Siemens S7-300/400 PLC Basic Maintenance & Troubleshooting (M&T)
Duration:
5 days
Prerequisites:
Delegates should have a basic understanding of PLCs or have attended one of our
Introductory or Multi-Skill courses & have some familiarity with PCs & Microsoft
Windows.
Aims:
The Basic M&T course equips maintenance personnel with the essential knowledge
& skills to maintain & troubleshoot S7 PLC systems. Attendees will be able to work
safely & competently with common S7 hardware, be able to connect a PC/laptop/PG
to the PLC, access the correct project/program & use the PLC to diagnose machine
or process problems.
Objectives:
For specific course objectives see Training Record Log.
Content:
Understand the Hardware
- Be able to identify & understand the function of the main S7 hardware components (Simatic 300/400 systems)
- Know the purpose of the external CPU switches & the effect on the operation of the S7 program & the I/O
- Understand the purpose of the different CPU communication ports & know where to connect the PC/laptop/PG comms cable
- Know how & where the program is stored, the importance of the battery (if fitted) & which areas of PLC memory are retentive
- Appreciate that different CPU models may use different memory technologies such as Flash/MMC
- Understand the wiring connections to the power supply module & power & field I/O connections to I/O modules
- Understand the effects on the operation of the PLC of cycling power or a mode change from STOP to RUN or RUN to STOP & what happens to the I/O
Understand the Terminology, Structure & Organisation of S7 Programs
- Understand the method for addressing field I/O points & internal markers in an S7 program
- Understand that there are 3 methods for writing & displaying S7 programs (LAD, FBD, STL), that they are not always interchangeable, how to choose the easiest mode for display & how to alternate between them
- Understand that S7 programs consist of many smaller sub-programs (Blocks) which are linked & know how to move between them to trace status
- Know the importance of Organisation Blocks (especially OB1) & the various Start-up routines & how to access, monitor & understand their operation
- Know what Functions (FCs) are used for, that some are in ROM (SFCs) & others user-written & how to access & monitor their operation
- Know what Function Blocks (FBs) are used for, that some are in ROM (SFBs) & others user-written & how to access & monitor their operation
- Understand how to correctly interpret screen highlights for the different contact & coil instructions & how to relate this to the state of I/O LEDs on I/O modules & the operation of devices in the field
- Understand the construction & display of the various Timer & Counter instructions, know how they work & the different ways to monitor them
- Introduction to Data Handling with S7 & the use of Comparators & simple
Arithmetic instructions
- Know how Analog signals are handled by S7, know how to find them in a program & the different ways to monitor them
- Introduction to Data Blocks, know how they can be structured, know how they can be used & know how to display them
Running & Using STEP 7 software
- Understand the key components of an installation of STEP7 software on a PC/laptop/PG & the importance of knowing the directory/folder structure used for Archiving & Retrieving programs
- Understand the concepts of a project, associated hardware and S7 Program Blocks
- Be able to identify & understand the different block types
- Know how to run the STEP 7 software, establish communications (go on-line) & access the S7 program from a PC/laptop/PG
- Understand the structure of the STEP7 software & be able to move around between the various options
- Know how to create a new project in order to Backup your PLC program
- Know how to Archive & Retrieve an S7 project
- Know how to access & monitor Organisation Blocks, Functions & Function Blocks, how to move between them
- When monitoring a program, understand where the logic you are seeing is coming from & the important implications for the user
- Know how to correctly interpret status in LAD code & simple examples of FBD & STL code
- Know how to generate Cross Reference data & know where this is stored
System Maintenance Procedures
- Know how to RUN & STOP the S7 (both hardware & software methods) & know what happens to the I/O in each mode
- Know how to correctly interpret the status of the battery (if fitted) & how to appropriately replace if necessary
- Know how to replace & reconfigure suspect power supply, I/O modules, racks & I/O interface modules
- Know how to replace a suspect or failed CPU module & how to reload the program
- Know how to Upload a station
- Know how to download block(s) to PLC
- Understand that the S7 program does contain the system & I/O configuration & the important implications of this for the user
- Know how to compare a program running in an S7 PLC with a program held on disk & be able to interpret the differences
- Know how to make minor modifications to an existing program to add functionality or as a temporary measure to enable a stalled program to continue
- Know how to transfer appropriate files to & from a working directory & to external disk
- Be aware that when attempting to monitor code offline, system may request a download and understand the implications of doing so
- Know how to use a printer to replace a page in a printout which is missing or where the program has been changed or to print a cross reference table
- Gain practical experience of a wide range of essential maintenance procedures
Diagnostic Tools & Troubleshooting Procedures
- Understand the reasons why most faults will not be PLC hardware or software & are much more likely to be due to field device failures or wiring problems
- Know the first level checks needed to begin to quickly distinguish between PLC & field faults
- Know typical fault symptoms for common PLC hardware (module) failures
- Be able to recognise & interpret the meaning of external system diagnostic
LEDs
- Be able to correctly interpret the status of I/O LEDs & relate these to the operation of field devices to distinguish between I/O module faults & wiring or field faults
- Know how & where to use a meter to check & confirm I/O module power supplies & for correct operation of digital I/O circuits
- Know how & where to use a meter to check analog I/O modules for correct circuit operation
- Know quick methods to identify a failed I/O module
- Know the symptoms of using a faulty comms cable or if connected to the wrong CPU comms port
- Understand how & when to use Overall Reset & understand the effect of this on system operation
- Know how to use the on-screen cross reference facility to move between blocks & to use the address Find & Go To tools in a program to trace I/O status
- Know how to update or generate cross reference information when troubleshooting a problem
- Know how to set up & use the Monitor/Modify Variables Display to monitor/modify multiple I/O points & data registers in the S7
- Know how to use the Force function with S7 & understand the dangers & the limitations
- Know how to access the Hardware Diagnostics facility & how to interpret the information provided to troubleshoot more difficult problems
- Be able to read an S7 program printout & interpret cross reference information to trace signals when troubleshooting
- Gain practical experience in distinguishing between PLC faults, I/O faults & field device faults
- Gain practical experience of a range of troubleshooting examples