Heath-consultants Aqua-Scop Manual de usuario descargar pdf (Pagina 27)

Inuence of the Leak Noise (Material of the Lines):

You should know the material of the line being tested as the sound

transmission of leak sounds vary greatly from cast iron, to steel, to asbestos

cement, and PVC. A simple example to clarify this: If a steel line, suspended

from a cable is struck with a hammer, it will sound like a gong. A plastic or

asbestos cement line would give a thumping noise on impact but it wouldn’t

resonate the sound at all.

Pressure in the Lines: The pressure in the line is also a very important factor.

High pressure normally gives a loud noise, a high frequency, and good sound

characteristics for localization. It generally can be said that a pressure of

twenty pounds per square inch (PSI) is sufcient enough to locate leaks.

Under twenty PSI it may be necessary to use auxiliary means.

Special Circumstances Encountered: The conditions of the cover over

the main will especially inuence the detection of the leak noise. A very

hard ground has a better efciency for sound transmission and is of higher

resonance than muddy ground or sod. Sand and compact sand and stony

grounds are very efcient sound transmitters.

On the other hand, the transmittance of sound under frozen ground may be

so excellent that it is very difcult to locate the maximum (Loudest Point)

since a large section of the frozen earth will be vibrating.

Surface: The surface in the environment can greatly inuence the detection.

It is necessary when pinpointing to consider the surface on which the Ground

Microphone is placed. A change in the kind of surface (from sod to asphalt,

for example) from one medium to the other may cause a very contradictory

test value. This can sometimes cause so many differences of noise that a

real comparison of noises for the leak detection may be difcult.

Time of Work: The choice of day or night testing is very dependent on the

local situation. In rural or residential areas work during the day is possible.

In areas with heavy trafc noise, loud machines, and/or factories, work

during evening or night hours may be necessary.

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Heath-consultants Aqua-Scop Manual de usuario Pagina 27