CIP Flow & Velocity Calculator (5 ft/s Rule, ASME BPE)
Sizes the CIP flow in gpm and L/min needed to hold the ASME BPE SD-6.3.5.2.1 target of 5 ft/s in a given tube ID, and inverts Q = 2.448·v·ID² to report the velocity in ft/s and m/s an available flow actually reaches, with PASS/FAIL.
Turbulent flushing of process lines is the piping half of CIP: BPE practice targets a mean velocity of 5 ft/s (≈1.5 m/s) in the largest line of the circuit. Enter the tube ID to get the required flow — or enter your available CIP supply flow to check the velocity actually achieved.
Method
Q (gpm) = 2.448 · v (ft/s) · ID² (in)
v = Q / (2.448 · ID²)
The 2.448 constant is the exact unit conversion for flow through a circular section (Q = v·A). Default target is 5 ft/s per SD-6.3.5.2.1; metric outputs are provided alongside.
| Inputs | ||
|---|---|---|
| ID | Tube / pipe inside diameter | in |
| target v | Target velocity (default 5) | ft/s |
| Q actual | Available flow (optional — enables the check mode) | gpm |
| Outputs | ||
| Q required | Flow for target velocity | gpm, L/min |
| v achieved | Velocity at available flow (check mode) | ft/s, m/s |
Limitations — what this calculator is not
- Full-pipe, single-phase flow assumed — partially drained returns or air-locked circuits will not see the computed velocity.
- Sizes the flow requirement only; pump head, circuit ΔP, and parallel-path balancing are hydraulic design beyond this card.
- 5 ft/s is the accepted practice minimum for line flushing, not a guarantee of soil removal — chemistry, temperature and time complete the cleaning equation.
Worked example — fixture-verified
2.0 in ID transfer line; find the CIP flow for 5 ft/s, then check a skid that can only deliver 60 gpm.
| Given | ||
|---|---|---|
| Tube ID | 2.0 | in |
| Target velocity | 5 | ft/s |
| Available flow (case 2) | 60 | gpm |
Step by step
- Required flow: Q = 2.448·5·2² = 2.448·5·4 = 48.96 gpm (185.3 L/min).
- Check mode: v = 60 / (2.448·4) = 60 / 9.792 = 6.13 ft/s (1.87 m/s) ≥ 5 → PASS.
| Result PASS | ||
|---|---|---|
| Required flow @ 5 ft/s | 48.96 | gpm |
| Required flow | 185.3 | L/min |
| Achieved velocity @ 60 gpm | 6.13 | ft/s |
| Verdict | PASS | — |
Both directions — flow-from-velocity and velocity-from-flow — are locked as separate fixture cases.
cip-velocity.json — case “2 in line, 5 ft/s target -> required flow” (tolerance 0.01) — in the
calc-core release gate. It re-runs on every commit; a red fixture blocks deployment.
See the validation methodology.Additional verified cases in this fixture
60 gpm available -> achieved velocity pass PASS
input: {"id":2,"actualFlowGpm":60}
expect: {"achievedVelocityFtS":6.1274,"achievedVelocityMS":1.8676}
tol: 0.001Sources & citations
- ASME BPE — SD-6.3.5.2.1, CIP line velocity practice.
Per the source & citation policy, allowable-stress and factor table values are user-supplied — this page and the app cite paragraph numbers and never reproduce ASME table data.
FAQ
Why 5 ft/s?
It is the industry-accepted threshold for fully turbulent, wall-shearing flow across hygienic tube sizes — enough shear to strip soil films and sweep particulates. BPE references it as accepted practice; individual owners sometimes specify 1.5 m/s, which the metric output shows directly.
Which line sets the CIP flow for a circuit?
The largest ID in the flow path — it needs the most flow to hold 5 ft/s. Smaller lines in series then run faster, which is acceptable; parallel paths need balancing so no branch starves.
Related calculators
- CIP Spray Device Flow Sizing Calculator (ASME BPE) — Vessel side of the same CIP circuit demand
- Dead-Leg L/d Ratio Calculator (ASME BPE) — Velocity won't clean branches beyond L/d of 2
- Hygienic Line Slope / GSD Drainability Calculator (ASME BPE) — Circuits must drain between CIP flush steps