What is Steam Traps? Types and Features

Steam Trap

A steam trap is an automatic valve that allows condensate, air, and other non-condensable gases (CO2) to be discharged from a steam system while holding or trapping the steam. As a result, Steam Traps separate the condensate from the mixture. The steam trap is essential to any steam system in power or processing plants. It keeps the steam within the process, allowing maximum heat utilization and thus increasing energy efficiency.

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Let us first try to understand how this Mixture Forms

Condensate

Condensate is a substance that develops whenever steam releases heat energy for any reason.

Air

When the system is cold, air exists in all steam pipes before the system startup. Through boiler water make-up systems and vacuum breakers, air can enter the system.

Non-condensable Gases

Other than air, non-condensable gases like carbon dioxide exist inside steam systems.

The primary function of Steam Traps is to remove liquid condensate from the mixture to avoid the formation of a two-phase flow. Furthermore, for overall efficiency and economy, the steam trap must include

  • There is little steam loss.
  • Long service life and dependability without rapid wear
  • Corrosion resistance to combat the corrosive effects of acidic or oxygen-rich condensate
  • Air venting is necessary for efficient heat transfer and to avoid system binding.
  • CO2 venting to prevent carbonic acid formation.
  • Operation in response to back pressure.

Depending on the system requirements, industrial steam traps can operate at various temperatures and pressures.

Applications of Steam Trap

As previously stated, steam traps are commonly used in steam lines to avoid two-phase flow and increase efficiency. Other important applications for steam traps include:

Drip Applications

When steam loses its heat energy and begins to condensate, a steam trap is used to remove the condensate.

Process Applications

Steam traps remove condensate and air from heat exchangers or radiators to improve heat transfer effectiveness.

Tracing Applications

Steam trams are used in steam tracing applications to remove the condensate that forms in these pipes.

Steam Jacketed lines

Types of Steam Traps 

According to International Standard ISO 6704, there are three major types of Steam Traps, which are listed below:

Thermodynamic Disc Steam Traps

Thermodynamic steam traps detect the velocity difference between entering fluids. When condensate enters the trap body, it moves slowly compared to the steam and is discharged freely. When flash or live steam moves across the underside of the disc, its velocity exceeds that of water, causing a pressure drop that closes the valve head. The valve remains closed until the pressure in the control chamber above the valve head drops, allowing the valve to open.

Thermostatic Steam Traps

Thermostatic steam traps detect the temperature difference between entering fluids. The valve closes when the fluid, typically hot condensate, reaches a temperature greater than or equal to a certain threshold value. The hot temperature causes a thermostatic element to move, causing a valve to close. This temperature is lower than that of saturated steam.

Bi-Metal Steam Trap

Bi-Metal steam trap elements comprise two dissimilar metal strips that are bonded together so that temperature changes cause a deflection in one direction or the other, actuating the valve.

Bellows balanced pressure steam traps are suitable for high capacity, whereas Wafer/Diaphragm balanced pressure steam traps are suitable for low capacity. Bi-metallic steam traps, on the other hand, can be used for both high and low capacity.

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