Away from the turbine hall, steam engineering is bookkeeping. Three relations cover most of a plant walk-down, and all three are mass balances in disguise.

What is that leak costing? Napier's rule: $\dot m = \dfrac{A\,P}{70}$, where $A$ is the orifice area of the hole, $P$ is the absolute pressure upstream and $\dot m$ is the leak rate. It is a straight-line fit to choked flow, honest between roughly 170 kPa and 7 MPa absolute, and it reads a few percent high — a reputation it has earned and kept. Absolute pressure, always: it is the pressure RATIO across the hole that chokes the flow, and a gauge does not know about ratios.

How much spray water to cool that steam? An energy balance across the station: $\dot m_w = \dot m_1\,\dfrac{h_1 - h_2}{h_2 - h_w}$. Here $\dot m_1$ is the steam rate in and $\dot m_w$ the spray water rate, both kg/h; $h_1$ is the inlet steam enthalpy, $h_2$ the target enthalpy leaving, and $h_w$ the spray water enthalpy, all kJ/kg. The top is what each kilogram of steam must shed; the bottom is what each kilogram of water can absorb on its way up to the target. The target is on BOTH sides of that fraction, and that is not a typo — it is the mixed stream leaving.

How big a trap does that coil need? $\dot m = \dfrac{\dot Q}{h_{fg}}$, with $\dot Q$ the coil duty in kW and $h_{fg}$ the latent heat at the coil pressure. Every kilogram that condenses gives up exactly its latent heat, so the duty divided by that price is the condensate load. One nugget from the trade: this is the RUNNING load, and traps are selected on two to three times it, because the worst moment is start-up with a cold coil.