FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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This subsystem was designed for repetitive scanning of heat exchanger tubes
with automatic stop and retract upon reaching a preprogrammed position or
under control from the data processing subsystem. The probe drive control
subsystem communicates status, position information, tube coordinates and
three twin analog channels to the data processing subsystem through a single
multi-channel link.
2.2.2 Probe Drive
The probe drive comprises four segments designed for easy access to congested
areas and assembly in minutes. The probe drive provides 400N (90 lbf) drive
force using four drive wheels for both plastic and steel wound cables. A
compact motor driven take-up reel with mercury-wetted slip rings is utilized.
An incremental shaft encoder allows for high resolution data collection and
accurate positioning. A flexible probe guide tube directs the probe cable
and probe to the heat exchanger tube. The probe guide normally connects to a
calibration tube and zero limit switch. This switch allows the system to
correct for positioning hysteresis effects. A second mechanical switch
placed within the probe guide tube just ahead of the drive wheels prevents
the probe from being withdrawn through the drive wheels.
2.2.3 Probe Drive Interface
The probe drive interface module contains the probe drive power supply, speed
regulation controller and manual probe drive controls. Manual probe drive
operation without position readout is possible with this module alone.
2.2.4 Probe Drive Controller
The probe drive controller is a microprocessor controlled module responsible
for the execution of preprogrammed scan patterns and manual scanning with
full distance display plus slip and jam detection. The probe drive
controller accepts input via two remote keyboards from either the operator or
the analyst. Shaft encoder and limit switch inputs provide positioning
information and three twin differential channels transmit eddy current data
to the data acquisition subsystem.
2.3 Stand-Alone Probe Controller
The stand-alone probe controller module is a scaled down version of the probe
drive interface and controller. This single module is fully programmable by
the operator via a hand held keyboard. The module contains the probe drive
power supply, speed regulator, and microprocessor control system. This
module allows repetitive scanning with automatic retraction, time delayed
repeat and jam detection. Programmed speeds and distance regions allow scan
speed variation in the U-bend region in both the retraction and insertion
phases of a scan. No eddy current signal transmitting capabilities are
included in this module.