Steam and condensate glossary

The pressure on the outlet side of a steam trap or valve. High back pressure in a condensate line reduces the pressure difference across the trap, so less condensate can drain.

Water deliberately removed from a boiler to keep dissolved solids below a set limit. Blowdown carries heat with it, which can be recovered with a flash vessel and a heat exchanger.

Vapour bubbles that form when the pressure at a pump inlet falls below the vapour pressure of the liquid, then collapse inside the pump. Common with hot condensate, it damages impellers and seals.

Steam generated from purified water in a dedicated generator, used where steam may contact product or sterile surfaces, for example in pharmaceutical manufacturing.

The hot water formed when steam gives up its latent heat. Condensate still holds useful heat and treated water, so returning it to the boiler saves fuel, water and chemicals.

The share of steam produced that comes back to the boiler house as condensate. A low or unknown return rate is often the first sign of avoidable losses.

A vessel that heats boiler feedwater, usually with steam, to drive out dissolved oxygen and carbon dioxide that would otherwise cause corrosion.

The proportion of a steam and water mixture that is vapour. Wet steam carries less usable heat and can cause erosion and poor process performance.

The water pumped into a boiler, made up of returned condensate and treated make-up water.

Steam formed when hot condensate under pressure is released to a lower pressure. It can be recovered in a flash vessel and used for low pressure heating.

A condition where the steam pressure inside a temperature controlled heat exchanger falls below the back pressure, so condensate cannot drain. It leads to waterlogging, temperature swings and water hammer.

The heat released when steam condenses to water at constant temperature. Most of the useful heat in steam is latent heat.

Fresh treated water added to the boiler to replace condensate and steam that are lost. In the GCC it often starts as desalinated water.

Selecting pipe diameters so that velocity and pressure drop stay within sensible limits. Undersized lines are noisy and lose pressure; oversized lines cost more and lose more heat.

A valve that lowers steam pressure to suit a user. Distributing at higher pressure and reducing close to the point of use allows smaller pipes.

Steam at the boiling temperature for its pressure. Most process heating uses saturated steam because it releases its heat at a stable temperature.

Heat that changes the temperature of water or steam without changing its phase. Condensate leaving a process still holds sensible heat.

An overview of how much steam is produced, where it is used and how much condensate returns. It is the basis for ranking energy savings.

An automatic valve that lets condensate and air out of steam equipment while holding steam in. Failed traps either leak steam or leave equipment waterlogged.

Steam heated above its saturation temperature. It is used for turbines and some processes, but is less effective for heat transfer than saturated steam.

Shock caused when slugs of condensate are driven by steam or when steam collapses in contact with cooler condensate. It is usually a drainage problem and can damage pipework and fittings.