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SchadenspiegelSpecial feature issueRisk factor of air

1/2008, 51st year Losses and loss prevention


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Dear Reader,

Air on the move is expensive for the insurance industry.

Windstorms can devastate whole regions and cause damage

costing billions. We have gathered together all you need to know

about this natural hazard in a special topic entitled Weather

phenomenon: Windstorm. We give you a picture of the loss

situation after Hurricane Wilma, which devastated the Mexican

holiday paradise of Yucatn in 2004 and led to business interrup-

tion losses whose adjustment was particularly tricky. And then

we show how arduous the salvage of a container vessel can be,

taking the example of MSC Napoli,which was stricken during

Winter Storm Kyrill in 2007.

The risk factor of air is not restricted to the windstorm hazard,

though. Cue: air pollution. Of the environmental media air, soil,

and water, it is the air that influences our physical well-being

most intensively. What about the expenditure for asbestos-

related occupational diseases or immission-related respiratory

diseases? And is air a friend to aviation or rather an incalculable

risk? We interview a pilot and aviation underwriter and find out

how dangerous turbulent air movements really are to air traffic.

Air can also catch fire. In this, the fourth and last special feature

issue in our series Water, fire, earth, air, our authors report

on the explosion hazard of combustible dust. They also address

the necessity of clean air in the production of semiconductors

and describe a defective wind turbine, whose rotor continued

turning at increasing speed until one of the rotor blades broke

off. Finally, this issue also contains our review of catastrophes

in 2007.

What do you think of this issue? Please write and tell us at:

[email protected]

Your Schadenspiegel team

Our publication portal at www.munichre.comis the place to go if you

wish to order past issues of Schadenspiegel since 2000 or download them

in pdf format.

Risk factor of air

Stormy, destructive,

dangerous

Editorial


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Renewable energyWhen the turning stopped:

Defective wind turbine

A rotor blade breaks off and is

wrapped around the nacelle.

Page 2

Fire risk

Dust explosions

When the air catches fire

Combustible dust threatens industry.

Page 6

Interview

Aviation risks

Wind shear and wake vortices

Modern technology makes aviation

risks manageable.

Page 14

Environmental risk

Air pollution and liability

Health risks from asbestos and

emissions.

Page 44

Special risk

Clean air in semiconductor

production

Why fire protection is so important

in this sector.

Page 50

Special topic:Weather phenomenon:Windstorm

Windstorm The most important

natural hazard worldwide

Loss prevention includes windproof

construction.

Page 19

Hurricane Wilma Adjustment ofbusiness interruption claims

How is compensation calculated?

Page 32

Winter Storm Kyrill MSC Napoli

Difficult salvage of vessel and

containers.

Page 38

Major losses in 2007Fires, aircraft accidents, natural

catastrophes.

Page 54

Readers letters

Page 57

Contents

1Munich ReSchadenspiegel 1/2008


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Renewable energy

When the turning stopped:Defective wind turbine

It was four months before a grave error made while servicinga 2.5-MW wind turbine developed into a spectacular loss. As sooften happens, it was the result of human error. The incidentnot only stopped operations abruptly but also made it necessaryto carry out lengthy and extensive repairs.

Authors

Winrich Krupp, Markus von Stumberg, Munich

A spectacular sight: one of the

turbines rotor blades wrappedaround the steel tower. Human

error and technical defects were

the cause of this loss.

2 Munich ReSchadenspiegel 1/2008


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The wind turbine was part of a wind farm, where

twenty turbines were linked up together. All the

turbines had been working for about a year without

any particular trouble. So when the manufacturer

carried out a routine servicing job, there were no

adverse findings. But in the process of servicing

one of the 2.5-MW turbines, a serious error wasmade that was not detected at first.

The loss event

It was not until four months later that an unfortu-

nate confluence with other cases of negligence and

adverse circumstances led to the loss occurrence.

What had happened?

On the day of the loss, the wind farms automatic

monitoring system registered a malfunction in the

high-voltage underground cable linking the wind

farm to a switching station about 10 km away. Asplanned, it automatically shut down the turbines

and disconnected them from the grid.

Servo-motors turned the rotor blades into what

is known as the feather position. In this position,

the angle of attack is reduced to a minimum and

the rotors come to a standstill. Brakes were also

applied to secure the rotors in that position.

But the coordinated shutdown routine was only

performed by nineteen of the twenty turbines.

One of them failed to conform to the automatic

sequence and none of the rotor blades were turnedto the feather position. On the contrary, since

the wind turbine was disconnected from the grid,

the rotor turned at increasing speed, until finally

one of the three blades could not withstand the

pressure and centrifugal forces any longer. The

38-m fibreglass-reinforced plastic blade broke off

and was wrapped around the nacelle at the top

of the 80-m steel tower.

But that was not all. The unbalance caused by the

turning rotor and the resulting forces and torque

were transmitted through the tower to the foun-

dations. Owing to the comparatively high elasticityof the material, the steel tower was practically

undamaged, but numerous cracks were later dis-

covered in the concrete foundations. They were

damaged so severely that they had to be demol-

ished and rebuilt.

The rotor and the two remaining blades had to be

replaced, too. Repairs were possible, however, onthe nacelle, which accommodates the generator,

gears, and bearings.

Result: Besides causing property damage of

around 2m, the accident put the turbine out of

service for several months.

The cause

The operator and the manufacturer were equally

intent on investigating the cause of loss as quickly

and precisely as possible not least in order to

prevent the same thing happening again.

Analyses of all the recorded operating data, the

service log, the plant software, and further investi-

gations both on-site and at the manufacturers

factory showed without any doubt that the person-

nel had switched off the monitoring alarms for

the routine servicing job (maintenance work) on

the wind turbine conducted months ago but had

inadvertently failed to reactivate them afterwards.

This error had far-reaching consequences because

nobody noticed a deep discharge of the off-line

battery system that powered the servo-motors for

adjusting the blades angle of incidence.

Cracks in the concrete left

no alternative but to remove

the foundations and rebuild

them.


Renewable energy


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This deep discharge was found to have been

caused by a faulty slip ring, which has the job of

supplying the battery charger with power, and a

corroded contact in the chargers wiring. Conse-

quently, the automatic plant control system could

not drive the rotor blades into the feather position

during the power outage.

Learning from experience

If the safety system had been fully activated, the

controls would have identified all the technical

deficiencies and would have shut down the plant

in good time. The damage to the turbine was def-

initely caused by the alarms being deactivated.

Even so, the turbine manufacturer responded in

exemplary fashion by introducing an array of

measures. The training of maintenance staff has

been further improved. Particular attention is nowgiven to providing them with even more in-depth

knowledge of the function and significance of the

safety systems. A change in the monitoring system

software will prevent the deactivation of crucial

alarms for such parameters as overspeed, vibra-

tions, temperatures, and battery status.

Additional safety is provided by stricter password

controls and more narrowly defined authority levels

in the operating software that are now needed to

bypass monitoring and safety devices. Last but not

least, a remote query system automatically checks

the monitoring system for full operational capabilityon a daily basis.

Conclusion

There is no doubt that manipulation of monitoring

and control systems whether during commission-

ing or in the operating phase always jeopardises

the safety of technical plant and equipment. When

there is no alternative to shutting down such sys-

tems, a maximum of care, knowledge, and reliabil-

ity on the part of the personnel responsible is

essential, because it is precisely this emergency

situation that often result in enormous losses.

Table 1 The components of a wind power plant

and the most frequent causes of loss

Source:

German Insurance

Association (GDV),

Berlin

Bearings and shafts

Wear and tear

Fatigue and cracks

Electric generator

Damaged windings

Asymmetry

Overheating and fire

Gearing

Worn teeth

Misalignment

Overloading

Eccentricity

Lubricant

Rotor blades

Lightning stroke

Ice load

Fatigue and cracksUnbalance

Tower

Vibrations

Fatigue and cracks

Way ahead of the rest:

Germany leads the field with

a total installed capacity of

22,247 MW. Further develop-

ment of the offshore segment

may also have a positive

effect on the proportion of

energy generated by the

wind.

Source: Global Wind Energy

Council (GWEC), Brussels

Fig.1 Top five countries: Installed capacity in 2007

Germany

United States

Spain

India

China

22,247 MW

15,145 MW

8,000 MW

6,050 MW

16,818 MW

0 5,000 10,000 15,000 20,000 MW


Renewable energy


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Wind sector on the up

But the loss potential is increasing

Schadenspiegel team

The total installed capacity of wind power plants in

the EU is currently in excess of 48,000 MW, repre-senting an increase of 300% in the European mar-

ket over the past five years. The fierce competition

among manufacturers has led to a continuous

increase not only in the number of plants but also

in the size and performance of the turbines.

Whereas European plants had an installed capacity

of less than 200 kW on average in 1992, the figure

for newly installed plants in 2006 was 1,800 kW.

Wind power is a risky business for the insurance

industry. Defective gears, overheated generators,

and worn bearings material fatigue and inad-

equate reliability of service and maintenance are

the main causes of losses. The higher their per-formance, the more vulnerable the plants become.

What is more, in such a young class of business,

practical experience values only go back a few

years. But it is already certain that the costs of

settling machinery and machinery loss of profits

claims for wind farms will go on rising in the coming

years.

In order to keep losses to a minimum, more time

must be invested in the development and testing

of new plants, and higher quality standards are

needed for manufacture, maintenance, and repairs.

In addition to a detailed and comprehensive riskassessment, insurers must encourage loss preven-

tion and loss avoidance. Service and maintenance

clauses should be an integral part of each insurance

contract and should specify how often the main

components are to be replaced or overhauled.Fig. 2 Schematic structure of wind turbine

Wind energy is converted into mechanical rota-

tional energy with the aid of rotors. Once used

directly by windmills for purely mechanical uses,

this energy is nowadays used to drive generators

that produce electrical energy.

The nacelle houses the hub, gearing, and gener-ator on the horizontal rotor shaft. It is turned to face

the wind and ensures that the rotor takes optimum

advantage of the prevailing wind conditions.

Incidentally, the operation of wind farms only

makes technological and economic sense if the

wind reaches what is called the start-up wind

speed.

Hub, shaft,

and blade

pitch

mechanism

Rotor blade

Rotor locking brake

Gearing

Electrical

switchgear and

control system

Nacelle

Electric generator

Tower

Transformer

Rotor shaft

Foundations

Diagram: Munich Re


Renewable energy


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Fire risk

Dust explosions When the air catches fire

It is estimated that not a day goes by in Europe withouta dust explosion. According to a current study fromthe United States, combustible dust represents a dangerin any industrial facility given an adequate concentrationin the air and an ignition source. The explosive mixcosts insurers millions of euros.

Author

Dr. Alfons Maier, Munich

Large-scale fire at Hayes Lem-merz International, a vehicle

components supplier: an alu-

minium dust explosion was fol-

lowed by a fireball with extremely

rapid fire development.



9/62

The fact is that the smaller the particles and the

finer their distribution in the air, the greater the

explosivity of combustible dust. The ignition

source may be no more than a small electrical dis-

charge triggered by a plug being removed from

a socket or a hot metal component.

Dust explosion is a familiar hazard particularly

in the woodworking, metalworking, plastics

processing, chemicals, paper, agricultural, food,

and fodder industries. Precautions are taken to

prevent such events from occurring, and many

facilities go on producing for years and years

without any mishap.

Statistics on dust explosion losses

In spite of all the precautions taken, the agricul-

tural and food industries are particularly known

for large losses and a certain loss frequency.Although large individual losses regularly occur

in other industries, too, meaningful statistics are

compiled and maintained only for individual fields

or branches of these industries and only for indi-

vidual countries. In most cases, it is almost impos-

sible to compare these statistics because they draw

on sources that differ in terms of the designation

and composition of dusts, facility types, and igni-

tion sources. In contrast, dust explosions in the

agricultural sector and coal dust explosions in

the mining industry, for instance are generally

well-documented.

What is a dust explosion?

In a dust explosion, a mixture of

dust particles ignites in the air. Forthis to happen, the particles must

consist of combustible material and

be smaller than about 500 m, and

their concentration in the air must lie

between the lower explosion limit

(LEL) and the upper explosion limit

(UEL). For many types of food dust,

the LEL is between 30 and 60 g/m3,

the UEL between 2 and 6 kg/m3.

In addition, oxygen and an ignition

source with a sufficient supply ofenergy must be present.

A distinction is made between pri-

mary and secondary dust explosions.

When a dust suspension in a con-

tainer, room, or system component,

for example ignites and explodes,

we speak of a primary dust explo-

sion. In a secondary dust explosion,

dust that has settled on the ground

or on other surfaces is stirred up by

the primary explosion and ignites.A chain reaction follows: the pressure

wave emanating from the secondary

dust explosion can stir up further

dust deposits and cause further dust

explosions.

Dust explosions in the US agricultural sector

In the dust explosion statistics of the US agri-

cultural sector there are records of

490 explosions from 1900 to 1956 with losses

of US$ 70m,


of US$ 55m,


of US$ 169m,


of US$ 163m.

This averages out at about one event a month.

The annual number of events ranges from six to 18,

with individual loss amounts of between US$ 4m

and US$ 56m.

The long-term trend that emerges in the agricul-

tural sector is that dust explosions mainly occur in

elevators (e.g. chain or bucket elevators operating

as grain conveyors), fodder and flour mills, and

silos.

Documentation of dust explosions in Germany

The institute for occupational health and safety of

the German statutory accident insurance institu-

tions has analysed 599 dust explosions that

occurred in different sectors of industry over a

period of about 25 years up to and including 1995.


Fire risk


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Since 1785, when the first dust ex-

plosion was documented in a flour

warehouse in the Italian city of Turin,

explosions have occurred with regu-lar frequency and have lost nothing

of their destructive force throughout

this time. In 1977, for example, five

dust explosions occurred at US silo

facilities, killing 59 people and injur-

ing 49.

A flour dust explosion at the Roland

Mill in Bremen, Germany, in 1979

caused property damage equivalent

to US$ 50m, with 14 people killed and

17 injured. Later that same year, it

was the turn of a feedstuff factory inLerida, Spain, leaving ten dead and

a badly damaged silo plant.

Although the design of grain eleva-

tors has improved considerably over

the years, explosions continue to

happen with disturbing regularity.

In 1997, twelve people died in a grain

elevator explosion in Blaye, France,

with property and BI losses amount-

ing to about 23m. Only 16 of the44 elevator cells were still in their

original shape after the incident.

For safety reasons, however, the

remaining parts of the plant were

detonated as well.

In 1998, a mixture of dust and air

exploded in a large grain elevator

in Haysville, Kansas. Seven people

were killed and ten were injured,

with property and BI losses estimated

at several million US dollars. The

costs for rescue, fire-fighting, andsubsequent operations amounted to

about US$ 850,000.

A terminal at the port of Puerto

General San Martn, Argentina, was

the scene of a severe dust explosion

in a silo in 2001, which killed three

people and injured seven. There was

a further explosion at a port terminal

only a month later, this time in Para-

nagu, Brazil. In this case, one of thewarehouses was a total loss. The

force of the explosion flung 300-kg

chunks of concrete several hundred

metres through the air, with some

roof sections landing up to 1 km

away. The grain continued burning

for almost three weeks.

In 2002, a dust explosion which

occurred when a vessel was being

loaded with soy beans in the port of

San Lorenzo, Argentina, destroyed

the entire terminal. Three peopledied, 19 were injured.

The overview shows that

the facilities in which dust

explosions occur most fre-

quently are grain elevators

and hoppers. They account

for the largest proportion

of explosions particularly in

the wood and coal dust

groups (34.7% and 22.2%

respectively).

Review:

Major dust explosions in the agricultural and food industries


Fire risk

Fig. 1 The facilities most frequently affected

in the various dust groups

Dust groups

Total

Wood products

Paper

Coal/Peat

Food and fodder

Plastics

Metals

Others

0 10 20 30 40 50

Silos and hoppers 19.4%

34.7%

25%

22.2%

26.9%

15.4%

44.1%

18.6%

Proportion (%)

Mills

Silos and hoppers

Mixing plants

Dust-removal facilities and separators

Conveyors and elevators

Silos and hoppers

Mills


11/62

Fig. 1 shows the facilities most frequently affected

in the various dust groups (wood/wood products,

paper, coal/peat, food and fodder, plastics, metals,

and others). The most frequent ignition sources in

the various dust groups are the mechanical ones

(cf. Fig. 2).

New findings:

Combustible Dust Hazard Study

The Combustible Dust Hazard Study of the US

Chemical Safety and Hazard Investigation Board

(CSB) from the year 2006 was the first study to

incorporate losses from different sectors of indus-

try in one single examination. It shows that there is

an explosion hazard in all industries that handle

combustible dust.

The study included the sectors of food, rubber,

metal, wood, pharmaceuticals, plastics, paints andcoatings, synthetic organic chemicals, and other

industries that are not fully covered by the compre-

hensive safety regulations of the Occupational

Safety and Health Administration (OSHA). Agricul-

ture and coal mining were not included because

they are subject to the Grain Handling Facilities

Standards and the Mine Health and Safety Act

respectively.

Facilities like hospitals, the armed forces, research

institutes, and the transport sector were not con-

sidered either.

In the period from 1980 to 2005, 281 major dust

explosions are listed with a total of 119 dead and

718 injured, clearly showing that dust explosionsrepresent a major safety problem for industry.

People were injured or killed in as many as 71% of

the loss events in different branches of industry.

The explosions happened in 44 federal states and

involved a variety of materials. On average, there

were ten dust explosion events every year in this

period. More than half of the events were recorded

in the following sectors: food (25%), wood (15%),

chemicals (12%), and metal (8%). The dust explo-

sions were caused by wood dust (24%), food dust

(23%), metal dust (20%), and plastic dust (14%).

Source of Figs. 1 and 2:

Jeske, Arno; Beck, Hartmut:

Documentation of dust

explosions Analysis and case

studies (in German), Haupt-

verband der gewerblichen

Berufsgenossenschaften

(HVBG) (ed.), St. Augustin,

BIA-Report 11/1997.

The chart shows the most

frequent ignition sources

in the various dust groups.

Mechanical ignition sources

are the most common except

in the coal/peat group.


Fire risk

Fig. 2 The most frequent ignition sources

in the various dust groups

Dust groups

Total

Wood products

Paper

Coal/Peat

Food and Fodder

Plastics

Metals

Others

0 10 20 30 40 50

32.7%

35.9%

50%

25.4%

35%

29.2%

30.8%

49.4%

23.7%

23.7%

Proportion (%)



Pockets of embers



Electrostatic discharge



Electrostatic discharge



12/62

Polyethylene dust exploded

at West Pharmaceutical

Services, Inc. The productionsection for pharmaceutical

products was completely

destroyed.

A series of phenol resin dust

explosions devastated the pro-

duction line at CTA Acoustics,

Inc. Substandard cleanliness was

one of the reasons why the resin

dust was able to ignite.


Fire risk


13/62

Loss examples

Three large dust explosions in the United States in

the year 2003, with a total of 14 people killed and 81

injured, were among the reasons for the CSB carry-

ing out the Combustible Dust Hazard Study. On the

basis of the cases examined, it is possible to deter-mine some of the typical factors that lead to explo-

sion losses.

West Pharmaceutical Services, Inc.

Six people were killed when polyethylene dust trig-

gered an explosion at West Pharmaceutical Ser-

vices, Inc., Kinston, North Carolina, on 29 January

2003. The plant, which was completely destroyed

in the incident, produced rubber pharmaceutical

goods. The production process, which involved

dipping strips of rubber into a mix of polyethylene

powder and liquid and then drying them in air,

resulted in fine polyethylene dust being released.In line with the stringent hygiene requirements

applying to pharmaceutical enterprises, the pro-

duction area was cleaned regularly. Nevertheless,

fine combustible plastic dust accumulated above

the suspended ceiling. Eventually it ignited, result-

ing in a dust explosion.

Some of the staff had known about the deposits,

but they had not been sensitised to the dangers of

dust explosions. The material safety data sheet for

the polyethylene mix did not contain any warnings

about possible dust explosions either. What is

more, the companys safety review process failedto take into account the danger of explosion during

this stage of production.

Although the plant had been inspected by the

OSHA, the local fire authority, and insurance and

hygiene experts, the dust explosion hazard had not

been identified. The electrical lines in the ceiling

area were therefore not designed adequately.

The CSBs conclusion is that the explosion could

have been prevented or at least restricted if the

National Fire Protection Associations standards for

combustible dust had been observed. According topress reports, the insured loss totalled US$ 41m

(property: US$ 32m, BI: US$ 9m). West Pharma-

ceutical Services, Inc. was faced with further costs

in the million dollar range primarily in the form of

its deductible, investigation costs, legal expenses,

and environmental costs.

Fire risk

CTA Acoustics, Inc.

On 20 February 2003, a series of dust explosions

occurred at CTA Acoustics, Inc. in Corbin, Kentucky,

which produces insulation materials for the motor

industry. The outcome: seven people killed, 37

injured, and a devastated production facility. Dur-

ing production, fibre glass mats were impregnatedwith phenol resins. On the day of the explosion, a

tempering furnace was kept open because of a

problem with the temperature. Workers who were

cleaning the production area near the furnace had

probably stirred up combustible resin dust, which

immediately ignited. According to the CSB, the

dust explosion is very likely to have been due to the

design of the facility, working practices, and prob-

lems with on-site housekeeping. Moreover, the

production building was not designed to minimise

secondary explosions: the area of flat surfaces on

which dust can settle had not been reduced, for

example, and there were no fire walls separatingthe production areas from each other.

The CSB also found that the safety data sheet for

the used resin did not give a clear enough indica-

tion of the dust hazard. What is more, the compe-

tent authorities had not imposed any special

requirements regarding the dust explosion hazard,

nor had the fire protection authority inspected the

facility. The insurers had not recognised the danger

of the phenol resin dust exploding either.

In this case, too, the CSB concluded that if the

National Fire Protection Associations housekeep-ing standards had been observed and fire and

explosion barriers erected, the explosions could

have been prevented or minimised.

According to press reports, protracted negotiations

were followed by a jury assigning the main respon-

sibility for the explosions to the company supply-

ing the resin, obligating it compensate CTA Acous-

tics, Inc. for the sum of US$ 123m. The reasoning

behind the decision was that the supplier had not

provided adequate safety instructions for handling

the resin and had not drawn attention to the explo-

sion hazard.



14/62

Hayes Lemmerz International

The third major loss occurred in Huntington,

Indiana, on 29 October 2003. In this case, it was

aluminium dust that exploded. One of the staff

was killed, several were injured. The explosion

occurred in the production area where cast alu-

minium and aluminium-based alloys for vehiclewheel rims are made. Aluminium scrap is crushed,

conveyed to the processing area, where it is

dried, and finally fed into the smelting furnace.

During the conveying and drying processes, com-

bustible aluminium dust is emitted into the air. The

dust is separated in a dust collector, and it is here

that the explosion probably occurred. The likely

explanation is that the collector had not been venti-

lated or cleaned sufficiently and was also too near

the processing area. The explosion propagated

through the exhaust-air ducts, finally producing a

large fireball that broke out in the furnace area.

The CSB ascertained that the dust collector was

not of dust-explosion-proof design. Furthermore,

no consideration had been given to the possibility

of dust explosions being transmitted along the

exhaust-air ducts. And there were other problems

as well. When the company had incorporated

the scrap-processing and dust-collecting system

into the existing facility, it had failed to implement

change management procedures. These might

have led to the danger being recognised. Further-

more, the dust deposits on the girder structure of

the manufacturing shop had not been removedand they triggered a secondary explosion, which

destroyed the shop roof.

Another failing was that the employees had not

been instructed on the dangers of dust explosions

due to aluminium dust, whilst the authorities had

not drawn attention to the dust explosion hazards

during past inspections.

Here again, the CSB came to the conclusion that

if the National Fire Protection Associations stand-

ards for combustible metals had been observed,

the explosion could have been prevented or atleast minimised.

Incidentally, the CSB recommends further research

into aluminium dust as a basis for long-term

improvements in the aluminium industry with

regard to dust explosion protection for dust separ-

ators.

Results: Combustible Dust Hazard Study

The Combustible Dust Hazard Study found that the

respective standards of the National Fire Protection

Association ought to have been observed in all of

these three cases. This alone can ensure that secur-

ity procedures are sufficient to reduce or even rule

out the risk of a dust explosion.

The factors leading to the damage in these three

large losses and in other cases examined by the

CSB include the following:

Facility management, official bodies, occupa-tional safety and health experts, and insurance

companies failed to identify the dust explosion

hazards and to recommend appropriate pro-

tective measures.

Housekeeping was inadequate. In most produc-

tion plants, there was an accumulation of danger-

ous, combustible dust.

Dust filters were not adequately designed to

withstand dust explosions or had not been given

proper maintenance.

Production processes were changed without a

sufficient examination of the possible dangers.

It is remarkable that, according to the CSB, only

about half of the safety data sheets for known com-

bustible materials are adequate sources of infor-

mation for users or employees on the dangers of

dust explosions. What is more, almost half (41%)

of the 140 safety data sheets for combustible dusts

did not contain a dust explosion warning. Only

seven made any reference to the National Fire Pro-

tection Associations standards on the prevention

of dust explosions.

The CSB study also contains a number of other

recommendations. These have already been taken

on board by the competent authorities in some

cases. It is to be hoped that their implementation

will gradually lead to improved dust explosion

protection in industry.


Fire risk


15/62

Sources

Jeske, Arno; Beck, Hartmut:

Documentation of dust explo-

sions Analysis and case stud-

ies (in German), Hauptverband

der gewerblichen Berufsgenos-

senschaften (HVBG) (ed.), St.

Augustin, BIA-Report 11/1997.

Schoeff, Robert W.: U.S. Agri-

cultural Dust Explosion Statis-

tics, Kansas State University in

cooperation with FGIS-USDA,

20 March 2006.

U.S. Chemical Safety and Haz-

ard Investigation Board (ed.):

Investigation Report Combust-

ible Dust Hazard Study, Report

No. 2006-H-1, November 2006.

Fire risk

A recent dust explosion loss at

the production facility of a US

sugar manufacturer. Sugar dustis assumed to have exploded.

Conclusion

As far as the risk of dust explosion is concerned,

the insurance industry has so far concentrated

primarily on large losses in the agricultural and

food industries. However, the CSBs current study

makes it clear that all branches of industry in whichcombustible dust occurs are equally exposed.

The institute for occupational health and safety of

the German statutory accident insurance institu-

tions, the current Combustible Dust Hazard Study

published by the US Chemical Safety and Hazard

Investigation Board, and Munich Res loss experi-

ence all indicate one thing: the risk factors that lead

to dust explosions are similar throughout the

world. And they need to be given more attention

with a view to attaining effective loss prevention.

Otherwise, we must continue to reckon with further

deaths, injuries, and large property and BI losses.

The devastating explosion probably of sugar

dust at the Imperial Sugar Company in Port Went-

worth, Georgia, on 7 February 2008 shows that the

subject of combustible dust has lost nothing of

its topicality. Fourteen people were killed and a

number were injured. The damage is considerable.

Munich Re is certain that companies, authorities,

and insurance companies must now do more than

ever to ensure that dust explosion risks in industry

are identified, controlled, and minimised.



16/62

Aviation risks

Wind shear and wake vortices

Air is a friend to aviation, countered Thomas Endriss,aviation underwriter and pilot, when we asked him aboutair as a risk factor in air travel. But we dig deeper: Andwhat about wind shear, wake vortices, and air pockets?

Interview

Thomas Endriss, Munich

The greatest risk in aviationis human error. Wind only

becomes dangerous when

it occurs unexpectedly

in the form of wind shear,

for example.



17/62

Endriss: Although wind shear and wake vortices

can lead to problems, the main risk in aviation is

and remains human error. People make errors,

draw wrong conclusions, take incorrect decisions

and even the best technology offers no safeguards

against that. It is not usually one single cause that

leads to damage or accidents but rather a chainof events.

Schadenspiegel: So how dangerous is wind

shear, then?

Endriss: Its only dangerous when it comes un-

expectedly, when the wind changes direction very

suddenly, as during a thunderstorm, for instance.

Aircraft are now protected against this by wind

shear detection systems, which were introduced

about eight years ago. They measure the air

density using radar and give an acoustic warning

as soon as pressure conditions become abnormal.Modern cockpit systems can even supply visual

clues to the threatening danger from shifting

winds. By the way, most airports frequently

affected by wind shear have such safety systems.

Schadenspiegel: And what does the pilot have

to do then?

Endriss: Simply increase speed on approach to the

runway and come down at a higher residual speed.

Because whenever possible, aircraft are flown

into the wind for landing. If an aircraft has already

reached landing speed, say about 160 km/h, andis just about to touch down with 20 km/h of head-

wind, its speed will suddenly drop relative to air

motion as soon as the wind turns to 20 km/h of tail-

wind, for instance. The aircraft consequently

crashes because there is no more lift available.

Schadenspiegel: And what about during take-off?

Endriss: During take-off, the pilot can either wait

for the wind shear to subside or simply fly around

it with the help of modern technology. Air traffic

control or the cockpit instruments provide so-

called vectors to navigate aircraft around the dan-ger area. By the way, wind shear does not usually

represent any danger in-flight. An average passen-

ger jet flies at a speed of 850880 km/h, for exam-

ple, so that if the wind speed changes by 100 km/h,

the aircraft merely gets a bit slower or a bit faster.

The passengers do not notice anything at all, apart

from what might be a quite unpleasant shaking

of the aircraft.

Schadenspiegel: So technology makes wind shear

controllable. Can you give us any examples of

accidents happening in spite of this?

Endriss: Fortunately, there are only a few. One of

these happened at Toronto Pearson International

Airport in Canada on 2 August 2005. A brand-newAir France Airbus A340 was on approach to

Toronto during a huge thunderstorm, along with

many other aircraft. While the other aircraft con-

tinued to circle in holding patterns, the A340 pilot

decided to land, but approached at much too high

a speed. He presumably wanted to prevent the air-

craft from getting too slow because of the shifting

thundersqualls. Theoretically, as I just explained,

this was the correct thing to do. However, the tail-

wind was far from being as strong as expected. So

the aircraft touched down far too late and could not

stop on the wet runway. It rolled a further 200 m

into a ditch, broke in two, and burst into flames.Fortunately, all the passengers managed to escape,

and only a few of them had slight or minor injuries.

Schadenspiegel: And this again highlights the

critical role of the pilots. When you assess an air-

line, how important is their training for you?

Endriss: This is very important. As the number of

risks is very limited, with roughly 600 airlines

worldwide, personal contact plays a leading role.

When we inspect the airlines flight training centres

and simulators, their risk managers go along with

us. And we want to know how flight training isorganised. But we also talk about numbers and

about how the fleet will develop in the future

away from old aircraft, for example, and towards

top modern models with state-of-the-art cockpit

technology. And, of course, we inspect the aircraft

and maintenance facilities. What do the hangars

look like? Are they clean or cluttered up with all

sorts of things?

Schadenspiegel: And which Munich Re employees

are responsible for assessing the airlines?

Endriss: Our underwriters have different qualifica-tions, which all go to make up our expert know-

ledge. They come from a wide variety of profes-

sions, ranging from insurance specialists with a

pilots certificate and a maintenance licence to

aviation engineers and lawyers.


Aviation risks


18/62

Schadenspiegel: Let us come back to wind shear.

Do you also enquire whether early-warning

systems are on board?

Endriss: Of course, especially if we do not know

an airline well. And if we know that airports are

involved which are known for wind shear con-

ditions. But almost all airlines have wind shear

detection systems nowadays.

Schadenspiegel: At which airports is this particu-

larly important?

Endriss: One of the notorious airports is Dallas Fort

Worth International Airport in Texas, for example.

Denver International Airport in Colorado may also

be affected by wind shear because the Rocky

Mountains have a weather phenomenon similar

to the one we know in the Bavarian Alps: the foehn.

What is more, all areas are affected where heavy

precipitation can occur out of the blue. This is pri-

marily the case in the Far East, at airports in Singa-

pore, Malaysia, and Indonesia.

Schadenspiegel: What about airports like Santa

Catarina on the Portuguese island of Madeira?The landing strip is partially built on columns, on

a steep slope directly beside the sea.

Endriss: This airport is extremely difficult to

approach. Due to its position in the southeast of

a hilly island, the wind comes from the wrong

direction, so to speak, from northeast to north-

west. Because of the air masses being conducted

over a mountain directly next to the landing strip,

eddies are generated. The wind forms a kind of

rotor, right there where the landing strip is built.

What is more, until recently the airport only had

a relatively short runway, so that it was impossibleto approach at a higher speed. However, the run-

ways were extended in 2000, albeit with some

difficulty. Schadenspiegel even had a report on

this case, I believe.

Schadenspiegel: Yes, thats right: in the 2/2000

issue. Cracks had formed in the columns, leading

to an insured loss of about 1.4m.

Endriss: Even with the extended runway, though,

pilots are only allowed to land at this airport if they

have received special training on the simulator.

Lufthansa requires this training twice a year, for

example.

Schadenspiegel: Another question concerns wake

vortices. What are they exactly?

Endriss: Wake vortices are generated on the trail-

ing edges of the aircraft wings. Now how does

this happen? The form of the wings accelerates

the air streaming over their upper surface. This

results in negative pressure, which gives the air-

craft lift. The air flowing beneath the wings is not

accelerated as much. When the faster air from

the upper surface meets that slower air from the

lower surface, it produces turbulence. Vortices aregenerated at the wingtips and revolve like small

tornadoes, which get bigger and bigger as they

move away.

Schadenspiegel: Something like the rings you

make when you throw a stone into the water?

Endriss: Exactly. But wake vortices also produce air

resistance. This has recently led to the increasing

use of what are known as winglets, little turned-up

airfoils that are mounted on the wingtips. They are

not there for optical reasons, but to reduce the air

resistance. The result is that less energy is needed,and the aircraft uses less jet fuel.

Cross-section of a thunder-

storm cell producing strong

wind and hail. The arrows

in orange represent the air

streams, the thin black

arrows indicate the possible

tracks of hailstones. Wind-

storm damage and wind

shear may occur along the

squall line.

Source: Diagram based on

Kurz, Manfred: Synoptische

Meteorologie, Deutscher

Wetterdienst (ed.), Offen-

bach am Main, 1990

Fig. 1 Wind development during thunderstorms

Tropopause

Altitude (km)

km10

Updraught

regionDowndraught region

8 6 4 2 0 2 4 6 8 10

Squall line

Updraught

region

40C

0C

HailRain

10

5

Track direction


Aviation risks


19/62

Schadenspiegel: Do wake vortices pose a danger

to air traffic?

Endriss: Not to the aircraft that produces the wake

vortices but to the aircraft following behind. And

this is particularly the case during take-off and

climbing, since aircraft are much slower in thesephases than in the cruising phase and therefore

more susceptible to wake vortices. At cruising

speed, they are no problem at all. I only know of

one serious accident involving an aircraft that flew

into the wake vortices of another aircraft. This

was on 12 November 2001, when an American

Airlines Airbus A300 crashed over the New York

City district of Queens.

Schadenspiegel: What happened?

Endriss: It was a sunny, windless day, so the wake

vortices stayed put and were not blown away bythe wind as usual. There are standard routes that

aircraft have to adhere to during take-off, because

of noise protection regulations, for instance. So

the Airbus A300 used exactly the same route as

an aircraft that had taken off in front of it. Only a

little lower. As a result, it got into the wake vortices

of the preceding aircraft and went into an extreme

sideways roll. In such situations, the manufactur-

ers instructions specify exclusive use of the

ailerons, but the pilot, presumably on instinct,

attempted to counteract the roll using the rudder.

As it was not designed to cope with such a load,

however, the rudder broke. The aircraft went outof control and crashed. All the passengers were

killed.

Schadenspiegel: Another case of human

error, then.

Endriss: Im afraid so. It wasnt the wake vortices

alone that caused the crash. And the interval

between the two aircraft taking off was in line with

the regulations, too. There was simply an unfavour-able interplay of different factors: the weather,

wake vortices, and the pilots incorrect response.

Schadenspiegel: One last question: what effect

do air pockets have?

Endriss: I find this word amusing. Air is perman-

ently in motion. It rises when it is warmed up by

the sun and falls when it cools down, e.g. behind

clouds. To maintain altitude in these permanently

changing conditions, aircraft must fly contrary to

these air movements. However, if you fly from a

sunny area into a shady one, the air suddenly stopsrising and the aircraft loses height. All this happens

relatively fast and, due to mass inertia, the passen-

gers are lifted from their seats for a short time.

They feel like theyre falling into a hole.

Schadenspiegel: But has this ever made an

aircraft fall from the sky?

Endriss: No, never. And this has nothing to do with

turbulence either, which is more likely to result

in the aircraft shaking. Nevertheless, both as a pilot

and as a passenger, my recommendation is as

follows: if you are asked to fasten your seat belt,then please do so. In this way, you can be sure that

nothing will happen, even if the plane gets into

heavy turbulence or air pockets.

Wake vortices are generatedon the trailing edges of the

wings. The vortices at the

wingtips rotate like small tor-

nadoes, getting bigger and

bigger as they move away.

They can become dangerous

particularly for following air-

craft in the take-off or climb-

ing phase.

Fig. 2 Wake vortices

Diagram: Munich Re


Aviation risks


20/62

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text, hier steht Blindtext,

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Special topic: Weather phenomenon:

Windstorm

We all talk about the weather but what dowe know about the wind? Where does it comefrom and what effective precautions can betaken to prevent windstorm damage to build-ings? Read about the destruction a hurricane

caused in a tourist area or what happenedwhen a container ship ran into a winter storm.We also present a chronology of devastatingwindstorm catastrophes worldwide from1970 to 2007.

More than just a mild breeze:

Wind causes more damage

than any other natural hazard

turbulent storms leave their

marks all around the globe.


Special topic: Weather phenomenon: Windstorm


21/62

Winter Storms Daria, Lothar, and Kyrill in Europe,

Typhoon Mireille in Japan, Hurricane Andrew

and Hurricane Katrina in the United States: just

a few of the major windstorm catastrophes of

recent years that have devastated whole areas,

destroyed forests and coastal resorts, and

cost billions of euros. The frequency and dimen-

sion of the losses have had a major impact onthe insurance industry around the globe.

Windstorm is the most important natural hazard

of recent decades, in terms of the frequency of

loss events, the total expanse of the areas affected,

and, above all, the scale of the damage caused.

The insurance industry has consequently had to

carry higher and higher losses due to windstorm,

the natural hazard responsible for about 79% of

the US$ 370bn (2007 values) which the insurance

industry had to pay for major natural disasters

between 1950 and 2007 (see Fig. 1).

What do we know about the wind?

Meteorological observations of windstorm events

have been documented for centuries for almost

as long, in fact, as written history. On the other

hand, instrumental measurements of wind fields

have only existed for a relatively brief one hundred

years. Moreover, since wind fields are very sensi-

tive to the coarseness of a region topography,

vegetation, built environment it is very seldom

possible to compare them with each other over

relatively long observation periods. This is one of

the reasons why there are few areas with indicativewind statistics and windstorm hazard zoning to

date. What is more, the windstorm hazard in moun-

tainous areas may be subject to extreme small-

scale changes due to topographical features like

river valleys. However, routine meteorological

monitoring networks are usually too large-meshed

to pick up local changes in wind fields or confined

windstorm phenomena like tornadoes and thun-

dersqualls.


Windstorm The most important naturalhazard worldwide

Author

Ernst Rauch, Munich

As fast as the wind

Observations of the wind present another prob-

lem, too: the winds speed increases with its

height above the ground usually following

power law. However, it also reacts strongly to

the coarseness of the earths surface. In short,

the smoother the surface, the less the wind cur-

rent is decelerated. For this reason, wind speeds

are on average much higher over the sea than

over a surface covered with vegetation or an

urban area.

Far ahead of the rest. Historically, windstorms

have been the most important natural hazard for

the insurance industry even more than earth-

quakes, volcanic eruptions, or floods. The loss

frequency, the scale of the damage caused, and not

least the high windstorm insurance penetration

are all responsible for this.

Weather-related

events

Windstorm

Flood

Temperature

extremes

Geological

events

Earthquake, tsunami,

volcanic eruption

Fig. 1 Great natural catastrophes, 19502007:

Global distribution of insured losses

Chart: Munich Re

10%

4%

7%

79%

Munich ReSchadenspiegel 1/2008 19


22/62

Since the height at which the wind is measured

plays such a decisive role, a standard reference

height of 10 m above the ground has been agreed

on for the purposes of comparison by the World

Meteorological Organization.

Turbulent risk assessment

For an accurate assessment of the windstorm risk,

however, the insurance industry needs even more

information. One of the essential parameters for

the extent of damage is the duration of wind stress.

Many losses are only caused by a multitude of

wind attacks or load changes, which cause ma-

terial fatigue and finally failure.

Besides speed and duration, the direction of the

wind is also decisive. Severe changes in direction

can influence the extent of loss considerably, if

trees with their root system and buildings withtheir specific load design cannot cope with them.

The wind is turbulent. The wind speeds of short

gusts are much higher than the average, with the

gust factor the ratio of gust speed to mean wind

speed usually being between 1.2 and 1.5. In very

rough terrain, however, values exceeding 2 may

also be reached. The Beaufort Wind Scale defines

windstorm strength as the ten-minute mean value.

Last but not least, the turbulent nature of the wind

leads to its kinetic energy fluctuating very strongly,too. Known as the energy spectrum of the wind,

this property has a decisive impact on the extent

of damage to trees and resonating structures, par-

ticularly bridges, towers, or chimney stacks.

Windstorms from tropical to wintry

In meteorological terms, windstorms can be essen-

tially divided into four classes: tropical cyclones,

extratropical storms (winter storms), regional

storms (including monsoon storms), and local

windstorms (tornadoes, thunderstorms/hail-

storms). The world map of windstorms on pages2829 present the typical tracks and origins of

the various windstorm types.

Fig. 2 Cross-section of a tropical cyclone (hurricane)

At least 27C

3

12

4 Heavy rainShower

Diagram: Munich Re

Hurricanes get their energy from the

evaporation of warm surface water.

This schematic drawing shows how

warm air rises in the central eyewall

of the hurricane (1). This is where

the strongest condensation of water

vapour occurs, consequently pro-

ducing extreme precipitation. Out-

side the eyewall (2) and in the eye of

the storm (3) a windless, dry zone

in the centre of the hurricane the air

cools and streams back downwards.

Over the sea surface (4) it takes on

heat and moisture again providing

additional fuel for the atmospheric

thermal engine. Over land areas,

however, the system loses energy

fast when the addition of water

vapour stops and friction with the

ground sets in.




23/62

The catastrophe potential of tropical cyclones is

exceptionally large in many coastal regions due to

the high concentration of values in such areas,

their high recreational value, and the associated

influx of people. This had a major impact on the

insurance industry again in 2005, when Hurricane

Katrina caused original insured losses of aroundUS$ 62bn.

Extratropical storm (winter storm)

Extratropical storms are different from tropical

storms not only in terms of their areas of formation

and their tracks but also, and above all, in terms of

their intensity and geographical size. They form in

the transition zone between subtropical and polar

climate zones (roughly between latitudes 35 and 70

north and south of the equator).

When outbreaks of cold polar air meet up with sub-

tropical warm air masses, extensive low-pressurevortices are generated. The storm intensity within

these vortices increases in proportion to the tem-

perature difference of the two air masses. It is high-

est in late autumn and winter, when the oceans are

already cold but the polar air is still warm hence

the designation winter storm. Their formation is

shown in Fig. 3.

Tropical cyclone

Tropical cyclones attaining hurricane force (Force 12

on the Beaufort Scale, i.e. 118 km/h) in the Atlantic

and Northeast Pacific are referred to as hurricanes;

they are called cyclones in the Indian Ocean, the sea

area around Australia, and the South Pacific, and

typhoons in the Northwest Pacific. Below hurricaneforce, i.e. in the 62117 km/h range (811 on the

Beaufort Scale), they are referred to as tropical

storms.

They can extend over large areas with wind

speeds exceeding 250 km/h and in individual cases

even 300 km/h. Coastal regions and islands

between latitudes 10 and 40 north and south of

the equator are particularly affected. The wind field

is usually 100500 km in diameter.

Tropical cyclones quickly get weaker inland, which

is primarily due to friction with the earths surfaceand the reduced energy input from water vapour.

Nevertheless, as the huge masses of water taken

up over the warm sea usually fall as rain on the

windward side of mountains, this may result in ex-

treme floods and landslides even far inland. Fig. 2

on page 20 shows how a tropical cyclone forms.

L

H

L

HH

L

H

Fig. 3 Development of an extratropical low-pressure system (winter storm)

H= High-pressure

system

L= Low-pressure

system

Cold front

Warm front

Diagram: Munich Re

L

An air mass boundary forms between

cold polar air in the north and warm

subtropical air in the south. The heav-

ier cold air starts moving southwards

close to the surface. At the same time,

the warm air advances northwards

at higher levels, with the result that

the pressure in the centre of the turbu-

lence falls. The faster cold air catches

up with the warm air, the two mix

leading to the formation of vortices.




24/62

Maximum wind speeds are 140200 km/h,

although winter storms can also reach speeds far

in excess of 250 km/h in exposed coastal locations

and on higher mountains. Extratropical storms

may have wind fields up to 2,000 km wide.

Ice storms and snowstorms (blizzards) are furthertypes of extratropical storm. The damage caused

by ice or snow load may as in the case of the

other extratropical storms, where high wind

speeds are the main cause of damage lead to

losses amounting to tens of billions.

An ice storm lasting from 28 January to 4 February

1951 covered huge areas of the United States

from New England to Texas with a layer of ice

up to 10 cm thick. In terms of its geographical

size, it was probably the largest ice storm of the

20th century.

Regional storm and monsoon

In meteorological terms, regional and monsoon

storms are mainly classed as orographic storms.

What they have in common is that they are formed

by air masses rising on the leeward side of moun-

tains. The air cools down in the process, condenses

when humidity has passed saturation point which

sometimes results in heavy rain and rushes down

into the valleys from mountain ridges or pass sum-

mits.

In the case of regional storms, too, wind speeds

increase with the difference in temperature and

height of fall. If orographic winds additionally

combine with a large-scale stream of air moving

in the same direction, speeds of up to 200 km/h

are possible.

The best-known examples of regional storms

are the Bora on the Adriatic Coast of Dalmatia,

warm winds like the foehn in the Alps, the Mistral

in the lower Rhne Valley, and the Chinook in the

Rocky Mountains. But such orographic winds

may occur in all mountains regions of the world,

particularly on the edge of temperate climate

zones. Their formation is so closely linked to the

respective topography that it is common for them

to occur repeatedly at the same place and with

the same wind direction.

These wind systems are most intensive on theextremities of the Antarctic and Greenland, where

the extremely cold air of the central plateaus

plunges to sea level sometimes by more than

3,000 m through narrow glacier valleys. In the

process, it frequently reaches and maintains

hurricane force for long periods of time.

The monsoon is a separate windstorm phenom-

enon of regional expanse. When the great land

surface of Asia heats up under the almost vertical

rays of the sun in early and mid-summer, it draws

in warm and moist air masses from the Indian and

Pacific Oceans. Incidentally, without this circula-tion, the entire Indian subcontinent and adjacent

regions would be uninhabitable deserts.

The squall line phenomenon. Beforea thunderstorm, the air that has been

warmed by the sun becomes lighter

and rises. On its way upwards, it

cools, water vapour condenses, and

clouds form the now colder air is

heavier and finally sinks. If it falls very

fast, it forms a visible squall line. The

hanging cloud parts are the typical

manifestation of colder, moister air

sagging into the warmer, drier layer

of air beneath.




25/62

Local storms (tornado, thunderstorm, hailstorm)

Thunderstorms are the result of vertical circulation

in the atmosphere. Cold, heavier air sinks, causing

the warm air in its path to rise. Especially when

thunderstorms form on a cold front, the air streams

down to the earths surface from a height of several

kilometres and shoots below the warm air in

tongue-form. This results in the typical squall line,

cf. photo on page 22.

As in the case of orographic storms, potential

energy is converted into kinetic energy. Gusts are

always particularly intense when a thunderstorm

is accompanied by heavy rain or hail. As a result of

the precipitation, the surrounding air also cools

down and is finally dragged down, too. Near

ground level, the stream of air veers into a horizon-

tal plane, steering raindrops or hailstones into a

sloping trajectory sometimes at an angle of more

than 45 from the vertical.

Tornadoes are small-scale storms that form in

intense thunderstorm systems when cold, dryair passes over warm, moist air masses. Given

suitable temperature differences, the cold air can

plunge downwards in a violent whirling motion

similar to the action of liquid when a bottle is

emptied quickly. On the edge of the whirling wind,

the warm air moving up replaces the cold air

moving down, condenses and thus makes the

whirling wind visible from the outside, as in

Fig. 4.

Condensation often forms at the centre of the tor-

nado, too, however. If the air pressure suddenly

falls by as much as 10% below normal, this also

leads to cooling and to droplet and cloud formation

as a result of over-saturation. The rotation of the

tornado funnel is determined, as a rule, by the

rotation of the earth, as with tropical cyclones.

Tornadoes therefore turn clockwise in the southern

hemisphere and anti-clockwise in the northern

hemisphere. However, there are also isolatedrecords of tornadoes rotating in the opposite direc-

tion.

The average width of tornado funnels is about

100 m and the average track length a few kilo-

metres, although widths of more than 1,000 m

and track lengths of up to 300 km have also been

observed. The maximum possible wind speed

on the edge of the funnel is estimated to exceed

500 km/h the highest speed of all windstorm

types. Tornadoes usually have an average wind

speed of just over 100 km/h and are most common

between latitudes 20 and 60 north and southof the equator.

As in the case of tropical cyclones, there also are

other names for tornadoes: in Japan they are called

tatsumaki and in Germany Tromben. Waterspout

is the term used when they form over water sur-

faces.

Of all wind systems, it is tornadoes

that attain the highest wind speeds.

They are generated whenever strong

vertical air movements occur in the

atmosphere and are therefore always

accompanied by intensive thunder-

storm cells. The schematic represen-tation on the left demonstrates the

air flows in and around a typical tor-

nado. Vortex formation is strength-

ened particularly by the cold, dry

air falling onto the warm, moist air

below.

Fig. 4 The formation of a local storm (tornado)

Cold, dry air

Warm, moist air

Diagram: Munich Re




26/62

Wind is moved air. If a structure is in

its path, the wind flows around it.

Dynamic pressure is generated on

the side facing the wind, whereas

suction forces are generated on the

side facing away from the wind. On

the corners and edges of the struc-ture, vortices are generated whose

pressure or suction forces can be

many times greater. The size, fre-

quency, and intensity of these vorti-

ces depend on both the wind speed

and the shape of the structure around

which the wind is flowing. Generally

speaking, the less regular the struc-

ture, the greater the vortex formation.

Fig. 5 Encircled by the wind

Pressure

Wind

Suction

Diagram: Munich Re

Turbulence

This photo of an Oklahoma

City motel taken after a tornado

in 2003 shows how severely

the wind can damage roofs and

faades. The damage is due to

pressure and suction forces

and to vortices which form in

the air field especially on the

corners and edges of a struc-

ture cf. Fig. 5.




27/62

The calm before the storm. Now is the time to

take precautions!

The best way to reduce windstorm damage in the

medium to long term or even to prevent it altogether

is to improve the resilience of buildings and their

components to wind. It also requires making appro-priatechanges to infrastructure installations like

bridges and means of transport (e.g. vehicle aero-

dynamics).

For the purposes of loss minimisation, all structural

components must be built to withstand the add-

itional loads generated during a storm blowing at

design wind speed. Both static and dynamic forces

must be considered, because during a windstorm

buildings are exposed to extremely volatile streams

of air that are constantly changing in strength and

direction, as Fig. 5 demonstrates.

Bad weather calls for good architecture

The influence of the wind on buildings is not one-

sided: wind flow is also influenced by the buildings

themselves. The vortices coming off the edges and

corners of a building intensify the load on it.

The resonance behaviour of the building also plays

a role. If it is an elastic structure with little damping,

strong vibrations can develop even when wind

speeds are relatively low. The constant trend

towardsmaking buildings bigger and lighter has

led to them being increasingly susceptible tovibrations.

What can be done to slow down or even halt this

loss-producing development? Here are some typ-

ical causes of damage and the corresponding loss

prevention measures:

Roofs

The roof is the part of the building that is most fre-

quently affected by windstorm damage. The rea-

sons for this are:

Wind speed increases with height. Sharp or pro-truding roof edges generate wind vortices.

Roofs, chimney stacks, roof superstructures, and

aerials, etc. are often not integrated securely into

the loadbearing structure of the building and/or

do not receive proper maintenance.

In order to avoid windstorm damage to roofs in

the long term, the following measures are recom-

mended:

When there is extensive roof cladding (e.g. corru-

gated sheet metal), screw it to the load-bearing

construction. Otherwise, fasten the individualroof elements or roofing tiles flexibly.

Anchor the roof construction in the masonry

using wall anchors, screws, and metal straps.

Simple nails are not suitable.

Building aerodynamics: Roofs that are too flat or

too steep or protrude too far should be avoided.

This will also reduce the pressure and suction

forces of the wind.

Prudent gardening: Sufficient distance will pro-

tect the building from windstorm damage causedby falling trees.

Supplies of materials: Replacement roof panels

or membranes make it possible to carry out fast

repairs and provide (at least temporary) protec-

tion against the elements.

Exterior walls, faades

Damage to the exterior walls of buildings usually

occurs only in particularly intense windstorms.

However, losses are accumulating due to the

increasing use of expensive and at the same time

sensitive wall-facing materials. Unlike conven-tional faades with masonry or plaster, these are

easy prey for the wind a really alarming develop-

ment. It makes no difference whether they involve

insulation against heat loss and moisture penetra-

tion (in the form of glued or screwed materials,

metal plates, or pressed plates) or whole faades

made of light metal or plastics.

Precautions that can be taken to prevent damage to

exterior walls and faades:

Anchor insulation and faade elements in the

loadbearing structure of the building.

Avoid soft faade materials in areas exposed to

hail.

Mount large-scale glass elements flexibly.

Ensure that the building is securely anchored in

the foundations.




28/62

Protecting mobile facilities against bad weather

Scaffolding, cranes

Scaffolding and cranes are typical storm-prone

temporary structures, as are air domes (covers

without any supporting structure, which are keptstable by internal pressure) and tents. Strangely

enough, inadequate attention is often paid to

anchoring these structures in the ground, with the

result that scaffolding or cranes not only suffer

severe damage themselves during a storm but also

cause damage to parked cars or other buildings in

the immediate vicinity if they fall down. People

are frequently injured, too.

The following loss prevention measures are

available:

Secure the scaffolding to the buildings both

during construction and in the course of repair

work.

Replace worn, corroded, or other unsafe com-

ponents and make regular controls.

In the case of cranes that run on rails, anchor

the chassis to the rail foundation with bolts and

latches.

Unlock the jib on a tower crane to permit flexible

alignment to the wind.

A general rule regarding cranes is always to

check the bearing capacity of the ground, par-ticularly in view of the severe one-sided load

during windstorms. If necessary, they should

be secured with a cable-tensioning system.

Germany

Besides the DIN series 1055 men-

tioned below, Germany has no ob-

ligatory standards or regulationsgoverning the prevention of wind-

storm damage to buildings.

DIN 1055-4 was introduced by the

building authorities and describes

the influence of wind loads on build-

ings, their components, and exten-

sions, and regulates the calculation

methods. Additional German docu-

ments in this series like Eurocode 1

on the subject of wind load impact

may be found at

www.eurocode-online.de

VdS Schadenverhtung GmbH has

published various leaflets, some

of which are available in English.

They can be obtained for a minimal

charge at the VdS website:

www.vds.de

United States

The American Society of Civil Engin-

eers has published structural stand-

ards for protection against naturalhazards, ASCE Standard No. 7-05,

in Minimum Design Loads for Build-

ings and Other Structures.

www.asce.org

Quite a number of supplements

have been incorporated in the Florida

Building Code in response to the

devastating hurricane seasons of

recent years, in which Florida was

particularly affected.

www.floridabuilding.org

The American Association for

Wind Engineerings website offers

a number of publications on the

subject of wind and windproof con-

struction. These include not only

structural guidelines and standards

but also publications dealing with

wind energy and hurricane risk

assessment.

www.aawe.org

Worldwide

The Journal of Wind Engineering

and Industrial Aerodynamics pub-

lished monthly by the InternationalAssociation for Wind Engineering

is written for architects, civil engi-

neers, and meteorologists through-

out the world. The ISSN number

is 0167-6105.

Storm-proof construction

Further information and regulations




29/62

The graph of expected losses as

a function of occurrence probability

or return period clearly shows that

hurricanes represent the most ex-

pensive windstorm hazard in the

United States. This is due, on the onehand, to the very high wind speed

they can attain over large areas and,

on the other, to the concentration

of values in US coastal regions like

those along the Gulf Coast or on

the southeast coast (e.g. Florida).

These two factors are not encoun-

tered in this combination either

in Japan or in Europe.

Motor vehicles, caravans

The insurance industry is always hit by extensive

losses in the motor own damage sector when there

is a major windstorm event. In regions with a high

property insurance density, the sum total of motor

own damage losses frequently amounts to 510%

of the total insured loss. This rate may also be con-siderably higher in emerging markets. Losses are

primarily the result of falling trees or branches,

roof panels, or faade components.

Possible prevention measures:

Put vehicles in the garage when there are storms

or severe weather warnings.

When there is a danger of heavy storm gusts,

close particularly exposed road sections and

bridges to large lorries and caravans.

At camp sites, secure caravans with cables.

In hail-prone areas, protect car depots with hail

nets.

A general rule is to repair damage quickly in

order to avoid corrosion and other consequential

damage.

Windstorm losses can be reduced considerably or

even prevented by precautionary measures. The

most effective way to prevent losses, however, is

to incorporate the factor of wind resistance in the

planning of infrastructure installations and all

buildings and their individual components. Land-

use restrictions in heavily exposed areas like those

on the coast are also of special significance.

Stormy days ahead

There is no doubt that losses from windstorm

events are going to increase worldwide, both from

hurricanes in the United States and from winter

storms in Europe. Fig. 6 provides a striking indica-

tion of expected losses as a function of their occur-

rence probability. How does this increase come

about? It is due to the increasing concentration of

values and also to the changes in weather patterns

as a result of global atmospheric warming. There is

hardly any line of insurance that has such a high

loss potential (in terms of single loss events) as

windstorm insurance.

Since the attitudes of the public, industry, and the

authorities are significantly influenced by insur-

ance terms and conditions, one of the insurance

industrys tasks is to advocate more effective pro-

tection. What measures are suitable in individual

cases? What prices must be charged and what

terms and conditions are needed to cover the risk

adequately? These are all questions that need to be

answered.

The suitable time to prepare for a changing risk

situation is the period of calm before the storm,

because when the storms have already begun,it is too late, as past events have so frequently

demonstrated.

Hurricane USA Windstorm Europe Typhon Japan

US$ bn

300

250

200

150

100

50

100 200 300 400 500 600 700 800 900 1,000

Years (return period)

Fig. 6 Windstorms worldwide: Expected losses as a function

of their occurrence probability

Source: Munich Re




30/62

World map of windstorms: from tropical to wintry

Tropical cyclone (hurricane, typhoon, cyclone)

Saffir-Simpson Hurricane Scale

m/s32.742.6

42.749.5

49.658.5

58.669.4

69.5

km/h118153

154177

178209

210249

250

mph7395

96110

111130

131155

156

Knots6482

8396

97113

114134

135

Force1

2

3

4

5

Australian Tropical Cyclone Severity Scale

m/s

25.034.5

34.647.0

47.162.362.477.6

77.7

km/h

90124

125169

170224225279

280

mph

5677

78105

106139140173

174

Knots

4767

6891

92121122150

151

Force

1

2

34

5

Extratropical storm (winter storm)

Beaufort scale

m/s00.2

0.31.5

1.63.3

3.45.4

5.57.9

8.010.7

10.813.8

13.917.1

17.220.7

20.824.4

24.528.4

28.532.6

32.7

km/h01

15

611

1219

2028

2938

3949

5061

6274

7588

89102

103117

118

mph01

13

47

812

1318

1924

2531

3238

3946

4754

5563

6472

73

Knots01

13

46

710

1115

1621

2227

2833

3440

4147

4855

5663

64

Force0

1

2

3

4

5

6

7

8

9

10

11

12

40N

0

40S

Local storm(tornado)

Extratropicalstorm(winter storm)

Extratropical storm (main tracks)

Tropical storm (main tracks)

Tornadoes (main areas of occurrence)

Tropicalcyclone(hurricane)

Extratropicalstorm(winter storm)




31/62

0 km/h 100 km/h 200 km/h 300 km/h 400 km/h 500 km/h

Local storm (tornado)

TORRO Scale

m/s1724

2532

3341

4251

5261

6272

7383

8495

96107

108120

121134

km/h6186

87115

116147

148184

185220

221259

260299

300342

343385

386432

433482

mph3954

5572

7392

93114

115136

137160

161186

187212

213240

241269

270299

Knots3347

4863

6480

81100

101119

120140

141162

163185

186208

209233

234260

Force0

1

2

3

4

5

6

7

8

9

10

m/s17.832.4

32.550.2

50.370.3

70.492.2

92.3116.3

116.4142.3

142.4169.4

km/h64116

117180

181253

254332

333418

419512

513610

mph4072

73112

113157

158206

207260

261318

319379

Knots3563

6497

98136

137179

180226

227276

277329

Force0

1

2

3

4

5

6

Typical tracks of the various storm types

Tropical cyclones usually develop in the tropical and

sub-tropical Atlantic or Pacific and then make landfall.

Winter storms, on the other hand, move as low-pressurevortices in the transition zone between cold polar air

and subtropical warm air masses. Tornadoes are devas-

tating small-scale storms, measuring between a few

dozen and several hundred metres in diameter. Individ-

ual scales are needed in order to classify the various

windstorm types because of the different wind speeds.

Significant historical windstorm events

Tropical cyclones

1970: Cyclone/storm surge, Bangladesh

1974: Cyclone Tracy, Australia

1983: Hurricane Alicia, USA

1991: Cyclone/storm surge, Bangladesh1991: Typhoon Mireille, Japan

1992: Hurricane Andrew, USA

1998: Cyclone 03A, India

1998: Hurricane Mitch, Middle America

2005: Hurricane Katrina, USA

Extratropical storms (winter storms)

1976: Winter Storm Capella, Europe

1990: Winter Storms Daria, Vivian, and Wiebke, Europe

1999: Winter Storms Anatol, Martin, and Lothar, Europe

2007: Winter Storm Kyrill, Europe

Local storms (tornadoes, thunderstorms/hailstorms)

1984: Hailstorm, Germany

2003: Tornado outbreak, USA

40N

0

40S

Tropical cyclone(typhoon)

Tropical cyclone(cyclone)

Diagram: Munich Re

Fujita Tornado Scale




32/62

Chronology of the most devastating stormsfrom 1970 to 2007(all loss amounts in original values)

Tropical cyclones

1991 Cyclone and storm surge,

Bangladesh

A good 20 years after the 1970 catas-

trophe, Bangladesh is again hit by a

severe storm. Almost 10% of the popu-

lation are made homeless in April 1991

by a cyclone with wind speeds reach-

ing 250 km/h.

1991 Typhoon Mireille, Japan

Massive damage to buildings and crops

are caused by Mireille as it crosses

Japan in September 1991. Generating

insured losses of US$ 7bn, it is the

costliest windstorm for the insurance

industry in the history of Japan.

1992 Hurricane Andrew, United States

At US$ 17bn, the largest insured loss

until then worldwide. Also the last loss

event for a number of primary insurance

companies: Hurricane Andrew forces

them into liquidation.

1998 Cyclone 03A, India

One of the strongest cyclones to hit India

in 25 years, 03A causes losses costing

US$ 1.7bn in June 1998 and is also

Indias most expensive storm of all time.

This high sum was due to the manyindustrial facilities that were hit: refiner-

ies, tanks, ports, and wind farms.

1998 Hurricane Mitch, Middle America

In October/November 1998, Mitch is

the tragic climax of an exceedingly

active hurricane season in the Atlantic.

The death toll is the highest for over

200 years: 9,700 people in MiddleAmerica lose their lives. Honduras and

magazin risk

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