EIT IDC Troubleshooting PLCs

7/27/2019 EIT IDC Troubleshooting PLCs

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TroubleshootingPLCs

By

Steve Mackay

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Welcome to this webinar

T h e r e a r e a t l e a s t 3 w a y s t o i n t e r a c t w i t h y o u r p r e s e n t e r

t o d a y .

1 . U s e t h e T e x t

T e x t T e x t

T e x t t a b , n e a r b o t t o m l e f t o f y o u r s c r e e n .

T y p e t h e m e s s a g e i n t h e s p a c e n e x t t o t h e “ S e n d ”

b u t t o n , t h e n e n t e r o r c l i c k S e n d . ( E n s u r e “ A l l ” i s

s e l e c t e d i n t h e d r o p - d o w n m e n u u n d e r t h e t y p i n g a r e a )

2 . U s e t h e E m o t i c o n s

E m o t i c o n s E m o t i c o n s

E m o t i c o n s s e l e c t i o n i n t h e t e x t w i n d o w –

c h o o s e a n e m o t i c o n t h e n c l i c k s e n d o r e n t e r .

3 . T a l k

T a l k T a l k

T a l k ! C l i c k t h e P u s h T o T a l k

P u s h T o T a l k P u s h T o T a l k

P u s h T o T a l k b u t t o n . T h e b u t t o n w i l l

c h a n g e t o y e l l o w w h e n y o u a r e q u e u e d , t h e n g r e e n t o

s h o w t h a t y o u r m i c r o p h o n e i s l i v e .

R e m e m b e r t o c l i c k i t a g a i n w h e n y o u h a v e s p o k e n

T h i s 4 5 m i n u t e s e s s i o n w i l l c o m m e n c e s h o r t l y

T h i s 4 5 m i n u t e s e s s i o n w i l l c o m m e n c e s h o r t l y T h i s 4 5 m i n u t e s e s s i o n w i l l c o m m e n c e s h o r t l y

T h i s 4 5 m i n u t e s e s s i o n w i l l c o m m e n c e s h o r t l y

RH

Troubleshooting PLCs

IDC Technologies and EIT



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EIT MicroCourse Series

• E v e r y t w o w e e k s w e p r e s e n t a

4 5 m i n u t e i n t e r a c t i v e c o u r s e

• P r a c t i c a l , u s e f u l w i t h Q & A

t h r o u g h o u t

• P I D l o o p T u n i n g / A r c F l a s h

P r o t e c t i o n p r e s e n t e d , s o f a r

• U p c o m i n g :

– F u n c t i o n a l S a f e t y

– T r o u b l e s h o o t i n g C o n v e y e r s

a n d m u c h m u c h m o r e … . .

• G o t o

h t t p : / / w w w . e i t . e d u . a u / f r e e -

c o u r s e s

• Y o u g e t t h e r e c o r d i n g a n d

s l i d e s





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Objectives• Quickly interpret,

isolate and fixcommon hardwareproblems related toPLC input/outputs

• Troubleshoot PLCsoftware

• Identify datacommunicationsproblems

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Topics

• Introduction to PLC

• Internal or External

Problem

• Internal Problems

• External Problems -

I/O and Comms

• Applications

• Conclusion





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Industrial Automation Skills“ T o d a y ’ s I n d u s t r i a l A u t o m a t i o n e n g i n e e r a n d t e c h n i c i a n s h o u l d b e a b l e t o

t r o u b l e s h o o t , i d e n t i f y , p r e v e n t a n d f i x c o m m o n P L C a n d S C A D A p r o b l e m s .

I f y o u h a v e w o r k e d i n i n d u s t r y , y o u a r e p r o b a b l y f a m i l i a r w i t h P L C s a n d

S C A D A s y s t e m s a n d u n d e r s t a n d t h e i r b a s i c o p e r a t i o n .

Y o u w a n t t o b e a b l e t o q u i c k l y d i a g n o s e p r o b l e m s u s i n g y o u r P L C s o f t w a r e ;

k n o w h o w t o c o n n e c t t o t h e r i g h t P L C p r o c e s s o r o n l i n e , m a k e m i n o r

c h a n g e s t o g e t t h e m a c h i n e r u n n i n g a n d h a v e t h e k n o w - h o w t o t e s t n e w

i d e a s a n d h a r d w a r e c o m p o n e n t s . I n a d d i t i o n , y o u w a n t t o b e a b l e t o d o

t r o u b l e s h o o t i n g a n d p r o b l e m s o l v i n g o f y o u r a s s o c i a t e d S C A D A s y s t e m ” .

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Introduction to the PLCIntroduction to the PLCIntroduction to the PLCIntroduction to the PLC





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Introduction to the PLC• “PLC” means “Programmable Logic Controller”. Theword “Programmable” differentiates it from theconventional hard-wired relay logic

• The PLC as a unit consists of a processor to executethe control action on the field data provided by inputand output modules

• In a programming device, the PLC control logic is firstdeveloped and then transferred to the PLC

• PAC or Programmable Automation Controller

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What can a PLC do?• It can perform relay-switching tasks.

• It can conduct counting, calculation and comparison of analogprocess values.

• It offers flexibility to modify the control logic, whenever required,in the shortest time.

• It responds to the changes in process parameters within

fraction of seconds.• It improves the overall control system reliability.

• It is cost effective for controlling complex systems.

• Trouble-shooting becomes simpler and faster.

• An operator can easily interact with the process with the help of the HMI (Human-Machine Interface) computer.





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Basic block diagram of the PLC

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Working of a PLC CPU





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Ladder diagram

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Ladder program execution





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Internal or ExternalInternal or ExternalInternal or ExternalInternal or External

ProblemProblemProblemProblem

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Internal or External Problem ?

• Over 80% of malfunctions are with I/O

modules and field equipment

• Problems related to specific I/O module or

I/O device are external problems

• Large groups of failures – internals of PLC





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Internal ProblemsInternal ProblemsInternal ProblemsInternal Problems

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Internal Problems

• Check earthing/grounding is correct

• Check power supply to PLC is within

correct range and ac ripple on dc supplies

is not excessive

• Batteries on PLC are OK

• PLC program hasn't been corrupted

• Examine internal diagnostics for a crash of

PLC program





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External Problems

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External Problems – digital

Inputs• Check Power supply to module

• Look for where power to digital Input

comes from

• Check fuses/breakers

• Adequate changes of voltage to Input

• Digital input fine ===> PLC program

problem





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Discrete DC input module

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External Problems – digital

outputs• Check Power supply to module

• Check power output from PLC

• Check fuses

• Force digital outputs on and off

• Use test load rather than open circuit –

why ?





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Discrete DC output module

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External Problems – analog

inputs• Move field device through

full range of current – 4-

20mA

• Hook up signal transmitter if you need to be absolutely

sure.





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External Problems – analog

outputs• Force output to specific value and observe

• Check external wiring

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ApplicationsApplicationsApplicationsApplications





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Remote troubleshooting

• Be careful with remote troubleshooting

about industrial network security

• Hackers are about 24x7

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Thorny transients

• Fiber Optics where possible

• Good earthing/grounding for data comms





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A typical shield

The purpose of the shield is to reduce the magnitude of the noisecoupled into the low-level signal circuits by electrostatic or magneticcoupling. This has brushed up the above-mentioned concepts up to some extent

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Opto-electric coupler circuit





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When in doubt -disconnect

• Test with dummy equipment not 1MW ball

mills

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Thank You For Your Interest

If you are interested in further training, please visit:

IDC Technologies Short Courses:

Two-day practical courses available to the public:

http://idc-online.com/workshops

IDC Technologies Conferences:

http://idc-online.com/conferences-main

The Engineering Institute of TechnologiesOnline Certificate and

Advanced Diploma programs:www.eit.edu.au


EIT IDC Troubleshooting PLCs

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