Module 2

Workbook

Influences on Real Vacuum Systems
Facilitator: adjust scaffolding level before distributing

Module 2 Workbook: Influences on Real Vacuum Systems

Estimated Completion Time: 45-60 minutes

Part A: Knowledge Check (20 marks)

Short-answer questions testing recall from Module 2 async learning content. 2 marks each. 10 questions.

A1. Name three sources of gas load in a vacuum system. For each source, explain in one sentence why gas continues to enter the chamber even while the pump is running.

(2 marks)

Clue: Think about the four types of gas source that can contribute to pressure in a vacuum system.
Guide: The four gas load sources: real leaks (atmosphere entering through gaps), outgassing (surfaces releasing absorbed/adsorbed gas), permeation (gas passing through solid materials), and backstreaming (pump oil vapour moving backward into the chamber).

A2. Identify two common sources of contamination that could be introduced into a vacuum chamber during routine use. For each, describe the effect it has on system pressure.

(2 marks)

Clue: Consider what happens to water molecules when they land on a surface, and what makes them leave.
Guide: Adsorption: water molecules from humid air stick to chamber surfaces when exposed to atmosphere. Desorption: under vacuum, these molecules gain enough energy to leave the surface. This is the main gas source in many vacuum systems — it takes time and/or heating to remove.

A3. Explain the difference between ideal vacuum behaviour and what happens in a real vacuum system. Why does a real system never reach zero pressure?

(2 marks)

Clue: Think about what makes a leak rate steady versus what makes an outgassing rate decrease.
Guide: A leak has an unlimited source (atmosphere) so the rate stays constant. Outgassing has a finite source (surface molecules) that gets depleted, so the rate decreases over time. This is the key diagnostic distinction in a rate-of-rise test.

A4. Describe how an elevated gas load affects pumpdown performance. If a system normally reaches a base pressure of 0.05 mbar but today stalls at 0.40 mbar with the pump running normally, what does this tell you about the gas load?

(2 marks)

A5. Explain why elastomers such as rubber and Viton contribute more gas load to a vacuum system than metals such as stainless steel. Describe the mechanism in plain language.

(2 marks)

A6. Distinguish between a gross leak and a minor leak. Describe one observable difference in system behaviour that would help you tell them apart.

(2 marks)

A7. Name three symptoms that indicate contamination is present in a vacuum system rather than a leak. Explain why contamination and leaks can sometimes look similar at first glance.

(2 marks)

A8. A system is being roughed and the pumpdown proceeds normally from 950 mbar to 1 mbar.

Below 1 mbar the pressure drops very slowly and stalls well above the normal base pressure. The pump sounds normal. Describe what this pumpdown behaviour indicates about the system.

(2 marks)

A9. State the purpose of a Residual Gas Analyzer (RGA). What kind of information does it provide, and why is that information useful when diagnosing vacuum system issues?

(2 marks)

A10. A rate-of-rise test is performed on an isolated chamber. In one test, the rate of pressure rise is constant over 10 minutes.

In a second test on the same chamber on a different day, the rate of rise starts high and decreases steadily over 10 minutes. Explain what each pattern indicates about the source of gas entering the chamber.

(2 marks)

Part B: Rig Interpretation (20 marks)

Students examine scenario data from the R1-A rig and answer questions about system behaviour. 4 marks each. 5 questions.

Scenario Reference

Card: SC-M02-01 — The Slow Climb: Outgassing or Leak? Description: R1-A has been roughed down to 0.08 mbar and then isolated.

Both valves are closed and the pump is off. The chamber pressure is rising slowly. The following rate-of-rise data was recorded.

Component State/Reading
R1-V-VENT CLOSED
R1-V-ISO CLOSED
R1-G-BX ~950 mbar
R1-P-RP OFF

Rate-of-Rise Data

Time after isolation R1-G-CH (mbar) Rise since last reading (mbar) Rate (mbar/min)
0 min 0.08 — —
1 min 0.20 0.12 0.12
2 min 0.29 0.09 0.09
5 min 0.44 0.15 0.05
10 min 0.56 0.12 0.024

B1. What system state is R1-A in? Name the state and describe the evidence from the valve positions, pump status, and gauge readings that confirms it. (4 marks)

Clue: Look at the rate-of-rise data carefully. Is the rate constant or changing? What does that pattern tell you?
Guide: Check whether the rate of rise stays the same between each interval or decreases. A constant rate points to a real leak. A decreasing rate points to outgassing from surface desorption.
Step by step
Apply R-I-C-E: Recognise the pattern in the numbers. Interpret what constant vs decreasing rate means (leak vs outgassing). Communicate your finding using specific values. Escalate with a recommended next step (e.g., re-pump and repeat to confirm).

B2. Examine the rate-of-rise column in the data table. Is the rate constant, increasing, or decreasing over the 10-minute test? Describe the pattern you observe and state what this pattern indicates about the source of the gas load. (4 marks)

B3. Explain why the rate of rise is highest in the first minute (0.12 mbar/min) and lowest in the last interval (0.024 mbar/min). Describe, in plain language, what is happening at the molecular level on the chamber surfaces as time passes. (4 marks)

B4. If this same test were repeated after re-pumping and isolating the chamber a second time, how would you expect the rate-of-rise pattern to change — and why? What does this tell you about the nature of an outgassing source compared to a leak? (4 marks)

B5. Write a three-sentence escalation note for a shift supervisor summarising: (1) what was observed during the rate-of-rise test, (2) what the evidence indicates about the gas source, and (3) whether any follow-up action is needed. Use specific readings and component IDs from the data. (4 marks)

Part C: Practical Reflection (10 marks)

Connects learning to real-world application. Open-ended. 5 marks each. 2 questions.

C1. Describe a situation where the concepts from this module — gas load, contamination, outgassing, or rate-of-rise interpretation — would matter in a vacuum-related setting. This could be:

Explain what someone in that role would understand differently about system behaviour with the knowledge from this module. Be specific — reference at least one concept by name. (5 marks)

C2. What was the most surprising or counterintuitive idea you encountered in this module? Why did it challenge your expectations?

If you have workplace experience, describe how this changes your understanding of something you have observed on the job. If you are new to vacuum technology, describe how this concept changes the way you would approach interpreting a vacuum system for the first time. (5 marks)

Marking Summary

Part Available Achieved
A: Knowledge Check 20
B: Rig Interpretation 20
C: Practical Reflection 10
Total 50

Assessor: ________________________________ Date: ________________________________ Comments: ________________________________________________________________________

Submit Your Workbook

When you have completed all sections, click below to submit your work to your facilitator.