WIKA PXA - Manual (Page 5)

INSTRUCTION MANUAL
NI-290E
Rev. 0 01/05
Fig. 8. Instruments installation
Group II Cat 1/2G Group II Cat 1/2D
8.6 SPECIAL NOTE FOR THE INSTALLATION OF
PRESSURE SWITCHES CATEGORY 3GD MODE OF
PROTECTION EEx - nC
Explosionproof instruments Series PXN are to be installed using
electric accessories prescribed for this execution. For instance,
junction boxes are to be suitable for mode of protection n. Apply
to standards EN-50021 for any construction detail and to EN-
60079-14, EN-50281-1-2 for installation.
9 - PUTTING INTO OPERATION
As the signal transmitted by the instrument is used in a complex
system, it is necessary that the means of putting it into operation
are established by those in charge of the plant.
The instrument starts operating as soon as the root valve is
opened. Any possible drainage of the connection tubing can be
carried out by removing the safety plug and opening the service
valve with the necessary caution.
In case of explosionproof instruments (Series PXA and PXN),
initial inspections are to be carried out according to customer
procedures and at least in accordance with Standards EN-60079-
17 and EN-50281-1-2.
10 - FUNCTIONAL VERIFICATION
It will be carried out according to customer control procedures.
Explosionproof instruments (Series PXA, PXN) installed in
hazardous areas due to the presence of inflammable dusts should
be periodically cleaned externally to avoid dust accumulation.
Instruments Series PXS may be checked on site if installation has
been made according to Fig. 9 to 12.
Instruments Series PXA, PXN may be checked on site but if
testing equipments are suitable for the environment and electric
supply is off.
Otherwise it is necessary to stop them working, remove them and
carry out checks in a test room.
The verification consists in checking the calibration value and
adjusting it if required (see §5).
In case of explosionproof instruments (Series PXA and PXN)
inspections of the electrical installation are to be carried out also
according to customer procedures and at least in accordance with
Standards EN-60079-17, EN-50281-1-1.
11 - TROUBLE SHOOTING
IMPORTANT NOTE: operations involving replacement of essential components must be carried out at our workshop, especially
for instruments with explosionproof certificate; this is to guarantee the user the total and correct restoration of the product
original characteristics.
MALFUNCTION PROBABLE CAUSE REMEDY
Set point shift
„ Permanent deformation of the sensitive element
due to fatigue or excess over-ranges.
„ Variation of the elastic features of the sensitive
element due to its chemical corrosion.
„ Recalibrate or replace the sensitive element.
„ Recalibrate or replace the sensitive element with
another made of a suitable material. If necessary
apply fluid separator.
Slow response
„ Clogged or obstructed connecting line.
„ Root valve partially closed.
„ Too viscous fluid. „ Check and clean line.
„ Open the valve.
„ Provide instrument with suitable fluid separator.
No actuation or
undue actuation
„ Root valve closed.
„ Microswitch contacts damaged.
„ Loosened electrical joints.
„ Interrupted or short-circuited line. „ Open the valve.
„ Replace
instrument.
„ Check all electrical joints.
„ Check conditions of the electric line.
Undue actuation „ Accidental shocks. „ Modify mounting.
12 - STOPPING AND DISMOUNTING
Before starting the following operations, ensure that plant and
equipments have been put in conditions allowing to carry out
them safely.
With reference to Fig 10.
Remove the power supply (signal) from the electric line. Close
the root valve (10) and open drain. Remove plug (5), open valve
(6) and wait for process fluid to drain out.
Do not dispose of the process fluid into the environment, if this
can cause pollution or damage to people.
Unscrew the three-piece joints (11) and (3) (electric cable tubing).
Remove cover from junction box and disconnect wires from
terminals and grounding screws. Remove the screws fixing the
box to the panel (or pipe) and remove the instrument taking care
to slide electric conductors out from the case.
Replace the cover on the box. Insulate and protect the
conductors remaining on the plant. Temporarily plug the tubing
(7). In case of explosionproof instruments (Series PXA, PXN) it is
recommended to follow - at least – the Standards EN-60079-17
and EN-50281-1-2 for the withdrawal from service of electrical
apparatus.
13 - DEMOLITION
The instruments are mainly made of stainless steel and
aluminium and therefore, once the electrical parts have been
dismounted and the parts coming into contact with fluids which
could be harmful
to people or to environment have been properly dealt with, they
can be scrapped.