Facilitator: adjust scaffolding level before distributing
Module 1 Workbook: Vacuum Fundamentals & System Orientation
Estimated Completion Time: 45-60 minutes
Part A: Knowledge Check (20 marks)
Short-answer questions testing recall from async learning content.
2 marks each. 10 questions.
A1. In your own words, explain what vacuum means in an industrial or scientific context. How does the pressure inside a vacuum chamber compare to the atmospheric pressure outside it?
(2 marks)
Clue: Think about what "vacuum" means relative to the pressure around us. How does inside compare to outside?
Guide: Vacuum means lower pressure than the surrounding atmosphere. At Selkirk, atmospheric is ~950 mbar. What does a reading of, say, 5 mbar inside a chamber tell you?
Step by step
A vacuum exists when the pressure inside a vessel is lower than atmospheric pressure outside. At Selkirk (~950 mbar atmospheric), a chamber at 5 mbar has 945 mbar less pressure than the surroundings. The molecules inside are much fewer and farther apart.
A2. Explain the difference between absolute pressure and gauge pressure. If a gauge pressure reading shows -950 mbar, what does that tell you about the actual (absolute) pressure inside the chamber?
(2 marks)
Clue: Think about what "zero" means on each scale. Where does each scale start?
Guide: Absolute pressure: 0 = perfect vacuum (no molecules). Gauge pressure: 0 = atmospheric. So a gauge reading of -950 mbar means the absolute pressure is approximately 950 mbar below atmosphere.
Step by step
Absolute pressure measures from true zero (perfect vacuum). Gauge pressure measures relative to local atmosphere. If gauge reads -950 mbar and atmosphere is ~950 mbar, then absolute pressure = 950 + (-950) = ~0 mbar — nearly a perfect vacuum. This course uses absolute (mbar) throughout.
A3. Name the three common pressure units used in vacuum technology and give an approximate conversion between them. Which unit is used as the standard throughout this course?
(2 marks)
Clue: The three units you have seen in the lessons — think mbar, Pa, and one more traditional unit.
Guide: mbar (millibar), Pa (Pascal), and Torr. 1 mbar = 100 Pa = 0.75 Torr approximately. This course uses mbar as the standard unit.
A4. Vacuum pressures are classified into ranges. Name three vacuum pressure ranges (for example, rough, medium, and high vacuum) and give an approximate pressure boundary for each in mbar.
(2 marks)
Clue: Recall the pressure ranges from the lessons — they span from atmospheric down to ultra-high vacuum.
Guide: Rough vacuum: 1000 to 1 mbar. Medium/fine vacuum: 1 to 10^-3 mbar. High vacuum: 10^-3 to 10^-7 mbar. Ultra-high vacuum: below 10^-7 mbar.
A5. Describe, without using equations, what happens to gas molecules inside a chamber as the pressure drops from atmospheric to rough vacuum. How does their behaviour change?
(2 marks)
Clue: Think about the mean free path — the average distance a molecule travels before hitting another molecule.
Guide: At atmospheric pressure, molecules collide frequently (short mean free path). As pressure drops, collisions become rarer and molecules travel further between hits. By rough vacuum, some molecules reach the chamber walls without colliding with other molecules.
A6. On the R1-A rig, identify the four major categories of component you would find: one that creates vacuum, one that holds the vacuum, one that controls gas flow paths, and one that measures pressure. Give one specific R1-A component ID as an example for each category.
(2 marks)
Clue: Think: what creates vacuum? What holds it? What controls the paths? What measures it? Use R1-A component IDs.
A7. Looking at a simplified vacuum schematic for the R1-A rig, what does a valve symbol in the closed position tell you about the gas flow through that section of the system? How would you visually distinguish an open valve from a closed valve on a schematic?
(2 marks)
Clue: On a schematic, look at the valve symbol. How does the symbol change between open and closed?
Guide: A closed valve symbol shows a blocked flow path — no gas can pass through that section. An open valve shows an unblocked path. On ISO schematics, the closed position is typically shown with a filled or blocked bowtie symbol.
A8. State the purpose of each of the following R1-A components: (a) the vent filter (R1-FLT-VENT), (b) the isolation valve (R1-V-ISO), and (c) the barometric reference gauge (R1-G-BX).
(2 marks)
Clue: For each component, think about its role in the gas flow path — what does it protect, control, or measure?
Guide: R1-FLT-VENT filters atmospheric air entering during venting (protects chamber from particles). R1-V-ISO separates the chamber from the pump (controls when pumping happens). R1-G-BX provides a local atmospheric pressure reference for comparison with chamber pressure.
A9. Atmospheric pressure at sea level is approximately 1013 mbar. At Selkirk College (530 m elevation), atmospheric pressure is approximately 950 mbar. Explain, in plain language, why the atmospheric pressure is lower at higher elevation and why this matters when you are reading gauges on the rig.
(2 marks)
Clue: Think about the column of air above you. How does altitude affect that column?
Guide: At higher altitude, there is less air above you pushing down. This means fewer molecules per unit area, so atmospheric pressure is lower. At 530 m, ~950 mbar vs ~1013 mbar at sea level. This matters because a gauge reading only makes sense relative to the local atmosphere.
A10. A roughing pump is used to bring a chamber from atmospheric pressure down into the rough vacuum range. In general terms, describe what a roughing pump does to the gas inside the chamber. Why does it take longer to remove the last bit of gas compared to the first large volume?
(2 marks)
Clue: Think about what happens as you remove molecules from a fixed volume. Does each "batch" get easier or harder to remove?
Guide: A roughing pump mechanically captures and expels gas molecules from the chamber. Initially, molecules are plentiful and flow easily into the pump (viscous flow). As pressure drops, fewer molecules remain, mean free path increases, and the molecules are harder to "catch" — the pump has to work harder for each further pressure reduction.
Part B: Rig Interpretation (20 marks)
Students examine a scenario card and answer questions about the rig state.
4 marks each. 5 questions.
Scenario Reference
Card: SC-02 — Roughing (Pump Down) Description: The R1-A rig is observed during an active pump down. The roughing pump is running, and the system has been pumping for several minutes. The following readings and positions are observed:
Component
State/Reading
R1-V-VENT
CLOSED
R1-V-ISO
OPEN
R1-G-CH
15 mbar (dropping)
R1-G-BX
~950 mbar
R1-P-RP
ON
B1. What state is this system in? Name the state and explain how you identified it using the valve positions, pump status, and gauge readings shown above. (4 marks)
Clue: Look at the valve positions and pump status in the scenario table. Which of the three R1-A states matches?
Guide: R1-V-VENT is CLOSED, R1-V-ISO is OPEN, R1-P-RP is ON, and pressure is dropping. The pump is connected to the chamber through the open isolation valve and actively removing gas. This matches one specific state.
Step by step
This is the ROUGHING state. Evidence: R1-V-VENT CLOSED (no air entering), R1-V-ISO OPEN (chamber connected to pump), R1-P-RP ON (pump running). R1-G-CH at 15 mbar and dropping confirms active pump-down. The path is open from chamber through foreline to pump.
B2. Trace the complete gas flow path from source to destination. Name every component the gas passes through, using the R1-A component IDs (for example, R1-CH, R1-V-ISO, etc.). (4 marks)
Clue: Start at the chamber and trace the path the gas takes to leave the system. Name every component it passes through.
Guide: Gas starts in R1-CH, passes through R1-V-ISO (which is OPEN), travels along R1-L-FL (foreline), enters R1-P-RP, and exits through R1-FLT-EXH and R1-L-EXH to atmosphere.
B3. The vent valve (R1-V-VENT) is closed during this pump down. Explain why it must remain closed. What would happen to the chamber pressure if someone accidentally opened the vent valve while the pump was still running? (4 marks)
Clue: Think about what the vent valve connects to. What would flow through it if it were open?
Guide: R1-V-VENT connects the chamber to atmosphere through R1-L-VENT and R1-FLT-VENT. If opened during pumping, atmospheric air (~950 mbar) would rush in, overwhelming the pump and raising the chamber pressure back toward atmospheric.
B4. Suppose the isolation valve (R1-V-ISO) is now closed while the pump continues to run.
Describe what would happen: What happens to the chamber pressure? What happens to the pump? What state has the system entered? (4 marks)
Clue: If the isolation valve closes, what is the chamber connected to? What can the pump reach?
Guide: With R1-V-ISO closed: the chamber is sealed (both valves now closed) — it enters the ISOLATED state. The chamber pressure holds where it was. The pump continues running but is now pumping only the foreline volume, not the chamber.
B5. The chamber gauge (R1-G-CH) reads 15 mbar and the barometric reference (R1-G-BX) reads 950 mbar. What pressure range is the chamber currently in? If the pump keeps running, what is the lowest pressure range you could expect this roughing pump to achieve on the R1-A rig, and roughly how low might the chamber gauge reading go? (4 marks)
Clue: Check the pressure range boundaries. Where does 15 mbar fall? What is the typical ultimate pressure for a roughing pump?
Guide: 15 mbar is in the rough vacuum range (1000 to 1 mbar). A roughing pump on R1-A can typically reach about 0.05 mbar — which is in the medium/fine vacuum range. The barometric reference at 950 mbar simply confirms local atmospheric pressure.
Part C: Practical Reflection (10 marks)
Connects learning to real-world application. Open-ended.
5 marks each. 2 questions.
C1. Describe a real or realistic situation where the concepts from this module would matter -- this could be from your current workplace, a previous role, a lab session, or a scenario you can envision in a vacuum-related industry. What would you (or someone in that role) do differently with this knowledge? (5 marks)
Clue: Think about a workplace scenario where knowing the system state or reading gauges correctly would matter. What decision would you make differently?
Guide: Consider: a maintenance technician arriving at a vacuum system on Monday morning. Knowing how to identify the system state from valve positions and gauge readings prevents incorrect actions — like opening a vent valve on a system that is supposed to be holding vacuum.
C2. What was the most surprising or counterintuitive thing you learned in this module? Why did it surprise you, and how has it changed the way you think about vacuum systems? (5 marks)
Clue: Reflect on something from the module content that challenged your initial assumptions about how vacuum works.
Guide: Many students are surprised that vacuum is not "sucking" — it is about removing molecules, and the atmosphere pushes things toward the lower pressure. Or that local atmospheric pressure varies with altitude, affecting how you read gauges.
