Dead-Leg L/d Ratio Calculator (ASME BPE) — Sample Report

1 · Design inputs

Instrument tee off a hygienic process line: dead-leg length 50 mm, branch ID 25 mm, standard limit of 2.

2 · Method

L/d ≤ 2 (target, ASME BPE SD-3.1.2.2)

margin = limit − L/d (negative = FAIL)

The calculator applies the screen in three steps. First, L is measured from the ID wall of the run — the surface the sweeping flow actually reaches — along the branch to the end of the cavity: for a valved branch, through the valve body to the seat. d is the branch inside diameter, and both entries share one unit, mm or inches, because the ratio is dimensionless. Second, L/d is compared against the limit — the SD-3.1.2.2 recommendation of 2 by default, or the tighter value your specification imposes. A ratio at or under the limit passes; over it fails, with a warning that exceedances must be identified and justified by the designer. Third, independent of the verdict, a branch diameter under 3/4 in (19 mm) triggers the SD-2.4.3.2 surface-tension advisory: at small bores, hold-up and drainability can defeat a geometry that passes on ratio alone. The same three steps run identically in mm or inches, and the fixture set locks metric, imperial, default-limit, failing and small-branch paths as separate release-gated verdict cases.

3 · Calculation

1. L/d = 50 / 25 = 2.0.
2. Margin = 2 − 2.0 = 0.0 → exactly at the target: PASS.

4 · Results PASS

5 · Verification statement

The result values above are locked as fixture dead-leg.json, case “at the limit -> pass”, tolerance 1e-9, in the calc-core continuous verification gate (see https://pipingtoolset.com/trust/validation.html). Allowable-stress and factor data are user-supplied inputs; citations: ASME BPE — SD-3.1.2.2, dead-leg L/d design target (embedded limit).