Contents
About this tool
The Pipeline (B31.4) tool checks one section of liquid pipeline, or of the piping in a tank farm, pump station or terminal: the wall thickness needed for the design pressure, the maximum pressure the installed wall allows, the hoop stress and surge, the hydrostatic test, and whether corrosion and dents found in service need repair.
Edition: upgrade due
Built on ASME B31.4-2016, the text on file. ASME B31.4-2022 is current and has not been compared; the tool will be upgraded when that text is available. The page, the report and this manual say so.
Data from outside the B31.4 text
Two inputs are not in B31.4 itself, and the tool says so where it uses them: the specified minimum yield strengths of the pipe grades (API 5L and ASTM published values; you can type your own), and the corroded-pipe equations of ASME B31G Level 1 (original and modified), which 451.6.2.2 names but which are a separate standard.
Scope (400.1.1)
Liquid pipelines (crude, products, LPG, NGL, liquid ammonia and similar) between production, storage, refineries, pump stations and terminals, and the piping within tank farms and terminals associated with them, at metal temperatures from −30 to 120 °C. Process piping inside a refinery or plant falls under B31.3 — use the Process Piping tool.
Quick start
- 1Load a sample or fill in Identification. Choose SI or US units; records are kept in SI.
- 2Section 1: pick the size (or type the OD), the nominal wall, the allowances, the grade and seam, the location and the design pressure. Add the surge pressure if you know it.
- 3Section 2: the test pressure at the high point, the elevation to the low point, the medium and the hold time.
- 4Section 3 (if corrosion was found): the deepest pit, the axial length, the wall at the area and the gap to any neighbouring area.
- 5Section 4 (if a dent was found): its depth and whether it holds a stress riser, crosses a weld or has metal loss.
- 6Read the summary and the checklist; save and print.
Wall thickness and pressure (403.2.1, 402.3)
| Quantity | SI (bar, mm, MPa) | US (psi, in.) |
|---|---|---|
| Allowable stress | S = F × E × Sy | same |
| Pressure design wall | t = Pi D / (20 S) | t = Pi D / (2 S) |
| Required nominal wall | tn ≥ t + A | same |
| Maximum pressure of the wall | P = 20 S (tn − A) / D | P = 2 S (tn − A) / D |
| Hoop stress | SH = P D / (20 t) | SH = P D / (2 t) |
| Factor | Value |
|---|---|
| F, design factor (Table 403.3.1-1) | at most 0.72 for pipelines; 0.60 for risers and platform piping on inland navigable waters |
| E, weld joint factor (Table 403.2.1-1) | seamless, ERW, SAW 1.00; A134 / A139 0.80; furnace butt 0.60; unknown seam 0.60 (NPS ≤ 4) or 0.80 (437.6.4) |
| Sy | specified minimum yield of the pipe specification (e.g. API 5L X52 359 MPa, X65 448 MPa) |
- The tool takes 0.72 when F is blank. A value above 0.72 fails.
- Surge (403.3.4): the surge pressure must not exceed 110 % of the internal design pressure.
- The graphic compares the design, operating, surge and maximum pressures against the wall.
Hydrostatic test (437.4)
| Line | Test | Hold |
|---|---|---|
| Hoop stress above 20 % of Sy | proof test at ≥ 1.25 Pi at all points | 4 h |
| …and not all pressured parts inspected visually during the proof test | add a leak test at ≥ 1.1 Pi | 4 h |
| Hoop stress 20 % of Sy or less | leak test (437.4.3) at ≥ 1.25 Pi, or pneumatic at ≤ 7 bar and ≤ 25 % Sy | 1 h |
- The test pressure is entered at the high point. The tool adds the static head ρ g Δh to find the low-point pressure and its hoop stress on the nominal wall.
- Low-point hoop stress above 90 % of Sy gives a warning (plan the test sections); above 100 % fails.
- The test medium is water, or a liquid petroleum that does not vaporize rapidly (437.4.1 c). Air is accepted only for the leak test of a low-stress line.
Corrosion found in service (451.6.2.2)
| Finding | Result |
|---|---|
| Depth more than 80 % of the wall | repair or remove |
| External corrosion no deeper than 20 % of the wall | no repair required (no B31G needed) |
| Between | acceptable if the B31G safe pressure is at least the maximum operating pressure |
| Grooving or selective corrosion of an ERW or flash-welded seam | repair or remove |
| B31G Level 1 | Equation (z = L² / D t) |
|---|---|
| Original | flow stress 1.1 Sy; for z ≤ 20, SF = Sflow (1 − ⅔ d/t) / (1 − ⅔ d/t / √(1 + 0.8 z)); for z > 20, SF = Sflow (1 − d/t) |
| Modified (0.85 dL) | flow stress Sy + 69 MPa; M = √(1 + 0.6275 z − 0.003375 z²) for z ≤ 50, else 0.032 z + 3.3; SF = Sflow (1 − 0.85 d/t) / (1 − 0.85 d/t / M) |
| Failure and safe pressure | PF = 2 SF t / D; safe pressure = PF × F |
- The tool reports both B31G methods; the modified method is the governing one for the check. Your company procedure may set otherwise.
- Neighbouring areas interact and are assessed as one when the circumferential gap is under 6 t (Type I) or the axial gap under 25.4 mm (Type II); the tool then lengthens the flaw over both areas and the gap.
- The B31G equations are from ASME B31G-2012, not from B31.4 itself.
Dents (451.6.2.4)
- A dent deeper than 6 % of the outside diameter (6.4 mm for NPS 4 and smaller) is repaired or removed.
- A dent of any depth is repaired or removed when it contains a gouge, groove, scratch, crack or other stress riser; when it affects the curvature at a girth or seam weld; or when it holds metal loss below the minimum wall of the specification.
Saving and the report
- Fill in Identification (company, tank or item ID, location) and the record type: Just for research stays private to you; Official is visible to your company.
- Calculate & Save stores the inputs and results in the
pipeB314Calcscollection. - Print / PDF report opens a printable page of everything on screen: identification, the standard and edition, each section’s inputs and results, and any notes. Use Save as PDF in the print dialog. The report states the edition (B31.4-2016, upgrade due to B31.4-2022) and the sources of the yield strengths and the B31G equations.
Limits
- ASME B31.4-2016 basis; the 2022 edition has not been compared.
- Pressure design of straight pipe only. Bends, branches, flanges, expansion and longitudinal stress (403.3.2, 403.3.3) are not checked.
- B31G Level 1 only. Level 2 (RSTRENG), Level 3 and crack assessment are outside the tool; use API 579-1 where needed.
- Yield strengths are published values: confirm them against the mill certificates and the edition of API 5L your pipe was bought to.