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plc software - 32.20

These design sheets are provided as examples. PLC vendors often supply similar sheets. Many companies also have their own internal design documentation procedures. If you are in a company without standardized design formats, you should consider implementing such a system.

32.6 COMMISIONING

When a new machine is being prepared for production, or has been delivered by a supplier, it is normal to go through a set of commissioning procedures. Some typical steps are listed below.

1.Visual inspection

verify that the machine meets internal and external safety codes

-electrical codes

-worker safety codes (e.g., OSHA)

determine if all components are present

2.Mechanical installation

physically located the machine

connect to adjacent machines

connect water, air and other required services

3.Electrical installation

connect grounds and power

high potential and ground fault tests

verify sensor inputs to the PLC

4.Functional tests

start the machine and test the emergency stops

test for basic functionality

5.Process verification

run the machine and make adjustments to produce product

collect process capability data

determine required maintenance procedures

6.Contract/specification verification

review the contact requirements and check off individually on each one

review the specification requirements and check off each one individually

request that any non-compliant requirements are corrected

7.Put into production

start the process in the production environment and begin normal use

32.7REFERENCES

Kenner, R. H., “The Use of Simulation Within a PLC to Improve Program Development and Test-

plc software - 32.21

ing”, Proceedings of the First Automation Fair, Philadelphia, 1990.

Paques, Joseph-Jean, “Basic Safety Rules for Using Programmable Controllers”, ISA Transactions, Vol. 29, No. 2, 1990.

32.8SUMMARY

Debugging and forcing are signs of a poorly written program.

Process models can be used to completely describe a process.

When programming large systems, it is important to subdivide the project into smaller parts.

Documentation should be done at all phases of the project.

32.9PRACTICE PROBLEMS

1. List 5 advantages of using structured design and documentation techniques.

32.10 PRACTICE PROBLEM SOLUTIONS

1. more reliable programs - less debugging time - more routine - others can pick up where you left off - reduces confusion

32.11 ASSIGNMENT PROBLEMS

1.What documentation is requires for a ladder logic based controller? Are comments important? Why?

2.When should inputs and outputs be assigned when planning a control system?

3.Discuss when I/O placement and wiring documentation should be updated?

4.Should you use output forces?

5.Find web addresses for 10 PLC vendors. Investigate their web sites to determine how they would be as suppliers.