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In the Heat of Process
Pipe Equivalent Length & Line Sizing Calculator — intheheatofprocess.nl
Calculator Tool — Step 2

Pipe Equivalent Length & Liquid Pressure drop Calculator

GPSA-style worksheet: fittings listed as rows, pipe segments laid out side-by-side as columns. Segments connect via their From/To labels, so a line can branch into multiple downstream lines at any point. Equivalent length comes from the Le/D ratio (Le = ΣN × (Le/D) × D), which then feeds straight into the velocity and frictional pressure drop for the same segment — Darcy-Weisbach with the Churchill (1977) friction factor, valid across laminar, transitional and turbulent flow. The pressure profile is a full extended Bernoulli balance: friction loss, static head from elevation change, and the dynamic (velocity head) pressure change wherever the pipe size changes — tracked independently down every branch.

Le = Σ N × (Le/D) × D  ·  V = 353.7·Q/di²  ·  P₁+½ρV₁²+ρgZ₁ = P₂+½ρV₂²+ρgZ₂+ΔP_f  ·  λ = Churchill
Note: This tool is intended for a quick scan / preliminary estimate only. Always check and verify against your own project's engineering standards and guidelines before final use. For reducing fittings (enlargements/contractions), D is the large-end nominal diameter — taken as the segment's own nominal size. Each segment's total equivalent length (straight + fittings) is used directly as the design length (L) in its pressure drop calculation. Items not covered by the reference table below should be entered under "User Defined" using manufacturer data or your project's own values.

Building a network / branches: the "From" and "To" fields are how segments connect — they're just labels, not fixed positions. To branch a line, add a new segment and set its "From" to an existing node's label (e.g. two segments can both have "From" = C, sending flow two different ways from that point). Flow (Q) is entered per segment, so double-check that a branch point's outgoing flows add up to what's coming in — the tool doesn't force that balance for you.
Grand Total Equivalent Length — All Pipe Segments
0,0
meters
Straight Length
0,0 m
Valves & Fittings Eq. Length
0,0 m
Critical End Pressure — Lowest Across All Branch Endpoints
0,000
barg  Outlet
Starting Pressure
0,000 barg
Σ Friction ΔP (all segments)
0,000 bar
Σ Friction ΔP
0,0 kPa
Σ Static Head ΔP
0,000 bar
Σ Velocity Head ΔP
0,000 bar
Σ Friction Head Loss
0,0 m
All Branch Endpoints — sorted lowest pressure first

Fluid Properties

Applied to all segments
P₀ is the applicable/available pressure at the start of the line (point A), taken at that point's actual flowing velocity (i.e. already inside the first segment — no separate stagnation/reservoir head is assumed). Q₀ is the total flow available at that same starting point — as you enter a flow rate for each branch, the worksheet shows how much of that budget is left, and flags it in red if a node's branches add up to more than what's coming in. Each segment's outlet pressure — adjusted for the Bernoulli velocity-head change wherever the pipe size changes — feeds into the next segment's inlet, giving a running pressure profile down to each branch's outlet. Defaults are water at ambient conditions in new commercial steel pipe. A commonly used preliminary liquid velocity range is roughly 0.5–5 m/s — adjust to suit your fluid and project criteria. See the reference panel below for other pipe materials.

Line Schematic

From → To
Show on drawing:

Equivalent Length & Line Sizing

Le = N × (Le/D) × D  →  ΔP = λ(L/Di)(½ρv²)

Valves & Fittings Summary

Print Version
SegmentCategoryValve / FittingQtyLe/DEq. Length
Valve & Fitting Equivalent Length (Le/D) Reference — GPSA-style Method
CategoryType of valve / fittingLe/D
Le/D values are fixed ratios per fitting/valve type ("Valve and fitting equivalent length" — a GPSA-style method). D is the nominal pipe diameter (D = NPS × 25.4 mm, e.g. 8" → 203.2 mm); for reducing fittings, D is the large-end nominal diameter and d is the small-end nominal diameter. Pick the row matching each fitting and enter the quantity in the worksheet, or use a "User Defined" row for anything not covered. This is a quick-scan reference — always confirm values against your own project standard.
Line Sizing Method & Pipe Roughness Reference

Velocity: V (m/s) = 353.7 × Q (m³/h) / di² (mm)
Reynolds number: Re = ρ·v·Di / η
Churchill friction factor (valid for laminar, transitional and turbulent flow):
λ = 8 × [ (8/Re)¹² + 1/(A+B)^1.5 ]^(1/12)
A = { 2.457 × ln[ 1 / ((7/Re)^0.9 + 0.27·ε/Di) ] }¹⁶    B = (37530/Re)¹⁶
Pressure drop (friction): ΔP_f (N/m²) = λ × (L/Di) × ½ρv²    Friction head loss: Δh (m) = λ × (L/Di) × v²/(2g)
Static head (elevation): ΔP_static = ρ · g · H   — H = elevation change (m), positive going up (costs pressure), negative going down (recovers pressure)
Segment ΔP (friction + static): ΔP_total = ΔP_friction + ΔP_static
Dynamic pressure / velocity head (Bernoulli, applied wherever the pipe size changes between segments):
ΔP_dynamic = ½ρ(V_prev² − V_this²)   — positive = pressure recovered (pipe gets bigger, V drops), negative = pressure lost to kinetic energy (pipe gets smaller, V rises)
Full pressure profile (extended Bernoulli / mechanical energy balance), carried segment to segment from the starting pressure P₀:
P_in(segment) = P_out(previous segment) + ΔP_dynamic    P_out(segment) = P_in(segment) − ΔP_total
L is each segment's total equivalent length (straight + fittings) from the worksheet above.

Pipe materialAbsolute roughness ε (mm)
Typical absolute roughness values for preliminary sizing — always confirm with your project's piping material specification. Drawn tubing (copper, brass, PVC, GRP) is generally treated as hydraulically smooth.

Preliminary Velocity & Pressure Drop Guidelines — Rule of Thumb

Water typeMin. velocityMax. velocity
Carbon steel		Max. velocity
Stainless / Titanium		Max. velocity
Cu-Ni		Max. velocity
GRP
Fresh / potable water1.5 m/s4 m/s5 m/s3 m/s6 m/s
Brackish / sea water1.5 m/s3 m/s5 m/s3 m/s6 m/s
For liquids other than water, a commonly used rule-of-thumb preliminary velocity range is roughly 0.5 – 5 m/s. Where the fluid carries sand or other abrasive solids, preliminary velocities are often kept lower to limit erosion — typically up to around 5 m/s in carbon steel and up to around 7 m/s in stainless / duplex stainless steel.
ServiceTypical pressure drop gradient
Pump suction — liquid near its boiling point≈ 0.03 – 0.08 bar/100 m
Pump suction — subcooled liquid≈ 0.15 – 0.4 bar/100 m
Pump discharge≈ 0.15 – 0.6 bar/100 m
Disclaimer: These are generic, rounded rule-of-thumb figures for a quick preliminary sizing pass only — not values from any specific company, licensor, or industry-code specification. Suitable ranges vary significantly with fluid, material, service, and criticality. Always confirm against your own project's design basis and piping specification before finalizing a line size.

How to Use This Calculator

Contents

  1. What this tool does
  2. Set your Fluid Properties first
  3. Build your first pipe segment
  4. Fill in the fittings worksheet
  5. Read the totals & results
  6. Branch into a network
  7. Let the flow budget auto-fill
  8. Check the pressure profile
  9. Use the Line Schematic
  10. Save, Open, and Autosave
  11. Print vs. Export to Excel
  12. Reference panels
  13. Limits & good practice
1

What this tool does

This is a single worksheet that takes a pipe route from start to finish (or a whole branching network) and, per pipe segment, works out:

  • The equivalent length of every valve and fitting on that segment, using the GPSA-style Le/D method
  • The resulting flow velocity and whether it falls inside your target range
  • The frictional pressure drop (Darcy-Weisbach with the Churchill correlation, valid for laminar through turbulent flow)
  • The static head from elevation change, and the dynamic (velocity-head) pressure change wherever the pipe size changes — a full extended Bernoulli balance
  • A running pressure profile from your starting pressure all the way to every branch endpoint

It works for one straight line or for a network with multiple branches off any point — the tool is not limited to any particular service (suction, discharge, utility, etc.).

Quick scan tool. This is built for a fast, defensible preliminary estimate. Always check the result against your own project's engineering standards before it goes into a design package.
2

Set your Fluid Properties first

Before touching the worksheet, fill in the Fluid Properties panel near the top — these apply to every segment in the whole network:

FieldWhat it's for
Starting Pressure P₀The available pressure (barg) at the very start of the line — the pressure profile counts down from here.
Total Starting Flow Q₀The total flow (m³/h) available at the source — used by the flow-budget check when you branch (Step 7).
Liquid Density ρkg/m³. Defaults to water.
Dynamic Viscosity ηcP (= mPa·s). Defaults to water.
Pipe Roughness εmm, absolute roughness — see the reference table (Step 12) for other materials.
Target Velocity Min / Maxm/s — drives the OK/LOW/HIGH badge under every segment's velocity result.

You can come back and change any of these later — everything recalculates instantly.

3

Build your first pipe segment

Each pipe segment is one column in the worksheet. Click + Add Pipe Segment at the bottom of the worksheet to add one, or edit an existing column directly.

For each segment, fill in:

  • Nominal Size (NPS) and Schedule — pipe data (OD, WT, ID, and nominal diameter D = NPS × 25.4 mm) fills in automatically from ASME B36.10M
  • P&ID nr — optional, for your own reference
  • From and To — free-text node labels (e.g. A, B). These are what connect segments together — see Step 6
  • Pipe straight Length (m) and Elevation change (m) — positive going up, negative going down
  • Liquid Flow Rate Q (m³/h) — auto-suggested for you, see Step 7
Tip: a new segment's "From" defaults to the previous segment's "To" — a straight continuation needs no extra typing. You only need to touch "From" when you want to branch off an earlier point.
4

Fill in the fittings worksheet

Below the header rows, every valve and fitting from Table 6 (GPSA-style Le/D method) is listed as its own row, grouped into collapsible sections:

Valves (Fully Open)FittingsEnlargement ContractionMiscellaneousUser Defined

Click any section's header to fold or unfold it — use ⊞ Expand All Sections / ⊟ Collapse All Sections above the table to jump between a full view and a compact one.

For each fitting you have on a segment, type the quantity in that segment's column. The equivalent length for that row (count × Le/D × D) appears automatically next to the input.

Anything not covered by the standard list goes in one of the three User Defined rows: give it a label, a quantity, and its own Le/D ratio.

Reducing fittings. For enlargements and contractions, D is the large-end nominal diameter — the tool uses the segment's own nominal size for this.
5

Read the totals & results

RowMeaning
TOTAL Le/DΣ (quantity × Le/D) across every fitting on that segment — dimensionless
TOTAL VALVES & FITTINGS EQ. LENGTHThe above × the segment's nominal diameter, in metres
TOTAL EQUIVALENT LENGTHStraight pipe length + fittings equivalent length — becomes "L" in the pressure drop calc
Velocity vFrom V = 353.7·Q/di², with an OK / LOW / HIGH badge against your target range
Re, ε/Di, λInputs to and output of the Churchill friction factor correlation
Friction Pressure Drop ΔPDarcy-Weisbach, using the segment's total equivalent length
Static Head ΔPρ·g·H from the segment's elevation change
Velocity Head ΔP (dynamic)The Bernoulli term — appears where the pipe size changes from the previous segment
Pressure In / OutThe running pressure at each end of the segment
6

Branch into a network

"From" and "To" are just labels — they're what connects segments, not their position in the worksheet. To split a line into two, add a new segment and set its From to a node that's already used as another segment's To. Both segments now branch from that same point.

P-1001 (A → B) A B P-1002 (B → C) C P-1003 (B → D) D P-1002 and P-1003 both have From = B
Two segments sharing "From = B" — the network branches at B into C and D.

Add as many branches as you need, at any point, to any depth. Each branch is calculated independently from its own branch point's pressure and velocity.

7

Let the flow budget auto-fill

Under every Liquid Flow Rate Q field there's a small live figure showing what's left of the flow budget at that node — it walks the same From/To connections, starting from Q₀ at the source.

Whenever you set or change a segment's "From", its Flow field is auto-filled with whatever's currently left at that node — a starting suggestion you're free to type over.

ExampleResult
Q₀ = 500 m³/h, first segment set to 500"0,0 m³/h left (of 500,0)" — green, balanced
Add a branch, type 400 for itNext branch from the same node auto-fills 100 (500 − 400)
A node's branches add up to more than what's coming inRed "⚠ over by X m³/h" warning on the offending branch
Not automatic mass balance. The tool checks and warns, but it won't force your numbers to add up — that's still on you.
8

Check the pressure profile

Near the top of the page, the Critical End Pressure panel shows the lowest pressure found across every branch endpoint — the branch with the most equivalent length and the highest pressure drop naturally shows up here as the worst case, flagged in red if it goes negative.

Below the headline number, All Branch Endpoints lists every endpoint's pressure, sorted lowest-first, so you can see at a glance how each branch compares.

Negative end pressure means the starting pressure can't overcome the drop on that branch — increase P₀, upsize the piping, or reduce flow.
9

Use the Line Schematic

The diagram redraws itself from your From/To connections — flat pipes for zero elevation change, straight up for positive elevation, straight down for negative. Branches fan out automatically with a dashed connector showing they share the same node.

Above the drawing:

  • Include drawing in print — untick this to leave the diagram out of your PDF/print output
  • Show on drawing — toggle Size, Length, Elevation, Flow Q, Velocity, ΔP, and Node Pressure individually, or all at once
10

Save, Open, and Autosave

  • 💾 Save — downloads your whole worksheet as a .json file
  • 📂 Open — loads a previously saved .json file back in
  • Autosave — your work is also saved automatically to this browser as you go; reopening the tool offers to restore it
  • ↺ Reset — clears everything back to the worked example
Tip: save a .json file for each line or project, so you can reopen and continue exactly where you left off.
11

Print vs. Export to Excel

🖨 Print / PDF

Gives you a clean report: your inputs, the results, a compact summary of only the fittings actually used, and the schematic if switched on. The full fittings worksheet (all the zero rows) is left out to keep the printout short.

In the print dialog, make sure "Background graphics" is switched on — otherwise the navy and orange highlighted rows will print blank.

📊 Export Excel

Downloads a fully-styled .xlsx workbook with three tabs: the complete worksheet (every fitting row), a Fittings Summary, and a Fluid & Endpoints sheet. Use this when you want to reformat, filter, or lay the data out your own way.

12

Reference panels

Two collapsible panels sit below the worksheet:

  • Valve & Fitting Equivalent Length (Le/D) Reference — every Le/D value used in the worksheet, in one table
  • Line Sizing Method & Pipe Roughness Reference — the full set of equations, a roughness table for common pipe materials, and a rule-of-thumb preliminary velocity / pressure-drop-gradient guideline table
13

Limits & good practice

  • This is a preliminary / quick-scan tool — always verify against your project's own engineering standards before it goes into a deliverable.
  • It handles branching networks but does not solve a coupled hydraulic network — each branch is evaluated independently from its own branch point; it does not iterate flow splits to force a pressure balance the way a full network solver would.
  • Liquid lines only — the velocity and pressure drop equations assume single-phase incompressible flow.
  • Le/D values come from a GPSA-style table; anything unusual belongs in a User Defined row with your own value.