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Section 1
1.6
1-9
2-12
INTRINSICALLY SAFE CONSIDERATIONS
The Pearpoint P374 system has been designed to be Intrinsically Safe even when
faults occur or when the equipment has been damaged due to misuse. However,
there are situations where the operator can cause a fire hazard if the following
guidelines are not adhered to:
Equipment earthing
The equipment must be operated at the same electrical potential as the subject
being inspected. This means that the P374 system and the subject being
inspected must be joined together electrically otherwise it is possible that a high
potential might exist between the equipment and the subject. Here are a few
examples:
Underground pipework. If the P374 is operated from a mains supply rather than
a generator there is usually no problem as any buried pipework will be at mains
earth potential ensuring that there is no potential difference between the camera
and subject. However, if the equipment is operated using a generator rather than
a mains supply then there is a possibility that a potential difference exists
between the P374 system and the pipework. As a general rule the potential
difference will not be sufficient to cause a problem as the P374 camera is
insulated to a voltage of greater than 500V. However, it is good practice to
ensure that the P374 system is bound to the same potential as the subject, this is
because an operator may build up a certain amount of static electricity and this
may be discharged through the P374 system.
When working with a generator it is imperative that the generator is earthed, this
can be done via the generator earthing point (see the generator manual for this
information). An earth wire must run from the generator to the subject, in the
case of underground pipes this can be an earthing stake. Where working on oil
platforms the metal structure of the platform can be used. If your generator does
not have an earthing point then an additional earth wire must be run from the
distribution connector (see your dealer for details).
When working with mains power ensure that the equipment is properly earthed,
be aware that some extension leads only carry 2 conductors for Live and Neutral
and miss out the earth conductor altogether. Also be aware that some isolating
transformers do not continue the earth conductor through between input and
output (although this is rare); ensure that the transformer you are using has a
continuous earth.
When working with the 12V supply input it is imperative that the negative
conductor is earthed. Quite often the 12V supply is derived from a motor
vehicle, this means that the P374 earthing system is connected to the chassis of
the vehicle and thus the P374 will assume the same potential as the vehicle. It is
well known that the chassis of vehicles can carry high voltages due to static
build-up and this voltage will be conducted to the P374 unit. For this reason the
chassis of the vehicle must be bonded to the subject being inspected, usually (in
the case of underground pipework) this means that the chassis of the vehicle is
connected to a ground-stake.
P374 System User Manual
© Pearpoint Ltd
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