chapter 6 selecting installing maintenance troubleshooting plc system

6.0 SELECTING, INSTALLING, 6.0 SELECTING, INSTALLING, 6.0 SELECTING, INSTALLING, 6.0 SELECTING, INSTALLING,

MAINTENANCE & MAINTENANCE & MAINTENANCE & MAINTENANCE &

TROUBLESHOOTING PLC SYSTEMTROUBLESHOOTING PLC SYSTEMTROUBLESHOOTING PLC SYSTEMTROUBLESHOOTING PLC SYSTEM

INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONAfter 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.

INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONThe 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.

INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION

6.1 EXPLAIN PLC SELECTION PROCEDURE6.1 EXPLAIN PLC SELECTION PROCEDURE6.1 EXPLAIN PLC SELECTION PROCEDURE6.1 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 UNIT

TYPES NO. MODEL CAPASITY

DC Input

CQM1-ID211 8 pointsCQM1-ID212 16 pointsCQM1-ID213 32 points

AC Input CQM1- IA121 8 pointsCQM1-IA221 8 points

OUTPUT UNIT

TYPES NO.MODEL CAPASITY

Relay Output

Units

CQM1-OC211 8 pointsCQM1-OC222 16 points

Transistor Output

Units

CQM1-OD211 8 pointsCQM1-OD212 16 pointsCQM1-OD213 32 pointsCQM1-OD214 16 pointsCQM1-OD215 8 points

AC Output Unit CQM1-OD221 8 points

Input / Output Unit Specifications


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)


6.1.3 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 Memory1K-word Data MemoryCQM1-CPU21-E

CQM1-CPU41-E7.2 K-word Program Memory

6K-word Data Memory

CQM1-CPU42-ECQM1-CPU43-ECQM1-CPU44-E

CPU unit specifications


6.1.4 Describe types of software language:

Ladder diagram most popular

Instruction list

Structured text

Sequential function chart

Function block diagram


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.


6.1.6 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 TECHNIQUE6.2 EXPLAIN INSTALLATION TECHNIQUE6.2 EXPLAIN INSTALLATION TECHNIQUE6.2 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 0C to 55C 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.


6.2.2 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 0C to

55C.

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 55C

The small PLC in panel

The big PLC in panel

2. Installing the CPU Unit & I/OUnit

The small PLC must be installed inthe position shown below to ensureadequate cooling.

See the picture below;

Do not install the small PLC in either of the following positions.

The small PLC can be installed ona horizontal surface or on a DINtrack.

See the picture below ;

Lower the small PLC so that thenotch on the back of the PLCcatches the top of the DIN Track.Push the PC forward until the locksnaps 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 havingtwo functions. The first is to providephysical support for the Units to bemounted to it.

The second is to provide the connectorsand electrical pathways necessary forconnecting the Units mounted to it. Thecore of the PLC is the CPU.

The CPU contains the program consistingof the series of steps necessary for thecontrol task. The CPU has a built-in powersupply, and fits into the rightmost positionof the Backplane.

The CPU of the big PLC has no I/O pointsbuilt in. So, in order to complete the PLCwe need to mount one or more I/O Units tothe Backplane.

Mount the I/O Unit to the Backplane bylocking the top of the I/O Unit into the sloton the Backplane and rotating the I/O Unitdownwards as shown in the followingdiagram.

Press down on the yellow tab at the bottomof the slot, press the I/O Unit firmly intoposition, 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 thevarious input devices and output devices. As you can see from the figureabove, 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 figurebelow 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 beinstalled 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 Railso that the claws on the MountingBrackets fit into the upper portion ofthe DIN Rail as shown below.

Loosen the screws attaching theMounting Brackets to theBackplane. Slide the Backplaneupward as shown below so that theMounting Bracket and Backplaneclamp securely onto the DIN Rail.Tighten the screws.


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 beaccessed for normal operation andmaintenance;

Provide a clear path to the PLC foroperation and maintenance. High-voltage equipment or power linescould be dangerous if they are in theway during routine operations.

The PLC will be easiest to access ifthe panel or cabinet is installed about3 to 5 feet above the floor

Installing Installing Installing Installing I/O devicesI/O devicesI/O devicesI/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 Wiring Wiring Wiring and connectionsand connectionsand connectionsand connections

Duct WorkDuct WorkDuct WorkDuct WorkHanging 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 connectionsConnect 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*As power supply circuit so that there isnt 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.

GroundingThis PLC has sufficient protection against noise, so it can be used without groundingexcept 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 100 or less).- When independent grounding is impossible, use the joint grounding method asshown 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 lugmust be tightened and soldered

- Grounding point should be as near as possible to the PLC to minimize the distanceof grounding cable.

Expansion unitExpansion unitExpansion unitExpansion 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 followingprocedure when connecting an Expansion Unitor Expansion I/O Unit;

-Remove the cover from the CPU Units or theExpansion I/O Units expansion connector.

-Use a flat-blade screwdriver to remove thecover from the Expansion I/O Connector.

Insert the Expansion I/O Units connecting cable into the CPU Units or the Expansion I/O Units expansion connector.

Replace the cover on the CPU Units or the Expansion I/O Units expansion connector.

For the big PLC use the following picture when connecting an Expansion Unit or Expansion I/O Unit;


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).

Its may limit the voltage spike as well as control the rate of

current change through the inductor.

6.3 EXPLAIN PLC MAINTENANCE & 6.3 EXPLAIN PLC MAINTENANCE & 6.3 EXPLAIN PLC MAINTENANCE & 6.3 EXPLAIN PLC MAINTENANCE &

TROUBLESHOOTING METHODSTROUBLESHOOTING METHODSTROUBLESHOOTING METHODSTROUBLESHOOTING METHODS

6.3.1 Determine PLC external faults:

1.1.1.1. Input & Output faults ( sensor & actuator)Input & Output faults ( sensor & actuator)Input & Output faults ( sensor & actuator)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).

2.2.2.2. Wiring faultsWiring faultsWiring faultsWiring faults Root cause:

Conductor in the cable disconnected.

Loose in terminal @ equipment connector.

The conductor become oxidize

3.3.3.3. Communication faultsCommunication faultsCommunication faultsCommunication 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.

3.3.3.3. Power supply interruption Power supply interruption Power supply interruption Power supply interruption

If the supply voltage reduce less that 85%, PLC will

automatically stop.



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.



1. Applying the safety procedure1. Applying the safety procedure1. Applying the safety procedure1. 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

PLC Maintenance

2. Checking the installation and power supply2. Checking the installation and power supply2. Checking the installation and power supply2. 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 PLC3. Maintain and repair the PLC3. Maintain and repair the PLC3. Maintain and repair the PLC

The maintenance and reparation of the PLC is all activity whichintentionally be done to the PLC by following a systematic procedurewith target so that the PLC which we own always can be used in thebest condition, fluent, peaceful and technically has along live.



6.3.5 Execute preventive maintenance methods:

Preventive maintenancePreventive maintenancePreventive maintenancePreventive 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 onlya few basic procedures which will greatly reduce the failure rate of systemcomponents.

The standard period for maintenance checks is 6 months to 1 year, butmore frequent checks are required if the PLC is operated in moredemanding conditions. When inspecting one or two times per sixmonths, check the following items.


Types of preventive maintenance should be done on the PLC:Types of preventive maintenance should be done on the PLC:Types of preventive maintenance should be done on the PLC: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 PLCs 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 consisted of several activity below;

Pre maintenancePre maintenancePre maintenancePre maintenancePre 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 maintenanceDaily maintenanceDaily maintenanceDaily maintenanceThe following table shows the inspection and items which are to be checked daily.

Periodic maintenancePeriodic maintenancePeriodic maintenancePeriodic maintenanceCheck 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 FusesCPU and Power Supply FusesCPU and Power Supply FusesCPU 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 FusesOutput Unit FusesOutput Unit FusesOutput 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 RelaysOutput Unit RelaysOutput Unit RelaysOutput 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. TheRelays are placed on the PLC boardsof individual Units as shown in thefigures 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.

BatteriesBatteriesBatteriesBatteries

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 thedata 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 powerOFF.) 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.


TROUBLESHOOTING METHODSTROUBLESHOOTING METHODSTROUBLESHOOTING METHODSTROUBLESHOOTING METHODS6.3.6 Execute steps for troubleshooting PLC systems:6.3.6 Execute steps for troubleshooting PLC systems:6.3.6 Execute steps for troubleshooting PLC systems: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 Check1. Main Check1. Main Check1. Main Check

2. Fatal Error Check2. Fatal Error Check2. Fatal Error Check2. Fatal Error Check

3. Non3. Non3. Non3. Non---- Fatal Error CheckFatal Error CheckFatal Error CheckFatal Error Check

4. I/O Check4. I/O Check4. I/O Check4. I/O Check

The I/O check flowchart is based on the following ladder diagram section.

5. Environmental Conditions Check5. Environmental Conditions Check5. Environmental Conditions Check5. Environmental Conditions Check

6. Memory Error Check6. Memory Error Check6. Memory Error Check6. Memory Error Check

chapter 6 selecting installing maintenance troubleshooting plc system

Documents

plc selection procedure6

plc canbe

plc io unit

number of special io

number of logical inputs

number of connection

scan time big programs

theresponse time