What is Barlow's formula?

Barlow's formula calculates minimum wall thickness for pipes under internal pressure: t = P × D / (2 × S × E), where P = internal pressure, D = outside diameter, S = allowable stress, E = weld joint efficiency factor.

What allowable stress should I use?

Allowable stress depends on material and temperature. For carbon steel (A106 Gr.B) at ambient: ~138 MPa (20,000 psi). For stainless 316 at ambient: ~138 MPa. Always refer to ASME B31.3 Table A-1 for design values.

What is the weld joint efficiency factor?

Weld efficiency (E) accounts for joint quality: E = 1.0 for seamless pipe, E = 0.85 for ERW (electric resistance welded), E = 0.60 for furnace butt welded. Higher E requires more inspection (radiography).

Do I need to add a corrosion allowance?

Yes. Add corrosion/erosion allowance (typically 1.5–3 mm for carbon steel in process service) to the calculated minimum wall thickness. Also consider manufacturing tolerance (typically -12.5% for seamless pipe).

What is the difference between Barlow and ASME B31.3?

Barlow's formula is a simplified version. ASME B31.3 uses t = PD/(2(SE+PY)), where Y is a temperature coefficient. For most cases at moderate temperatures, Y ≈ 0.4. The ASME formula gives slightly thinner walls.

मोफत अभियांत्रिकी साधन — #154

पाईप भिंतीच्या जाडीचा गणक — Barlow सूत्र

Barlow सूत्र वापरून अंतर्गत दाबाखालील पाईप्ससाठी किमान भिंत जाडीची गणना करा: t = P×D/(2×S×E). यात गंज भत्ता आणि सहनशीलता समाविष्ट आहेत.

t = PD/(2SE)ASME B31.3गंज भत्ता

Results

किमान आवश्यक भिंत जाडी (गंज & सहनशीलतेसह)

—

गणिती t (Barlow)

—

+ गंज भत्ता

—

फुटण्याचा दाब (2×S×E×t/D)

—

आतील व्यास

—

Barlow सूत्र

गंज आणि सहनशीलतेसह

P — रचना दाब
D — पाईप बाह्य व्यास
S — रचना तापमानावरील अनुमत ताण
E — वेल्ड जॉइंट कार्यक्षमता (1.0 seamless, 0.85 ERW, 0.60 FBW)
c — गंज/झीज भत्ता
tol — उत्पादन सहनशीलता (सामान्यतः 12.5%)

उदाहरण — 10 MPa वरील DN100

Given: OD = 114.3 mm, P = 10 MPa, S = 138 MPa, E = 1.0

t = 10 × 114.3 / (2 × 138 × 1.0) = 4.14 mm

+ 1.5 mm गंज = 5.64 mm

÷ (1 − 0.125) = किमान 6.45 mm

या सेवेसाठी Sch 80 (8.56 mm wall) निवडा.

⚠️ Note: हे Barlow चे सुलभित सूत्र आहे. code compliance साठी Y factor समाविष्ट असलेले ASME B31.3 Eq. 3a वापरा. गणिती किमान मूल्यापेक्षा पुढील मानक pipe schedule नेहमी निवडा.