2. The Instructor Station¶
The Instructor Station owns the training session: it runs the plant at the speed you choose, freezes it while you talk, takes snapshots you can return to, and keeps a journal of everything the plant, the trainee and you did.
What you will learn
- Start, freeze, single-step and stop a session; the speed factor
- What the status line tells you about the integration
- Snapshots and backtracking
- Reading and exporting the journal
- What happens when a step fails to solve
Prerequisites
- Page 1, with
ots_separator.dwxmzopen in dynamic mode
Opening it¶
Operator Training > Instructor Station. The window can stay open next to the flowsheet; the trainee's windows (pages 5 and 6) are separate.
The toolbar¶
| Control | What it does |
|---|---|
| Start | Starts a fresh session: restores the schedule's initial state, resets alarms, trends and the score, and runs. After a Freeze, the same button resumes. |
| Freeze | Stops at the end of the current step and keeps everything. Use it to explain something, to take a snapshot, or before restoring one. |
| Step | Solves exactly one step. From idle it also starts a fresh session. |
| Stop | Ends the session. The next Start begins again from the initial state. |
| Speed (x) | Simulated seconds per wall-clock second, 0.1 to 20. With a 5 s step, 1x means one step every 5 s of your time, 10x one every 0.5 s. Changeable while running. |
| Schedule | The dynamics schedule the session runs (its integrator, initial state and event list). |
| Flowsheet in control panel mode | Switches the flowsheet window to control panel mode, where the trainee can touch controllers and valves on the drawing. Pages 5 and 6 give the trainee better windows; this checkbox is for quick demonstrations. |
| Operator panel... | Opens the trainee's panel (page 5). |
| Interlocks... | Opens the interlock editor and status (page 8). |
| OPC UA... | The OPC UA server (page 9). |
| Stations... | Remote operator stations (page 10). |
| P-F network | The pressure-flow network solver (page 11); on by default. |
The status line¶
RUNNING · Time 00:02:35 · Step 31 · 180 ms/step · Overruns 0 · Failed steps 0 · Alarms 1 · Network: no junctions
- Time is simulated time since Start.
- ms/step is how long the last step took on the wall clock. The session sleeps the rest of the step budget (
step / speed). - Overruns counts steps that took longer than their budget. A few are harmless; a steady stream means the speed factor is higher than the PC can deliver. Lower it, or increase the integration step in the Dynamics Manager.
- Failed steps counts steps the solver could not complete (see below).
Try it¶
- Set the speed to
10, press Start. The status line starts counting; the flowsheet updates every step. - After 30 simulated seconds press Freeze. Note the time.
- Press Step twice: the time advances by 5 s each.
- Press Start again to resume, then Stop.
Snapshots and backtracking¶
The Snapshots tab:
- Save snapshot (with a name) stores the whole plant state. Freeze first; the button refuses while running.
- Restore brings the plant back to a snapshot; the session stays frozen so you can resume from there.
- Backtrack (simulated seconds) rewinds the plant by that many seconds using the historian. It needs Enable historian in the Dynamics Manager, which records every step of the run.
Snapshots are the same objects as DWSIM's stored flowsheet states, so they are saved with the file and can serve as a scenario's initial state (page 4).
Teaching with backtrack
When the trainee has just made a wrong move, freeze, backtrack 60 s, explain, and resume. The journal keeps both attempts.
The journal¶
The Journal tab lists everything with its simulated time and wall-clock time, in categories you can filter with Show:
| Category | Examples |
|---|---|
| Session | Session started, stopped, resumed; scenario loaded; scheduled events that fired; remote stations connecting |
| Instructor | Freeze, single step, snapshot saved or restored, backtrack, malfunction activated by hand |
| Operator | Set point changed, controller to manual, valve opened, pump started, alarm acknowledged |
| Alarm | Alarm active or cleared, with the value and its units |
| Trip | Interlock tripped, reset, bypassed; its first-out condition |
| Malfunction | Scheduled fault armed, activated, cleared |
| Solver | Steps that failed and why; pressure-flow network notes |
Export CSV writes the whole list for the debriefing; Clear empties it.
Operator actions are detected in two ways: anything done through the OTS windows is journaled directly with the trainee's text ("PID-012 set point -> 2.5 bar"), and changes made on the flowsheet in control panel mode are picked up by comparing controllers, valves and switches between steps.
When a step fails¶
Dynamic solves fail now and then: a flash does not converge, a vessel runs empty. The classic integrator stops. The OTS session instead:
- Restores the state from before the step.
- Journals
Step failed to solve, plant held at the last good state: <reason>in the Solver category. - Counts it in Failed steps and tries the next step.
After ten consecutive failures it freezes itself and journals why, so a broken plant does not run away while you are talking to the trainee. Fix the cause (usually a fully closed valve with a fixed-flow feed, or a holdup that emptied) and resume.
The next page adds the instructor's main tool: malfunctions.