I am going to describe how to delete unwanted or orphaned workflow column from a List.it can be done simply by writing few lines of powershell command as below.
  1. function Delete-WorkflowColumn ($webURL, $listName, $columnName)
  2. {
  3. #Setup variables from the user input
  4. $web = Get-SPWeb $webURL
  5. $list = $web.Lists[$listName]
  6. $column = $list.Fields[$columnName]
  7. #Make sure the column is not hidden or read only
  8. $column.Hidden = $false
  9. $column.ReadOnlyField = $false
  10. $column.Update()
  11. #Delete column and dispose of the web object
  12. $list.Fields.Delete($column)
  13. write-host "Deleted column"
  14. $web.Dispose()
  15. }
  18. Delete-WorkflowColumn -webURL http://ServerName/ -listName "ERP Request" -columnName
  20. "Approval Workflow"
save above notepad with the name of delete.ps1 and then from powershellscript do as below
  1. PS D:\> .\delete.ps1
  2. Deleted column
  3. PS D:\>