HMI lockout

[ptonsparky]

Setting up PLC with two HMIs. Lot easier than I thought it would be so far.

The 2nd HMI will sit in the Plant Managers office totally programed and set up for a spare if needed. Last time a screen failed it was 4 days of down time, not my system. This HMI is set up so that he may monitor alarms and trends. The only control that he will have ready access to is a "Fire Stop". Activation of the screen to full control will require a password and total shut down of the plant. Not worried about unathorized use here, however the working plant HMI has the same OFFICE screen available although password protected. Once on this screen, all access to plant operations is lost until it is shutdown. Passwords enough or maybe some additional failsafes?

Stopping the plant causes loss of revenue and additional startup costs, no additonal safety hazard

 

[Strahan]

First I'm curious how you are going to shut a plant down using an HMI? Just curious
Next Doesn't really matter what type of HMI, but why not remove the GoTo screen button on the one being placed in the plant? Sure this might cause you to have two different apps but the only difference would be the GoTo button.
Last from my experience unless you work with different types of people than I do I can almost garuntee you that the password will leak out to someone who should not have it!:grin:

 

[ptonsparky]

Just the process gets shut down. Three maintained Stop buttons at various location & an HMI Stop drops out a control relay that shuts down the process. Feedback to the HMI from the control relay doesn't allow the screen change button to be visible unless the contacts are open. Then a password.

The password sharing is what causes me grief. Two apps would be the most idiot proof.

Most likely I, or my help, would be there if an HMI failed anyway.