Winterthur / Switzerland
6.186(a), (b) Taciak AG
Nordkirchen / Germany
6.238, 6.240 Technische Universit~it Braunschweig
Braunschweig / Germany
6.143, 6.144 Victor Products Ltd
Newcastle upon Tyne/UK
6.47(a), (b), 6.48 WAGO Kontakttechnik GmbH
Minden/Germany
6.45 WeidmLiller GmbH & Co.
Paderb orn / Germany
9.9 WEIER Electric GmbH
Eutin/Germany
102.6 WIKA Alexander Wiegand GmbH & Co. KG
Klingenberg / Germany
Chapter 1
Basic principles of
explosion protection
1.1 Introduction
In general, an explosion is an exothermic chemical reaction between two com-
ponents. A well-known example is the reaction between the oxygen content of
the atmospheric air and a combustible substance like petrol. As an exception,
there are very few substances - such as acetylene - which are thermodynam-
ically unstable and tend to exothermic self-decomposition. An explosion can
start only with an ignition source and a volume or mass ratio of the two com-
ponents in such a manner that the reaction zone is sustained by itself. Typical
values of the peak explosion pressure - when starting with components at
atmospheric pressure in a constant volume - are I MPa (10 bar) and a propa-
gation velocity of the reaction zone up to 102m/s (as an order of magnitude).
These basic facts can be summarized as:
Explosions can be avoided, if at least one of the three parts- component 1,
component 2 or the ignition source - is absent.
This is the fundamental rule of the primary type of explosion protection: the
existence of hazardous fuel-air mixtures shall be prevented by an artificial or
natural ventilation of plant installations and/or an equivalent tightness of
manufacturing equipment.
In addition, explosion protection by using inert gases can be derived from
this rule: in the presence of combustible substances, the oxygen content of
the surrounding atmosphere will be reduced to a safe level - some per cent
by volume - by dilution with an inert gas such as nitrogen or carbon dioxide.
The rule described above forms a basis for the secondary type of explosion
protection, which results in the avoidance of ignition sources, e.g. by using
either a flameproof enclosure of a commutator motor or the pressurized
enclosure of a gas analyser, or by limiting the electrical values in intrinsically
safe circuits.
This secondary type of explosion protection will be the main object
throughout all the following chapters. It covers burnable substances like
gases, vapours, mists as well as dusts, and usually refers to atmospheric air
as the second component forming a hazardous atmosphere. 'Atmospheric
conditions' are defined as total pressures from 8.104pa (0.8 bar) to 1.1-10Spa
2 Explosion Protection
(1.1 bar) as absolute pressure values (referring to vacuum) and temperatures
from -20~ to +60~ All these values refer to the stationary (non-reacting)
mixture of air with a burnable substance.
In the field of explosion protection of electrical apparatus and systems, the
upper temperature limit is normally decreased to +40~ and this fact should
be noticed throughout all the following chapters.
'Exotic reactions' like the ignition of a Ha-C12 mixture by optical radiation
will not be covered in this book.
1.2 Sources of ignition
Combustions of gas-air mixtures as self-sustained chemical reactions
occur only within well-defined volumetric ratios. The gas concentration - by
volume - is limited by a lower value - Lower Explosive Limit (LEL) - and
an upper value - Upper Explosive Limit (UEL) - in order to maintain an
expanding reaction zone in the gas-air mixture. Below the LEL and above the
UEL an explosive gas-air atmosphere will not be formed. Table 1.1 summa-
rizes LEL and UEL for gases in chemical plants, the oil and gas industry and
in coal mines.
:etoN
For methane, CH ,4 LEL and UEL refer to pure methane.
In coal mines, in the unavoidable presence of coal dust, hybrides
(methane-coal dust-air) show decreased values for LEL 2.
Acetylene, ,2H2C is an important example of a substance with a
thermodynamic instability. Without any additional component, it can
decompose into hydrogen and soot. Therefore, UEL = 100% (v/v).
The mixing ratio of two gas components (in steady state) can be defined -
besides their volume ratio- by their partial pressures.
It is:
The sum of the partial pressures iP of n components in a multi-component
gas mixture equals the total pressure
~Pi
=Pt
i=1
Example :1 A mixture with 2HP = 3.2" 401 Pa for hydrogen, H2, and
riaP -- 6.5 (cid:12)9 401 Pa for air forms a total pressure
Pt = 2HP -4 riaP
Pt = 9.7" 401 Pa
Basic principles of explosion protection 3
Table 1.1 LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit)
values for gas-air mixtures, valid for a total pressure of 1.013.105pa and a
temperature of +20~ (= + 68~
Gas Formula Gas concentration
LEL UEL
% (v/v) % (v/v)
Acetylene C2H 2 1.5 (2.3)* 100"*
Benzene C6H 6 1.2 8.0
Carbon disulphide 2SC 0.6 (1.0)* 60
Ethane C2H 6 3.0 (3.2)* 12.5 (15.5)*
Ethylene C2H 4 2.7 28.5 (34)*
Hydrogen H 2 4.0 75.6 (77.0)*
Methane CH 4 4.4 (5.0)* 15.0 (16.5)*
Propane CBH 8 1.7 (2.1)* 9.5 (10.9)*
* Different values given in the literature
** Thermodynamic instability
And, in addition:
The partial pressures iP of n components in a multi-component gas mixture
show the same ratio as their volumetric ratios (volumes Vi, total volume )tV
Pi/Pj = Vi/Vj, especially Pi/Pt = Vi/Wt
Example :2 The volumetric ratios of the gas-air mixture of example I are:
for hydrogen: Vi/Vt = Pi/Pt = 32.99%
for air: Vj/Vt = Pj/Pt-- 67.01%
In atmospheric air, the oxygen concentration is 21% (v/v), the nitrogen con-
centration is 78% (v/v); 1% (v/v) is due to CO2, argon etc.
Therefore, the volumetric ratio is:
for :20 Wo2--- 21% (cid:141) 67.01% = 14.07%
for N2: 2xW = 78% (cid:141) 67.01% = 52.27%
Note:
The H2 concentration is between LEL and UEL, this mixture is burnable!
Example :3 In example 1, the partial pressure of air is 6.5 (cid:12)9 104pa.
The oxygen (02) content is 21% (v/v), the nitrogen (N2) content is 78% (v/v).
Calculate the partial pressures of 02 and !2N