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Spark Resistance Parts Matrix

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About This MicroSim

Spark resistant Types A, B and C differ in which airstream parts they make non-ferrous. This matrix asks you to commit a prediction for every part before you see FanPedia's answer. The rows are six components of a centrifugal fan; the columns are the three types. Each of the 18 cells takes one of three states: Non-ferrous, Steel or Not listed (the type's page does not list the part).

The answer table comes from the "Non-Ferrous Construction" and "Steel Construction" lists on FanPedia's centrifugal fan pages for Type A (p. 104), Type B (p. 105) and Type C (p. 106):

Component Type A Type B Type C
Housing / frame Non-ferrous Steel Steel
Impeller Non-ferrous Non-ferrous Steel
Inlet funnel Non-ferrous Steel Non-ferrous
Rub plate Not listed Non-ferrous Non-ferrous
Shaft Steel Steel Steel
Pedestal Steel Steel Steel

The pattern is the point: Type A makes almost every airstream part non-ferrous, Type B makes the impeller (and its rub plate) non-ferrous, and Type C protects only the likely contact points, the inlet funnel and the rub plate. The shaft and the pedestal are steel in all three. After the answers are revealed, a note adds two rules: bearings are not allowed in the airstream in any of the three types, and Type C at 501°F and above uses a steel funnel with a rubbing band and rubbing bars instead of the aluminum funnel.

The first Check is the recorded score. Mastery is 15 of 18 cells correct on the first Check.

How to Use

  1. Open any component name (Housing / frame, Impeller, …) to read what the part is. The description appears in the line under the question. Opening a description is exploration, not evidence.
  2. Set every cell to Non-ferrous, Steel or Not listed. Check stays unavailable until all 18 cells are set; the line beside it says how many cells remain empty.
  3. Press Check. Each cell is marked ✓ Correct (solid green border) or ✗ Not quite (dashed red border), and every row with a wrong cell shows a hint underneath (the question to ask for that component, not the answer). The feedback reads "You matched n of 18 cells." followed by "You can tell the three types apart part by part." (15 or more) or "Look at the Impeller and Inlet funnel rows first; they carry the main difference between B and C." (below 15).
  4. Press Try Again to clear only the wrong cells (the correct ones stay locked), set them again and press Check a second time. The first-Check score stays the recorded score.
  5. The second Check, or Show Answers at any time after the first Check, reveals the answer in every cell, every row's reason and the note on bearings and the 501°F funnel.
  6. Press Start over to clear the matrix and the score.

Keyboard: Tab moves from cell to cell and to the buttons. In a cell, the arrow keys change the state (or type S for Steel, N for Non-ferrous or Not listed). Enter or Space on a component name opens its description; Enter on a button presses it.

Data label: "Source: FanPedia, Spark Resistant Construction, Centrifugal Fans, pp. 104-106", shown under the matrix.

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Lesson Plan

Learning Objective

The learner will differentiate spark-resistant Types A, B and C on a centrifugal fan by predicting, for six fan components, whether each type makes the component non-ferrous, leaves it steel, or does not list it, with at least 15 of 18 cells correct on the first attempt (Bloom: Analyze, verb: differentiate).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration

10-15 minutes

Prerequisites

  • Spark resistant construction and Types A, B and C
  • Non-ferrous material
  • Rub plate and inlet funnel
  • Pedestal (Chapter 3)

All are defined in the section "Spark Resistant Construction" of Chapter 20.

Activities

  1. Predict (5 min): Fill all 18 cells without notes and press Check. This first Check is the recorded score.
  2. Repair (3 min): Read the hints under the wrong rows, press Try Again, fix the cleared cells and Check again.
  3. Find the pattern (3 min): With the answers revealed, describe each type in one phrase (A: almost everything in the airstream; B: the impeller; C: the contact points).
  4. Discuss (3 min): Why does Type A's list have no rub plate? Why is a stainless steel set screw not "non-ferrous"? What does the 501°F note change on a Type C order?

Common Misconceptions Addressed

  • Type C makes the impeller non-ferrous: the Impeller row shows Steel for Type C.
  • Type B makes the whole airstream non-ferrous: only the impeller and the rub plate are non-ferrous; the housing and the inlet cone stay steel.
  • Spark-resistant construction makes the shaft non-ferrous: the Shaft row is Steel in all three types.

Assessment

  • First-Check score shown as "First Check: n of 18 cells (recorded)"; mastery is 15 of 18 on the first Check, and the feedback adds "Mastery reached (15 of 18 needed)." or "Mastery needs 15 of 18 on the first attempt."
  • Follow-up: a Type B fan has an outside protruding hub. Which cell of the matrix could change, and why? (FanPedia p. 105: the rub plate is then not required.)

References

  1. FanPedia: Spark Resistant Construction, Centrifugal Fans - Twin City Fan. Type A (p. 104), Type B (p. 105) and Type C (p. 106) component lists, the source of every cell in the answer table.
  2. FanPedia (PDF edition) - Twin City Fan, the printable edition with the same page numbers.
  3. Chapter 20: Construction Classes, Materials and Spark Resistance - the chapter section this sim belongs to.
  4. Non-ferrous metal - Wikipedia, background on why iron-free metals are used where sparks matter.