4003_5001_D02
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4.14.
RECOMMENDED MAGNET ARRANGEMENT
Refer to the table below for recommended quantities and type of magnets required for pipeline
diameter and wall thickness. The magnets should be spaced equally around the pig body with
all magnets oriented with the same poles facing outwards e.g. all north poles facing outwards
(as shown) or all south poles facing outwards. It is critical that the magnets are not oriented
with a mixture of north and south poles facing outwards as this may result in ‘dead
-
spots’ in the
magnetic field around the pig. Magnets may be fixed to the pig body, embedded in the pig discs
or embedded in foam pigs. The cost of quality magnets is insignificant compared to the potential
cost of a lost pig which is more likely if unsuitable, cheaper magnets are used. Effective pig
detection is dependent on several factors including:
PIPE WALL THICKNESS
–
The thinner the pipe wall, the stronger the magnetic signal.
PIPELINE MATERIAL
–
Different materials cause different attenuations to the magnetic
signals. For example, 50mm of concrete will affect the signal considerably less than 50mm of
mild steel.
DISTANCE BETWEEN MAGNET AND SENSOR
–
The closer the magnets are to the magnetic
sensor, the stronger the magnetic signal.
NUMBER OF MAGNETS FITTED TO PIG
–
The more magnets which are placed around the pig,
the more uniform and effective the overall magnetic field is.
STRENGTH OF MAGNETS
–
The stronger the magnets, the stronger the magnetic signal.
BACKGROUND MAGNETIC NOISE
–
The more magnetically quiet the surrounding area is, the
more sensitive the signaller can be set without the risk of false triggers. Movement of magnetic
objects close to the signaller should be avoided to prevent false triggers.
PIPELINE
DIAMETER
PIPELINE WALL
THICKNESS
MAGNET TYPE & DIMENSIONS NUMBER OF MAGNETS
EQUISPACED AROUND
PIG
10”
10.2mm
NdFeB N35 ø20x20mm
8
10”
10.2mm
NdFeB N35 ø48x18mm
4
12”
11.3mm
NdFeB N35 ø20x20mm
8
12”
11.3mm
NdFeB N35 ø48x18mm
4
14”
12.1mm
NdFeB N35 ø20x20mm
8
14”
12.1mm
NdFeB N35 ø48x18mm
4
16”
13.2mm
NdFeB N35 ø20x20mm
8
Содержание 4003 MAGSIG
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