schallemissonspruefung_EN_web.pdf

8/20/2019 schallemissonspruefung_EN_web.pdf

http://slidepdf.com/reader/full/schallemissonspruefungenwebpdf 1/8

Efficient testing at reduced costsAcoustic Emission Testing

T Ü V A

U S T R I A S

E R V I C E S



Acoustic Emission Testing (AT) is a non-destructive

testing and monitoring method to detect and locate

hidden defects in steel construction components,

plant components and pressure equipment com-

ponents in good time. In this context, the acoustic

emission analysis provides overall information on

the physical condition and the leakproofness of the

tested object.

In order to detect and locate possible defects and

leakages in the tested structure, Acoustic Emission

Testing applies a classical physical principle that

is used to the industry’s advantage by means of

state-of-the-art data reception and processing.

The acoustic signals involved in the testing are

caused by metallurgical changes and physical

phenomena in the material. When a component is

stressed, the built-up state of stress spontaneously

discharges at a leak, thereby generating soundimpulses. The energy thus discharged is received

by sensors applied to the surface of the tested ob-

ject. The signals are received at different times by

different sensors. By measuring these differences

in time, the sound source can be located using

mathematical locating algorithms. To verify the test

results, they are subsequently subjected to a con-

ventional non-destructive test using ultrasound, for

example.

Inspection during operation

An essential advantage of Acoustic Emission Te-

sting is that it allows components to be inspected for

material defects, leakages and active corrosion du-

ring operation or in the course of minimal outages.

The information gained about the state of a

component using AT is usually much more re-

liable than when applying other test methods.

Plants quickly available

The versatile testing procedure combines the ut-most safety and optimal availability of production

plants. TÜV AUSTRIA is currently a Europe-wide

leader in the field. Production plants are fully ope-

rational again in a short time – a major advantage

for TÜV AUSTRIA’s customers.

The economical test method for steel construction,plant and pressure equipment components



Flat-bottom tanks – detectingcorrosion and leakages when full

Flat-bottom storage tanks with a storage volume

of up to 150,000 m³ are used all over the world.

The flat bottom can neither be accessed nor

inspected from outside. The tanks must be

checked at specified intervals since – despite

the product loss – an undetected leak can cause

incalculable environmental damage entailingconsiderable legal consequences for the operator.

The conventional inspection method requires

emptying, opening and cleaning of the tanks for

internal visual inspection.

No loss of time as a result of the inspection

This takes time during which the tanks are not

available. By means of Acoustic Emission Testing

the floors of storage tanks can be checked for lea-

kages and active corrosion when full – time-consu-

ming emptying and refilling is not necessary.

High reliability

The information thus gathered is considerably more

reliable compared to stationary tests and internal

visual inspections.

Ofcially recognised test method

To carry out the test, sensors evenly distributed

around the circumference must be applied to the

exterior wall and, if possible, invasive interior sen-

sors are lowered into the storage product. The

measurement takes only a couple of hours during

which the tank is kept on its maximum filling level.

The metallurgical and physical processes caused

by active leakages and/or corrosion emit signals

that can be recorded using the applied sensors.

Based on the frequency pattern of the transient si-

gnals and the different points in time at which they

reach the sensors, the sound source can be loca-

lised. The reliability of the test method has been

confirmed in the scope of a European research

project. Hundreds of tanks of up to 100 m in dia-

meter have already been tested.

Using frequency-based signal pattern recogni-

tion, leakages can be distinguished from corro-

sion damage and registered with a high degree

of location accuracy. Location accuracy is ±D/10

(D=diameter) for tanks with many fittings (heaters)

and ±D/20 without fittings.

In Austria, leak testing of flat-bottom storage tanks

using AT is an officially recognised test method in

accordance with the Ordinance on the Storage of

Flammable Liquids.

Experts in Acoustic Emission

Testing

TÜV AUSTRIA has been using Acoustic Emis-sion Testing (AT) since the 1970s and hascontinually further developed and enhanced thetest method.

Our customers can rely on decades of expe-rience and expertise.



Spherical vessels for thestorage of gases

Conventional testing involves spherical storage

vessels being subjected to a water pressure test.

Besides the stress load, this means a considera-ble weight load on the bearings and foundations

to an extent that they never occur in operation with

gaseous filling.

Safe and economical alternative to water

pressure test

The pressure test using acoustic emission

measurement is a safe alternative: since AT serves

as an early-warning system and can detect even

subcritical crack growth, the storage medium can

be stress-loaded directly.

Customer benefits: more safety and lower

testing costs since the expensive water pressure

test is not necessary and thus the vessel is not

unavailable for a long period of time as a result.

In addition to many other reference projects,

TÜV AUSTRIA experts have successfully tested

Europe’s largest spherical gas storage vessel in

Berlin (40 m in diameter).

Testing of LPG storage vessels –safe and problem-free

Small liquefied petroleum gas (LPG) vessels

with a storage capacity of 5.6 t maximum are still

frequently subjected to a water pressure test these

days.

Even though considerable problems may arise

during testing as well as in the operation period

after the testing.

For this reason, TÜV AUSTRIA has developed a

special test method whereby the load may be in-

creased in the vessel as required directly with the

operating medium.

Ecological and economical

A testing procedure that is neither economical nor

can be justified ecologically as it involves the use

of precious water is therefore a thing of the past.

Besides reducing testing costs, this is also be-

neficial to the environment, since there is neither

water contamination nor pollution resulting from

escaping residual gas.

Cooperation with inspectionbodies throughout Europe

TÜV AUSTRIA has a patent valid throughoutEurope for this type of load increase.

Several thousand vessels are tested accor-ding to this method every year. Inspectionbodies in France, Germany, the Czech Re-public, Slovenia, Italy, Switzerland, Roma-nia, Portugal and Turkey work in cooperationwith TÜV AUSTRIA in compliance with thismethod developed in Austria.



Reactors in the chemical andpetrochemical industries

Most conventional inspection methods require

cost-intensive plant downtime and involve local

spot checks. In some cases, the shutdown and the

opening of the reactors may destroy the expensive

catalyst inside the reactor.

Cost-saving, reliable, according to standard

Acoustic Emission Testing considerably reduces

costs as it is carried out in-service with the opera-

ting medium.

This testing option increases a company’s compe-

titive edge by optimising plant availability. What is

more: as a result of its reliability it has become a

European Standard.

Drying cylinders in the paper industry

Drying cylinders as used in paper machines

are pressure equipment and must as such be

subjected to periodical repeat inspections.

For economic (plant downtime) and production-

related reasons this requirement cannot be met

by applying the conventional testing procedures

available. The only alternative is an air pressure

test with accompanying AT. For the paper indus-

try, this means a considerable decrease in costs

and ensures that the drying cylinders can continue

to be used safely.

These types of cylinder are regularly and cost-

efficiently tested by TÜV AUSTRIA with success

for operational safety (static internal pressure

and varying bending stress as a result of the high

rotational velocity).



ALARM – detecting andregistering pig

Transporting water-contaminating liquids in pipes

and pipelines, such as, for example, hydrocarbon

products, involves a high risk for the environment.

When there is a leakage on such pipes this leads

to product loss and environmental damage. While

the use of intelligent pigging systems enables a

comprehensive status assessment of such pipe

systems, they cannot prove the pipes’ technical

leakproofness.

By means of AT so-called “acoustic leakages” can

now be detected:

Benefits of pigging:

The pig is completely self-sufficient and does

not require any connecting or power supply

cables

During normal operation, the autonomous pig

is transported through the pipe with thetransport medium and can be used for

between 24 and 100 hrs, depending on its size

The available dimension ranges for the pipe

diameter are between 100 mm and 450 mm

(4“-18“).

Lowest identifiable leak rates.

High location accuracy: 0.5% of the distance

between the nearest artificial and natural

markers.

Recording of pressure and temperature curves

along the entire length of pipe.

A 380-km long off-shore pipeline in the Chinese

Sea has been tested using this technology.

Two leakages were detected with high location

accuracy. They could thus be found and rectified

quickly

In case of shorter pipe systems with a maximum

of 800 metres, the acoustic signals can be ana-

lysed once they have been received by sensors

permanently fitted onto the pipe system’s exterior.

This AT procedure based on the cross-corre-lation technique is also successfully applied

by TÜV AUSTRIA.



Many years of experience, compre-hensive references and satisedcustomers

Due to our many years’ practical experience we

can provide comprehensive references in the fol-

lowing fields:

Accompanying AT of pressure equipment

during initial pressure tests (also gas pressure

tests)

Accompanying AT of pressure equipment

during repeat pressure tests with a gaseous

storage medium or with water

Leak tests using AT of pressure equipment and

storage vessels as part of pressure tests

Leak tests using AT of pressure equipment

and storage vessels during regular operation

Accompanying AT of steel constructions in

bridge-building during load/stress tests

Much large pressure equipment has been tested

successfully and to our customers’ satisfaction. Ex-amples include:

Spherical and cylindrical natural gas tanks

Drying cylinders in paper factories

Reactors in the chemical and petrochemical

industries

Reactors, filters and storage vessels in air

separation systems

LPG storage tanks

Hardening furnaces

Sterilisation equipment and autoclaves

Excess pressure and decompression chambers

Moreover, thousands of vessels have been tested,

such as, for example:

Above-ground and underground LPG storage

tanks with a storage capacity of up to 5.6 t

Pressurised gas cylinders and hydraulic

accumulators

In the field of leakage tests, the most successful

areas of application are:

Flat-bottom storage tanks

Long-distance pipelines

Pipe systems in refineries and chemical factoriesPressurised vessels, for example heat exchangers

and suchlike



© T

Ü V A U S T R I A 0 4 /

1 1

P h o t o s : i S t o c k p h o t o ( L a j o s R e p a s i ) , T Ü V a r c h i v e

TÜV AUSTRIA SERVICES GMBH

Acoustic Emission Testing DivisionHead: Peter Tscheliesnig

Deutschstraße 10, 1230 Vienna

Tel: +43 (0)1 610 91-6630

Email: [email protected]

www.tuv.at

On the safe side –with TÜV AUSTRIA

TÜV AUSTRIA has stood for technical safety in

the broadest sense for around 140 years. What is

more: TÜV considers itself as a service provider

that additionally optimises economic efficiency for

its customers through the optimal employment of

materials and considerate use of resources.

Utmost competence forcomprehensive service

The TÜV AUSTRIA team of experts from various

specialist fields are competent partners in all mat-

ters concerning technical safety as a result of their

experience, education and further training.

The broad spectrum of expertise means that the

range of services can be expanded as a result of

numerous synergy effects – with economically at-tractive overall packages.

International and nationalrecognition

The TÜV AUSTRIA Group is active both nationally

and internationally and is therefore up-to-date with

worldwide developments. Documents issued by

TÜV AUSTRIA are recognised in the entire Eu-

ropean Economic Area and far beyond. For our

customers this means legal security, approval by

industry, the authorities and the public.

Objectivity guarantees optimal per-formance!

TÜV AUSTRIA is independent and has no business

relationships or relationships of dependence with

authorities, industry, commerce, trade, operators or

other parties.

Customer benefits: safety, reliability and a new di-mension of economic efficiency.

schallemissonspruefung_EN_web.pdf

Documents

Transcript of schallemissonspruefung_EN_web.pdf