Every tool, by discipline
Each page explains the method behind the calculation — governing formulas, the standard it follows, typical values and a worked example — and leads to the calculator itself.
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Hydraulics 18
Pumps, gravity lines, multi-branch networks, control and safety valves, orifice plates and water hammer.
Discipline overview →-
Pump Sizing Calculator
Size a centrifugal pump: total dynamic head TDH = static head + friction loss (Darcy-Weisbach / Colebrook-White), operating point and available NPSH.
TDH = H_static + h_friction + h_fittings ; h_f = f · (L/D) · v²/2g -
Parallel Pump Curves Explained
Build the parallel pump curve — Q_comb = N·Q_1 at the same head — find the operating point against the system curve and get the real flow per pump.
H_comb(Q) = H_1(Q/N) ⇔ Q_comb = N x Q_1 at the same head H -
Pumps in Series
Pumps in series add HEAD at the same flow rate: build the combined curve H = H₁ + H₂, find the operating point and the head delivered by each pump.
H_comb(Q) = H_1(Q) + H_2(Q) at the same flow rate Q -
Pump Minimum Flow
Size the minimum-flow recirculation line: the bypass flow as a share of BEP, the two valves, and the effect on the operating point of the main line.
Q70 = 0.70 · Q_cat , with Q_cat = positive root of a·Q² + b·Q + c = 0 -
Pump with Control Valve
Size the control valve on a pump discharge: Cv per IEC 60534-2-1, the head loss it adds and how that shifts the system curve and the operating point.
Cv = Q · sqrt(SG / ΔP) -
Orifice Plate in Pump Systems
Size an orifice plate on a pump discharge per ISO 5167-2: beta ratio, discharge coefficient C, the measured ΔP and the non-recoverable pressure loss.
qm = (C / sqrt(1 - β⁴)) · ε · (π/4) · d² · sqrt(2 · ΔP · ρ₁) -
Restriction Orifice for Pump Minimum Flow
Size the restriction orifice on a minimum-flow recirculation line: the bore for the target bypass flow, the ΔP and the non-recoverable pressure loss.
Q_discharge + Q_recirc = Q70 = 0.70 · Q_max -
Gravity Flow Pipe Calculator
Gravity flow in a full pipe: the elevation head available, friction loss by Darcy-Weisbach / Colebrook — not Hazen-Williams — and the resulting flow rate.
H_available = ΔZ = h_friction(Q) + h_fittings(Q) → solve for Q -
Gravity Flow with Control Valve
Size a control valve on a gravity line: Cv per IEC 60534-2-1 from the available static head, the cavitation index σ and the flashing check.
ΔZ = h_dist + h_loc + h_valv -
Branched Pipe Network Calculator
Solve the flow distribution of a branched network with one pump and up to 20 branches: Newton-Raphson at the nodes, head loss by Darcy-Weisbach.
Σ Q_in(node) − Σ Q_out(node) = 0 -
Looped Pipe Network Calculator
Solve a closed-loop pipe network: flow balance at the nodes and zero net head loss around the loop — the Hardy Cross problem, solved by Newton-Raphson.
Σ Q_in = Σ Q_out at every node and Σ h_f = 0 around each loop -
Control Valve Cv Calculator for Liquids
Size a liquid control valve per IEC 60534-2-1 / ISA 75.01.01: Cv = Q·√(SG/ΔP), the FL choked-flow limit, cavitation index and the Kv ↔ Cv conversion.
Cv = Q x √(SG / ΔP) ; Kv = 0.865 x Cv ; ΔP_choked = FL² · (P1 − FF·Pv) -
Steam Control Valve Cv Calculator
Size a steam control valve per IEC 60534-2-1 (Eq. N6): required Cv/Kv, expansion factor Y, xT, choked flow and the outlet steam velocity check.
W = 31.6 x Kv x Y x √(x · P1 · ρ1) , x = ΔP / P1 , Y = 1 − x/(3·Fγ·xT) -
Relief Valve Sizing API 520
Size a liquid PSV per API 520: area A = Q/(38·Kd·Kw·Kc·Kv)·√(G/ΔP), the Kd/Kw/Kc/Kv factors and the next standard API 526 orifice letter.
A = Q / (38 x Kd x Kw x Kc x Kv) x √(G / ΔP) -
Steam Safety Valve Sizing API 520/526
Size a steam PSV per API 520: required discharge area from the relieving capacity, the KN and KSH correction factors and the next API 526 orifice letter.
A = 190.5·m / (P₁·Kd·Kb·Kc·KN·KSH) -
Orifice Plate Calculator ISO 5167-2
Size an orifice plate per ISO 5167-2: beta ratio β = d/D, the Reader-Harris/Gallagher discharge coefficient C, the ΔP and the permanent pressure loss.
q_m = (C / √(1 − β⁴)) · ε · (π/4) · d² · √(2 · Δp · ρ) , β = d / D -
Joukowsky Equation Calculator
Joukowsky equation ΔP = ρ·a·ΔV (head: ΔH = a·ΔV/g) for water hammer, with Korteweg wave speed a, critical time Tc = 2L/a and Michaud gradual closure.
ΔP = ρ x a x ΔV (in head: ΔH = a x ΔV / g) -
Quick hydraulic calculators
Free online hydraulic calculators, no sign-up: flow velocity v = Q/A, pipe ID, pump power ρ·g·Q·H/η, affinity laws, tank fill time, Cv to Kv and Joukowsky.
v = Q / A = 4·Q / (π·D²) (Q in m³/s, D = inside diameter in m)
Reference tables
Electrical 13
Short-circuit, demand, cable list, trays, protection, MCC, DC systems, grounding and distribution panels.
Discipline overview →-
Short-Circuit Calculator (IEC 60909)
Peak factor kappa = 1.02 + 0.98 x e^(-3 x R/X) and ip = kappa x √2 x Ik″ per IEC 60909-0 (Eq. 55/56), with Ik″, minimum Ik″ and a worked example.
kappa = 1.02 + 0.98 x e^(-3 x R/X) → ip = kappa x √2 x Ik″ -
Cable Sizing Calculator
Size power cables: design current Ib, ampacity with grouping and temperature correction (NBR 5410 Tab. 36/37) and the voltage drop over the run.
Ib = P·1000 / (√3·V·PF·η) [three-phase] -
Electrical Demand Calculator
Turn a connected load list into demand: P_demand = Σ(Pi × FDi), the demand and diversity factors, and the resulting transformer and feeder rating.
P_demand = Σ (P_i x FD_i) ; FD = demand factor ; FS ≠ FD -
MCC Sizing Calculator IEC 61439
Size a motor control centre per IEC 61439: drawer per motor, columns, main busbar at 125 % of the load current and the short-circuit withstand Icw.
I_brk = next(1.15 · In, breaker_series) -
Distribution Board Calculator
Size a distribution board: busbar current rating and temperature rise, main and outgoing breakers, short-circuit withstand and the DIN module count.
In = P / (V · fp) -
Capacitor Bank Calculator
Size a power factor correction bank: Qc = P·(tanφ₁ − tanφ₂), the step split, the resonance check against harmonics and the IEC 60831 capacitor rating.
Qc = P x (tan φ₁ − tan φ₂) , φ = arccos(PF) -
Surge Arrester Sizing IEC 60099-4
Select a metal-oxide (ZnO) arrester per IEC 60099-4: Uc/MCOV above the continuous voltage, Ur for the TOV, and the protective margin over the BIL.
U_L-N,max = (Um/√3)·(1 + reg) -
SPD Sizing Calculator IEC 61643-11
Select a surge protective device per IEC 61643-11: Type 1/2/3 by installation point, Uc above the system voltage and Up below the equipment withstand.
Uc ≥ 1.1·Uo (TN) ; Uc ≥ 1.55·Uo (TT, L-PE) ; Uc ≥ √3·Uo (IT without neutral) -
CT and VT Sizing IEC 61869
Size instrument transformers per IEC 61869-2/-3: CT ratio, metering (0.2/0.5) vs protection (5P/10P) accuracy class, burden in VA and saturation.
Ipn = next_standard( max(margin · In, 1) ) ; ratio = Ipn / Isn -
Cable Tray Fill Calculator
Compute cable tray fill: fill % = Σ cable cross-sections / usable tray area, the 50 % limit for power cables and conduit occupancy on the same run.
Fill % = (Σ π·(d_i/2)²) / A_usable x 100 -
Grounding Grid Calculator IEEE 80
Design an earthing grid per IEEE 80 / NBR 15751: grid resistance Rg, ground potential rise GPR, mesh voltage Em and the tolerable touch and step limits.
R = ρ·[ 1/L + 1/√(20·A) · (1 + 1/(1 + h·√(20/A))) ] -
Battery Bank Sizing Calculator IEEE 485
Size a stationary battery bank per IEEE 485/1115: the DC duty cycle, required Ah with aging and temperature correction, cell count and series-parallel.
I_load = P / (V_bus · η) | I_load = I (current mode) -
DC Cable Sizing Calculator
Size DC cables for 24, 48 or 125 V systems: section from the voltage drop A = 2·L·I·ρ/ΔV, the ampacity check and the short-circuit thermal limit.
A = (2 x L x I x ρ) / ΔV_allowed
Reference tables
Automation 14
Field instrumentation, industrial networks and control logic: flow meters, dP accuracy, thermowells, temperature and level, PROFIBUS, DeviceNet, ControlNet, Ethernet-APL, relay and Ladder logic.
Discipline overview →-
Thermocouple and RTD conversion
Convert mV to temperature per ITS-90 and ohms to temperature per IEC 60751, with declared reference junction, tolerance class and lead error.
E = Σ cᵢ·tⁱ + a₀·exp[a₁·(t − a₂)²] | E_terminals = E(t_measuring) − E(t_reference) -
Type K thermocouple mV to °C
Type K thermocouple mV to °C per ITS-90, with cold junction compensation. Type K table and a free calculator — no sign-up required.
t = E^-1( E_measured + E(t_ref) ) with E(t) = c0 + c1*t + ... + c9*t^9 + a0*exp(a1*(t - a2)^2) -
19 inch rack size calculator
19 inch rack size calculator: count the U for switches, patch panels, ODFs, servers and NVRs, plus cable managers, fibre slack, power strips and spare.
U_block = U_switch + U_manager + U_patch panel = 1 + 1 + 1 = 3U -
Ethernet-APL spur length and power class calculator
Check Ethernet-APL spurs (length, class A/C, voltage drop), 2-WISE, field switch ports and consumption and network load per the Engineering Guideline.
U = 9.6 V − 0.05556 A × 55.74 Ω/km × 0.2 km = 8.98 V < 9.0 V -
Radar level transmitter installation
Check that the radar or ultrasonic beam reaches the bottom without touching the shell and get the minimum distance from the wall in tanks and silos.
d_min = r_ant + (L + H) · tan(α/2) + m = 50 + (160 + 5,980) × tan 4° + 50 = 529.4 mm -
Magnetic flow meter sizing
Size a magnetic flow meter by velocity — line and sensor velocity at Qmin and Qmax, recommended band per fluid class, turndown and bore reduction.
v = (Q/3600) / (π·(D/1000)²/4) | clean: 1.5 ≤ v ≤ 3.0 m/s · abrasive: 1.5–2.0 · fouling: 2.0–3.0 -
Differential pressure transmitter accuracy
Differential pressure transmitter accuracy: combine reference and thermal error of an electronic or conventional dP by RSS for level, density and flow.
A_Diff = √[(A_HP·URL_HP)² + (A_LP·URL_LP)²] | E_total = √(A_Diff² + T_Diff²) -
Thermowell wake frequency calculator (ASME PTC 19.3 TW-2016)
Check a thermowell per ASME PTC 19.3 TW-2016 — wake frequency vs natural frequency, in-line resonance, static and fatigue stress and external pressure.
fs = Ns × V / B | r = fs / fnc < 0.4 (0.8 if the in-line resonance stress passes) -
PROFIBUS PA segment calculator
Size a PROFIBUS PA segment — coupler current, voltage at each instrument, cable length, spur limit, FISCO, cyclic bytes and cycle time per IEC 61158-2.
V_node = V_parent − I_downstream × R_loop × L_section ≥ 9.0 V -
PROFIBUS DP cable length calculator
Check PROFIBUS DP segments — length by data rate, spur capacitance, 32 stations, addresses, hub and OLM cascade, slot time, fibre, cycle and TTR.
L_trunk + Σ L_spur ≤ 1200 m (≤ 93.75 kbit/s) · 1000 m (187.5) · 400 m (500) · 200 m (1500) · 100 m (3–12 Mbit/s) -
DeviceNet voltage drop calculator
Size a DeviceNet trunk per ODVA PUB00027R1 — length by data rate and cable, 6 m drops, 4.65 V drop budget, supply current and node voltage.
dV = sum[ I_section × (L × Rc + 0.005 ohm per tap) ] <= min(4.65 V ; (V_supply,min − V_node,min) / 2) -
ControlNet segment length calculator
Check ControlNet coax segments (1000 − 16.3 m per tap), repeaters, fiber links, propagation delay, SMAX/UMAX and NUT/RPI/API per Rockwell manuals.
L_max = 1000 m − 16.3 m × (N_taps − 2), N_taps <= 48 -> 250 m at 48 taps -
Relay logic circuits
Relay logic simulator: draw a contactor control circuit and check seal-in, interlock, NC emergency stop and safety relay EDM by exhaustive truth table.
K1 = (S1 + K1) · ¬S0 · ¬EMG -
Ladder logic simulator
Ladder logic simulator for PLC rungs (IEC 61131-3, Siemens LAD, Studio 5000): check seal-in, TON timers, double coils and emergency stop reach scan by scan.
K1 = (S1 + K1) · S0 · EMG
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