Videotec EXPT - Manual (Page 9)

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nstruc
tions manual
7
4.1.2 Version with glass protection
device
The EXPT series of explosion-proof pan & tilt devices
can be fitted with a glass protection device, installed
on the front opening of the housing. It comprises a
flange for linking with the housing, a closing flange
and a central, explosion-proof body containing a
strong, transparent glass, a 24Vdc motor, two winders
and transparent Mylar film, installed in front of the
glass.
The motor uses 4 bevel gears to pilot a winder for
recovering dirty film, while the other winder issues
clean film. The motor is remotely controlled by a two-
wire ON-OFF contact (one common and one +24Vac/
Vdc, Fig. 13, page 19).
h The control unit for the glass protection
device is supplied by the customer.
The transparent Mylar film can be fed forward about
350 times.
When the film is dirty the operator starts the motor,
so that the film is fed forward until a clean image is
obtained (to completely replace the dirty film in one
step, about 50mm of clean film should be fed).
The end of the tape is marked by printing on the last
50cm of film.
Film feed can also be started automatically by a
timing device if a suitable control system is used (this
is not supplied).
To change the film, see the Videotec spare part
handbook (code OEXMYLAR).
The central body contains the two potentiometers for
the preset option and the indispensable electronic
parts for automatic operation, plus the junctions for
connecting the input cable via an Ex d 3/4" NPT IP66
barrier armoured cable gland, complying with the
housing markings.
The central body contains the motors for horizontal
and vertical movements. The EXPT series P&T use
single phase, synchronous AC motors; the motors
transmit horizontal and vertical motion via a
wheel-pinion and link chain, with rotation in both
directions plus immediate stop and reverse. Inside
the movement mechanism there is a worm screw /
crown wheel system to ensure complete absence of
mechanical play during operation.
The housing body also comprises a cylindrical,
aluminium tube, closed by a flange that houses a
strong, transparent glass; on the opposite side there
is another flange that, as well as closing the cylinder,
supports the plate to which the camera is to be
attached.
The P&T has an IP66 protection degree.
4.1.1 Version for thermal imaging
cameras
When using thermal imaging cameras, which are able
to detect heat emission, a special filter on the front
of the housing should be used. This housing differs
in that it has a window made mainly of germanium,
which guarantees the same strength and security
properties as those for standard glass. Range of
application from 7.5 to 14µm.