Transcript 6.0 selecting, installing, maintenance & troubleshooting

6.0 SELECTING, INSTALLING,
MAINTENANCE &
TROUBLESHOOTING PLC SYSTEM
INTRODUCTION
After the planning phase of the design, the equipment can be ordered. This decision
is usually based upon the required inputs, outputs and functions of the controller. The
first decision is the type of controller; rack, mini, micro, or software based. This
decision will depend upon the basic criteria listed below.
• Number of logical inputs and outputs.
• Memory - Often 1K and up. Need is dictated by size of ladder logic program. A ladder
element will take only a few bytes, and will be specified in manufacturers documentation.
• Number of special I/O modules - When doing some exotic applications, a large number of
special add-on cards maybe required.
• Scan Time - Big programs or faster processes will require shorter scan times. And, the
shorter the scan time, the higher the cost. Typical values for this are 1 microsecond per
simple ladder instruction
• Communications - Serial and networked connections allow the PLC to be programmed
and talk to other PLCs. The needs are determined by the application.
• Software - Availability of programming software and other tools determines the
programming and debugging ease.
INTRODUCTION
The process of selecting a PLC can
be broken into the steps listed below.
1. Understand the process to be
controlled
• List the number and types of inputs
and outputs.
• Determine how the process is to be
controlled.
• Determine special needs such as
distance between parts of the
process.
2. If not already specified, a single
vendor should be selected. Factors
that might be considered are :
• Manuals and documentation
• Support while developing programs
• The range of products available
• Support while troubleshooting
• Shipping times for emergency
replacements
• Training
• The track record for the company
• Business
practices
(billing,
upgrades/obsolete products, etc.)
3. Plan the ladder logic for the
controls.
4. Count the program instructions
and enter the values into the
sheets. Use the instruction times
and memory requirements for each
instruction to determine if the PLC
has sufficient memory, and if the
response time will be adequate for
the process.
INTRODUCTION
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.1 Define input/output capacity:
 The number of connection terminal at PLC I/O unit
 Including local expansion & I/O network.
 The total of Discrete vs Analog
Input / Output Unit Specifications
INPUT UNIT
TYPES
DC Input
AC Input
NO. MODEL
CAPASITY
CQM1-ID211
8 points
CQM1-ID212
16 points
CQM1-ID213
32 points
CQM1- IA121
8 points
CQM1-IA221
8 points
OUTPUT UNIT
TYPES
NO.MODEL
CAPASITY
Relay Output
CQM1-OC211
8 points
Units
CQM1-OC222
16 points
Transistor Output
CQM1-OD211
8 points
Units
CQM1-OD212
16 points
CQM1-OD213
32 points
CQM1-OD214
16 points
CQM1-OD215
8 points
CQM1-OD221
8 points
AC Output Unit
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.2 Define types of input / output:
• Every programmable logic controller must have some
means of receiving and interpreting signals from real-world
sensors such as switches, and encoders, and also be able
to effect control over real-world control elements such as
solenoids, valves, and motors.
• This is generally known as input/output
• To select the I/O, must know;
 Types of supply connected?– AC/DC
 Switching technique? – Relay(normal
condition)/Transistor(fast condition)/ AC(High voltage)
• The I/O Unit has two type;
i- Discrete I/O:
ii- Analog I/O
i- Discrete I/O:
•
A “discrete” data point is one with only two states on & off.
•
Digital I/O modules have digital I/O circuits that interface
to on/off sensors such as push-button and limit switches
and on/off actuators such as motor starters & pilot lights
•
Digital I/O modules cover electrical ranges from 5 to 276 V
AC or DC, and relay contact output modules are available
for ranges from 0 to 276 V AC or 0 to 175 V DC.
ii- Analog I/O
• Analog I/O modules perform the required A/D and D/A
conversions using up to 16-bit resolution.
• A range of analog signal levels can be accommodated,
including standard analog inputs and outputs and direct
thermocouple and RTD temperature inputs
• Analog I/O is commonly available for modular PLCs for
many different analog signal types, including:
• Voltage (0 to 10 volt, 0 to 5 volt)
• Current (0 to 20 mA, 4 to 20 mA)
• Thermocouple (mV)
• RTD (mV)
• Strain gauge (mV)
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.3 Define memory size:
 The ability to store a program in the PLC.
 1K, 6K, 8K, 12K, 14K
No. Model
Memory size
CQM1-CPU11-E
3.2 K-word Program Memory
CQM1-CPU21-E
1K-word Data Memory
CQM1-CPU41-E
CQM1-CPU42-E
7.2 K-word Program Memory
CQM1-CPU43-E
6K-word Data Memory
CQM1-CPU44-E
CPU unit specifications
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.4 Describe types of software language:
 Ladder diagram – most popular
 Instruction list
 Structured text
 Sequential function chart
 Function block diagram
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.5 Describe future system expansion:
• Today, the industry control system having a transformation
from traditional control method to automation control
system.
• Most popular automation system:
– Flexible Manufacturing System (FMS)
– Computer Integrated Manufacturing (CIM).
• PLC become the main agent for the automation system.
6.1 EXPLAIN PLC SELECTION PROCEDURE
6.1.6 Describe support & backup:
• Industrial automation control system need support &
backup units to carry out the existing control system in
case of damage.
• PLC is the most convenient control system for backup.
• PLC system is fast & easy to be install.
6.2 EXPLAIN INSTALLATION TECHNIQUE
6.2.1 Define site installation condition consideration:
- The PLC is resistance to harsh conditions & highly reliable,
but installing the PLC in a favorable site will maximize its
reliability & operating lifetime.
- Avoid installing the PLC in a site with any of the following
conditions:
- direct sunlight
- the ambient temperature exceeds the 0°C to 55°C range.
- the relative humidity exceeds the 10% to 90% RH range.
- consideration occurs due to sudden temperature changes.
- A site with corrosive gases, flammable gasses/ salt.
- A site with water, oil, @ chemical sprays.
- A site subjected to direct vibration @ shock.
6.2 EXPLAIN INSTALLATION TECHNIQUE
6.2.2 Define panel/ cabinet
installation:
• Consider PLC operation,
maintenance, and surrounding
conditions when installing the
PLC in a panel or cabinet.
• The operating temperature
range for the PLC is 0°C to
55°C.
• Be sure that there is adequate
ventilation for cooling.
– Allow enough space for air
circulation.
– Do not install the PLC above
equipment that generates a
large amount of heat, such as
heaters, transformers, or large
resistors.
– Install a cooling fan or system
when the ambient temperature
exceeds 55°C
The small PLC in panel
The big PLC in panel
2. Installing the CPU Unit & I/O
Unit
The small PLC must be installed in
the position shown below to ensure
adequate cooling.
See the picture below;
Do not install the small PLC in either of
the following
positions.
The small PLC can be installed on
a horizontal surface or on a DIN
track.
See the picture below ;
Lower the small PLC so that the
notch on the back of the PLC
catches the top of the DIN Track.
Push the PC forward until the lock
snaps into place.
See the picture below ;
For the big PLC before installing,
the Units have to compiled one
by one. There is no single Unit
that can be said to constitute a
Rack PLC. To build a Rack PLC,
we start with a Backplane. The
Backplane for the Omron PLC is
shown below.
The Backplane is a simple device having
two functions. The first is to provide
physical support for the Units to be
mounted to it.
The second is to provide the connectors
and electrical pathways necessary for
connecting the Units mounted to it. The
core of the PLC is the CPU.
The CPU contains the program consisting
of the series of steps necessary for the
control task. The CPU has a built-in power
supply, and fits into the rightmost position
of the Backplane.
The CPU of the big PLC has no I/O points
built in. So, in order to complete the PLC
we need to mount one or more I/O Units to
the Backplane.
Mount the I/O Unit to the Backplane by
locking the top of the I/O Unit into the slot
on the Backplane and rotating the I/O Unit
downwards as shown in the following
diagram.
Press down on the yellow tab at the bottom
of the slot, press the I/O Unit firmly into
position, and then release the yellow tab.
The figure below shows one I/O Unit mounted directly to the left of the CPU.
I/O Units are where the control connections are made from the PLC to all the
various input devices and output devices. As you can see from the figure
above, there is still some space available on the left side of the Backplane.
This space is for any additional I/O Units that may be required. The figure
below shows a total of eight I/O Units mounted to the Backplane.
•After the big PLC compiled in the backplane then the big PLC can be
installed on the DIN Rail.
•The DIN Rail Mounting Bracket shown below is necessary for mounting
the PLC to the DIN Rail.
•The following diagram is a view of the back of the Backplane. Attach one
Mounting Bracket to the left and right sides of the Backplane as shown
below.
Mount the Backplane to the DIN Rail
so that the claws on the Mounting
Brackets fit into the upper portion of
the DIN Rail as shown below.
Loosen the screws attaching the
Mounting
Brackets
to
the
Backplane. Slide the Backplane
upward as shown below so that the
Mounting Bracket and Backplane
clamp securely onto the DIN Rail.
Tighten the screws.
6.2 EXPLAIN INSTALLATION TECHNIQUE
6.2.3 Define precautions for wiring:
I/O Lines Noise
Power lines & high-voltage equipment
can cause electrical noise in the PLC ;
• Do not install the PLC in a panel or
cabinet with high-voltage equipment
• Do not run CPM1A I/O lines in the
same duct @ conduit as power lines.
• Allow at least 200 mm between the
PLC and nearby power lines
See the picture below;
Ensure that the PLC can be
accessed for normal operation and
maintenance;
• Provide a clear path to the PLC for
operation and maintenance. Highvoltage equipment or power lines
could be dangerous if they are in the
way during routine operations.
•The PLC will be easiest to access if
the panel or cabinet is installed about
3 to 5 feet above the floor
Installing I/O devices
I/O devices are attached at the place have been determined in the work
plan and wiring diagram. For switches are usually attached at the panel
while the sensor, selenoid and motor is usually placed at the machine to be
controlled.
Wiring and connections
Duct Work
Hanging Ducts If power cables carrying more
than 10 A 400 V, or 20 A 220 V must be run
along side the I/O wiring (that is, in parallel with it),
at least 300 mm must be left between the
power cables and the I/O wiring as shown below.
Floor Ducts
If the I/O wiring and power cables must be placed in the same duct (for
example, where they are connected to the equipment), they must be shielded
from each other using grounded metal plates.
Conduits
if Separating the PLC I/O lines, power and control lines, and power cables, as
shown in the following diagram.
I/O connections
Connect the I/O Devices to the I/O Units. Use 1.25-mm2 cables or larger The
terminals have screws with 3.5-mm diameter heads and self-raising pressure
plates. Connect the lead wires to the terminals as shown below. Tighten the
screws with a torque of 0.8 N _ m.
If you wish to attach solderless type terminals to the ends of the lead wires,
use terminals having the dimensions shown below.
The following diagrams show
the input configurations.
This input configuration depend on
specification of the Input Unit will
be used.
**See the specification before
install.
The following diagrams show the
output configurations.
This output configuration depend on
specification of the Output Unit will be
used.
**See the specification before install.
Power supply wiring (100 to 240 VAC)
-Wire a separate circuit for the CPM*A’s power supply circuit so that there isn’t a
voltage drop from the inrush current that flows when other equipment is turned
on.
-When several CPM*A PLCs are being used, it is recommended to wire the PCs
on separate circuits to prevent a voltage drop from the inrush current @ incorrect
operation of the circuit breaker.
-Use twisted power supply wires to prevent noise from the power supply lines.
Adding 1:1 isolation transformer may reduce electrical noise even further.
-The following example show the proper way to connect the power source to the
PLC.
-Use 1.25-mm2 cables or larger. The terminal blocks have screws with 3.5-mm
diameter heads and self-raising pressure plates.
-For connecting to the terminal blocks, use round crimp terminals for 3.5-mm
diameter heads. Directly connecting stranded wires to the terminal blocks may
cause a short-circuit.
Grounding
This PLC has sufficient protection against noise, so it can be used without grounding
except for special much noise.
However, when grounding it should be done conforming to below items:
- Ground the PLC as independently as possible.
- Class 3 grounding should be used (grounding resistance 100Ω or
less).
- When independent grounding is impossible, use the joint grounding method as
shown in the figure below (B).
- Use thicker grounding wire. Make sure the cable used for grounding at least 2mm2.
- Grounding site and the green cable must be terminated at the cable lug. Cable lug
must be tightened and soldered
- Grounding point should be as near as possible to the PLC to minimize the distance
of grounding cable.
Expansion unit
- The Expansion Unit or Expansion I/O Unit are usually attached when
amount of I/O devices to be controlled increase
- its amount over than capacities of the existing I/O Unit or attached
when needed to a special need like temperature sensor.
- The following shown the example of Expansion Units.
Expansion Unit of the big PLC
For the small PLC, use the following
procedure when connecting an Expansion Unit
or Expansion I/O Unit;
Insert the Expansion I/O Unit’s connecting cable into
the CPU Unit’s or the Expansion I/O Unit’s expansion
connector.
-Remove the cover from the CPU Unit’s or the
Expansion I/O Unit’s expansion connector.
-Use a flat-blade screwdriver to remove the
cover from the Expansion I/O Connector.
Replace the cover on the CPU Unit’s or the Expansion
I/O Unit’s expansion connector.
For the big PLC use the following picture when connecting an
Expansion Unit or Expansion I/O Unit;
6.2 EXPLAIN INSTALLATION TECHNIQUE
6.2.4 Define technique to solve instable voltage &
voltage spike problems:
• Voltage spike: A sudden, short surge in voltage. Voltage
spikes can be caused by lightning, power outages, short
circuits, or power transitions in large equipment on the same
power line.
• To avoid voltage spike (suppression of Inductive Loads):
– Install a snubber circuit, typically a resistor/capacitor network (RC).
– Install metal oxide varistor (MOV).
• It’s may limit the voltage spike as well as control the rate of
current change through the inductor.
6.3 EXPLAIN PLC MAINTENANCE &
TROUBLESHOOTING METHODS
6.3.1 Determine PLC external faults:
1. Input & Output faults ( sensor & actuator)
•
•
60% - 80% of the automation system faults is because of the
input & output equipment (sensor & actuator).
Root cause:
–
–
–
The sensor position change.
The internal contact of the sensor disconnected.
The motor winding @ solenoid valve @ sensor become short circuit
(overload).
2. Wiring faults
•
Root cause:
• Conductor in the cable disconnected.
• Loose in terminal @ equipment connector.
• The conductor become oxidize
3. Communication faults
•
Root cause:
• Conductor in communication cable disconnected.
• Connection pin damage.
• Loose in terminal connection.
• Interference in communication connection cable
(motor, coil, high voltage, etc)
• Short circuit.
3. Power supply interruption
• If the supply voltage reduce less that 85%, PLC will
automatically stop.
6.3 EXPLAIN PLC MAINTENANCE &
TROUBLESHOOTING METHODS
6.3.2 Determine PLC internal faults:
• Internal damage may happened because;
–
–
–
–
Short circuit in transistor at output module.
Optocoupler in input module malfunction.
Short circuit (fuse, microprocessor, RAM, ROM).
Backup batteries malfunction.
6.3 EXPLAIN PLC MAINTENANCE &
TROUBLESHOOTING METHODS
PLC Maintenance
1. Applying the safety procedure
During execution of the work, the safety procedure must be executed
truly so that the risk of the work accident can be avoided.
Example of applying the safety procedure;
• Use the safety equipment
• Follow the instruction of safety procedure
• Comprehending fringe of writing on the wall or emergency
2. Checking the installation and power supply
To do the maintenance and reparation of the PLC system, one of the
important matter that must be done is perform the inspection to the PLC
installation as according to the manual instruction, for example;
3. Maintain and repair the PLC
The maintenance and reparation of the PLC is all activity which
intentionally be done to the PLC by following a systematic procedure
with target so that the PLC which we own always can be used in the
best condition, fluent, peaceful and technically has along live.
6.3 EXPLAIN PLC MAINTENANCE &
TROUBLESHOOTING METHODS
6.3.5 Execute preventive maintenance methods:
Preventive maintenance
• The main system components of a PLC system are semiconductors, and
it contains few components with limited lifetimes. Poor environmental
conditions, however, can lead to deterioration of the electrical components,
the harsher the environment, the more frequent the maintenance
necessary.
• Preventive maintenance of programming controller systems includes only
a few basic procedures which will greatly reduce the failure rate of system
components.
• The standard period for maintenance checks is 6 months to 1 year, but
more frequent checks are required if the PLC is operated in more
demanding conditions. When inspecting one or two times per six
months, check the following items.
Preventive maintenance
Types of preventive maintenance should be done on the PLC:
• Periodically clean @ replace any filters that have been installed in
enclosures at frequency dependent on the amount of dust in the area.
• Do not allow dirt and dust to accumulate on the PLC’s components;
the central processing unit and I/O system are not designed to be dust
proof.
• Periodically check the connections to the I/O modules to ensure that
all plugs, sockets, terminal strips, and modules have good
connections. Also, check that the module is securely installed.
• Ensure that heavy, noise-generating equipment is not located too
close to the PLC.
• Make sure that unnecessary items are kept away from the equipment
• inside the enclosure.
• If the PLC system enclosure is in an environment that exhibits
vibration, install a vibration detector that can interface with the PLC as
a preventive measure.
Preventive maintenance
Preventive maintenance consisted of several activity below;
Pre maintenance
Pre maintenance is a preparation activity, matters which require
to be prepared for example;
• Prepare the maintenance equipment
• Prepare the maintenance material especially weared routinely,
for example; cleanser material, Lubricant material, corrosion
preventative material, etc.
• Prepare the maintenance documentation
• Prepare the power supply and air compressor
Daily maintenance
The following table shows the inspection and items which are
to be checked daily.
Periodic maintenance
Check the following items once or twice every six months, and
perform the needed corrective actions.
Several example of the maintenance
activity on the Omron PLC is shown
below;
CPU and Power Supply Fuses
To replace a fuse, follow the steps below:
• Turn OFF the power to the PLC.
• Remove the fuse holder by turning it
approximately 50/ counterclockwise with a
standard screwdriver.
• Remove the fuse from the holder.
• Insert a new fuse.
• Reattach the fuse holder by turning it
approximately 50/ clockwise with a
standard screwdriver.
Output Unit Fuses
To replace a fuse, follow the steps below. Use only UL/CSA certified
replacement fuses.
• Turn OFF the power to the PLC.
• Detach the terminal block by
unlocking the lock levers at the top and
bottom of the terminal block.
• While pushing down the lock lever on
the Backplane with a screwdriver as
shown below, remove the Output Unit.
• Remove the screw from the top
of the Unit (Phillips screwdriver).
• Detach the case from the Unit
(flat-blade screwdriver).
• Pull out the printed circuit board.
• Insert a new fuse. A spare fuse
is provided inside the rear of the
case when the Unit is delivered.
• Reassemble in reverse order of
assembly.
Output Unit Relays
To replace a Relay, follow the steps
below:
• Turn OFF the power to the PLC.
• Detach the terminal block by
unlocking the lock levers at the top
and bottom of the terminal block.
• While pushing down the lock lever
on the Backplane with a screwdriver
as shown below, remove the Output
Unit.
•Remove the screw from
the top of the Unit
(Phillips screwdriver).
•Detach the case from the
Unit (flat-blade
screwdriver).
Pull out the printed circuit board. The
Relays are placed on the PLC boards
of individual Units as shown in the
figures below :
•A Relay puller is provided inside the rear of the case when the
Unit is delivered. Use the Relay puller to pull out the Relay as
shown below. Insert a new Relay.
•Reassemble in reverse order of assembly.
Batteries
Some RAM Packs use a battery. When the battery is nearly
discharged, the ALARM indicator blinks and the message “BATT
FAIL” appears on the Programming Console. When this occurs,
replace the battery within one week to avoid loss of data. The battery
comes together with its connector as a set. To replace the Battery
Set, follow the steps below. The entire replacement must be
completed within five minutes to ensure that the
data will not be lost.
If you are using model C200H-CPU11-E as the CPU, the battery is
installed in the Unit upon delivery.
•Turn OFF the power to the PLC. (If the power was not already ON,
turn the power ON for at least one minute before turning the power
OFF.)
• Remove the cover from the battery compartment of the RAM Pack.
• Remove the old Battery Set.
• Install the new Battery Set as shown in the following diagram.
•Replace the cover of the battery compartment.
•Press CLR, FUN, MONTR, MONTR or just turn the power to the
PC OFF and then ON again to clear the error message on the
Programming Console.
6.3 EXPLAIN PLC MAINTENANCE &
TROUBLESHOOTING METHODS
6.3.6 Execute steps for troubleshooting PLC systems:
•The following example
explains the procedure
for determining the
cause of troubles as well
as the errors and
corrective actions to the
Omron PLC.
•Use the following
flowcharts to
troubleshoot errors that
occur during operation.
1. Main Check
2. Fatal Error Check
3. Non- Fatal Error Check
4. I/O Check
The I/O check flowchart is based on the following ladder diagram
section.
5. Environmental Conditions Check
6. Memory Error Check