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6.4.3 Intrinsically Safe signal cable
For general information, the Intrinsically Safe (I/S) signal cable between the EPU and the skid has a
nominal 0,5 mm² diameter, 7 cores of 2 twisted pairs with an overall screen.
(EG Helkama RFE-HF60V)
The signal cable makes use of the same cable transit system as is used for the air pipelines to ease
installation of the system.
BEFORE OPERATION:
It is vital to ensure that the equipment supplied exactly meets your needs and that it is
certified for a safe use in your expected operating conditions. For the components such
as the measurement cell and EPU items of equipment are certified. See section 16 for
certification standards.
All circuits are connected to the energy limiting circuits within the EPU. These circuits limit the
voltage by means redundant zener diodes, all connected to the same ground connection. The
current is limited by means of resistors. Each circuit is thermally protected by means of a fuse.
The ratings of the circuits to the measurement cell is such that even in case of an total short circuit
of all the circuits together, the energy within that short is still within non-ignitive intrinsically save
energy levels (including a safety factor of 1.5) The additional position detection circuits are
separated from the circuits to the measurement cell. The EPU contains two other energy limited
circuits for connection to the approved dP/I sensors. These circuits are separated from the
aforementioned circuits.
WIRING PROCEDURE:
Prior to initiating work on the wiring, be sure to turn OFF the main power.
Cables, cable glands and plugs certified in accordance with the considered zone must
be used.
More, whatever the protection mode, only use plugs or cable glands with a protection
degree of at least IP 65.
Be sure that the cable diameter complies with the selected cable gland.
Tighten the cable gland in accordance with supplier’s instructions.
Never forget to mount the covers and tighten then correctly.
REPLACEMENT PARTS:
The replacement of components can only be done by personnel trained to act on
equipment intended for use in potentially explosive atmospheres. Spare parts must only
be genuine parts supplied by VAF Instruments. During installation there is no need to
operate the system and thus to switch the EPU on.
Reference drawings
Control drawing for Mark 6M Oil Discharge Monitor 0806-0005
Schematic installation diagram Oilcon Monitor System with 1x dP/I
transmitter Mark 6 0806-8035
Bulkhead penetration and piping diagram Mark 6M 0806-8038
Multi cable transit Ballast Monitor Mark 6 0806-8070
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