DeltaV PK controller Unlock Inhibit and Unlock Allow

The DeltaV PK controller must be unlocked to commission, decommission, download, upgrade, or access the node's privileged menus (for example, Telnet access). Locking also prevents a user-initiated switchover when the controllers are redundant. You lock and unlock the controller (when the controller is in one of the Unlock Allow states) in DeltaV Explorer through the controller's context (right-click) menu.

To unlock the controller through DeltaV Explorer, one of the following is true:

The key switch is not enabled.
The physical key switch is in the unlocked position (Unlock Allow) for less than the Auto Lock limit or has been in the unlocked position (Unlock Allow) for more than 5 seconds but less than 10 seconds before returning to the locked position (Unlock Inhibit).

Physical key switches

The physical key switch on the controller's carrier can be used to control the software Lock and Unlock functions. The key switch requires physical presence by plant personnel before the controller's locked state can be altered and therefore before any functions controlled by the locked state can be initiated.

There are two positions for the physical key switch:

Unlock Allow

This is the shown as the unlocked symbol on the carrier. When it this position, the controller can be unlocked in DeltaV Explorer. When unlocked, you can perform certain functions (such as downloading, commissioning, upgrading, and so on). The Unlock Allow position is further controlled by the Auto Lock option and its Time Limit value, which locks the controller after the time specified. Auto Lock is set on the controller's Properties dialog's Security tab.

In this position, the KeyLockStatus diagnostics parameter's value is one of the following:

Controller Unlock Allowed
Single Unlock Allowed

Unlock Inhibit

This is the shown as the locked symbol on the carrier. When it this position, the controller cannot be unlocked in DeltaV Explorer. Because the controller is locked, you cannot perform certain functions (such as downloading, commissioning, upgrading, and so on). The Unlock Inhibit position is the default operating position when the Enable Unlock Inhibit Key Switch option is enabled.

In this position, the KeyLockStatus diagnostic parameter's value is Controller Unlock Inhibited.

Enable the physical key switch

Enable or disable the physical key switch with the Enable Unlock Inhibit Key Switch option on the controller's Properties dialog's Security tab.

The Unlock Inhibit Key Switch must be enabled (and the physical key switch must be switched into the unlocked position) for the unlock states to become active.

Controller Unlock States

The following are the valid states for the controller's KeyLockStatus diagnostic parameter (viewed in DeltaV Diagnostics by selecting the controller from the hierarchy).

Unlock Allowed State: This state allows the controller to be unlocked multiple times.; To enter the Unlock Allowed state, turn the key switch to the unlock position until the red LED flashes slowly on the controller's carrier (flashing starts 5 seconds after turning the key). The red LED remains blinking slowly for 5 seconds at which point (provided the key remains in the Unlock Allow position) the LED stops flashing and turns off.; If, during the 5 seconds that the red LED is flashing slowly, the key is turned to the Unlock Inhibit position, the controller enters into the Single Unlock Allowed state.; Note
If Auto Lock is enabled (on the controller's Properties dialog's Security tab), the controller is locked after the Auto Lock time limit is reached. The RelockTimer diagnostics parameter counts down the remaining time until the controller is locked.
Single Unlock Allowed State: This state allows only one (single) unlock to occur and then locks the controller again. The physical key is left in the Unlock Inhibit position eliminating the chance of leaving the controller unlocked.; To enter the Single Unlock Allow state, turn the key switch to the unlock position until the red LED flashes slowly on the controller's carrier (flashing starts 5 seconds after turning the key). Then turn the key switch back to the lock position while the red LED is flashing slowly (at greater than 5 seconds and less than 10 seconds post first turning the physical key).; You are then able to perform one single unlock through DeltaV Explorer.; Note

You have 5 minutes to perform this action. If the controller is not unlocked during the 5 minute window, the controller will automatically change back to Unlock Inhibited state (matching the key position).
Unlock Inhibited State: This state disallows unlocking the controller from DeltaV Explorer.; To enter the Unlock Inhibited state, turn the key switch to the locked position (Unlock Inhibit position) at any point except when the red LED is flashing.; Note

Turning the key to the locked (Unlock Inhibit) position while the red LED is flashing first enters you into the Single Unlock Allowed state.
Disabled: This state means that the physical key switch does not control the ability to lock or unlock the controller in DeltaV Explorer.; To enter the Disabled state, do not enable the Enable Unlock Inhibit Key Switch option on the PK controller's Properties dialog's Security tab.

Lock/unlock options

You can set limits and alerts for the controller's locked state. These options are set on the controller's Properties dialog's Security tab

Auto Lock

Automatically puts the controller in a locked state after the configured time limit.

The limit can be set for 10 minutes to 24 hours.

Unlocked Alert

Generates an alert when all of the following is true:

the controller remains in one of the Unlock Allowed states; and,
the physical key is in the Unlocked Inhibit position; and,
the configured time is exceeded.