the explosion risk

The Explosion Risk

How to treat it ?

S.Radandt

Risk Definitions

Definition From Guide 51risk

combination of the probability of occurrence of harm and the severity of that harm

Definition From Guide 73risk

combination of the probability of an event and its consequences

note: the term risk is used when there is at least the possibility of one negative consequence.

RISK MANAGEMENT

RISK ASSESSMENT

RISK ANALYSIS

SOURCE IDENTIFICATION

RISK ESTIMATION

RISK EVALUATION

RISK TREATMENT

RISK AVOIDANCE

RISK OPTIMIZATION

RISK TRANSFER

RISK RETENTION

RISK ACCEPTANCE

RISK COMMUNICATION

Determination of thelimits of the system

Risk evaluation

Risk reduction

Start

ENDYES

NO

Risk analysis Risk assessment

Hazard identification

Is the systemsafe?

Risk estimation

Risk Management System

financeswork-structurework-processes quality environment

plant and processestechnology

• supplier• product liability• consumer safety

fitness of workers

machinery processessubstances

health knowledge

specific hazards

explosions dangerous substances

Management System withSpecific Targets Set and Strategies Used by a GivenOrganisation/Company

019

Explosion venting of a 250 m³ vessel

Rapidly developing dust explosion( KSt-value = 300bar. m/s )

Long flame jet

Explosion venting of a 250 m³ vessel,

Less rapidly developing dust explosion ( kSt-value < 200 bar. m/s )

Venting of a silo bin into a machineryroom,

Secondaryexplosion in themachinery room

Explosion venting of a bucket elevator

Dust explosion in a feedproduction plant

Disaster: Structure of Causes

Disaster

En(and) En(or)

E1 E2 En E1 En

Conditions/Causes

Conditions/Causes

!En Event with „and“ condition P(En)=P(E1)× P(E2)×……P(En)

En Event with „or“ condition P(En)=P(E1)+P(E2)+……P(En) !!P(En) Probabilities of events

Important informations aboutpossible causes

Near miss:A hazardous situation, event or unsafe act where thesequence of events could have caused an accident ifit had not been interrupted.

Incident: Undesired events

Direct cause: The immediate reason why an incident occurred.

Root cause: The factors in a system which allow the direct cause to arise.

Assessment of explosion risks 1

Any assessment shall be based on :

The likelihood that explosive atmospheres will occur and their persistenceThe likelihood that ignition sources will bepresent and become effectiveThe scale of anticipated effects


Ignitability shall be assessed by taking intoaccount,in particular :

The degree of dispersion of flammable and/orcombustible substancesThe concentration of flammable and/orcombustible substances


Explosion risk shall be assessed overall.The following are of particular importance :

InstallationsSubstances usedProcessesAnd their possible interaction

Places which are or can be connected via openingsshall be taken into account in assessing explosionrisk

Explosion risks must be assessed overall.

Important factors are:

the work equipment used;

the building fabric and configuration;

the substances used;work and process conditions;

their possible interactions with each other and the working environment.

I s t h e f o r m a t i o n o f a e x p l o s i v ea t m o s p h e r e p o s s i b l e ?

N o e x p l o s i o np r o t e c t i o n m e a s u r e sn e c e s s a r y

A r e f l a m m a b l e s u b s t a n c e sp r e s e n t ? N o

Y e s C a n s u f f i c i e n t d i s p e r s a l i n a i r g i v e r i s et o a n e x p l o s i v e m i x t u r e ? N o

Y e s

W h e r e c a n e x p l o s i v e a t m o s p h e r e so c c u r [ 2 . 2 . 3 ] ?

P r e v e n t t h e f o r m a t i o n o f h a z a r d o u s e x p l o s i v ea t m o s p h e r e s a s f a r a s p o s s i b l e

I s t h e f o r m a t i o n o f h a z a r d o u se x p l o s i v e a t m o s p h e r e sr e l i a b l y p r e v e n t e d ?N o

Y e s

I s t h e i g n i t i o n o f h a z a r d o u se x p l o s i v e a t m o s p h e r e s h i g h l yi m p r o b a b l e ?

Y e s N o

A v o i d e f f e c t i v e i g n i t i o n s o u r c e s i np l a c e s w i t h h a z a r d o u s e x p l o s i v ea t m o s p h e r e s a s p e r z o n i n g

Y e s N o

C o n t .

T o w h a t z o n e s c a n t h e p l a c e s w i t hh a z a r d o u s e x p l o s i v e a t m o s p h e r e s b ea s s i g n e d C o n t .

F u r t h e r e x p l o s i o n

p r o t e c t i o n m e a s u r e s n e c e s s a r y

E x p l o s i o n p r o t e c t i o n

m e a s u r e s n e c e s s a r y



F u r t h e r e x p l o s i o n

p r o t e c t i o n m e a s u r e s

n e c e s s a r y

M i t i g a t e t h e d e t r i m e n t a l e f f e c t s o f a n e x p l o s i o n s o a s t o e n s u r e t h e h e a l t h a n d s a f e t y o f w o r k e r s .

A p p l y a d e q u a t e a n d p r o p o r t i o n a t e m i t i g a t i o n m e a s u r e s

A p p l y a d e q u a t e e x p l o s i o n p r o t e c t i o n m e a s u r e s

Explosion pressure depending on the filling method

Belt Conveyor

Concentration = 538mg/m³

No Zone

Zone 21

No Zone

Filling of a funnel: concentration = 592 mg/m³

Filling of a silo-car

concentration = 569mg/m³

No Zone

Build up of a Slag-heap

concentration = 632mg/m³

No Zone

Zone 21 No Zone

No Zones

C = 41.5 mg/m³ C = 20.07 mg/m³

Filling of a Truck - Container

No Zone

concentration = 650.4 mg/m³

concentation = 60 mg/m³

No Zone

No Zone

No Zone

Surface temperature of the engine: 280°C

Dust layers at the engine

Burned dust layers

Silo plant

Grain elevator plant

Produktsilos, Verladung, etc.

Lager- Silos

E l e v a t o r

E l e v a t o r

Sieb-maschine

Waage

Vorbehälter

Hammer-mühle

Bunker

Trogkettenförderer

Ignition Hazard AssessmentProcedure for Equipment

The assessment procedure is divided into four steps:1. analysis of the ignition hazards and their

causes2. assessment of the ignition hazards regarding

frequency of occurrence3. determination of required protective measures4. concluding assessment and determination of the

equipment category

Afterwards these ignition sources should be considered separately with regard to differences in

Intended use or possible application,

constructional variants,

operating conditions or working cycles including their variations (start, stop, load alternations etc.),

influences of the ambience (temperature, pressure, humidity, energy supply etc.),

material parameters or their interdependencies (metal, synthetic material, electrostatic chargeable liquids etc.),

interdependencies with components or other pieces of equipment and interdependencies with and between persons

Zone 2/22 outside

Connected to Zone 1/21

Axial Fan for cat. 2 meetsexplosive atmosphereconnected to it and explosive atmosphereof surrounding

1 Blade tips/ 2 Hub to internal circular housing running clearance /3 Blade operating clearance /4 Internal anti-sparking impeller housing liner/ Motor spigot located on mounting flange/ Impeller housing

Feed Material Input

Zone 21Zone 21

Feed Throat

Productcontainer

Connected to explosive atmosphere

Surrounding Condition

Zone22

Outsideignitionsourceduringmalfunction

Insideignitionsourceduringnormal operation

Assembly:single function is grinding

Information for use: e.g. inerting

Avoidance of explosive atmosphere: inerting

Potential Ignition Sources outside

Feed Screw

Rolling Bearings

Belt Drive

(Inherent safe: v <1m/s)

Potential Ignition Sources outside

ElectricalMotor

Gear Drive

Belt Drive

Cover

Prevention of and protectionagainst explosions

Technical and/or organizational measuresappropriate to the nature of the operation in order of priority and in accordance with thefollowing principles :

Prevention of formation of explosive atmospheresAvoidance of ignition of explosive atmospheresMitigation of detrimental effects of an explosion to the health and safety of workers to an adequatelevel

Planning principles

When planning new installations or themodification of existing ones , attentionshall be paid, in particular, to :

Normal operating conditions , including maintenanceworkConstructional factorsCommissioning and decommissioningMalfunctions , forseeable fault conditionsMisuse which may reasonable be anticipated

Combine technical and organisationalmeasures

If there is a potential risk of explosion at a workplace, this also implies that the work organisation must meet certain requirements. Organisational measures must be taken where technical measures alone cannot ensure and maintain explosion protection at the workplace. In practice, the work environment can also be made safe by combining technical and organisational measures.

The following organisational measures must be carried out:

• produce written operating instructions, where required by the explosion protection document;

• instruct workers in explosion protection;• ensure workers have adequate competence;• apply a permit-to-work system for dangerous work, where

required by the explosion protection document;• carry out maintenance;• carry out inspection and surveillance;• mark hazardous places, where necessary.

The risk assessment by the manufacturer of equipment shall always be carried out for each individual situation.

Risk assessment includes the following elements:

a) Hazard identification. The safety data assist in the identification of hazards by demonstrating whether substances are flammable and indicate their ease of ignition;

b) determine whether an explosive atmosphere is likely to occur and the amount involved

c) determine the presence and likelihood of ignition sources that are capable of igniting the explosive atmosphere

d) determine the possible effects of an explosione) evaluate the riskf) consider measures for the minimization of risks

The risk assessment shall take into account the ignition and explosion hazard from

- the equipment, protective systems, and components itself;

- the interaction, between the equipment, protective systems, and components and the substances being handled;

- the particular industrial process in the equipment, protective systems, and components;

- interactions of individual processes in different parts of the equipment, protective systems, and components;

- the surroundings of the equipment, protective systems, and components and possible interaction with neighbouring processes.

Ignition hazard assessment

All equipment and all parts of it shall be subjected to a hazard analysis that identifies and lists all of the potential sources of ignition by the equipment and the measures to be applied to prevent them becoming effective.

Examples of such sources include:hot surfaces, naked flames, hot gases/liquids, mechanically generated sparks, adiabatic compression, shock waves, exothermic chemical reaction, thermite reactions, self ignition of dust, electrical arcing and static electricity discharge.

The Role of intended Use

It is the manufacturers provision to determine the intended use as a starting point for the ignition hazard assessment procedure.

The instructions shall contain all restrictions and information necessary for a correct putting into service and a following safe operation.

It determines the intended use of the equipment as the essential precondition for the explosion protection.

- ensure that ignition sources cannot arise

- ensure that ignition sources cannot become effective

- prevent explosive atmosphere reaching the ignition source

- contain the explosion and prevent flame propagation.

Protective measures/types of protection shall be considered and/or applied in the following order:

Specify the service conditions

All intended service conditions for the equipment (e.g. rough handling, humidity effects, ambient temperature and pressure variations, effects of chemical agents, corrosion, vibration) shall be specified by the manufacturer and included in the required instructions for use.

Technical measures for explosion protection

Prevent the formation of hazardous explosive atmospheres

Limiting of concentrationsInertingPreventing or limiting the formation of explosive atmospheres in the vicinity of plant( e.g. ventilation )Removal of dust depositsGas alarm

Avoid the ignition of hazardous explosive atmospheres

Zoning of hazardous placesAvoidance of ignition sources

Mitigate the effects of explosions so as to ensure thehealth and safety of workers

Mitigation of the effects of explosion( mitigation measures )

Explosion resistant designFor maximum explosion overpressureFor reduced explosion overpressure associatedwith explosion relief or suppression

Explosion reliefExplosion suppressionPrevention of flame and explosionpropagation

Weakexplosion

Strongexplosion

Venting of Silo-Buildings

What is?Danger

condition, circumstanceor occurrence, which can result in damage

HazardWhat is a

?

danger related to aparticular person, an object, propertyor a situation;

Hazardous event

a) event that can causedamage;

b) a triggering event(cause) is required toinitiate a hazardousevent;

Damage

physical impairmentand/or damage tohealth or property

Zone 0

Zone 1

Zone 2

Surface ofthe liquid

Example of zoning at a tank for flammable liquids

Sump

Zone 22

Zone 20

Zone 21

Example of zoning for flammable dusts

the explosion risk

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