WE-7 Operating Instructions
4
while Yoke is turned on. If the Field Selection Switch is changed when the Yoke
is on, an overload may occur. When overloaded, the Control Printed Circuit
Board my fail, resulting in a partial or complete failure to this component, and/or
the electrical breaker the Yoke is supplied from (Mains) may be tripped.
DO NOT CHANGE THE FIELD WITH THE PUSH BUTTON DEPRESSED.
4. Operational Parameters
–
The Operational Parameters or Duty Cycle for
the WE-7 operation is set to avoid damage to the internal coil or the Control
Printed Circuit Board, and must be observed.
AC Operation:
It is recommended that the operator does not keep the Yoke on
for more than ½ hour at a time, as the Yoke housing may get too warm to hold.
However, the basic design of any Yoke inherently produces heat. Typical
operation is 5 - 15 seconds on, while applying inspection media, followed by 5 -
15 seconds off repositioning the yoke to the target area.
DC Operation:
At the maximum setting, the Yoke should not be kept on for
more than 10 minutes at a time, and should be followed by an equal cool down
time. Typical operation is 5 - 15 seconds on, while applying inspection media,
followed by 5 - 15 seconds off repositioning the yoke to the target area. In this
typical operation the unit can be operated for extended periods of time, however
the Yoke housing may get to warm to hold.
If the Yoke is used for prolonged periods of time of continuous cycling, such as 2
to 3 hours in AC mode or 60 to 90 minutes in DC mode, as outline above, the
Yoke may get hot. If the WE-7 is used in this manner the operator must provide
time for a sufficient cooling period, or components in the Electronic Control
Module may fail.
Do not change the FIELD SETTING while the unit is activated.
5. Field Characteristics
AC Field –
AC Magnetic Fields are sensitive to surface and near surface defects
due to the ‘Skin Effect’ as the field travels from one Pole Piece to another. The
Inspection Media (Dry Powder or Wet Method Particles) has a tendency to
migrate toward interruptions (or defects) in the field. The direction and intensity
of an AC Field, by it’s nature, alternates causing high particle mobility, so defects
tend to be revealed immediately.
.
DC Field –
The Pulsed DC Magnetic Field is stronger than an AC Field and
tends to penetrate the work piece more deeply, however DC is still sensitive to
surface defects. Inspection media tends to adhere to the entire target area of the
work piece, due to the reduced particle mobility, and may need to be ‘blown off’
to fully reveal an indication. The intensity of a DC Field, by it’s nature, is fixed but
the Yoke does Pulse the field providing some stimulus for the particles to migrate
to defects.
