Module 5 Scenario Cards: Chambers, Components, Valves & System Layout

R1-A Component Reference

R2-A Extended Component Reference

SC-M05-01: Valve Sequencing Logic — Pump-Down and Vent Sequence on R2-A

Module: M05 Rig Config: R2-A Competency: M05-COMP-02 Indicators Assessed: M05-IND-02.02, M05-IND-02.03

System State

State Name: SEQUENCING (conceptual pump-down and vent) One-line description: The facilitator presents the R2-A system in a fully vented state and asks students to work through the correct conceptual pump-down sequence, then the correct vent sequence — identifying which valves open and close at each step and explaining why order matters.

Background Information (Provided to Students)

R2-A is a high-vacuum system with two pumps (roughing pump R2-P-RP and turbomolecular pump R2-P-HV), four valves (gate valve R2-V-GATE, roughing valve R2-V-ISO, foreline valve R2-V-FORE, vent valve R2-V-VENT), two gauges (chamber gauge R2-G-CH, foreline gauge R2-G-FL), and a foreline trap (R2-TRP-FL).

The system is currently in the VENTED state: all valves closed, both pumps off, chamber at ~950 mbar.

The target is to pump the system down to high vacuum (below 10^-5 mbar), hold at base pressure, then vent back to atmosphere.

Starting Valve Positions

Starting Gauge Readings

Pump Status (Starting)

Student Prompt

Teaching Points (Facilitator Notes)

Expected pump-down sequence:

Expected vent sequence:

Key learning moments:

• Crossover pressure (~0.1 mbar): This is the pressure at which the roughing pump has removed enough bulk gas for the turbo pump to safely take over. Below this pressure, the gas load is low enough that the turbo can handle it. Above this pressure, the turbo would be overloaded. The exact crossover depends on the system design and turbo pump specifications.

• Why close the roughing valve before opening the gate valve: If both are open simultaneously, the roughing pump's higher-pressure exhaust side could contaminate the low-pressure turbo inlet through unexpected flow paths. More practically, once the turbo takes over, the roughing valve is no longer needed for chamber pumping — it must close so the roughing pump serves only as the turbo's backing pump through the foreline.

• Why close the gate valve before venting: If the vent valve opens while the gate valve is open, atmosphere floods through the chamber and into the turbo pump — violating Rule 1. The turbo's spinning blades at atmospheric pressure can be mechanically damaged. The gate valve must isolate the turbo before any gas is admitted to the chamber.

Model observation note: "R2-A pump-down: R2-P-RP started, R2-V-FORE opened to evacuate foreline; R2-P-HV started once R2-G-FL confirmed below 1 mbar; R2-V-ISO opened to rough chamber — R2-G-CH dropped from 950 mbar through viscous flow phase to crossover pressure of approximately 0.1 mbar. R2-V-ISO closed, R2-V-GATE opened — R2-P-HV took over, pulling R2-G-CH through molecular flow to base pressure below 10^-5 mbar. Crossover from roughing to high-vacuum pumping occurred at 0.1 mbar with no turbo overload."

Common student errors:

• Opening the gate valve before roughing down (violates Rule 1 — turbo exposed to atmosphere)
• Forgetting to start the roughing pump and prepare the foreline before starting the turbo
• Not closing the gate valve before venting (violates Rule 3 — turbo exposed to atmosphere during vent)
• Describing the sequence without explaining why each step happens in that order
• Confusing the roughing valve with the foreline valve — these control different paths

SC-M05-02: Feedthrough Leak Path — Diagnosing a Leak at a Motion Feedthrough

Module: M05 Rig Config: R1-A (conceptually extended with feedthroughs for this scenario) Competency: M05-COMP-01, M05-COMP-02 Indicators Assessed: M05-IND-01.03, M05-IND-02.01, M05-IND-02.02

System State

State Name: ISOLATED (diagnostic hold) One-line description: R1-A (conceptually extended with two feedthroughs on the chamber) has been roughed to base pressure, isolated, and is now under a rate-of-rise test. The test reveals a real leak, and the evidence points to one of the feedthroughs as the source.

Background Information (Provided to Students)

For this scenario, imagine that R1-A's chamber (R1-CH) has been modified for a research application. Two feedthroughs have been added to the chamber:

• FT-1: An electrical feedthrough (ceramic-to-metal braze) for powering a small heater inside the chamber. Installed six months ago. Has never been removed since installation.
• FT-2: A rotary feedthrough (bellows-sealed) for rotating a sample stage. Recently removed and reinstalled two weeks ago to replace a worn bellows.

The system was roughed normally (R1-V-ISO open, R1-V-VENT closed, pump on). The fast phase from 950 to 1 mbar completed in the normal ~90 seconds.

Below 1 mbar, the pump-down slowed more than expected. After 30 minutes, R1-G-CH read 0.15 mbar — the expected base pressure is 0.05 mbar.

The operator isolated the system (R1-V-ISO closed, R1-V-VENT closed, pump off) and performed a rate-of-rise test.

Valve Positions

Gauge Readings

Rate-of-Rise Test Data

Additional Information

• The pump was tested independently (foreline disconnected, gauge at pump inlet): pump reaches 0.008 mbar — within specification.
• The chamber was solvent-cleaned three weeks ago and has been pumped down multiple times since. No contamination is suspected.
• FT-1 (electrical feedthrough) has been in place for six months with no issues.
• FT-2 (rotary feedthrough) was removed, the bellows replaced, and reinstalled two weeks ago. The reinstallation was performed by a trainee under supervision.

Pump Status

Student Prompt

Teaching Points (Facilitator Notes)

Expected student observations:

• The rate of rise is constant at 0.06 mbar/min across all intervals (1, 3, 5, 10, 15 minutes)
• A constant rate indicates a real leak — atmosphere is providing a steady gas source
• A decreasing rate would indicate outgassing — this is not what the data shows
• The pump meets specification independently — the pump is not the problem
• The chamber is clean — contamination/outgassing is not the primary source

Key learning moments:

• Constant rate = real leak, not outgassing. This is the definitive diagnostic: 0.06 mbar/min at every interval, with no decrease over 15 minutes. Outgassing produces a concave, decreasing curve. A constant rate means an unlimited external gas source — atmosphere — is entering through a fixed-size opening.

• FT-2 is the leading hypothesis. Evidence chain: (1) the rate-of-rise confirms a real leak, (2) FT-2 was recently removed and reinstalled — introducing a new seal that could be improperly seated, (3) the reinstallation was performed by a trainee (increased risk of installation error), (4) FT-2 is a dynamic feedthrough that was disassembled (the bellows-to-flange seal, the new bellows itself, or the flange gasket could be compromised). FT-1, by contrast, has been in place for six months with no issues — a ceramic-to-metal braze is a static, robust seal that does not degrade from routine system cycling.

• Evidence against FT-1: FT-1 has not been disturbed. Ceramic-to-metal brazes are among the most reliable vacuum seals. The leak appeared after FT-2's reinstallation, not after any event involving FT-1.

• Evidence against valve seats: While R1-V-ISO and R1-V-VENT seats could theoretically leak, neither was recently serviced, and the system performed normally before FT-2's reinstallation.

Model diagnostic finding: "With R1-V-ISO and R1-V-VENT both closed, R1-G-CH shows a constant rate of rise of 0.06 mbar/min over 15 minutes — consistent with a real leak into the isolated chamber zone, not outgassing. The only recent change to the vacuum boundary is the reinstallation of FT-2 (rotary feedthrough, bellows replaced two weeks ago by a trainee). The evidence supports FT-2 as the leading leak source: constant rate indicates a fixed-size opening at the vacuum boundary, and FT-2's recent disassembly and reassembly introduced new seal surfaces that may be improperly seated or damaged."

Research experiment impact: At 0.06 mbar/min leak rate, the system cannot reach 0.01 mbar — the pump would stall at a pressure where the pump speed equals the leak rate divided by the effective speed. The research experiment requiring 0.01 mbar would be impossible.

The evidence indicates FT-2's flange seal and bellows installation as the leading hypothesis. Additional information needed: visual inspection of the gasket condition and bolt torque on FT-2, followed by a confirmation rate-of-rise test, would help confirm the diagnosis.

Common student errors:

• Attributing the constant rate of rise to outgassing (outgassing produces a decreasing rate)
• Saying "it must be FT-2" without citing the specific evidence (constant rate, recent reinstallation, trainee installation)
• Not ruling out FT-1 explicitly — strong analysis eliminates alternatives, not just supports the hypothesis
• Forgetting to name the isolation state (both valves closed) when explaining why the rate-of-rise test is valid
• Listing both feedthroughs as equally likely without ranking based on maintenance history and seal type

SC-M05-03: Isolation Point Identification on a Multi-Zone Coating System

Module: M05 Rig Config: Extended system (based on R2-A principles) Competency: M05-COMP-02 Indicators Assessed: M05-IND-02.01, M05-IND-02.02, M05-IND-02.03

System State

State Name: MULTI-ZONE DIAGNOSTIC One-line description: A multi-zone coating system has three chambers sharing a common pumping manifold. Pressure data from isolated zones is provided. Students must identify all isolation points on the schematic, determine which zone contains the problem, and explain how the isolation points enabled the diagnosis.

Background Information (Provided to Students)

A thin-film coating facility operates a multi-zone vacuum system with the following architecture:

Chambers:

• Chamber A — Substrate loading chamber (small, frequently vented)
• Chamber B — Coating process chamber (large, rarely vented, contains two electrical feedthroughs and one fluid feedthrough for cooling water)
• Chamber C — Quality inspection chamber (medium, occasionally vented, contains a viewport and one electrical feedthrough)

Pumping:

• All three chambers connect to a common pumping manifold (MANF-1) through individual isolation valves
• The manifold is pumped by a shared roughing pump (P-RP) through a manifold isolation valve
• Chamber B also has a dedicated turbomolecular pump (P-HV-B) connected through a gate valve

Valves:

• IV-A — Isolation valve, Chamber A to manifold
• IV-B — Isolation valve, Chamber B to manifold
• IV-C — Isolation valve, Chamber C to manifold
• IV-M — Manifold isolation valve (manifold to roughing pump)
• GV-B — Gate valve, Chamber B to turbo pump
• VV-A — Vent valve, Chamber A
• VV-B — Vent valve, Chamber B
• VV-C — Vent valve, Chamber C

Gauges:

• G-A — Chamber A gauge
• G-B — Chamber B gauge
• G-C — Chamber C gauge
• G-M — Manifold gauge

System History

The system has been operating normally for three months. Yesterday, a routine maintenance session was performed on Chamber B: the fluid feedthrough (cooling water line) was inspected and re-torqued, and the two electrical feedthroughs were visually checked (no disassembly). The system was re-pumped this morning.

This morning's pump-down: Chambers A and C reached their expected base pressures (0.05 mbar each) within 10 minutes. Chamber B roughed normally from 950 to 1 mbar but then stalled — after 45 minutes, G-B reads 0.30 mbar. The expected base pressure for Chamber B (with the turbo pump) is 5 x 10^-6 mbar.

The operator performed a systematic isolation diagnostic.

Isolation Diagnostic Data

Step 1: All isolation valves closed, all vent valves closed, all pumps off.

Step 2: Chamber B further investigated — GV-B closed (isolating turbo pump from Chamber B), IV-B closed (isolating manifold from Chamber B), VV-B closed.

Valve Positions (During Step 1)

Student Prompt

Teaching Points (Facilitator Notes)

Expected isolation point identification:

Total: 8 isolation points. Each one defines a zone boundary.

Expected diagnostic interpretation:

Step 1 data conclusively localises the problem:

• Chamber B: constant rate of rise at 0.05 mbar/min — real leak. The constant rate over 10 minutes is the definitive evidence. With all of Chamber B's isolation valves closed (IV-B, GV-B, VV-B), the leak source must be within Chamber B's sealed boundary.
• Chamber A: decreasing rate at 0.002 mbar/min — normal outgassing. No leak.
• Chamber C: decreasing rate at 0.001 mbar/min — normal outgassing. No leak.
• Manifold: decreasing rate at 0.002 mbar/min — normal outgassing. No leak. This confirms the leak is not in the shared pumping infrastructure.

Step 2 confirms the finding: even with Chamber B fully isolated from all paths (GV-B closed, IV-B closed, VV-B closed), the rate of rise persists at 0.05 mbar/min. The leak is within Chamber B's physical boundary.

Expected leak location ranking within Chamber B:

1. Fluid feedthrough (cooling water line) — most likely. This feedthrough was physically disturbed yesterday (re-torqued). Re-torquing can damage gaskets, shift seal surfaces, or introduce misalignment. Additionally, fluid feedthroughs carry the catastrophic risk of water ingress if the internal tube fails — though in this case the constant air-leak pattern suggests a flange seal issue, not a tube failure.

1. Chamber B vent valve seat (VV-B) — possible but less likely. VV-B was not serviced during yesterday's maintenance. However, valve seats can degrade over time (compression set on the O-ring — Module 4 concept). If VV-B's seal is marginal, the system may show a slow leak that mimics an external leak. Lower probability because the timing correlates with the feedthrough maintenance, not with any valve event.

1. Electrical feedthroughs — unlikely. These were visually inspected but not disassembled. Ceramic-to-metal brazes are static, robust seals. Unless physical damage was introduced during the visual inspection (unlikely), these are low probability.

1. Chamber wall or weld — very unlikely. Chamber welds that have held for three months do not spontaneously develop leaks. No thermal cycling or mechanical stress events are reported.

1. Gate valve seat (GV-B) — very unlikely. GV-B was not serviced and has been functioning normally.

Key learning moments:

• Isolation points enable divide-and-conquer diagnostics. Without the ability to isolate each zone independently, the operator would have to guess which chamber has the problem. The isolation valves transform a complex multi-zone system into independent, testable zones.

• The manifold gauge is the key discriminator. If the manifold showed a leak instead of (or in addition to) Chamber B, the problem could be in the shared pumping infrastructure rather than in Chamber B. The manifold's clean data rules out the shared components.

• Maintenance history drives ranking. The fluid feedthrough was the only component physically disturbed. The timing correlation (maintenance yesterday, problem today) combined with the feedthrough's seal being newly made provides the strongest hypothesis. Students should not list all feedthroughs as equally likely.

• Explicitly name the isolation. Strong communication says: "With IV-B, GV-B, and VV-B all closed, Chamber B is isolated from the manifold, turbo pump, and atmosphere respectively. The constant rate of rise in the isolated chamber zone at 0.05 mbar/min confirms the leak is within Chamber B's physical boundary." This explicitly names the isolation points and explains how they account for the gauge behaviour.

Model diagnostic report: "Systematic isolation diagnostic on the multi-zone coating system confirms a real leak in Chamber B. With IV-B (manifold isolation), GV-B (turbo pump isolation), and VV-B (vent isolation) all closed, G-B shows a constant rate of rise of 0.05 mbar/min over 10 minutes — while Chambers A, C, and the manifold all show only normal outgassing patterns (decreasing rates below 0.002 mbar/min).

The leak source is within Chamber B's sealed boundary; the fluid feedthrough (cooling water line), which was re-torqued during yesterday's maintenance, is the leading hypothesis based on the timing correlation and the fact that it is the only component whose seal was physically disturbed. Additional information needed: visual inspection of the fluid feedthrough flange seal and gasket condition, followed by a confirmation rate-of-rise test, would help confirm this hypothesis."

Escalation — process impact: The coating process requires 5 x 10^-6 mbar. With a constant leak rate of 0.05 mbar/min (50 mbar in approximately 16.7 hours if fully sealed), the leak introduces gas far faster than even a turbo pump can remove at those pressures.

The system will stall at a pressure where the turbo pump's throughput equals the leak throughput — well above the 5 x 10^-6 mbar target. The coating process cannot proceed until the leak is repaired. At the current leak rate, the equilibrium pressure would be orders of magnitude above the process requirement.

Common student errors:

• Failing to identify all 8 isolation points (often missing the vent valves as isolation points)
• Not using the manifold gauge data to rule out shared infrastructure problems
• Listing all feedthroughs as equally likely leak sources without considering maintenance history
• Using "it must be the fluid feedthrough" instead of evidence-based ranking language
• Not connecting the isolation point names to the gauge behaviour in their diagnostic report
• Forgetting that the rate-of-rise pattern (constant vs decreasing) is the key discriminator between a leak and outgassing

End of Scenario Cards — Module 5