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FEL-3 engineering calculators
that actually work

Nine process engineering tools covering the full pre-FEED scope — from pipe sizing to project economics. Rigorous methodology. Decision-grade outputs. Built by engineers who got tired of rebuilding the same spreadsheet.

Explore all nine tools → See the methodology
9Engineering modules
100%Free, no account
AACEClass 3 methodology
API520 / 521 / 526
Standards
API 520 / 521 / 526 ASME Section VIII TEMA Standards Darcy-Weisbach AACE Class 3 Lang / Hand Factors CEPCI Escalation
The FEL-3 Engineering Suite

Nine modules. One coherent platform.

Each calculator runs entirely in your browser. No installation, no account, no data sent anywhere.

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MODULE 01
Liquid Hydraulics & Line Sizing
Pipe diameter selection, pressure drop, pump head and motor sizing. Darcy-Weisbach with Colebrook-White or Hazen-Williams. Full NPS sensitivity table.
Darcy-WeisbachColebrook-WhitePump sizing
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MODULE 02
Gas Hydraulics & Line Sizing
Compressible flow with real gas density correction. API 14E erosional velocity, Mach number check, compressor sizing. Three flow correlations.
WeymouthPanhandle BAPI 14E
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MODULE 03
Shell & Tube Heat Exchanger Design
Full TEMA thermal design. LMTD-Ft correction, U coefficient with fouling, tube count, shell diameter. NTU-effectiveness cross-check. Auto-generated datasheet.
TEMALMTD-FtNTU-ε
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MODULE 04
Relief Valve Sizing
API 520 vapor, liquid, and two-phase (Omega method) sizing. Six relief scenarios, ASME accumulation check, API 526 orifice selection, PRV type recommendation.
API 520API 526ASME VIII
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MODULE 05
Pump Selection & System Curve
H-Q and system curve intersection, NPSH cavitation check, BEP deviation, affinity laws at three speeds, specific speed and pump type recommendation.
H-Q curveNPSHAffinity laws
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MODULE 06
Mass & Energy Balance Engine
Multi-stream process balance with stream table, component closure check, Sankey diagram, and annual energy figure. Five process templates pre-loaded.
Stream tableSankey5 templates
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MODULE 07
Equipment Cost Estimator
Factored CAPEX from purchased equipment to total project cost. Lang or Hand factor toggle, CEPCI escalation, location factor. Six equipment types.
Lang / HandCEPCIAACE ±30%
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MODULE 08
Project Economics Engine
Full DCF model — NPV, IRR, payback periods, phased CAPEX, depreciation, tax, escalation. Waterfall chart, NPV profile, sensitivity tornado chart.
NPV / IRRDCFTornado
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MODULE 09
FEL-3 Project Dashboard
Executive gate review summary. Traffic light readiness, economics snapshot, CAPEX range, risk register, assumptions table. Editable values, PDF-ready print.
Gate reviewTraffic lightsPDF export
How it works

Open. Enter. Decide.

No setup, no account, no data uploaded anywhere. Every calculation runs locally in your browser.

01
Open any calculator
Click a module above. It opens instantly — nothing to install, no login screen. Works on any browser, any device, including tablets on site.
02
Enter your process data
Every module loads with realistic default values so you see it working immediately. Replace with your project data and results update in real time.
03
Get deliverable-ready outputs
Results are formatted as engineering deliverables — datasheets, stream tables, sensitivity tables, charts — ready for a process design package or gate review.
Engineering rigor

Not approximations. Real methodology.

Every calculation uses published industry standards and peer-reviewed engineering references — not simplified rules of thumb.

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Colebrook-White iterative solver
Friction factor solved by 50-iteration Newton-Raphson converging to 10⁻¹⁰ — the same algorithm used in commercial simulation software.
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API 520 orifice sizing equations
Vapor (critical and subcritical), liquid (Bernoulli with Kw), and two-phase (Omega method, API 520 Appendix D) all implemented.
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LMTD-Ft Bell-Delaware correlation
Ft factor from R and S parameters for 1-2 and 2-4 exchanger configurations with proper singularity handling at R=1.
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Newton-Raphson IRR solver
IRR by 200-iteration Newton-Raphson on the free cash flow stream, converging to 10⁻⁸. Handles non-standard cash flow profiles.
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Hand factors from Turton et al.
Eight equipment-specific installation cost components per equipment type — erection, piping, instrumentation, electrical, civil, structural, insulation, painting.
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TEMA bundle diameter correlations
Shell diameter from K₁/n₁ layout constants for triangular and square pitch per TEMA standards.
Why free?

Good engineering tools should be accessible.

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No paywalled methodology
The Colebrook-White equation does not cost $50,000 per seat. Core FEL-3 calculations are free at ProcessDesk — always.
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Full transparency
Every equation, every assumption, every correlation is visible. You can see exactly how the answer was derived — because you need to defend it.
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Your data stays yours
All calculations run in your browser. No process data is transmitted to any server. No cloud dependency. No vendor lock-in.
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Sustained by the community
ProcessDesk is free because of non-intrusive advertising and optional Pro subscriptions. If it saves you time, share it with a colleague.
// Colebrook-White — iterative solver
function colebrook(Re, eps_D) {
  if (Re < 2300) return 64/Re;
  let f = 0.02;
  for (let i=0; i<50; i++) {
    const fn = 1/(-2*log10(
      eps_D/3.7 + 2.51/(Re*√f)
    ))**2;
    if(|fn-f| < 1e-10) break;
    f = fn;
  }
  return f;
}

// The actual equation. Solved properly.
// Not a lookup. Not a shortcut.
Pricing

Start free. Upgrade when you need more.

The full calculation suite is free forever. Pro adds workflow features for engineers using ProcessDesk regularly on real projects.

Free
$0 /forever
Full access to all nine FEL-3 engineering calculators. No account, no credit card.
✓
All 9 calculation modules
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Full industry-standard methodology
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Sensitivity tables and charts
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Auto-generated engineering datasheets
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No data uploaded, ever
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Pro
$19 /month
For engineers running FEL-3 studies regularly who need to save, export, and share their work.
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Everything in Free
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PDF export of calculation sheets
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Save and reload project data
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Project library
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Shareable calculation links
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Team
$49 /month
For engineering teams who want shared project libraries and consistent methodology across projects.
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Everything in Pro
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Up to 5 team members
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Shared project library
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Custom equipment databanks
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Priority support
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Ready to use it

Stop rebuilding the same spreadsheet.

Open any calculator, enter your data, get a defensible FEL-3 output in minutes. No setup. No account. No cost.

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