NI-221E
INSTRUCTION MANUAL
Rev. 1 11/02
DIAPHRAGM PRESSURE SWITCHES
WEATHERPROOF:SERIES MW EXPLOSIONPROOF: SERIES MA
Models: MW-MWH Models: MA-MAH-MAG
A = pressure attachment
B = cable entry
WEIGHT 1,8 kg dimensions in mm WEIGHT 3,2 kg 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:
1
GENERAL NOTES
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 TROUBLESHOOTING
11 STOPPING AND DISMOUNTING
12 DEMOLITION
SAFETY INSTRUCTIONS FOR USE IN HAZARDOUS ATMOSPHERES.
RECOMMENDATIONS FOR PRESSURE SWITCH SAFE USE.
A = pressure attachment
B = cable entry
RELATED DOCUMENT
To authentified document with certificate
N° CESI 02 ATEX 144
All data, statements and recommendations supplied with this manual are based on information believed by us to be
reliable. As the conditions of effective use are beyond our control, our products are sold under the condition that the
user himself evaluates such conditions 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 that 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
Pressure exceeding the working range can be occasionally tolerated provided they remain within the limits stated
in the instrument features (vacuum or 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 overages can have a
destructive effect on the switch.
1.3 MECHANICAL VIBRATION
Can generally lead to the wearing of some parts of the
instrument or cause false actuation. It is therefore recommended that the instrument be installed in a place where
there are no vibrations. In cases where this is impossible it
is a good idea to take measures to lessen the effects
(elastic supports, installation with the peg of the microswitch positioned at right angles to the vibration plane).
1.4 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° to +70°C).
Therefore, in case it does, suitable measures (protection
against heat radiation, fluid separators, cooling coils,
heated lockers) must be taken.
2 OPERATING PRINCIPLE
• The pressure, acting on the sensitive element (dia-
phragm), determines its elastic deformation which is used
to activate one or two electric microswitches regulated at
set point values. The microswitches are of the rapid release type with automatic rearm. When the pressure
moves away from the set values, returning towards the
normal values, the switch is rearmed. The differential gap
(difference between the set point value and the reset
value) can be set or adjustable (letter R in the contact
codes).
• Piston activated diaphragm instruments (MWH - MAH)
differ from the former as the pressure, acting on the piston
Fig. 2 - Electrical connections and adjustment screws
NI-221E
Rev. 1 11/02
element, generates a force which, applied to the diaphragm, causes an elastic deformation. This deformation
is then used as in the previous case, to activate one or two
microswitches.
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 MA) – also the markings prescribed by
standard CEI EN 50014. Fig.1 shows the plate mounted
on explosionproof instruments.
Fig. 1 - Explosionproof instruments plate
1 CE marking and identification number of the notified body
responsible for production surveillance.
2 Apparatus classification according to ATEX 949 CE directive.
3 Type of protection and ambient temperature limits of opera-
tion.
4 Notified body that issued the type certificate and number of
said certificate.
4 SET POINT REGULATION
Each microswitch is independent and can be regulated by
means of a screw (for adjustment) in such a way that it is
released when the pressure reaches (increasing or decreasing) the desired value (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 rating plate showing the
set point calibration value. With factory calibration the
values are not indicated on the ratings, as these are temporary and will be modified with the definitive values. Prior
to installation the instrument must be calibrated and the
definitive calibration values written on the adhesive rating
plate using a suitable indelible ink pen.
1- Microswitch 1 set point
calibration screw
2- Microswitch 2 set point
calibration screw
3- Electrical connection identifi-
cation plate
4- Terminal block
Designation of the contacts:
C - Common
NA - Normally open
NC - Normally closed
INSTRUCTION MANUAL
If the instrument has been ordered with a specific cali-
bration, it is a good rule to check the calibration values
marked on the relevant adhesive label, prior to installation.
The position of the adjustment screw is given in figure 2.
The effect that the direction of rotation of the adjustment
screw has is described on the adhesive plate.
5 SET POIT CALIBRATION
In order to proceed with the calibration and the periodical
functional verification of the instrument a suitable calibra-
tion circuit (fig. 4) and an adequate pressure source is
required.
5.1 PRELIMINARY OPERATIONS
5.1.1 Weatherproof pressure switches (Series MW)
Remove the blocking device fixed to the side of the instrument case (Fig. 3).
Remove the cover by rotating it in an anticlockwise direction.
Fig. 3 - Weatherproof pressure switch blocking device
NI-221E
Rev. 1 11/02
• If the circuit is open at the working pressure, the switch
closes the circuit as the pressure increases when the
desired value is reached.
• If the circuit is closed at the working pressure, the switch
opens the circuit as the pressure decreases when the
desired value is reached.
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.
• If the circuit is open at the working pressure, the switch
closes the circuit as the pressure decreases when the
desired value is reached.
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 pointing downwards.
Fig. 5 - Calibration circuit
a - Plumbing wire
b - Plumbing
5.1.2 Explosionproof pressure switches (Series MA)
CAUTION: do not open the cover of explosionproof pres-
sure switches (Series MA) when energized, in explosive
atmospheres.
Loosen the locking headless screw situated on the cover
using a 1,5 hexagonal key then unscrew the cover. (Fig.
4).
Fig. 4 - Explosionproof pressure switch blocking device
c - Nut
d - Blocking bracket
5.2 CALIBRATION CIRCUIT AND OPERATIONS
Prepare the control circuit as indicated in Fig.5.
The warning lamps should be connected to contact 1 or 2
in the NO or NC position according to the required contact
action.
Connection of C and NO terminals
PS - Pressure switch
CA - Test pressure gauge
V1 - Inlet valve
V2 - Discharge valve
P - 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 in the contact codes) before proceeding
with the following operations it is necessary to proceed
with the adjustment of the dead band (see attachment NI-
706).
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. Act on the adjustment
screw of the second contact.
Repeat calibrating operations on the first contact, then 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.
Test fluid:
air for P ≤ 10 bar
water for P > 10 bar
INSTRUCTION MANUAL
5.3.1 Weatherproof pressure switches (Series MW)
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 blocking device as in Fig. 3.
5.3.2 Explosionproof pressure switches (Series MA).
Screw on the cover and block it using the headless screw
with which it is equipped (Fig. 4)
Mount on pressure connection and cable entry the protection caps supplied with the instrument. 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. 7 e 8). ). In this
case, during set point calibration the negative or positive
head must be taken into account (distance h in Fig.7 e 8).
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 leakages 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 MA) 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. 7 or 8 is therefore recommended..
CAUTION: fittings used for the electrical connection of
the pressure switch Series MA (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
(16AWG) are recommended using the pre-insulated fork
2
NI-221E
Rev. 1 11/02
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. 3
and 4.
6.4 SPECIAL NOTE FOR INSTALLATION OF
CATEGORY 1 / 2 G PRESSURE SWITCHES
Explosionproof pressure switches (Series MA) can be
installed on processes requiring apparatus of group II
category 1 in an ambient requiring apparatus of group II
category 2 (see Fig. 6).
Fig. 6 - Installation of Group II Cat. 1 / 2 G instruments
7 INSTRUMENT PLUMBING
7.1 Weatherproof p ressure switches (Series MW)
The plumbing, aimed as a guarantee against possible
tampering of the calibration and electrical connections,
can be carried out using a flexible steel wire (c) inserted
into the holes in the screw (a) and the bracket (e) provided
for this purpose (see Fig. 3).
7.2 Explosionproof pressure switches (Series MA )
Plumbing is not necessary as the cover is blocked with a
headless screw and the instrument does not have to be
opened when installed (see Fig. 4).
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 those in charge of the
plant.
The instrument comes into operation 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 MA), initial
inspections are to be carried out according to customer
procedures and at least in accordance with Standard EN60079-17.
NI-221E
INSTRUCTION MANUAL
9 FUNCTIONAL VERIFICATION
This will be carried out according to the Client’s control
procedures. Series MW and MWH instruments can be
verified on the plant if installed as illustrated in Fig. 7 e 8.
The instruments Series MA may be checked on site only if
apparatus suitable for explosive atmospheres 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.
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
Set point shift
Poor repeatability
Slow response
No actuation or
undue actuation
Undue actuation
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 7 e 8
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 MA) when energized, in explosive
atmospheres.
Unscrew the three-piece joint (10) (electrical cable tubing).
Permanent deformation of the sensitive ele-
ment due to fatigue or non-tolerated overages.
Variation of the elastic features of the sensitive
element due to its chemical corrosion.
O-ring wear (only MWH and MAH)
O-ring wear (only MWH and MAH)
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 electrical line.
Accidental shocks or excessive mechanical
vibrations.
CAUTION: do not open the cover of explosionproof pres-
sure switches (Series MA) when energized, in explosive
atmospheres.
Verification consists in checking the calibration values
and possibly regulating the adjustment screw (see §4 )
Verification consists in checking the calibration value
and possibly regulating the adjustment bush (see §5).
In case of explosionproof instruments (Series MA), 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.
Recalibrate or replace the sensitive element.
Recalibrate or replace the sensitive element
with another made of a suitable material. If
necessary apply a fluid separator.
Replace the piston subgroup and recalibrate.
Replace the piston subgroup and recalibrate.
Drain the process connection line and if
necessary modify it.
Check and clean line.
Open valve.
Provide instrument with suitable fluid separa-
tor.
Open the valve.
Replace the Microswitch.
Check all electrical joints.
Check the conditions of the electrical line.
Modify the mounting.
Remove the instrument cover and disconnect the electrical
cables from the terminal block and earth screws.
Remove the screws 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 MA) it is
recommended to follow - at least – the standard EN60079-17 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.
Rev. 1 11/02
NI-221E
INSTRUCTION MANUAL
WEATHERPROOF EXPLOSIONPROOF
Fig. 7 - Example of connections Fig. 8 - Example of cpnnections
Rev. 1 11/02
Fig. 9 - Example of mounting
Surface mounting
Montaggio a parete
2” pipe mounting
Montaggio su staffa da 2”
NOTE 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. 7 e 8).
In this case, during set point calibration the negative or
positive head must be taken into account. (distance h
in Fig.7 and 8).
LEGEND
1 - Fitting
2 - Drain plug
3 - Service valve
4 - Piping
5 - Three piece fitting
6 - Root valve with drain
7 - Process piping
8 - Three piece fitting
9 - “T” fitting
10 - Three piece fitting
11 - Curve
12 - Blocking joint
13 - M6 screws (No4)
14 - Bracket for 2” pipe
15 - Horizontal pipe
16 - Vertical pipe
ETTORE CELLA SPA Viale de Gasperi, 48 - Casella Postale (P.O. Box) 96 - I 20010 Bareggio (MILANO) ITALY
Telefoni +39 029036.1146/1147/1237/1241 - FAX +39 029036.1331 E-mail: cella@ecellaspa.com
Loading...