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TRBS 2152 Part 4

Hazardous explosive atmosphere
- Constructive explosion protection measures that limit the effects of an
explosion to a harmless level
Issue: February 2012
GMBl 2012 p. 387 [No.21]
T EC HNIC AL REGELS FOR ECONOMICALPRODUC
TION
PUBLISHED BY KÜPPERS ENGINEERING
 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
for Constructive explosion protection measures that limit the effects of Issue: February 2012
operational safety an explosion to a harmless level Page: 2 / 16

Preliminary remark
The Technical Rules for Operational Safety (TRBS) reflect the state of
the art, occupational medicine and occupational hygiene, as well as other
proven ergonomic findings for the provision and use of work equipment and
for the operation of systems requiring monitoring.
They are determined or adjusted by the Committee for Operational Safety
and published by the Federal Ministry of Labour and Social Affairs in the Joint
Mini- sterial Gazette.
This TRBS specifies the requirements of the Ordinance on Industrial Safety
and Health within the scope of its application. By complying with the
technical rules, the employer can assume that the corresponding
requirements of the ordinance are met. If the employer chooses a different
solution, he must achieve at least the same level of safety and health
protection for employees.

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
for Constructive explosion protection measures that limit the effects of Issue: February 2012
operational safety an explosion to a harmless level Page: 3 / 16

Contents
1 Scope of application
7 Explosion decoupling for gases, vapours and mists
2 Definitions 7.1 General
2.1 Expected explosion pressure (perw) 7.2 Flame arresters
2.2 Explosion pressure (pex) and maximum explosion pressure (pmax) 7.3 Flow-monitored backfire-proof devices
2.3 Reduced explosion pressure (pred) 7.4 Flame penetration during continuous fire
2.4 Explosion-proof design 8 Decoupling devices for dusts
2.5 Explosion venting 8.1 General information
2.6 Explosion venting devices 8.2 Quick-closing gate valve, quick-closing damper
2.7 Explosion suppression 8.3 Quick-closing valve (explosion protection valve)
2.8 Explosion suppression system 8.4 Rotary valves
2.9 Explosion decoupling 8.5 Double slide systems
2.10 Decoupling devices 8.6 Extinguishing agent barriers
3 General requirements 8.7 Relief vent
8.8 Product template
4 Requirement for explosion-proof design
9 Explosion decoupling for hybrid mixtures
5 Requirements for explosion venting

6 Explosion suppression requirements

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
for Constructive explosion protection measures that limit the effects of Issue: February 2012
operational safety an explosion to a harmless level Page: 4 / 16

1 Scope of application 2 Definitions

(1) This TRBS describes the following measures for constructive explosion protection Remark:
protection, which limit the effect of an explosion to a harmless level. Explosion pressures are specified as explosion overpressures in relation to
atmospheric pressure (1 bar): atmospheric pressure (1 bar).
- explosion-proof design, 2.1 Expected explosion pressure (p )
erw
- Explosion pressure relief, The expected explosion pressure (perw) is the maximum pressure that
can be expected in
- Explosion suppression, a part of the system with a realised protection concept, taking into account
- explosion decoupling (of flames and pressure). of the given systems and processes as well as of all possible
operating parameters and operating conditions can occur.
(2) The measures listed in this technical rule apply - insofar as
they contain requirements for the condition - only apply to systems, The expected explosion pressure may be
Appliances and equipment other than appliances and protective systems as defined by a) the maximum explosion pressure (pmax),
of the Explosion Protection Ordinance (11th ProdSV). b) a maximum explosion pressure (p ) that deviates upwards or
downwards from the maximum explosion pressure (p ).
max
Deviating system and process-specific explosion pressure
Note: or
Many of the protective systems described in this technical rule are c ) a reduced explosion pressure (pred).
considered autonomous protective systems within the meaning of the Explosion Protection Ordinance, Note 1:
(11th ProdSV), e.g. explosion venting systems, explosion protection systems, explosion protection devices, etc., are placed on the market. The expected explosion
pressure may be lower than the maximum explosion pressure.
explosion suppression systems, flame arresters, rapid explosion pressure , if, for example, the container is only partially filled with a hazardous
extinguishing agent barriers is unfavourable for the explosion processes or cooling effects are
atmosphere, the mixture composition of .
caused by
Such systems are predominantly designed in accordance with harmonised standards extensive installations occur.
and conformity assessed. In addition to the requirements for conformity assessment, these standards contain Note 2:
The expected explosion pressure may be higher than the maximum selection and correct use and operation of these protective systems. explosion
pressure, e.g. if an inlet pressure is present in the system or
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 increased turbulence (compared to laboratory conditions).

Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4

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 Note 3: (2) System components are explosion pressure resistant if they can
withstand the expected explosion pressure, which corresponds to the reduced explosion pressure, without permanent deformation.
pressure if the system is protected by explosion suppression or explosion venting.
(3)
System components are explosion pressure shock resistant if they can withstand the expected explosion pressure without rupturing.
explosion pressure without rupturing, whereby, however
permanent deformations are permissible.
2.2 Explosion pressure (pex) and maximum explosion pressure (pmax)
Explosion pressure (pex) is the pressure under specified test conditions. 2.5 Explosion pressure relief
In the case of explosion venting, defined openings are released in the event of an
explosion in an explosive atmosphere with a certain composition, so that the system component does not occur. beyond its explosion
resistance.
Maximum explosion pressure (pmax) is the highest explosion pressure determined,
which occurs when the fuel content changes (see TRBS 2152 number
2.6 Explosion venting devices
2.3 paragraph 12).
Explosion venting devices can be, for example, rupture discs
or explosion flaps or permanent openings. Safety valves
2.3 Reduced explosion pressure (pred) are not explosion venting devices. Reduced
explosion pressure (pred) is the pressure in an explosion chamber created by explosion pressure
explosion suppression of containers protected against explosion venting or explosion suppression.
2.7 Explosion suppression
Explosion pressure.
(1) Explosion suppression is a method of suppressing the explosion pressure.
Combustion of a potentially explosive atmosphere in a closed
2.4 Explosion-proof design or essentially closed volumes are recognised and described in the
(1) Plant components such as containers, apparatus and pipelines are explosion-proof if they are constructed in such a way that they can
withstand the expected explosion pressure without
rupturing. (2) An explosion shall be deemed to be suppressed if it is
pressure (p ) by
possible to reduce the maximum explosion adding a suitable extinguishing agent: maximum
explosion pressure
Explosion-proof (p ) toincludes
design a reduced explosion pressure (p )
explosion-pressure-resistant and explosion-
max red
i.e. the expected explosion pressure is reduced.
pressure shock-resistant design.
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 2.8 Explosion suppression system 3 General requirements
The entirety of devices for the realisation of explosion suppression. (1) When selecting and dimensioning as well as installing, operating,
maintaining and testing The explosion suppression system essentially consists of detection and repair equipment for constructive explosion
, a control centre and pressurised extinguishing agent containers.
protection The main risks are influences that impair function, e.g. corrosion, ageing,
abrasion, process control or environmental influences.
2.9 Explosion decoupling Note:
Explosion decoupling prevents the spread of an explosion (pressure and/or flame) to other parts and areas of the system,
The information on installation must be provided by the manufacturer,
z. e.g. via connecting pipes or ducts. Operation, maintenance, testing and repair in the operating instructions
to note.
2.10 Decoupling devices (2) To protect against the effects of an explosion, decoupling devices may be
used in the con-
(1) The following measures can be used in various combinations to realise explosion-structural explosion protection: decoupling :
- Mechanical quick shut-off, - explosion-proof design,
- Extinguishing flames in narrow gaps or using extinguishing agents - Explosion pressure relief,
trag, - explosion suppression,
- Flames are stopped by high counterflow, - Explosion decoupling.
- immersion, (3) If, in the event of an explosion, its propagation from one part of the installation
- airlocks. In addition to the explosion- Note: In the case of explosions of
gases, vapours and mists mixed with air, explosion decoupling must be part of the explosion protection design.
due to the possibly very high propagation velocities Note 1:
(detonations) active shut-off or extinguishing systems are often too slow, When explosions spread from one part of the system to others, passive
elements, e.g. band fuses or diverters, may be preferred. Pre-compression, high turbulence and/or systems with a high counterflow
may be favoured. extremely effective flame jets. These effects can

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 in connected or neighbouring parts of the system can lead to particularly violent secondary explosions. - The effectiveness of upstream measures (e.g.
volume or concentration of secondary explosions, which can be minimised by means of constructive explosion control, inerting).
tration limitation, inertisation),
be
The effectiveness of explosion pressure-reducing measures (e.g. explosion pressure relief, explosion suppression, explosion protection cannot safely
controlled with reasonable technical effort. explosion pressure relief, explosion suppression, explosion
Note 2: Decoupling),
When subdividing the interior of equipment or when connecting
containers, e.g. through pipelines, can be released during an explosion in the container.
Note 1:
the pressure in one partial volume is increased in the other partial volume
If only one partial volume in a container is always filled with an
(precompression) atmosphere or if the concentration of the flammable
explosive atmosphere or can the concentration of the flammable
Note 3: The concentration of the substance must be limited so that the
optimum fuel concentration
An explosion that is initiated at an increased outlet pressure (e.g. due
to precompression ) may lead to a higher explosion pressure than
that expected in the system/equipment.
explosion pressure to be expected under atmospheric conditions (the
explosion pressure is directly proportional to the outlet pressure).
Note 2:
For explosions in pipelines or elongated equipment
(4) To determine the expected explosion pressure, the following boundary conditions/influencing variables in particular
must be taken into account: The following boundary conditions/influencing
variables must be taken into account. Thereby
- Fuel type and concentration/explosion parameters, local short-term pressure surges occur, the peak values of which are several
times higher than
- system geometry, of the maximum explosion pressure. Turbulence-increasing
Installations, e.g. orifice plates, valves, pipe bends or cross-sectional
- Manufacturing or processing method,
changes can significantly reduce the run-up distance for detonations.
- oxygen concentrations, reduce. In the case of gases and vapours, such pressure loads are
- Partial filling of system components with explosive mixture, not to be expected due to shock fronts with L/D < 5 (D = diameter).
- Pressure conditions,
- Turbulence,

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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4 Requirements for explosion-proof construction 5 Requirements for explosion pressure relief

(1) Explosion-proof system components must be constructed in such a way that they can withstand an in load
The inner surface must be able to withstand an explosion without rupturing. In the case of (1) Explosion venting is not permitted if the explosion-
proof design can endanger employees or third parties. The explosion-proof design distinguishes between "explosion
pressure resistant" and "explosion pressure shock resistant" construction. Explosion pressure resistant
(2) Explosion venting shall be carried out in
and explosion pressure shock resistant design are minimised with regard to the protection objectives of the
such a way that hazards for
measures equivalent to the Ordinance on Industrial Safety and Health.
by
employees and third parties, e.g. due to pressure and flame effects or
ejected parts are avoided. The measures taken for explosion
(2) The minimum design pressure for system components and apparatus in explosion- pressure relief must be taken into account.
The expected explosion pressure (see numbers
(3) Explosion pressure relief into the working area must always be provided.
2.1 and 2.3). avoid.
Note: (4) Explosion pressure relief should be carried out on the shortest possible
and straightest possible The design of pipework and elbows for nominal pressure 10 bar (PN 10).
is not recommended when using tough materials and under atmospheric conditions. Note:
sufficient to ensure that non-curved pipework is not subjected to detonation stresses. If an exhaust pipe is connected to the explosion venting device, the
withstand stresses. In particular, elbows withstand the stress In particular, it must be taken into account that
due to detonations of saturated hydrocarbons mixed with air, 1. the reduced explosion pressure in the part of the system to be
protected
if the deflection angle is not more than 90 degrees. For differently shaped raised and
system parts (e.g. changes in cross-section, constrictions) and in the case of
Particularly reactive mixtures can result in higher recoil forces. 2. increased recoil forces can occur.
pressure stage, the nominal pressure must be 10 bar (PN 10). (5) The explosion vent shall be designed so that the pressure caused by the
explosion pressure relief to the reduced pressure in the system.
(3) After an explosion or detonation event, the affected parts must be able to withstand be able to withstand explosion pressure.
The system components must be checked to ensure that they are explosion-proof (6) Explosion venting devices and discharge pipes must be
checked regularly to ensure that they are in perfect condition. In doing so, any damage caused by environmental influences, e.g. snow
load or icing, must also be taken into account.
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 take into account.

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 (7) The safe functioning of an explosion venting device must 7 Explosion decoupling for gases,
be verifiable. Proof is deemed to have been provided, for example, if the explosion vapour and
mist venting device has been placed on the market as an autonomous protective system in accordance with
the Explosion Protection
7.1 General
Ordinance (11th ProdSV) has been placed on the market
and is used as intended. (1) In the case of openings in parts of the installation in which a hazardous
explosive atmosphere
If a potentially explosive atmosphere is present and the design is not
sufficiently explosion-proof, the need to protect the system
components against the ingress of explosions must be checked.
6 Explosion suppression requirements Note 1:
(1) When using an explosion suppression system, this may also be necessary, for example, for venting and venting devices,
level indicators, hazards for employees or third parties due to the release of the filling and emptying lines, but also connection lines to other explosion
suppressants, e.g. during maintenance measures, plant components.
must be taken into account.
Note 2:
(2) The explosion suppression system is to be designed in such a way that the explosion caused by In the case of connected system parts, an explosion can
occur in a connection area.
The system parts protected by the explosion suppression system can withstand the precompression of explosive atmospheres at reduced explosion
pressure. other part of the system, so that the expected explosion pressure
(3) When designing the explosion suppression system, it must be taken into account that the The pressure in this part of the system can be considerably
higher. To reduce
It should be borne in mind that its effectiveness depends, among other things, on the given system and pressure load, flame decoupling may
be necessary, e.g. through process engineering, operating parameters such as temperature and pressure, and a suitable flame arrester.
the properties of the substances used and the explosion suppressor.
of the ignition medium. (2) Openings in plant components through which explosions can propagate
and thus endanger employees or third parties must be protected against
flame transmission. This may include filling, emptying and vapour
recovery connections, but also intake openings and exhaust pipes of
combustion engines. Possible further hazards from hot gases,
pressurisation or combustion products, for example, must be taken into
account.

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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operational safety an explosion to a harmless level Page: 10 / 16

(3) In the case of interconnected system components, the necessity of a (4) If there is a flow of explosive atmosphere and thus protection against the
propagation of an explosion must be checked. This can e.g. stabilised burning in/at the flame arrester
B. in the case of vapour recovery systems and systems that are not
permanently filled with liquid , the flame arrester must be equipped with a monitoring device that detects
the presence of a flame arrester. 7.4 does not apply, with a monitoring device for detecting the presence of a
flame arrester.
stabilised firing and for which, taking into account any
be suitable for the expected duration of burning (e.g. shutting off the
7.2 Flame arresters must
mixture supply, injecting inert gas or air).
(1) Flame arresters are devices that are installed at the opening of a
system or in connecting pipelines of system components. tanks or containers in the course of vapour return and gas collection
lines
and whose intended function is to allow the flow of gases, vapours, mists and liquids
to not
be stabilised, but which are equipped with
monitoring devices to detect burning.
to prevent flame penetration. Note:
Flame arresters may only be able to withstand burning
(2) The mode of operation of a flame arrester is generally based on one or more of the following mechanisms The flame arresters work for a limited
period of time (service life) and then lose their flame- arrester function mainly due to one or more of the following mechanisms: flame arrester. The service
life can be found in the operating instructions of the
- Extinguishing flames in narrow gaps and ducts (e.g. conveyor belts). manufacturer.
sintered metals),
- (5) Flame arresters must be suitable for the possible explosion velocity of the unburned mixtures (high velocity capable
mixtures (ignition proof standard gap widths) and the valve), operating conditions (pressure and temperature of the mixtures).
- Stopping a flame front by means of liquid deposits (e.g. safety
or liquid seals). (6) Flame arresters must not lead to dangerous pressure increases in the
system due to their flow resistance.

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 (3) Depending on the installation situation and operating conditions, either
deflagration or detonation flame arresters must be used as flame
arresters.

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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(7) The risk of clogging, e.g. due to dirt, polymerisation and sublimation as (3) The required minimum flow velocities for explosive mixtures with
well as freezing, must be taken into account, as must the loss of the safe substances of explosion groups IIA and IIB can be found in Table 1. The
function of the flame arrester, e.g. due to corrosion. values in the table are regarded as safe limit values for the explosive
(8) Flame arresters must be installed as close as possible to the tank or mixtures of these substances when flowing out of pipes without turbulence-
container and arranged in such a way that they can be easily increasing construction. In cases of increased turbulence and for other
maintained. If installation on the tank roof is not possible for structural explosive mixtures, the minimum flow velocities must be determined
reasons, the flame arrester can be positioned directly next to the tank, experimentally.
provided that the pipework between the tank and the flame arrester is
positioned directly next to the tank wall. The flame arrester must be
arranged in such a way that an explosive atmosphere in the tank or in Table 1: Required minimum flow velocities
the pipework cannot be ignited by a continuous fire at the flame arrester. Substances of the Substances of the
7.3 Flow-monitored backfire-proof devices Explosion group IIA Explosion group IIB
Nominal diameter ≤ 20 ≤ 200 ≤ 20 ≤ 200
(1) Flow-monitored backfire-proof devices maintain a flow velocity of gases
in mm
or vapours at the outlet opening above the flame propagation velocity in
order to prevent flashback. Flow-monitored backfire-proof devices are Velocity in m/s at ambient ≥4 ≥8 ≥6 ≥12
temperature at the inlet
suitable for introducing explosive atmospheres into systems with elevated
opening
temperatures (temperature above the ignition temperature of the
flammable gases and vapours). z. e.g. with a torch)
Velocity in m/s at increased ≥8 ≥ 16 ≥ 12 ≥24
(2) The flow velocity of the gases and vapours must be monitored in a temperature at the inlet
suitable manner. If the flow velocity falls below the required minimum, the opening
supply of explosive atmosphere must be interrupted immediately. (e.g. on a combustion chamber)

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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(4) The necessary protective measures against flame transmission must be (5) An independent measure in accordance with paragraph 4 sentence 2 is
implemented in stages, taking into account the probability of the given if detonation flame arresters tested for stable detonation in
occurrence of explosive atmospheres (zones) and the ignition possibilities accordance with DIN EN 16852 or the former DIN EN 12874 are used. A
available in a recovery or exhaust air purification system. Table 2 flow-monitored backfire-safe inflow is only considered an independent
applies to the number of measures to be applied simultaneously and protective measure if another independent protective measure (e.g. a
independently of each other to achieve flame transmission safety. detonation flame arrester in accordance with sentence 1) is present.
Note: (6) The functional safety of a flow-monitored backfire-safe inflow must
A flow-monitored backfire-safe inflow is not considered an autonomous be verified.
protection system within the meaning of Directive 94/9/EC.

Table 2: Number of protective measures for the protection of exhaust air ducts

Probability of occurrence of effective Number of protective measures in place

ignition sources in the recovery or of the following zones in the exhaust air system
exhaust air purification system Zone 0 Zone 1 Zone 2
constantly or
3 2 1
frequently (e.g.
burner flame)
occasionally
2 1 0
(e.g. in the event of foreseeable faults)

rare
1 0 0
(e.g. for rare disorders)

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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7.4 Flame penetration in case of continuous fire 8 Decoupling devices for dusts
Openings to the outside of tanks and installations from which vapour/air 8.1 General information
mixtures can escape for more than a short time must be fitted with a The explosion isolation devices mentioned for gases and vapours cannot
device that can withstand the combustion of escaping explosive mixtures generally be used for dusts (risk of clogging, etc.). A distinction is made
under all conditions of use without flame propagation (endurance burning between two systems for explosion isolation devices suitable for dusts:
flame arresters). In the event that suitable endurance burning flame arresters
cannot be used (e.g. for vapours of a specific flammable liquid such as Complete decoupling and partial decoupling
alcohols), detonation flame arresters may be used in ventilation ducts as an 1. With complete decoupling, both the spread of the flame and the pressure
alternative to sentence 1 if the distance between the detonation flame are prevented. In this case, explosion-proof components are generally no
arrester and the opening of the ventilation duct leading to the outside is at longer required downstream of the decoupling device.
least the length specified below. Sentence 2 is fulfilled, for example, if 2. Partial decoupling generally only prevents the spread of flame or
detonation flame arresters tested for stable detonations are used. pressure. Additional measures may be required for the system components
located downstream of the decoupling device (e.g. sufficient explosion
resistance).
Table 3: Minimum lengths of pipework

Nominal diameter of the Length of the pipework

Remark:
pipework in mm in m
The distinction between complete decoupling and partial decoupling is
15 0,5 important for practical application, as the need for complete decoupling with
20 1 regard to flame and pressure does not exist in all cases, but in some cases only
25 1,5 the achievement of flame isolation or pressure limitation is sufficient.
32 2
40 3
Note:
50 4
Suitable for installation in pipework systems or for product discharge are
65 6
z. e.g. the facilities mentioned under points 8.2 to 8.8.
80 8
100 to 200 10

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 Technical rules Hazardous explosive atmosphere TRBS 2152 Part 4
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8.2 Quick-closing valve, quick-closing flap If the quick-closing valve does not close, an externally energised quick-
closing valve
(1) The explosion to be decoupled is recognised by suitable detectors.
A trigger mechanism is activated via a
is detected and the quick-closing valve closes the
control unit, which slide or flap(s) by
means of an auxiliary flow within a sufficiently short time (e.g. blowing nitrogen onto the closing body) in good time (before pressure
and flame have reached the slide or flap(s)).
(2) The pressure required for the effectiveness of quick-closing slides or flaps is
The required installation distance must be observed. (3) The installation distance required for the effectiveness of quick-closing valves
shall be
Note: Observe the distance.
For explosion decoupling by means of a quick-closing slide valve Note:
or butterfly valve is a complete decoupling. In the case of explosion decoupling by means of a quick-closing valve
is a complete decoupling.
8.3 Quick-closing valve (explosion protection valve)
(1) When a certain flow velocity is exceeded in the
Pipeline closes the valve automatically and then remains in 8.4 Rotary valves
closed position. The flow velocity required for closing
the rotary
valves for explosion decoupling must be explosion-proof and flameproof for the expected explosion pressure.
Previously known quick-closing valves may only be installed in horizontally laid
pipework can be installed.
be shut down
Note 2: (2) I n the event of an explosion, the rotary valve must
so that the discharge of burning product
automatically, e.g. via a quick-closing valve suitable only for relatively low dust loads, (e.g. clean air side
of filter systems) into downstream system parts is prevented.
Note:
(2) If the expected increase in the flow velocity due to the pressure wave of the explosion is sufficient to
trigger a rapid decoupling system in good time, the explosion

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 is completely decoupled.

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 8.5 Double slide systems Remark:
(1) Double slide gate valve systems generally consist of two slide valves, each designed for the It should be
noted that, as a result of the pressure propagation, both extinguishing agents are explosion-proof and flameproof and unburnt dusts and combustion
products are forced through the pipework to form an airlock. These are pressed through a pipe and discharged into other parts of the
system or into the environmentThe corresponding function-tested control system ensures that can reachparts of the system.
at least one slide valve is always in the closed position.
8.7 Relief vent
(2) In the event of an explosion, a double-slide system must be shut down automatically, e.g. via
(1) A venting vent is a decoupling device that can be used
to shut down an explosion detector so that the discharge of flammable gases is prevented.
The discharge of flaming explosives is prevented
by changing
product intothe direction of
downstream flow by
system 180 degrees.
components is prevented.
while at the same time relieving pressure at the deflection point.
Note: This is achieved by means of a special pipe design and arrangement The
explosion decoupling by means of a double slide valve system (see Fig. 1) and usually by using a pressure relief device (e.g. bursting disc)
at the deflection point.
8.6 Extinguishing agent barriers (2) For the use of the discharge chimney, the following applies in essence
(1) Extinguishing agent barriers essentially consist of one or more detectors, a control unit and one or more extinguishing agent container(s) .
An incipient explosion shall be pressurised by detectors (see number 5, paragraphs 1 to 3).
recognised that the injection of extinguishing agent into the pipework between the
to be decoupled. The extinguishing agent extinguishes the (3) Since the explosion flame is extinguished when pressure relief
devices are used on a pressure relief vent. The spread of the explosion pressure may not be prevented by the extinguishing agent barrier.
If the extinguishing agent barrier is used on a fire extinguisher, the functionality
of the venting device for this
(2) The installation procedure required for the effectiveness of extinguishing agent barriers must be proven. application must be proven.
status must be observed. (4) In the case of explosion decoupling by means of a relief vent
(3) Explosion decoupling by means of an extinguishing agent barrier is a partial decoupling. The restrictions compared to a complete decoupling are
partial . The possible increase in pressure may require additional
measures to be taken into account for the system components arranged behind the extinguishing agent
barrier in the design of the system components arranged behind the extinguishing agent barrier.
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operational safety an explosion to a harmless level Page: 16 / 16

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 Note 1: 8.8 Product template
Explosion transmission cannot always be reliably prevented by the explosion vent(1) In
conjunction with the "explosion-proof design" protective measures. However, the propagation of the flame front is disturbed to
such an extent that the explosion can initially be expected to start slowly
in the downstream pipe section. A suitable measure for decoupling the explosion can be taken
with a sufficient filling height.
be. This requires a sufficiently rigid discharge device on which
Note 2: on which the product is "placed" (e.g. rotary valve, screw conveyor If the
separator is decoupled from or process valve in the case of object extraction ). The
discharge device itself does not have to be flameproof for this purpose.
suction line can be safely excluded, despite the above-mentioned (2) The product overlap must be high enough to ensure that sufficient
protection of the product cannot occur under explosion pressure restrictions with the relief vent. The required level of protection
cannot be achieved. The required employees and third parties must be reached (see paragraph 3). The minimum fill level must be
ensured in a suitable manner.

9 Explosion decoupling for hybrid

mixtures
Due to the dust content, measures from number 8 can be considered for
explosion decoupling in hybrid mixtures if these devices also sufficiently safely
limit the explosion effects caused by the vapour or gas content.

Remark:
Figure 1: To prevent the propagation of explosions with dust contents above
Schematic connecting pipelines, conveyor systems or similar as well as a flame
Representation of a The flames that are usually used to represent a leakage from plant components are those
mentioned in point 7.
Relief vent The use of a venting vent is not suitable for use with a venting vent due to the risk of
clogging.

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