WIKA APA10 - Manual (Page 4)

INSTRUCTION MANUAL
NI-205
Rev. 1 12/02
The pressure switch must be mounted in the normal
installation position, i.e. with the pressure connection
pointing downwards.
Fig. 6 - Calibration circuit
Pressione
assoluta
PS - Pressure switch
CA - Test pressure gauge for
absolute pressuures
V1 - Inlet valve
V2 - Outlet valve
P -
Absolute pressure
source
Avoid forcing the elastic support of the microswitch by
hand or with tools. This could affect the instrument
functioning.
CAUTION: if the switch is of the kind with adjustable
dead band (letter R of contacts code) before proceeding
with the following operations it is necessary to proceed
with the adjustment of the dead band (see attachment
NI-704).
Increase the pressure in the circuit up to the desired set
point value for the first microswitch.
Use a wide bladed screwdriver, as indicated on the
adhesive plate, until the relative lamp turns on (or turns
off).
- If the instrument is equipped with only one contact the
calibration is complete.
- If it is equipped with two contacts continue in the
following manner.
Vary the pressure until the desired set point value for
the second microswitch is reached (fig. 3).
Act on the adjustment screw of the second contact.
Repeat former operations on the first contact, then
operations on the second contact, until the required set
point precision is obtained. This is necessary due to the
reciprocal influence which the microswitches have on
the sensitive element of the instrument.
Check the calibration values (varying the pressure in the
circuit accordingly) and record them on the adhesive
plate using a pen with indelible ink.
5.3 FINAL OPERATIONS
Disconnect the instrument from the calibration circuit.
Weatherproof pressure switches (Series APW)
Take the cover, ensure that the sealing gasket is
correctly fitted into its seat, and insert the cover onto the
case, with the blocking gap positioned in
correspondence to the blocking bracket. Turn the cover
clockwise closing it tightly. Mount the adjustment screw
access plate, then the blocking device as in Fig.4.
Explosionproof pressure switches (Series APA).
Insert the closure plugs of the adjustment screw access
holes, block them using the internal device and if
necessary seal them with plumbing. Screw on the cover
and block it using the headless screw with which it is
equipped (Fig. 5).
Replace the supplied protection caps on the pressure
attachment and cable conduit.
IMPORTANT: the protection caps should only be
definitively removed during the connection steps (see
§6).
6. MOUNTING AND CONNECTIONS
6.1 MOUNTING
Surface mount the instrument by means of the holes
provided, or pipe mount using the appropriate bracket
(see Fig. 9). The chosen position must be such that
vibrations, the possibility of shocks or temperature
changes are within tolerable limits. The above also
applies to direct mounting. With gas or vapour process
fluid, the instrument must be positioned higher than the
pipe inlet (see Fig. 8). With a liquid process fluid, the
instrument can be positioned higher or lower,
indifferently (see Fig. 8 and 9). ). In this case, during set
point calibration the negative or positive head must be
taken into account (distance h in fig.8 and 9).
6.2 PRESSURE CONNECTIONS
For a correct installation it is necessary to:
Mount a shut-off valve with drain (root valve) on the
process tube to allow the instrument to be excluded and
the connection tubing to be drained. It is recommended
that said valve has a capstan-blocking device aimed at
preventing it being activated casually and without
authorisation.
Mount a service valve near the instrument to permit
possible functional verification on site. It is
recommended that the service valve is closed with a
plug to prevent the outlet of the process fluid caused by
the incorrect use of said valve.
Mount a three-piece joint onto the threaded attachment
of the instrument to permit the easy mounting or
removal of the instrument itself.
Carry out the connection using a flexible tube in such a
way that variations in the temperature of the tube itself
do not force the instrument attachment.
Ensure that all the pressure connections are airtight. It
is important that there are no leakage in the circuit.
Close the root valve and the relative drain device. Close
the service valve using a safety plug.
6.3 ELECTRICAL CONNECTIONS
It is recommended to carry out the electrical
connections according to the applicable standards. In
case of explosionproof instruments (Series APA) see
also the Standard EN-60079-14. If the electrical
connection is carried out in a protected tube, it shall be
made so that condensate is prevented from entering
instrument enclosure.
The arrangement shown in fig. 8 and 9 is therefore
recommended.
CAUTION: fittings used for the electrical connection of
the pressure switch Series APA (explosionproof) shall
be certified to Standards EN 50014 and 50018, and
shall guarantee instrument degree of protection (IP65).
Check that there is no power in the lines. Remove the
cover and carry out the cabling and connections to the
terminal block (see Fig. 3). Flexible cables with a
maximum section of 1.2 mm
2
(16AWG) are
recommended using the pre-insulated fork thimbles. Do
not touch the adjustment screws and do not bend
the elastic microswitch supports in order to prevent the
instrument calibration being altered. Ensure that no
deposits or wire ends remain inside the case.
As soon as connection steps are completed, mount the
cover on and make sure it is tight and blocked. See Fig.
4 and 5.
Absolute
pressure