Preventive Maintenance Checks; General; X-Ray Tube Feedback System - Planmeca ProMax Technical Manual

Chapter D - PREVENTIVE MAINTENANCE
Exposure switch
Confirm that the exposure switch requires continuous activation to maintain the exposure.
Releasing the exposure switch during the radiation should stop the exposure and produce an
error message. Make a visual check and check for possible wear or damage of the exposure
switch spiral. Replace if necessary.
Emergency stop button
Confirm that activating the emergency stop button will stop the X-ray unit operating. Pressing
the emergency stop button should block all movements of the X-ray unit, disable radiation
and produce a help message.
Labels
Check that no labels are detached or worn and that they are all legible.

2 PREVENTIVE MAINTENANCE CHECKS

2.1 General

Annually, or after every 10 000 exposures (whichever appears first), the electrical exposure
parameters of the ProMax X-ray should be checked in order to ensure the initially accurate
operation of the equipment, despite of the possible long term component value drifts.
There are no adjustments in the equipment because of its self-calibrating system - therefore
no actual parameter trimming of the kV, mA and exposure time can be done. If one of the
parameters to be checked is found to be beyond the limit allowed, the corresponding module
is to be changed in whole, or a factory- type recalibration should be performed.

2.2 X-ray tube feedback system

The unit performs a complete check on the feedback system before every exposure. Any
found errors or deviations are reported as error messages (exposure is prevented). Therefore
the actual need for this annual test is dictated by the local authorities and respective regula-
tions. Please be sure to perform all tests required by the authorities.
There are two ways of doing most of the tests, either non-invasively (from the radiation beam)
or invasively (from the units feedback signals). Both are presented here. Please note that not
all tests can be performed both ways.
CAUTION Radiation is emitted during all these tests. Proper protection against
unnecessary exposure to radiation must be considered.
2.2.1 NON-INVASIVE TESTING (directly from the radiation)
A non-invasive method can be used for checking the kVp, radiation quality (half-value layer)
and the exposure time. This method is efficient since no covers need to be opened, and it
gives a "second" opinion on the measured parameters. However, care must be taken when
selecting the appropriate non-invasive X-ray meter; older meters calculate the kVp avg based
on the assumption that the kV waveform is AC. The Planmeca ProMax has DC high voltage
with very small high frequency ripple, so the accurate measurement of kV waveform can be
D-2 Planmeca ProMax
PREVENTIVE MAINTENANCE CHECKS
Technical Manual