Engineering blog
Applied articles on hydraulic and electrical sizing: the mistakes that reach the field, what the standard actually requires, and worked numbers you can check.
- Hydraulic
Pipe head loss calculation: Darcy-Weisbach and Colebrook, step by step
Pipe head loss is calculated with Darcy-Weisbach, h_f = f·(L/D)·(v²/2g), using the Colebrook friction factor. This article works the full calculation for a 4" Sch 40 line carrying 104 °F (40 °C) water — and shows where it goes wrong when a step is skipped.
- Hydraulic
Water hammer on pump trip — the case that sets your pipeline's pressure rating
You choose how fast the valve closes. You do not choose when the power fails — and that is the event that sets the highest pressure your pipeline will ever see. This article shows why, with the numbers from a 1,200 m case.
- Hydraulic
Pumps in parallel: why two identical pumps don't double the flow (operating point worked example)
Two identical pumps in parallel deliver the sum of their flows only at the same head — and the system will not stay at the same head. In the worked case below, the second pump adds 36.8% of flow, not 100%, and the third adds only 9.4% more.
- Electrical
IEC 60909 peak short-circuit current — the kappa formula κ = 1.02 + 0.98·e^(−3R/X), explained and worked out
The peak short-circuit current is ip = κ·√2·Ik″, and κ comes only from the R/X ratio of the equivalent fault impedance: κ = 1.02 + 0.98·e^(−3R/X). On a 1000 kVA, 440 V board that gives κ = 1.619 and ip = 52.6 kA — the number that the breaker making capacity and the busbar peak withstand must cover.