Engineering guides, theory made practical.
Concise guides explaining the engineering concepts behind the calculators and unit conversions on ProcessConvert. Each guide covers the definition, formula, worked example, common mistakes, and links to the relevant calculator.
These guides complement the interactive calculators with theory and context. Grouped by engineering area so you can find the right reference in one scan.
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Guides by topic
Electrical & Instrumentation
4 guidesTheory behind circuit calculations, signal conditioning and temperature measurement.
Ohm's Law Explained
Ohm's Law relates voltage, current, and resistance in a DC or purely resistive circuit: V = IR. Learn the three forms of the equation, common units, and when to use each.
Electrical Power Explained
Electrical power is the rate of energy transfer in a circuit: P = VI. Learn the three equivalent DC power formulas, common units (W, kW, hp), and limitations.
Voltage Drop Explained
Voltage drop is the loss of voltage across a conductor as current flows through its resistance. Learn the formula, percent drop, and the difference between calculation and cable sizing.
RTD Temperature Explained
A resistance temperature detector (RTD) measures temperature via the change in resistance of a platinum element. Learn the Pt100/Pt1000 linear approximation, default alpha, and limitations.
Fluid Mechanics
14 guidesPressure, head, flow types and dimensionless numbers for fluid systems.
Pressure vs Head Explained
Pressure is force per area; head is equivalent fluid column height. Learn how density connects them and when to use each.
Mass Flow vs Volumetric Flow
Volumetric flow measures volume per time; mass flow measures mass per time. Learn the density relationship and when each matters.
Reynolds Number Explained
The Reynolds number is a dimensionless ratio that indicates whether flow is laminar, transitional, or turbulent. Learn the formula, flow regime thresholds, and common mistakes.
Pipe Pressure Drop Explained
What pressure drop in a pipe really means and what drives it — velocity, diameter, length, fluid density and viscosity, roughness, fittings, and elevation. Learn the difference between pressure drop and head loss and why min/normal/max flow cases matter.
Darcy-Weisbach Equation Explained
The Darcy-Weisbach equation in practical terms — the friction factor, the length-to-diameter ratio, the velocity head term, and the Darcy-vs-Fanning trap. Learn when Darcy-Weisbach is the right tool for pipe friction loss.
Friction Factor Explained
Why the friction factor is not a universal constant — how it depends on Reynolds number and relative roughness, the laminar f = 64/Re result, the transitional caution zone, the Moody chart, and the Swamee-Jain and Colebrook approximations.
Minor Losses vs Friction Losses
The difference between straight-pipe friction losses and the fitting, valve, bend, entrance, and exit losses lumped together as "minor" losses — the K-value method, the equivalent-length method, and why minor losses are often not minor at all.
The Moody Chart Explained
What the Moody chart shows and how engineers use it — the Reynolds-number axis, relative roughness ε/D, the Darcy friction factor, the laminar line, the transitional caution band, and turbulent smooth/rough behaviour. Includes the Darcy-vs-Fanning trap and why calculator results differ slightly from a chart reading.
Darcy-Weisbach vs Hazen-Williams
Two ways to calculate pipe pressure drop: the physically general Darcy-Weisbach equation (density, viscosity, Reynolds number, roughness, friction factor) and the empirical Hazen-Williams water-flow formula (C-factor). When each is used, why Hazen-Williams is water-only, and why Darcy-Weisbach is the default for general engineering work.
Laminar vs Turbulent Flow
Why pipe flow switches between laminar, transitional, and turbulent regimes and why that changes the friction factor and pressure drop. Covers the Reynolds-number thresholds (laminar Re < 2300, transitional ~2300–4000, turbulent Re > 4000), the laminar f = 64/Re result, and why viscosity dominates at low Reynolds number.
Equivalent Length Explained
How fittings, valves, bends, entrances, and exits can be represented as an equivalent length of straight pipe — the equivalent-length method, how it relates to the K-value method, when each is clearer, and why equivalent lengths depend on diameter, fitting type, and assumptions and should not be added blindly.
Pipe Velocity Guidelines
How velocity guides preliminary pipe sizing — why it sits between flow, diameter, pressure drop, erosion, noise, and cost, what too-low and too-high velocity each risk, and why service type matters more than any single universal limit.
Cv Flow Coefficient Explained
What the valve flow coefficient Cv really means, how the water-service definition relates flow to pressure drop, why valve ΔP is only part of system pressure drop, and why Cv is a screening tool — not a universal valve-sizing shortcut for viscous, flashing, cavitating, gas, or two-phase service.
Open Channel Flow Basics
How open-channel flow with a free surface differs from full-pipe pressurised flow — why slope and gravity drive it instead of a pressure gradient, the role of depth, slope, hydraulic radius and roughness, the Manning concept at a high level, and why pipe pressure-drop calculators should not be used blindly on channels, launders, and drains.
Heat Transfer
10 guidesThermal properties, heat duty and energy balance fundamentals.
Heat Duty Explained
Heat duty is the rate of heat transfer needed to change a fluid temperature. Learn the sensible heat formula, required inputs, and common mistakes.
What Is Specific Heat Capacity?
Specific heat capacity (Cp) is the energy required per unit mass per degree of temperature change. Learn why it matters in heat duty calculations and how units relate.
Sensible Heat vs Latent Heat
Sensible heat changes temperature; latent heat changes phase. Learn how they differ, why the heat duty calculator covers sensible heat only, and what latent heat requires.
Heat Exchanger Sizing
A structured methodology overview for preliminary heat exchanger sizing — covering duty, LMTD, U-values, fouling, area calculation, and design margin. Links to all calculators and references in the heat exchanger sizing cluster.
Sizing Heat Exchangers for Slurry Service
Practical engineering considerations for preliminary heat exchanger sizing in slurry and solids-bearing liquid services — covering velocity, fouling, plugging, erosion boundaries, and why vendor experience matters.
Sizing Sulfuric Acid Cooling Heat Exchangers
Preliminary sizing considerations for sulfuric acid cooling heat exchangers — covering concentration-dependent corrosion, materials boundaries, U-value caution, temperature approach, and the need for specialist review.
Spiral Heat Exchanger Sizing
When to consider spiral heat exchangers, how preliminary sizing relates to area estimation, fouling and slurry service advantages, and why detailed vendor rating is still required for final design.
LMTD vs NTU Method: Which Heat Exchanger Sizing Method to Use
When to use the LMTD method versus the NTU/effectiveness method for preliminary heat exchanger calculations. Compares the two methods, when each is easier, and the limitations of both for preliminary sizing.
Cooling Water Heat Exchanger Sizing
Practical preliminary sizing considerations for cooling-water heat exchanger service — duty, cooling-water temperature rise, approach temperature, fouling, U-values, seasonal temperature effects, and water-side velocity limits.
Steam Condenser Sizing
Preliminary steam condenser sizing logic and the difference between sensible cooling and latent heat condensation. Covers duty, condensing temperature, cooling-water flow, LMTD, vacuum/pressure context, and why detailed condenser design requires specialist methods.
Process Design
14 guidesVessel sizing, throughput and residence time concepts.
Residence Time Explained
Residence time is the average time material spends inside a vessel, equal to volume divided by volumetric flow rate. Learn the formula, units, and common mistakes.
Tank Volume Explained
Tank volume is the internal geometric capacity of a vessel. Learn formulas for rectangular tanks, vertical cylinders, and horizontal cylinders, and when each applies.
Tank Turnover Explained
Tank turnover is how many tank volumes pass through a vessel over time. Learn the turnover rate, turnover time, and how tank turnover differs from residence time.
Tank Turnover vs Residence Time
Turnover time and hydraulic residence time use the same V/Q arithmetic but answer different questions — and neither equals real mixing time. Learn how dead zones, short-circuiting, and plug-flow vs mixed assumptions change the picture.
Residence Time Design Margin
A preliminary τ = V/Q result is a nominal number, not a design. Learn why working volume, surge allowance, dead volume, flow turndown, and control range mean the design residence time must carry margin over the operating residence time.
Tank Sizing Explained
Preliminary tank sizing ties together volume, flow, residence time, working volume, surge allowance, geometry, and fill level. Learn the practical method and where it stops short of mechanical design.
Tank Geometry Volumes
Volume formulas for vertical cylindrical, horizontal cylindrical, cone-bottom, and rectangular tanks — and which calculator to reach for, plus the partial-fill and calibration caveats.
Working Volume vs Total Volume
Total geometric volume is not usable volume. Learn how working volume, operating levels, freeboard, dead volume, and surge volume differ — and how each affects residence time and control.
Tank Freeboard Explained
Freeboard is the headroom above the operating level, not wasted volume. Learn how it relates to working volume, ullage, overflow risk, foam, wave action, and the control range — and why standards set it.
Surge Volume vs Residence Time
Residence time is volume divided by flow; surge volume is the capacity to absorb flow imbalance and upset. The same tank can provide both, but they are not the same design basis. Learn the difference.
Batch vs Continuous Tank Sizing
Batch tanks size from batch size, batch count, fill fraction, and heel; continuous tanks size from flow and residence time or surge. Learn why the design basis must be clear before sizing a tank.
CSTR vs Plug Flow Residence Time
The same nominal residence time τ = V/Q can mean very different performance in a well-mixed (CSTR), plug-flow, or non-ideal vessel. Learn why the residence-time distribution — not just the average — governs conversion, and why short-circuiting and dead zones break the nominal number.
Leach Tank Residence Time
How residence time is used to size hydrometallurgical leach circuits — nominal τ = V/Q on a slurry working-volume basis, CSTR-in-series tank trains, and why residence time must be read together with leach kinetics, solids concentration, slurry density, mixing, and testwork. Not a leach kinetics or recovery model.
Calciner Residence Time
A preliminary, conceptual look at residence time in calcination and thermal solids processing — solids feed rate, hold-up, and nominal residence time — and why temperature profile, particle size, reaction kinetics, bed behaviour, and equipment type mean residence time alone does not guarantee conversion. Not a calciner, kiln, or kinetics design model.
Process Utilities
7 guidesDilution, concentration and solids content in process streams.
Dilution Explained
Dilution reduces concentration by adding solvent or increasing final volume. Learn the C1V1 = C2V2 formula, how to calculate added solvent volume, and common mistakes.
Concentration Explained
Concentration is the amount of solute per amount of solution. Learn the difference between mass concentration and percent by mass, with worked examples and common mistakes.
Percent Solids Explained
Percent solids is the mass fraction of solid material in a slurry. Learn the formulas for solids mass flow, liquid mass flow, and slurry mass flow, with a worked example.
Slurry Density Explained
What slurry density is, why it differs from liquid density, how mass percent and volume percent solids relate to it, and why it matters for pumps, pipes, tanks, and mass balance.
Percent Solids by Mass vs Volume
Mass percent solids (Cw) and volume percent solids (Cv) are not interchangeable. Learn the difference, why mass percent is usually higher for dense solids, and the common mistake of treating 30 wt% as 30 vol%.
Thickener Underflow Density Explained
What thickener underflow density means, how it relates to percent solids and slurry density, why it matters for underflow pumping and tailings water recovery, and why target densities are always site-specific. A concept guide — not a thickener design model.
Marcy Density Cup Guide
What a Marcy density cup (pulp density scale) is, how plant operators use it to read slurry density and infer percent solids, why the solids SG matters, and the common measurement mistakes that make a reading misleading. A concept guide — not an operating procedure or a substitute for lab testwork.
Pumps & Rotating Equipment
6 guidesPump head, affinity laws and hydraulic system fundamentals.
What Is Pump Head?
Pump head is energy per unit weight of fluid, expressed as an equivalent height of liquid column. Learn why it matters for pump selection and how it relates to pressure.
Pump Affinity Laws Explained
The pump affinity laws relate flow, head, and power to pump speed for the same pump and impeller. Learn the three scaling formulas, a worked example, and key limitations.
Pump Sizing
A preliminary pump sizing hub: how flow, head, pressure, system losses, power, NPSH, and service conditions connect when you size a centrifugal pump. Links the head, power, friction-loss, and NPSH tools into one workflow.
Slurry Pump Head Sizing
Preliminary pump head considerations for slurry service in mining and mineral processing: slurry SG and solids loading, why clean-water friction estimates are only a starting point, deposition velocity, wear, settling, and why experienced slurry-pump review is required.
System Curve vs Pump Curve
How the system curve and the pump curve interact, why the operating point is where they intersect, and how static head, friction, valve throttling, and speed move each curve — with what low flow can be telling you.
Low-Flow Pump Troubleshooting
A practical sequence for diagnosing why a centrifugal pump delivers less flow than expected — measurement first, then suction, system head, speed/rotation, impeller wear, NPSH/cavitation, fluid properties, and valves — and when to escalate.
Instrumentation
8 guidesSignal scaling and sensor range concepts for process instruments.
How 4–20 mA Scaling Works
The 4–20 mA current loop is the dominant analogue signal standard in process instrumentation. Learn the scaling formula and how to convert between signal and process value.
Percent Span Explained
Percent span expresses a process value as a percentage of the instrument range (LRV to URV). Learn the formula, the difference from 4-20 mA scaling, and common mistakes.
4–20 mA Signal Scaling Explained
How a 4–20 mA instrument signal is scaled to a process value and back, why 4 mA is a live zero, and how span, percent of span, over-range, and under-range fit together.
Instrument Range vs Span
The range is the pair of endpoints LRV and URV; the span is the width URV − LRV. Learn why a range can cross zero, how elevated and suppressed zeros work, and how range and span drive signal scaling.
Live Zero vs Dead Zero Signals
Why 4–20 mA uses 4 mA as a live zero instead of 0 mA, how a live zero lets 0 mA flag a broken wire or lost power, and what under-range and over-range readings tell you.
Square Root Extraction Explained
Differential pressure across a flow element is proportional to flow squared, so flow is the square root of differential pressure. Learn why 25% ΔP is 50% flow, where extraction happens, and the low-flow cutoff.
DP Flow Measurement Explained
Differential-pressure flow measurement infers flow from the pressure drop across an orifice, nozzle, or venturi. Learn the square-root relationship, extracted vs non-extracted signals, and the installation cautions.
Instrument Error vs Percent Span
Instrument error can be read as a process-unit error, a percent of span, and an equivalent mA error. Learn why span sets the apparent severity and why tolerance must be defined before pass/fail.
These guides cover the engineering theory behind pump head, pressure/head conversion, mass and volumetric flow, 4–20 mA instrumentation scaling, and sensible heat duty. Each guide includes formulas, worked examples, and links to the relevant interactive calculator. Additional guides are planned for future releases.