Module 1 Scenario Cards: Vacuum Fundamentals & System Orientation

Module: M01 — Vacuum Fundamentals & System Orientation Rig Configuration: R1-A (Simple Single-Pump Roughing Rig) Cards: SC-01 through SC-04

R1-A Component Reference

Component ID	Name	Type
R1-CH	Chamber	Volume
R1-P-RP	Roughing Pump	Pump
R1-V-VENT	Vent Valve	Valve
R1-V-ISO	Isolation Valve	Valve
R1-G-CH	Chamber Gauge (Pirani)	Gauge
R1-G-BX	Barometric Reference	Indicator
R1-FLT-VENT	Vent Filter (sintered metal)	Filter
R1-FLT-EXH	Exhaust Filter (oil mist)	Filter
R1-L-FL	Foreline	Line
R1-L-VENT	Vent Line	Line
R1-L-EXH	Exhaust Line	Line

SC-01: System Vented (Atmospheric)

Clue: Look at all the valve positions and the pump status. Which of the three R1-A states does this configuration match?

Guide: Both R1-V-VENT and R1-V-ISO are CLOSED, and R1-P-RP is OFF. Compare R1-G-CH to R1-G-BX — are they approximately equal, or very different? The relationship between these two readings tells you whether the chamber is at atmosphere or below it.

Step by step

With both valves closed and pump off, the system is sealed. R1-G-CH (~950 mbar) approximately equals R1-G-BX (~950 mbar), meaning the chamber is at atmospheric pressure. This is the VENTED state — the chamber was previously vented to atmosphere, then all valves were closed.

Module: M01 Rig Config: R1-A Competency: M01-COMP-01, M01-COMP-02 Indicators Assessed: M01-IND-01.01, M01-IND-01.04, M01-IND-02.01, M01-IND-02.03

System State

State Name: VENTED One-line description: The system is at rest with the chamber sitting at local atmospheric pressure — no pumping, no gas flow, everything closed and idle.

Valve Positions

Valve ID	Valve Name	Position	Why
R1-V-VENT	Vent Valve	CLOSED	No venting is needed; the chamber is already at atmospheric pressure.
R1-V-ISO	Isolation Valve	CLOSED	The pump is off and disconnected from the chamber to prevent any backflow of oil vapour or exhaust gas into the chamber.

Gauge Readings

Gauge ID	Gauge Name	Expected Reading	Unit	What It Tells You
R1-G-CH	Chamber Pirani	~950	mbar	The chamber is at local atmospheric pressure. At Selkirk College (530 m elevation), atmospheric pressure is approximately 950 mbar rather than the sea-level standard of 1013 mbar.
R1-G-BX	Barometric Reference	~950	mbar	Confirms the current local atmospheric pressure. When the chamber gauge and the barometric reference read the same value, the chamber is fully vented to atmosphere.

Gas Flow Path

Active path: None. All valves are closed and the pump is off. There is no gas flow anywhere in the system. Blocked paths: The vent line is blocked at R1-V-VENT (vent valve closed).

The foreline path from chamber to pump is blocked at R1-V-ISO (isolation valve closed).

Pump Status

Pump ID	Pump Name	Status	Notes
R1-P-RP	Roughing Pump	OFF	The pump is not running. In this idle state, keeping the isolation valve closed prevents oil vapour from the pump migrating back toward the chamber.

Student Prompt

A technician approaches the R1-A rig and observes that both valves are closed, the pump is off, and the chamber gauge reads approximately 950 mbar — the same as the barometric reference. What state is the system in? What two conditions would need to change before the system could transition to a pump-down state, Which condition must be established first, and why?

Key Teaching Point

The vented state is the safe starting point and default resting condition of the system. Recognising that the chamber gauge matches the barometric reference is how the chamber is confirmed to be at atmosphere. Confirming atmospheric pressure by comparing gauge readings is a fundamental interpretation skill.

Visual Prompt (for AI image generation)

A simplified schematic of the R1-A rig showing: the chamber (R1-CH) in the centre with the Pirani gauge (R1-G-CH) displaying ~950 mbar; both the vent valve (R1-V-VENT) and isolation valve (R1-V-ISO) shown in the CLOSED position with red fill; the roughing pump (R1-P-RP) shown as OFF (greyed out); the barometric reference (R1-G-BX) displaying ~950 mbar; no flow arrows anywhere; vent filter and exhaust filter shown but inactive. Calm, static layout. Colour-coded.

SC-02: Roughing (Pump Down)

Clue: Which components are creating a flow path from the chamber to outside? Follow the gas from source to exhaust.

Guide: R1-V-ISO is OPEN, connecting the chamber to the pump through R1-L-FL. R1-P-RP is ON, actively removing gas. R1-V-VENT is CLOSED, preventing air from entering. The dropping pressure on R1-G-CH confirms active pumping.

Step by step

ROUGHING state: R1-CH -> R1-V-ISO (OPEN) -> R1-L-FL -> R1-P-RP (ON) -> R1-FLT-EXH -> R1-L-EXH -> atmosphere. Gas flows from the chamber through the open isolation valve, along the foreline, into the running pump, and is exhausted. The closed vent valve prevents atmospheric backfill.

Module: M01 Rig Config: R1-A Competency: M01-COMP-01, M01-COMP-02 Indicators Assessed: M01-IND-01.01, M01-IND-01.04, M01-IND-01.05, M01-IND-02.01, M01-IND-02.02, M01-IND-02.03

System State

State Name: ROUGHING One-line description: The roughing pump is running and actively pulling gas out of the chamber through the open isolation valve, steadily reducing chamber pressure from atmospheric toward rough vacuum.

Valve Positions

Valve ID	Valve Name	Position	Why
R1-V-VENT	Vent Valve	CLOSED	Must be closed to prevent atmospheric air from flowing into the chamber while the pump is trying to remove gas. Opening this valve during pump down would fight against the pump.
R1-V-ISO	Isolation Valve	OPEN	Connects the chamber to the roughing pump through the foreline, allowing the pump to pull gas out of the chamber.

Gauge Readings

Gauge ID	Gauge Name	Expected Reading	Unit	What It Tells You
R1-G-CH	Chamber Pirani	950 dropping toward 1	mbar	The pressure is actively falling. This reading decreases over time — quickly at first (when there is a lot of gas to remove), then more slowly as the chamber empties. A typical rough pump on a small clean chamber might reach below 1 mbar within a few minutes.
R1-G-BX	Barometric Reference	~950	mbar	Remains steady at local atmospheric pressure. The growing difference between R1-G-CH and R1-G-BX indicates how much vacuum has been achieved.

Gas Flow Path

Active path: Chamber (R1-CH) → Isolation Valve (R1-V-ISO, OPEN) → Foreline (R1-L-FL) → Roughing Pump (R1-P-RP) → Exhaust Filter (R1-FLT-EXH) → Exhaust Line (R1-L-EXH) → Atmosphere. Blocked paths: The vent line is blocked at R1-V-VENT (vent valve closed). Atmospheric air cannot enter the chamber through the vent path.

Pump Status

Pump ID	Pump Name	Status	Notes
R1-P-RP	Roughing Pump	ON	Running and actively pulling gas from the chamber. The pump is typically audible during operation. As chamber pressure drops, the sound of the pump may change — this is normal and reflects the decreasing gas load.

Student Prompt

The pump has been running for two minutes. The chamber gauge reads 15 mbar and is still dropping. The barometric reference reads 950 mbar. The vent valve is closed and the isolation valve is open. Trace the path the gas takes from the chamber to atmosphere. Why must the vent valve remain closed during this operation?

Key Teaching Point

During roughing, the pump removes gas molecules from the chamber and exhausts them to atmosphere. The vent valve must stay closed — otherwise the system would be trying to empty the chamber while simultaneously refilling it.

The pressure drop is fast at first because there are many gas molecules to move, and slows as the chamber empties. This is the first encounter with the concept that vacuum work is about removing gas, not creating emptiness.

Visual Prompt (for AI image generation)

A simplified schematic of the R1-A rig showing: the chamber (R1-CH) with the Pirani gauge (R1-G-CH) displaying a dropping value (use an arrow pointing downward next to the reading, showing ~15 mbar); the vent valve (R1-V-VENT) shown CLOSED with red fill; the isolation valve (R1-V-ISO) shown OPEN with green fill; the roughing pump (R1-P-RP) shown as ON (highlighted/active); blue directional flow arrows tracing the gas path from chamber through the isolation valve, along the foreline, through the pump, through the exhaust filter, out the exhaust line to atmosphere; the barometric reference (R1-G-BX) displaying ~950 mbar. Colour-coded.

SC-03: Rough Vacuum Hold (Isolated)

Clue: Both valves are closed and the pump may or may not be running. What matters is whether the chamber pressure is above or below atmospheric.

Guide: R1-V-VENT CLOSED + R1-V-ISO CLOSED = chamber is sealed. R1-G-CH reads well below R1-G-BX, confirming the chamber holds a vacuum. The pump status is irrelevant — both valves are closed, so the pump is disconnected from the chamber.

Step by step

ISOLATED state: chamber sealed with vacuum held. Both valves closed creates a sealed volume. R1-G-CH << R1-G-BX proves the chamber is below atmospheric. Whether R1-P-RP is on or off does not matter — R1-V-ISO is closed, so no gas flows between pump and chamber.

Module: M01 Rig Config: R1-A Competency: M01-COMP-01, M01-COMP-02 Indicators Assessed: M01-IND-01.01, M01-IND-01.04, M01-IND-01.05, M01-IND-02.01, M01-IND-02.02, M01-IND-02.03

System State

State Name: ISOLATED (ROUGH VACUUM HOLD) One-line description: The isolation valve has been closed after a pump down, sealing the chamber at its achieved vacuum level. The pump may be on or off — the chamber is disconnected from everything and holding whatever pressure it reached.

Valve Positions

Valve ID	Valve Name	Position	Why
R1-V-VENT	Vent Valve	CLOSED	The chamber must remain sealed. Opening the vent valve would flood the chamber with atmospheric air and destroy the vacuum.
R1-V-ISO	Isolation Valve	CLOSED	Disconnects the chamber from the pump and foreline. This seals the vacuum inside the chamber so it holds at the achieved pressure.

Gauge Readings

Gauge ID	Gauge Name	Expected Reading	Unit	What It Tells You
R1-G-CH	Chamber Pirani	1 to 10 (stable or slowly rising)	mbar	Shows the pressure the chamber was pumped down to before isolation. In a clean, well-sealed system, this reading should hold steady. A slow rise over time would indicate a small leak or outgassing from chamber surfaces.
R1-G-BX	Barometric Reference	~950	mbar	Still at local atmospheric pressure. The large difference between R1-G-CH and R1-G-BX confirms the chamber is holding vacuum.

Gas Flow Path

Active path: None. Both valves are closed. The chamber is a sealed volume — no gas is flowing in or out. Blocked paths: The vent line is blocked at R1-V-VENT. The foreline path is blocked at R1-V-ISO. The chamber is completely isolated from both atmosphere and the pump.

Pump Status

Pump ID	Pump Name	Status	Notes
R1-P-RP	Roughing Pump	ON or OFF	Either state is acceptable. If the pump is left running, it is simply idling against the closed isolation valve. If it is turned off, that is also fine since the chamber is sealed. In a teaching environment, turning the pump off saves wear and reduces noise.

Student Prompt

The R1-A rig has been pumped down and the isolation valve is now closed. The chamber gauge reads 5 mbar and the barometric reference reads 950 mbar. Both valves are closed. Over the next ten minutes, the chamber gauge reading slowly creeps up to 8 mbar. First, identify the current system state. What does this indicate about the system? Name two possible reasons the pressure is rising.

Key Teaching Point

The isolated hold state is how a vacuum system is tested to confirm it is truly sealed. A perfectly leak-tight, clean chamber would hold its pressure indefinitely.

In practice, a slow pressure rise is common and can result from small leaks (air finding its way in through a seal) or outgassing (gas releasing from the chamber walls and internal surfaces). Watching the rate of rise is one of the simplest and most important diagnostic techniques in vacuum work.

Visual Prompt (for AI image generation)

A simplified schematic of the R1-A rig showing: the chamber (R1-CH) with the Pirani gauge (R1-G-CH) displaying ~5 mbar; both the vent valve (R1-V-VENT) and isolation valve (R1-V-ISO) shown CLOSED with red fill; the roughing pump (R1-P-RP) shown with a dashed outline or neutral colour indicating it may be on or off; no flow arrows anywhere — the system is static and sealed; the barometric reference (R1-G-BX) displaying ~950 mbar; a small annotation or subtle upward arrow near the chamber gauge suggesting a possible slow pressure rise. Colour-coded.

SC-04: Controlled Vent (Return to Atmosphere)

Clue: This scenario involves a pressure anomaly. Look at the readings carefully — is something unexpected happening?

Guide: Compare the expected behaviour to what is observed. If the system should be holding vacuum but the pressure is changing, ask: which direction is it changing, and at what rate? The rate and pattern tell you whether this is a leak or outgassing.

Module: M01 Rig Config: R1-A Competency: M01-COMP-01, M01-COMP-02 Indicators Assessed: M01-IND-01.01, M01-IND-01.04, M01-IND-01.05, M01-IND-02.01, M01-IND-02.02, M01-IND-02.03

System State

State Name: CONTROLLED VENT One-line description: The vent valve is opened slowly to allow filtered atmospheric air to flow gently back into the chamber, bringing it from vacuum back up to atmospheric pressure in a controlled manner.

Valve Positions

Valve ID	Valve Name	Position	Why
R1-V-VENT	Vent Valve	OPEN (opened slowly)	Allows filtered atmospheric air to enter the chamber through the vent line. Opening slowly is important — a sudden rush of air into a vacuum chamber can disturb loose items inside, stir up particles, and create unnecessary turbulence.
R1-V-ISO	Isolation Valve	CLOSED	Must remain closed to prevent atmospheric air from rushing backward through the foreline into the pump. Venting through the pump path could push contaminants into the pump or damage it.

Gauge Readings

Gauge ID	Gauge Name	Expected Reading	Unit	What It Tells You
R1-G-CH	Chamber Pirani	Rising from achieved vacuum toward ~950	mbar	The pressure is climbing as air fills the chamber. The reading increases steadily until it matches the barometric reference, confirming the chamber is fully vented.
R1-G-BX	Barometric Reference	~950	mbar	The target value. When R1-G-CH matches R1-G-BX, the vent is complete and the chamber is at atmospheric pressure.

Gas Flow Path

Active path: Atmosphere → Vent Filter (R1-FLT-VENT) → Vent Line (R1-L-VENT) → Vent Valve (R1-V-VENT, OPEN) → Chamber (R1-CH). Blocked paths: The foreline path is blocked at R1-V-ISO (isolation valve closed). No air reaches the pump — it is completely isolated from this operation.

Pump Status

Pump ID	Pump Name	Status	Notes
R1-P-RP	Roughing Pump	OFF	The pump must be off during venting. There is no reason to run the pump while bringing the chamber back to atmosphere. The isolation valve is closed, so the pump is disconnected from the process regardless.

Student Prompt

The chamber is currently at 5 mbar with both valves closed and the pump off. A controlled vent has been initiated. Describe the gas flow path that will bring the chamber back to atmospheric pressure. Why is the vent filter important in this process? What would happen to the system if the isolation valve were opened instead of the vent valve?

Key Teaching Point

Controlled venting is not just opening a valve — it is a deliberate procedure. The vent filter (R1-FLT-VENT) prevents dust and particles from being drawn into the chamber by the inrushing air. Opening the vent valve slowly avoids a sudden pressure shock that could disturb chamber contents or create particle contamination.

Venting is always performed through the dedicated vent line, never backward through the pump. When R1-G-CH matches R1-G-BX, this confirms the vent is complete and it is safe to open the chamber.

Visual Prompt (for AI image generation)

A simplified schematic of the R1-A rig showing: the chamber (R1-CH) with the Pirani gauge (R1-G-CH) displaying a rising value (use an arrow pointing upward next to the reading, showing it climbing toward ~950 mbar); the vent valve (R1-V-VENT) shown OPEN with green fill; the isolation valve (R1-V-ISO) shown CLOSED with red fill; the roughing pump (R1-P-RP) shown as OFF (greyed out); blue directional flow arrows tracing the air path from atmosphere through the vent filter (R1-FLT-VENT), along the vent line (R1-L-VENT), through the vent valve, into the chamber; the barometric reference (R1-G-BX) displaying ~950 mbar. Colour-coded.