What is a Steam Trap?

What is a Steam Trap?

 

 

 Steam traps are a type of automatic valve that filters out condensed steam as well as non-condensable gases such as air without letting steam escape. Steam is used in industries regularly for heating or as a force for mechanical power and used in these applications to ensure that steam is not wasted.

inside steam trap

 

Steam traps can be found anywhere there is a steam-powered system used to discharge condensate, that is, the liquid that builds up in the pipelines, along with other non-condensable gases, to relieve the pressure in the lines and regulate the flow of steam within in it.

steam trap

A little bit of science

Steam is formed when water vaporizes to form a gas. For the vaporization process to occur, the water molecules must be given enough energy that the bonds between the molecules (hydrogen bonds, etc.) break. This energy given to convert a liquid into a gas is called 'latent heat'.

Steam-based heating processes use latent heat and transfer it to a given product. When the work is done (i.e. steam has given up its latent heat), steam condenses and becomes condensate. In other words, condensate does not have the ability to do the work that steam does. Heating efficiency will therefore suffer if condensate is not removed as rapidly as possible, whether in steam transport piping or in a heat exchanger.

Types of Steam

In steam-using industries, two common types of steam are dry steam (also called ”saturated steam”) and wet steam.

  • Dry steam applies to steam when all its water molecules remain in the gaseous state. It's a transparent gas.
  • Wet steam applies to steam when a portion of its water molecules have given up their energy (latent heat) and condense to form tiny water droplets.

Take the example of a kettle boiling water. Water is first heated using an element. As water absorbs more and more heat from the element, its molecules become more agitated and it starts to boil. Once enough energy is absorbed, part of the water vaporizes, which can represent an increase as much as 1600X in molecular volume.

Sometimes a mist can be seen coming out of the spout. This mist is an example of how dry steam, when released into the colder atmosphere, loses some of its energy by transferring it to the ambient air. If enough energy is lost that intermolecular bonds start forming again, tiny airborne droplets can be seen. This mixture of water in the liquid state (tiny droplets) and gaseous state (steam) is called wet steam.

Wet and Dry steam

What about a manual valve?

It is sometimes believed that the load of condensate can be regulated with a regular valve instead of a steam trap by simply adjusting the valve opening manually to match the amount of condensate generated.

Theoretically, this is possible. However, the range of conditions necessary to achieve this are so limited that in practice it is not a realistic solution.

The largest problem with this method is that having the valve opening set to discharge a fixed amount of fluid means that fluctuations in the load of condensate cannot be compensated for. Indeed, the amount of condensate generated in a given system is not fixed. In the case of equipment, the load of condensate at start-up differs from that during normal operation. Fluctuations in the product load also result in differences in the amount of condensate generated. Similarly, in the case of steam transport piping, the load of condensate may differ depending on outdoor air temperature or as a result of heavy rain or snow.

If the device can't respond to fluctuations in condensate load, condensate that should be discharged will instead pool inside the equipment/pipe and heating efficiency will suffer. On the other hand, when the condensate load lessens, steam leakage will occur, and steam will be wasted.

The correct steam trap for the job

Various types of steam trap mechanisms (operation principles) have been developed to automatically discharge condensate and non-condensable gases. The most widely used mechanisms are those that rely on differences in temperature, specific gravities, and pressure. Each of these types of steam traps has its own advantages and applications.

Valves online technical team can provide free technical advice on all steam trap applications, to provide quality and competitive solutions.

Offering a wide range of steam traps:

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To read more about TLV Free Float Steam Traps and TLV Thermodynamic Steam Traps, see our blogs below:

Steam traps are a type of automatic valve that filters out condensed steam as well as non-condensable gases such as air without letting steam escape. Steam is used in industries regularly for heating or as a force for mechanical power and used in these applications to ensure that steam is not wasted.

TLV Thermodynamic Steam Traps TLV Free Float Steam Traps
TLV Thermodynamic Steam Traps TLV Free Float Steam Traps

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