What is condensate piping?

What is condensate piping?

Schedule 40 steam pipe

After the Filomena storm and the cold wave that followed, we have seen the consequences in many homes that were not prepared for the extremely low temperatures. One of them has been the clogging of heating systems, so we talked to you about how to defrost a condensate pipe.

During the colder winter months, the risk of boiler pipes freezing increases.  The one most at risk is the condensate pipe, since it is responsible for removing from the circuit the waste water generated when the boiler extracts the energy from the combustion gases in condensing boilers. This process creates acidic water when the boiler cools down and must be removed from the pipes to avoid corrosion. This is a necessary process as this method saves energy by harnessing the energy created by condensation.

To avoid freezing, it is best to set the boiler at a higher flow temperature to reduce the amount of condensed water and thus the likelihood of ice forming. The downside is that we will pay more on the bill, so we must remember to lower the thermostat as soon as the cold snap passes.

Steam condensate return

Condensate discharged from steam traps is handled in two ways. It either goes to the drain just after exiting the trap, which represents the loss of the energy contained in the water; or it is piped elsewhere, ideally to the recovery system.

Two-phase flow refers to steam (either flash steam, boiler steam or a mixture of both) flowing through the pipeline along with the liquid condensate. Although they flow together, this does not mean that they flow in two well separated phases. The flow pattern inside the pipe can also be a mixture, as seen in the animation below.

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This is due to a phenomenon called flash evaporation, which occurs when condensate is formed at high pressure and reaches a lower pressure system, such as the condensate return at the steam trap outlet. In this case, since the pressure at the inlet of the steam trap is higher than at its outlet, part of the condensate flashes into steam instantaneously when it is discharged from the trap.

Condensate recovery pdf

In a heating process, condensate is the result of steam that transferred part of its heat energy, known as latent heat, to the product, line or equipment to be heated.

In industries that use steam, Latent Heat refers to the energy required by water to become steam, also known as Enthalpy or Heat of Vaporization. When it absorbs this latent heat, the water is transformed into steam, and when it transfers it, the steam returns to form hot water (condensate).

When the steam condenses, at the very moment it changes phase, the condensate has the same temperature as the steam because only the latent heat has been lost and all the sensible heat remains. This condition is known as “Saturated Water”. Not wasting, but instead recovering and reusing as much sensible heat as possible is one of the main reasons why condensate is recovered.

A change in the temperature of a solid, liquid or gas represents an increase/decrease in its sensible heat. A change of state, as when ice turns to water or water to steam, represents an increase/decrease in latent heat.

Steam piping characteristics

Condensate carried with steam is the cause of most erosion. By repeatedly striking the pipe at the elbows, condensate can cause gradual thinning of the pipe wall, as its mass and high velocity upon impact have a similar effect as industrial water jet cutters. This type of erosion – caused by condensate droplets – is typically referred to as Liquid Droplet Pitting Erosion.

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Erosion resistance varies depending on the material. For installation cost reasons, carbon steel is typically the standard material for steam distribution piping, although it is less resistant than stainless steel. The use of stainless steel piping is usually limited to pharmaceutical, biotechnology, clean steam or other sterile applications.

Preventing erosion in steam distribution piping is generally simpler, and typically requires the removal of condensate droplets carried by the steam. This means installing a steam-condensate separator.

What is condensate piping?
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