OT: Owning after program changes, (or lack there of)

Hello,

I was wondering if anyone else experiences this....

Scenario: One of our older machines, (purchased from an OEM, not built here), had an old HMI on it that died. This particular HMI is now obsolete. I was then tasked with doing an upgrade. I programmed the new HMI to function exactly as the old one did. No program changes were made to the PLC. The only difference is appearance. (Monochrome to vivid color....big difference!)

Long story short...4 days after the HMI was installed, the machine had a sensor that was intermittently working on the night shift causing the machine to fault irregularly. The instant diagnosis was "the program was different now and thus the machine wasn't functioning properly." The machine was left down for about 4 hours until I got to work the next morning. Everyone seemed suprised when I didn't grab the laptop. After less than 10 minutes of troubleshooting, the machine was running and I handed the bad proxy to the maintenance tech and asked, if the old screen was on there, would you have left the line down for me?

His answer was, no, probably not.

Hopefully, lesson learned.

I've had a number of these scenarios, particularily whenever we put a new piece of machinery on the floor, we own it until everyone gets used to it.

-Dave

Well, that's actually guilt from proxy, not guilt by proximity, so it's really not that bad. I've been called about equipment shutting down, and been standing in the exact control room for that piece of equipment, maybe updating field prints or taking down some part numbers. I walk out of the C.R. to see why the operators called, and they say "I saw you go in the control room, and all of a sudden the equipment shut down. What did you do?" I usually look at the HMI or get on the intercom to find out who or why the line stopped. So yes, there's guilt by proxy, but there's also guilt by proximity. Same difference I guess.

A complaint I get is that when an error has been detected, it's not the fault of the error condition as shown on the screen, it is somehow the fault of the error detection logic itself.

Basic law of programming Rule #32:

Rule # 32 states : Last one in, first one blamed.

curlyandshemp said:

Basic law of programming Rule #32:

Rule # 32 states : Last one in, first one blamed.

Click to expand...

Rephrased:
"You touch it, You own it".

OkiePC said:

Rephrased:
"You touch it, You own it".

Click to expand...

That's Rule #33

curlyandshemp said:

That's Rule #33

Click to expand...

Where aere the rest of thes Rules?. They seem pretty good and right on point.

The Plc Kid said:

Where aere the rest of thes Rules?. They seem pretty good and right on point.

Click to expand...

You had to ask. Enjoy the read.


http://forums.mrplc.com/index.php?showtopic=9522

Heh, what about ''I know what's wrong.. The fuse is bad''

Oh god, gets me everytime.

Many an eager electrician/Technician has pulled a machine apart only to find the fuse was blown.
there was a breakdown flow chart to find the fault.
All ends in "did you F,,,,, (Mess) with it ---- You poor Bugger"

This one...

One of the first things I tell our maintenance electricians is:-
When called to a problem DO NOT under any circumstances take a laptop with you on your first investigation.
The moment a laptop appears the problem is in the PLC as far as everybody else is concerned. Since this is not hte case 99% of the time you will only need to go back for the computer on very rare occasions. Of course we have the luxury of being able to get on line from our desk if further investigation is needed but most of the time problems are caused by simple failures which can be found by a quick visual check.

Thats the one Daba

Andybr - i agree

Look for the fault light

If the machine has been running and just stopped and there is NO fault light on the PLC then your problem is very unlikely to be the PLC. I find it suprising how many people think the PLC can just change its program on it own.

Gremlins - Clay