Kobold SCH-27 User manual

Operating Instructions
for
Pressure Switch
Model: SCH-27/SCH-28

SCH-27/-28
page 2 SCH-27/-28 K04/0722
We don’t accept warranty and liability claims neither upon this publication nor in
case of improper treatment of the described products.
The document may contain technical inaccuracies and typographical errors. The
content will be revised on a regular basis. These changes will be implemented in
later versions. The described products can be improved and changed at any time
without prior notice.
© Copyright
All rights reserved.

SCH-27/-28
SCH-27/-28 K04/0722 page 3
1. Contents
1. Contents .......................................................................................................3
2. Note..............................................................................................................4
3. Instrument Inspection....................................................................................4
4. Regulation Use .............................................................................................5
5. Mechanical Connection.................................................................................5
5.1 Important Information...........................................................................5
5.2 Installation ...........................................................................................7
6. Electrical Connection....................................................................................8
6.1 Set Point Calibration............................................................................9
7. Commissioning ...........................................................................................10
8. Working Limits ............................................................................................11
8.1 Working temperature.........................................................................11
8.2 Working pressure ..............................................................................11
8.3 Cyclic and dynamic pressures...........................................................11
8.4 Overpressure.....................................................................................11
8.5 Vibrations...........................................................................................11
8.6 Micro-switch.......................................................................................11
8.7 Differential .........................................................................................12
8.8 Protection degree..............................................................................12
8.9 Corrosive fluids and gas liquids.........................................................12
9. Improper usage...........................................................................................12
9.1 Failure for fatigue...............................................................................12
9.2 Failure for overpressure.....................................................................13
9.3 Failure for corrosion...........................................................................13
9.4 Failure for explosion ..........................................................................13
9.5 Failure for vibrations..........................................................................13
9.6 Stress for vibrations...........................................................................13
9.7 Mechanical stress..............................................................................14
10. Maintenance...............................................................................................14
10.1 Regular check....................................................................................14
10.2 Recalibration......................................................................................14
11. Technical Information..................................................................................15
12. Order codes................................................................................................17
13. Dimensions.................................................................................................19
14. Disposal......................................................................................................23
15. EU Declaration of Conformance .................................................................24
Manufactured and sold by:
Kobold Messring GmbH
Nordring 22-24
D-65719 Hofheim
Tel.: [phone]
Fax: [phone]
E-Mail: [e-mail]
Internet: www.kobold.com

SCH-27/-28
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2. Note
Please read these operating instructions before unpacking and putting the unit
into operation. Follow the instructions precisely as described herein.
The instruction manuals on our website www.kobold.com are always for currently
manufactured version of our products. Due to technical changes, the instruction
manuals available online may not always correspond to the product version you
have purchased. If you need an instruction manual that corresponds to the
purchased product version, you can request it from us free of charge by email
([e-mail]) in PDF format, specifying the relevant invoice number and
serial number. If you wish, the operating instructions can also be sent to you by
post in paper form against an applicable postage fee.
The devices are only to be used, maintained and serviced by persons familiar
with these operating instructions and in accordance with local regulations
applying to Health & Safety and prevention of accidents.
When used in machines, the measuring unit should be used only when the
machines fulfil the EC-machine guidelines.
as per PED 2014/68/EU
PS ≤ 200 bar
In acc. with Article 4 Paragraph (3), "Sound Engineering Practice", of the PED
2014/68/EU no CE mark.
PS > 200 bar
Category 1, module A
3. Instrument Inspection
Instruments are inspected before shipping and sent out in perfect condition.
Should damage to a device be visible, we recommend a thorough inspection of
the delivery packaging. In case of damage, please inform your parcel service /
forwarding agent immediately, since they are responsible for damages during
transit.
Scope of delivery:
The standard delivery includes:
•Pressure Switches model: SCH-27 or SCH-28

SCH-27/-28
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4. Regulation Use
Any use of the Pressure Switch, model: SCH-27 or SCH-28, which exceeds the
manufacturer’s specification, may invalidate its warranty. Therefore, any resulting
damage is not the responsibility of the manufacturer. The user assumes all risk
for such usage.
5. Mechanical Connection
5.1 Important Information
The instrument described in this manual has been designed and produced in
conformity to the following standards in force. All components are submitted to
severe quality and traceability controls. The quality management system is
certified according to the ISO 9001 standard. This manual contains important
information about the use and the installation of the gauge in safe conditions.
Therefore, it is highly recommended to read carefully the following instructions
before using the instrument.
The instrument works in safe conditions when correctly selected and installed in
the system and when the rules concerning the product as well
as the maintenance procedures established by the manufacturer are respected.
The staff charged with the selection, installation and maintenance of the
instrument must be able to recognize the conditions that may
negatively affect the instrument's ability to work and which may lead to premature
breakage. The staff must therefore be technically qualified
and properly trained, and must carry out the procedures called for in the plant
regulations.
Warning!
-The manufacturer disclaims all responsibility in case of damages
caused by the improper use of the product and by the non-respect
of the instructions reported in this manual.
-Follow carefully the specific safety rules an case of measuring
oxygen pressure, acetylene, inflammable or toxic gas or liquids.
-Disconnect the instruments only after depresurrization of the
system.
-The process fluids residuals in the disassembled instruments
could affect people, the environment and the system. It is highly
recommended to take proper precautions.

SCH-27/-28
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Attention!
-Before installation be sure that the right instrument has been
selected following the working conditions and in particular range,
the working temperature and the compatibility between the
material used and the process fluid.
-This manual does not concern the instruments conforming to
standard 2014/34/EU (ATEX).
-The product warranty is no longer valid in case of non-
authorized modifications and of wrong use of the product.
-The user is totally responsible for the instrument installation and
maintenance.

SCH-27/-28
SCH-27/-28 K04/0722 page 7
5.2 Installation
Fix the instrument thread forcing by a key which should fit with the process
connection without forcing by hand on the case. As for the cylindric thread
process connection is concerned (Gas or metric) a head gasket compatible with
the fluid or gas to measure should be used. (Fig.1).
In case of conic connection thread (NTP or Conic gas), a PTFE tape on the male
thread (Fig.2) ensures the sealing before proceeding to screw and then to the
fixing.
In case of conic connection thread (NTP or Conic gas), a PTFE tape on the male
thread (Fig.2) ensures the sealing before proceeding to screw and then to the
fixing.
In both cases it is necessary to fix the instrument through two keys: one on the
flat sides of the instrument process connection, the other one on the pressure
output. All instruments should be mounted in a vertical position unless otherwise
shown on the label.
In order to make the instrument dismounting easier it is recommended to mount a
shut-off valve between the system and the instrument.

SCH-27/-28
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6. Electrical Connection
Pressure switches type: SCH-27 are equipped with micro-switch suitable for
direct connection through fork wire terminal screws and clamp for ground
connection both internal and external provided of cable terminal.
Differential pressure switches model SCH-28 are provided of internal terminal
blocks with screws terminals (Figure 5) with cables whose maximum section
should be di 2.5 mm² and terminal block for ground connection both internal and
external provided of wire terminal. In order to perform the electrical connection,
proceed to unplug the pressure switch case top. For connection, use cables
whose section is adequate to the requested electrical charge (1.2...2.5 mm2 -
14...16 AWG) in conformity to the technical requirements concerning connection
and commutation instruments. The cable diameter should be suitable for passing
through cable glands.
Wiring:
- do not torch or pull the cable excessively;
- cables should not be frayed and the isolating sheath should not be cut or
damaged;
- false contacts should be prevented and the terminal screws should be properly
tightened;
- calibration should not be modified (factory calibration).
No residue should remain inside the case and the top should be fastened by a
lock nut.

SCH-27/-28
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6.1 Set Point Calibration
If not otherwise specified in the order the instrument is supplied with a set point
calibrated on the lowest possible value. Calibration must be performed fixing the
pressure switch and a laboratory instrument for the pressure measuring in
parallel to a pressure output. And (Fig. 6). For calibration, please proceed as
follows:
Instrument provided of 1 micro-switch
1. Connect the micro-switch to warning lamp or a sound source as shown in fig.5
in order to be warned if any malfunction should occur during operation;
2. apply a pressure or a vacuum whose value should be the same as the value of
operation;
3. when the proper operation pressure value is reached and no warning signal
hasn’t been detected, it is necessary to rotate the microswitch adjustment screw
until the successful operation signal is on;
4. conversely, if the operation signal is shown before reaching the expected
pressure value, rotate the adjustment screw clockwise until the operational
signal is off.
5. proceed by producing several pressure ups and downs in order to verify the
set point accuracy as described in points 8 and 9.
Instrument provided of 2 micro-switches
The calibration procedure is the same as described for instruments provided with
1 microswitch considering that these operations should be repeated for one
micro-switch at a time alternatively until the desired operation accuracy is
reached. This is necessary because the two micro-switches interaction on the
same measuring instrument.

SCH-27/-28
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7. Commissioning
Commissioning should always be performed carefully in order to prevent any
shock or sudden temperature variations. Slowly open the shut-off valves placed
between the instrument and the process.
As for differential pressure switches model SCH-28, please refer to figure 7 and
follow the following instructions:
1. open the by-pass valve “1”;
2. open the root valve “3”;
3. open the shut-off valve “2” of the positive side (+);
4. shut the by-pass valve “1”;
5. open the shut-off valve “2” of the negative side (-).
All obstruction of the sensing element pressure abduction pipe should be avoided
in order to prevent any repeated and unnecessary rearm of the micro-switch. In
case of malfunction, the instrument must be completely depressurized and
isolated through a shut-off valve before removal.
Figure 7