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Split Housing Selector

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About This MicroSim

A split housing is built in sections that bolt together. FanPedia names three kinds for centrifugal fans, each by where the cut runs: the horizontal split (the standard split, along the horizontal centerline), the three-way split (three sections, up to 180 degrees) and the pie split (a wedge at 90 degrees or greater, in Mohawk or standard style). This MicroSim gives you eight illustrative job situations in a fixed order and asks which split, if any, each one calls for.

For each situation you make two decisions:

  1. Recommend. Choose one of five recommendations: Horizontal split; Three-way split; Pie split, Mohawk style; Pie split, standard style; No split recommended. The choice locks.
  2. Justify. Four FanPedia rules appear in shuffled order. Pick the one that justifies the right choice for this fan. The options are the situation's own rule plus the rules of the next three situations whose recommendation is different, so no wrong option is a valid reason for the same split.

A situation counts as correct only when both the recommendation and the justification are right. Situations 3, 4, 5 and 7 all involve a pie split; the style follows only from the facts stated in each situation (inlet side left whole, double width, attached inlet box, matching an older split).

There is one attempt per situation. Mastery is 6 of 8 situations correct on the first attempt.

# Correct recommendation FanPedia rule
1 Horizontal split Standard split on the horizontal centerline; the shop may split size 807 and above for shipping
2 Three-way split Needed to ship a fan or to enter a specific sized opening
3 Pie split, Mohawk style Splits between the scroll and the inlet side; the inlet side has no split
4 Pie split, standard style The Mohawk style is not used on double width fans
5 Pie split, standard style Arr. 3SI includes a pie split; no Mohawk with attached inlet boxes
6 No split recommended Split housings are not recommended for nominally leak-tight construction
7 Pie split, standard style The older standard style runs down to the funnel or inlet plate
8 Three-way split Fits the opening; needs extra drafting and engineering time in the quote

Work through the sim before you read the table.

How to Use

  1. Read the situation and the question "Which split, if any, should this fan have?"
  2. Choose a recommendation with the buttons in the Split row or keys 1 to 5. It locks and shows a ✓ mark.
  3. Read the four rules, A to D, and choose one with the Reason buttons or keys A to D.
  4. Read the feedback:
    • Both right: "✓ Correct:" with the recommendation and its rule.
    • Wrong recommendation: "✗ Not quite. The better choice is" the right split, followed by its rule.
    • Right recommendation, wrong rule: "✗ Right split, wrong reason." followed by the rule. The right rule is marked ✓ in the list and your pick, if different, ✗. The running count "Situations correct: n of 8" is at the top.
  5. Press Next situation (or Enter). After situation 8, See summary shows your first-attempt score, whether you reached mastery, and a table of your answers beside the correct splits. Press Start over to try again.

Keyboard: 1–5 choose the split, A–D choose the reason, Enter goes to the next situation. After a split locks, focus moves to the reason buttons; after a reason, to Next situation.

Data label: "Illustrative situations · Source: FanPedia pp. 120, 156–157, 164–168, 194", shown at the bottom left of the drawing area.

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Lesson Plan

Learning Objective

The learner will recommend a horizontal, three-way, Mohawk pie, standard pie or no split housing for eight described centrifugal fan situations, justifying each choice with a FanPedia rule (Bloom: Evaluate, verb: recommend).

Audience

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

Duration

10-15 minutes

Prerequisites

  • Chapter 7, section "Split Housings", and the warning on splits in leak-tight housings.
  • Chapter 3: split housing, attached inlet box, double width fan.
  • The term nominally leak-tight construction (Chapter 21 gives the details).

Activities

  1. Situations (8 min): Work through all eight situations. Before you press a reason, say out loud which fact in the situation text decided the split.
  2. Review (3 min): Read the summary table. For every "wrong reason" row, find the rule in the chapter's split table.
  3. Discuss (3 min): Situations 3, 4, 5 and 7 all need a pie split. List the facts that rule the Mohawk style out, and the one fact that rules it in.

Common Misconceptions Addressed

  • Any split will let the impeller out without touching the ductwork: only the pie split is described as removing the impeller "without disturbing inlet or outlet"; situations 1, 2 and 8 use other splits for shipping and openings.
  • The Mohawk pie split works on any fan: situations 4 and 5 rule it out for double width fans and fans with attached inlet boxes.
  • Adding a split is always harmless: situation 6 asks for no split in nominally leak-tight service, and situation 8 costs drafting and engineering time.
  • A horizontal split is only for maintenance, never shipping: situation 1 is a shipping split for size 807.

Assessment

  • First-attempt score shown as "First-attempt score: n of 8"; mastery is 6 of 8 situations with both the recommendation and the justification correct. The running line shows "Situations correct: n of 8".
  • Follow-up question: a quote calls for a three-way split on an RTO fan. What two concerns should you raise before it goes out?

References

  1. FanPedia: The Fan & Blower Encyclopedia (PDF) - Twin City Fan & Blower; pp. 156–157 and 194 describe the split housing types and styles, pp. 164–168 the arrangements with pie splits, and p. 120 the leak-tight limitation.
  2. FanPedia online - Twin City Fan & Blower's online version of the encyclopedia.
  3. Chapter 7: Housing Construction and Exploded Views - the section "Split Housings" and its summary table.
  4. Chapter 21: High-Temperature, Leak-Tight and RTO Construction - gasketing, bolt spacing and centering plates when a split is used on a tight housing.