NI-281E
A
c
c
A
A
INSTRUCTION MANUAL
Rev. 5 11/02
COMPACT PRESS. SWITCHES SERIES PCS & PCA
WEATHERPROOF EXPLOSIONPROOF
SERIES PCS SERIES PCA
B
B = Cable entry
A = Pressure connection
WEIGHT 1kg dimensions in mm
NOTE: dimensions and weights are not binding unless released on certified drawings.
CAUTION
• Before installing, using or carrying out maintenance on the instrument it is necessary to read and understand the indications given in
the attached Instruction Manual.
• The instrument must only be installed and maintained by qualified personnel.
• INSTALLATION IS TO BE CARRIED OUT ONLY AFTER CHECKING THAT INSTRUMENT CHARACTERISTICS ARE
CONSISTENT WITH PROCESS AND PLANT REQUIREMENTS
• The functional features of the instrument and its degree of protection are shown on the identification plate fixed to the case.
CONTENTS:
GENERAL NOTES
1 -
2 - OPERATING PRINCIPLE
3 - IDENTIFICATION PLATE AND MARKINGS
4 - SET POINT REGULATION
5 - SET POINT CALIBRATION
6 - MOUNTING AND CONNECTIONS
7 - INSTRUMENT PLUMBING
8 - PUTTING INTO OPERATION
9 - FUNCTIONAL VERIFICATION
10 - FUNCTIONAL VERIFICATION
11 - STOPPING AND DISMOUNTING
12 - DEMOLITION
SAFETY INSTRUCTIONS FOR USE IN HAZARDOUS ATMOSPHERES.
RECOMMENDATIONS FOR PRESSURE SWITCH SAFE USE.
B = Cable entry
A = Pressure connection
WEIGHT 1kg dimensions in mm
B
RELATED DOCUMENT
To authentified document with certificate
N° CESI 02 ATEX 118
ll data, statements and recommendations supplied with this manual are based on information believed by us to be reliable. As the
onditions of effective use are beyond our control, our products are sold under the condition that the user himself evaluates such
onditions before following our recommendations for the purpose or use foreseen by him.
The present document is the property of ETTORE CELLA SPA and may not be reproduced in any form, nor used for any purpose
other than for which it is supplied.
INSTRUCTION MANUAL
1 - GENERAL NOTES
1.1 FOREWORD
The wrong choice of a series or a model, as well as the incorrect
installation, lead to malfunction and reduce instrument life. Failure
to abide by the indications given in this manual can cause
damage to the instrument, the environment and persons.
1.2 ALLOWED OVERRANGE
Pressures exceeding the working range can be occasionally
tolerated provided they remain within the limits stated in the
instrument features (proof pressure). Continuous pressures
exceeding the working range can be applied to the instrument,
provided they are clearly stated in the instrument features. The
current and voltage values stated in the technical specifications
and ratings must not be exceeded. Transitory over-ranges can
have a destructive effect on the switch.
1.3 TEMPERATURE
Due to the temperature of both the environment and the process
fluid, the temperature of the instrument could exceed the allowed
limits (normally from -20°C to +70°C). Therefore, in case it does,
suitable measures (protection against heat radiation, fluid
separators, cooling coils, heated lockers), aimed at limiting the
value, must be taken.
2 - OPERATING PRINCIPLE
A pressure-tight diaphragm (or an O-ring sealed piston) applies a
force to a stiff disc. This force is directly proportional to the
pressure value and is contrasted by an helicoidal spring charged
by a suitable bush. When the force balance point is exceeded, the
stiff disc shifts and, by means of a rigid rod, actuates one or two
simultaneous release electric microswitches. The
microswitches are of the snap acting type with automatic reset.
When the pressure moves away from the set values, returning
towards the normal values, the switch is reset.
3 - IDENTIFICATION PLATE AND MARKINGS
The instrument is fitted with a metal plate bearing all its functional
characteristics and – in case of explosionproof execution (Series
PCA) – also the markings prescribed by standard CEI EN 50014.
Fig. 1 shows the plate mounted on explosionproof instruments.
Fig. 1 - Explosionproof instruments plate
NI-281E
Rev. 5 11/02
Prior to installation the instrument must be calibrated and the
definitive calibration values written on the label using a suitable
indelible ink pen.
If the instrument has been ordered with a specific calibration, it
is a good rule to check the calibration values marked on the
relevant adhesive label, prior to installation.
The position of the adjustment bush given in Fig. 2.
Fig. 2 - Electrical connections and adjustment screws
(one contact/two contact instruments)
1 - External earth screw
2 - Hole for test plug
3 - Adjustment rod for set point calibration
4 - Adjustment bush access plate
5 - Adjustment bush
6 - Screw for fixing the adjustment bush access plate
7 - Internal earth screw
8 - Terminal block for the second microswitch
9 - Terminal block for the first microswitch
10 - Pre-insulated thimbles
⊗ - Ventilation path
Microswitch electrical circuit. State of the contacts at atmospheric
pressure
1 CE marking and identification number of the notified body
responsible for production surveillance.
2 Apparatus classification according to ATEX 94/9 CE
directive..
3 Type of protection and ambient temperature limits of
operation.
4 Notified body that issued the type certificate and number of
said certificate.
4 - SET POINT REGULATION
The charge of the helicoidal spring can be regulated by means of
the bush (for adjustment) in such a way that the switch is released
when the pressure reaches (increasing or decreasing) the desired
values (set point). The instrument is usually supplied with the
switches set at the setting range value nearest to zero (factory
calibration).
The instrument is supplied with an adhesive label showing the set
point calibration value. With factory calibration the values are
not indicated on the label as these are temporary and will be
modified with the definitive values.
Designation of the
contacts:
C - Common
NA - Normally open
NC - Normally closed
The effect of the direction of rotation of the adjustment bush has
is described on the adhesive plate.
The bush must be turned by means of the special adjustment rod
which comes with the instrument (Fig.2).
5 - SET POINT CALIBRATION
In order to proceed with the calibration and the periodical
functional verification of the instrument a suitable calibration
circuit (Fig. 4) and an adequate pressure source is required..
INSTRUCTION MANUAL
5.1 PRELIMINARY OPERATIONS
CAUTION: do not open the cover of explosionproof pressure
switches (Series PCA) when energized, in explosive
atmospheres.
With reference to Fig. 3 unscrew the screw (b) until the blocking
device (a) can be turned 180°; then unscrew the cover.
Fig. 3 - Weatherproof pressure switch cover blocking
CALIBRATION CIRCUIT AND The warning lamps should be
connected to the contacts in the NA or NO position according to
the required contact action.
If the instrument is equipped with two microswitches, take into
account that they actuate simultaneously within rated tolerances.
The warning lamps can either be connected by means of a
thimble with a maximum diameter of 2.5 mm or by means of a test
plug with a diameter of 2 mm to be inserted in the appropriate
holes situated frontally beside the terminal screw (see Fig. 2).
Connection of C and NA terminals
• If the circuit is open at the working pressure, the switch closes
the circuit as the pressure increases when the desired values is
reached (MAX. closing).
• If the circuit is closed at the working pressure, the switch opens
the circuit as the pressure decreases when the desired value is
reached (MIN. opening).
Connection of C and NC terminals
• If the circuit is closed at the working pressure, the switch opens
the circuit as the pressure increases when the desired value is
reached (MAX. opening).
• If the circuit is open at the working pressure, the switch closes
the circuit as the pressure decreases when the desired value is
reached (MIN. closing).
The test instrument should have a measurement range
approximately equal to or slightly wider than the pressure switch
range and should have an accuracy consistent with the precision
required to calibrate the set point.
The pressure switch must be mounted in the normal installation
position, i.e. with the pressure connection downwards.
Avoid forcing the microswitch by hand or with tools. This could
affect the instrument functioning.
With reference to Fig.3, free the access to the adjustment bush by
loosening the screw (c) which holds the closure plate (f).
Increase the pressure in the circuit up to the desired microswitch
set point value.
Turn the adjustment bush using the adjustment rod with which the
instrument is equipped (Fig. 2) until the relative lamp turns on (or
turns off); then turn it in the opposite direction until the lamp turns
off (or on). Slowly turn the bush again until the lamp turns on (or
off).
device and plumbing
a. Cover blocking
device
b. Blocking screw
c. Screw blocking
the adjustment
bush access
plate
d. Flexible steel
wire
e. Plumbing
f. Adjustment
bush access
plate
NI-281E
Rev. 5 11/02
Fig. 4 - Calibration circuit
PS - Pressure switch
CA - Test gauge
V1 - Inlet valve
V2 - Discharge vale
P - Pressure source
Check the calibration value (varying the pressure in the circuit
accordingly) and register it, using a pen with indelible ink, on the
ratings.
5.2 CALIBRATION USING REGULATION SCALE
See the specific instructions attached with instruments with this
option.
5.3 FINAL OPERATIONS
Disconnect the instrument from the calibration circuit.
With reference to Fig. 2, insert the adjustment rod into the
appropriate seat; close the access to the adjustment bush by
rotating the closure plate (4) and tighten the relative screw (6).
Take the cover, ensure that the sealing gasket is correctly fitted
into its seat, insert the cover onto the case and turn it clockwise
until the cover is closed.
With reference to Fig. 3 turn the blocking device (a) 180° sliding
the tongue into the appropriate seat in the cover; tighten the
blocking screws (b).
Mount on pressure connectionn and cable entry the protection
caps supplied with the instrument.
CAUTION: the protection caps should only be definitively
removed during the connection steps (see § 7).
6 - INSTRUMENT PLUMBING
The plumbing, aimed as a guarantee against possible tampering
of the calibrations, can be carried our using a flexible steel wire
(d) inserted into the holes in the screw (c) and the adjustment
bush closure plate provided for this purpose (see Fig. 3).
7 - MOUNTING AND CONNECTIONS
7.1 MOUNTING
Surface mount the instrument by mean of the holes, or pipe
mount using the appropriate bracket (see Fig. 8) or mount directly
on the plant in a vertical position (with the pressure connection
downwards). The chosen position must be such that 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. 7). With a liquid process fluid, the
instrument can be positioned higher or lower, indifferently (see
Fig. 6 and 7). In this case, during set point calibration the
negative or positive head must be taken into account.
CAUTION: positions other than vertical are allowed provided
environmental conditions do not cause condensation to form or
water to enter the instrument through the ventilation path.
7.2 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 capstanblocking 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
Test fluid:
air for P <
water for P > 10 bar
10 bar
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
the tube itself does not force the instrument attachment due to
variations in temperature.
Ensure that all the pressure connections are airtight. It is
important that there are no leakages in the circuit.
Close the root valve and the relative drain device. Close the
service valve fitted with a safety plug.
INSTRUCTION MANUAL
7.3 ELECTRICAL CONNECTIONS
It is recommended to carry out the electrical connections
according to the applicable standards. In case of explosionproof
instruments (Series PCA) 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. 5 or 6 is therefore recommended.
CAUTION: fittings used for the electrical connection of the
pressure switch Series PCA (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. 2).
Flexible cables with a maximum section of 1,2 mm
recommended using the pre-insulated thimbles with a maximum
diameter of 2,5 mm supplied with the instrument.
When inserting cables into the enclosure pay attention not to
force the microawitch with cable or tools, otherwise instrument
calibration or even its operation could be compromised. The
microswitch has been factory mounted and positioned in order to
obtain the best performances. Any tampering made on site
without following instructions authorised by the E. CELLA SPA
may result in instrument malfunction.
Ensure that no deposits or wire ends remain inside the case.
Once the connection operations have been completed, replace
the cover and ensure that it is properly sealed and blocked. See
Fig. 3.
7.4 SPECIAL NOTE FOR INSTALLATION OF
CATEGORY 1 / 2 G PRESSURE SWITCHES
Explosionproof pressure switches (Series PCA) can be installed
on processes requiring apparatus of group II category 1 in an
ambient requiring apparatus of group II category 2 (see Fig. 5).
2
(16AWG) are
NI-281E
Rev. 5 11/02
Fig. 5 - Installation of Group II Cat. 1 / 2 G instruments
8 - 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 personnel in charge of the plant.
The instrument comes into operations 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 PCA), initial
inspections are to be carried out according to customer
procedures and at least in accordance with Standard EN-60079-
17.
9 - FUNCTIONAL VERIFICATION
This will be carried out according to the Client’s control
procedures. Series PCS instruments can be verified on the plant if
installed as illustrated in Fig. 6 and 7.
The instruments Series PCA may be checked on site only if
apparatus suitable for explosive atmosphere are used and
provided that the electric line is not energized.
If this is not the case it is necessary to stop operation, dismount
by means of the three piece joints and carry out the verification in
a test room.
CAUTION: do not open the cover of explosionproof pressure
switches (Series PCA) when energized, in explosive
atmospheres.
Verification consists in check the calibration value and possibly
regulating the adjustment bush (see §5).
In case of explosionproof instruments (Series PCA), inspections
of the electrical installation are to be carried out also according to
customer procedures and at least in accordance with Standard
EN-60079-17.
NI-281E
INSTRUCTION MANUAL
10 - TROUBLESHOOTING
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
Permanent deformation of the sensitive element
due to fatigue or excess over-ranges.
Set point shift
Poor repeatability
Slow response
No actuation or
undue actuation
Undue actuation
Variation of the elastic features of the sensitive
element due to its chemical corrosion.
O-ring wear (only PCS2P, PCS3P, PCA2P and
PCA3P).
O-ring wear (only PCS2P, PCS3P, PCA2P and
PCA3P).
Air bubbles or condensation (only for types with
pressure < 1 bar).
Clogged or obstructed connection line.
Root valve partially closed.
Too viscous fluid.
Root valve closed.
Microswitch contacts damaged.
Loosened electrical joints.
Interrupted or short-circuited.
Accidental shocks. Modify the mounting.
11 - STOPPING AND DISMOUNTING
Before proceeding with these operations ensure that the plant or
machines have been put into the conditions foreseen to allow
these operations.
With reference to figures 6 or 7
Remove the power supply (signal) from the electrical line.
Close the root valve (6) and open the drain.
Remove the plug (2), open the valve (3) and wait until the process
fluid has drained from the tubing through the drain.
Do not dispose of the process fluid into the environment, if this
can cause pollution or damage to people.
Unscrew the three piece joint (8).
CAUTION: do not open the cover of explosionproof pressure
switches (Series PCA) when energized, in explosive
atmospheres.
Unscrew the three piece joint (10) (electrical cable tubing).
Remove the instrument cover and disconnect the electrical cables
from the terminal block and earth screws.
Remove the screw fixing the case to the panel (or pipe) and
remove the instrument, taking care to slide the electrical
conductors out from the case.
Mount instrument cover. Insulate and protect cables around, if
any. Temporarily plug pipes not connected to the instrument. In
case of explosionproof instruments (Series DE) it is
recommended to follow - at least – the standard EN-60079-17 for
the withdrawal from service of electrical apparatus.
12 - 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 the environment have been properly
dealt with, they can be scrapped.
Recalibrate or replace the sensitive element.
Recalibrate or replace the sensitive element with
another made of a suitable material. If necessary
apply fluid separator.
Replace the piston subgroup and recalibrate.
Replace the piston subgroup and recalibrate.
Drain the process connection lines and if necessary
modify them.
Check and clean line.
Open valve.
Provide instrument with suitable fluid separator.
Open the valve.
Replace the microswitch.
Check all electrical joints.
Check the conditions of the electric line.
Rev. 5 11/02
NI-281E
INSTRUCTION MANUAL
WEATHERPROOF EXPLOSIONPROOF
Fig. 6 - Example of connections
Fig. 7 - Example of connections
Rev. 5 11/02
Fig. 8 - Surface or bracket mounting for 2" pipe
(weatherproof and explosionproof instruments)
LEGEND
1 - Fitting 9 - "T" fitting
2 - Drain plug 10 - Three piece fitting
3 - Service valve 11 - Blocking joint
4 - Piping 12 - Curve
5 - Three piece fitting 13 - M5 screws (No. 2)
6 - Root valve with drain 14 - Bracket for 2" pipe
7 - Process piping 15 - Vertical pipe
8 - Three piece fitting 16 - Horizontal pipe
NOTE: With gas or vapour process fluid, the instrument must
be positioned higher than the pipe inlet (see Fig. 5). With a
liquid process fluid, the instrument can be positioned higher or
lower, indifferently (see Fig. 5 and 6). In this case, during set
point calibration the negative or positive head must be taken
into account (distance h in Fig.5 and 6).
ETTORE CELLA SPA Viale de Gasperi, 48 - Casella Postale (P.O. Box) 96 - I 20010 Bareggio (MILANO) ITALY
Telefoni +39 029036.1146/1237/1241 - FAX +39 029036.1331 e-mail: cella@ecellaspa.com
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