Does your maintenance personnel work with PLCs following written company or corporate policy and procedures?

It seems that in our industrial culture, if policy and procedures are not written and enforced, we eventually stray back to the old unreliable ways. I have reviewed many policy and procedures as well as books on the topic matter and hardly ever see maintenance management of the PLCs included. It amazes me how an organization can write guidelines for what they believe is the health of the entire organization’s body, and leave out the brain (the PLC). Once again, a complete PLC policy and procedure manual is out of the scope of this article. However, I will donate a few random items below to get you started.

1. Write PLC policies and procedures into your existing maintenance policy and procedures. (SOP)
2. All personnel working with PLCs will be trained on that PLC equipment.
3. Backup copies of the PLC programs will be made every 6 months regardless of change status.
4. If a PLC program has been changed ...
• It will be documented in the software copy, in the printed copy and in the CMMS program.
• Copies of the PLC program will be stored on a media more reliable than floppy disk (CD, USB, etc.).
• Multiple copies will be stored on laptop, maintenance manager’s office and off site (corporate).
• If available, EEPROM will be updated with new changed program.
• If outside vendor changes, a-d will be performed by maintenance personnel
5. Future equipment purchases ...
• A common PLC brand in all equipment will be sought out (Standardization of PLC types)
• OEM will be required to provide a descriptor copy of PLC programs in the customer’s native language.
• All PLC 110v control voltage will have a line filter on it.
• All PLCs will have the backup EEPROM option for zero downtime in some failure modes.
6. Forcing inputs and outputs on or off shall be treated as a Safety issue. (See safety SOP)
7. Inputs and outputs shall not be forced on or off with out a clear understanding of complete effect on PLC program and a second opinion.
• If forces are installed, they shall be removed with in 24 hours and a more permanent solution found.
• All forces should be documented in software and a written log before being enabled.
8. Online programming is somewhat of a safety risk, normal procedure is to change offline and download to the PLC.

Hope this helps, if you have a specific question you can find me in our PLC discussion area at the PLC Discussion Forum.

Don Fitchett (President)
Business Industrial Network
PLC Training - The best for less
www.bin95.com