Saturated Steam Table

Reading the Six Columns

Each row of the saturated steam table describes one point on the boundary between water and vapour. The pressure and temperature columns are locked to each other; the three enthalpy columns split the energy; the last column gives the volume that one kilogram occupies.

The arithmetic check is simple: liquid enthalpy plus latent heat equals total steam enthalpy. At 0.10 bar absolute the saturated steam table gives 191.83 + 2392.8 = 2584.7 kJ/kg, and every other row behaves the same way. If a value copied from a datasheet fails that addition, the value is wrong.

Turning a Heat Duty into kg/h

This is the calculation the saturated steam table exists for. Take the latent heat at the working pressure and divide the process duty by it. A heat exchanger absorbing 300 kW at 4 bar absolute, where the latent heat is 2133 kJ/kg, needs 300 ÷ 2133 = 0.141 kg/s, which is about 506 kg/h of steam.

That kg/h figure is the input to everything downstream: the pipe diameter, the control valve Kv, the trap capacity and the condensate return line. Reading the saturated steam table is therefore the first step of a steam sizing exercise, not a detail checked at the end.

Only the Latent Heat Does the Work

In an ordinary heat exchanger the steam condenses and leaves as hot condensate, so only the latent heat column of the saturated steam table is transferred to the process. The liquid enthalpy leaves the exchanger still in the water, which is exactly why condensate recovery is worth the pipework: that energy has already been paid for at the boiler.

The saturated steam table also shows a result that surprises people the first time they see it. Latent heat falls as pressure rises: 2392.8 kJ/kg at 0.10 bar against roughly 1640 kJ/kg near 51 bar. Raising the distribution pressure therefore means more kilograms of steam for the same duty, not fewer.

Specific Volume Sets the Pipe Bore

The last column is the link between the saturated steam table and pipe sizing. One kilogram of steam occupies 14.674 m³ at 0.10 bar and only a fraction of that at working pressures, which is why low-pressure and vacuum steam lines look so oversized next to a high-pressure main carrying the same mass flow.

Multiply the required kg/h by the specific volume from the saturated steam table and divide by the velocity chosen for the line, and the cross-section falls out directly. The steam pipe capacity table is that calculation already done for the usual velocities.

The Vacuum Rows

The rows above the first gauge-pressure entry are sub-atmospheric. They matter for vacuum drying and for any process that has to stay below 100 °C while still using steam, and the saturated steam table is what makes that possible to plan: at 0.10 bar absolute the steam condenses at 45.81 °C.

Two practical points follow. Air leaks inwards rather than outwards, so non-condensable gases collect and blanket the heat transfer surface, and vacuum-rated equipment and proper air venting are needed. The saturated steam table gives the temperature, but only good venting delivers it.

From the Table to the Valve

Valve selection reads two columns of the saturated steam table. The temperature column decides body rating, gasket, seat and packing material, while the kg/h derived from the latent heat column decides the Kv and therefore the size. A control valve is sized from flow and pressure drop, so it is usually smaller than the line; an isolating valve stays full bore and line size.

The companion charts complete the set: the steam saturation temperature table gives pressure against temperature in technical atmospheres, and the saturated steam table adds the energy and volume behind each of those points.