I received an email with a question:
I just enjoyed your blog on Tips When Using DeltaV PID Control [link]. I am new to DeltaV and have a question that is probably very elementary. However I have not been able to find it in DeltaV BOK. How do I use the ? to troubleshoot module errors? I know it means I have a block error but I don’t see how to find the error. Any input will be appreciated.
I bounced to question by our DeltaV Educational Services team and have this reply to share with everyone:
With Control Studio On-line or Debug simply select the block with the ?. In the parameter window double click the Block_ERR parameter is should be reading Non-Zero. This will list the conditions causing the block error. Also the detail display for the PID loop dynamo in Operator Interface has those parameter displayed as well.
Does anyone else have anything more to add?
Every DeltaV Module has a MERROR and MSTATUS parameter. Each of these is called an Option Bitstring of indvidual bits with a defined meaning. Open these in control studio and you see the textual description of the bit's meaning. They have an associed Mask parameter that you can use to select those bits to drive the BAD_ACTIVE parameter. The unselected bits will drive the ABNORMAL_ACTIVE parameter.
MERROR has a bit called FB BAD ACTIVE, and MSTATUS has a bit called FB ABNORMAL ACTIVE, Each FB in the module has a BLOCK_ERR and mask that is used to drive the blocks BAD_ACTIVE or ABNORMAL ACTIVE.
By setting the associated masks for the BLOCK ERR, MSTATUS and MERROR, the module is able to report significant errors by setting the BAD_ACTIVE parameter, which in turn sets the ? icon in DeltaV Explorer.
So, by evaluating MERROR, and MSTATUS, you can determine the root cause. If an FB condition exists, you would launch Control Studio on line and look for FB's in the module that have the ? icon on them. On these blocks, you would look at BLOCK_ERR to see the underlying cause.
You can also use DIAGNOSTICS to view multiple modules at a time. Under the controller, select the Assigned Modules container. On the right hand Pane, the modules will be listed, and to the right of them, you will have a matrix that represents the individual bits of the MERRO and MSTATUS parameters. You can sort on these columns to find all the modules with say an IO Input error, or a block error, etc.
Although you can can adjust the masks to change what sets the BAD block or BAD module, you should only enable bits that you need to act on. You can always used diagnostics to view lists of modules status and error bits without enabling a module BAD Active status. Look to the DeltaV templates to provide a guide on what mask conditions should be considered, and only enable additional mask bits once you understand what sets the error/status and how it should be responded to.
Andre Dicaire