Steam Trap Working and Types

Steam Trap Working Principles

Steam Trap Working and Types

Energy is getting more important day by day. According to the diminishing of energy sources all the industry sectors searching for alternative sources for increasing the productivity.

In this case steam which is one of the energy carrier is also getting more important. Trapping of steam and using more heat of steam is up to choosing right steam traps. Although steam traps look simple and small their obligation is very complex. Saving more energy is related to the right chosen steam trap type and sizes. Working principles should be known well for choosing the right steam trap for the process.

Purpose of Steam Traps

The aim of a steam trap is discharging the condensate from the steam pipe line while trapping the steam. Steam use its potential heat during the applications and by the radiation heat loses on pipelines, steam turns to condensate. In case this condensate not discharged from the pipeline, it causes cavitation and water hammer beside reducing the quality of the steam.

An ideal steam trap should have the ability of air venting together with discharging the condensate. There is no “Universal Type Steam Trap” that has no disadvantages according to the application conditions. All the steam trap types have different working principles that has advantage and disadvantages. In general there is always a best trapping solutions for all kind of steam applications with its alternative. This solution depends on the temperature, pressure and amount of the condensate.

In principle steam traps have to do the followings;

• Discharging the condensate from the pipeline
• Trapping the steam
• Discharging the air and gas

Types of Steam Traps

Mechanical Steam Traps

Most important characteristic of the mechanical steam traps is that they operate according to the difference of the density of steam and condensate which allows the condensate to flow.

The weight of the float, acting through the lever, keeps the valve closed when the trap is empty. As the condensate enters the trap, it raises the float and opens the valve overcoming the pressure acting on it. If no more condensate load is steady the float sets to produce a continues discharge. The condensate level in body is always above the valve creating perfect water seal the closed float trap is able to discharge the air through thermostatic air venting unit installed inside the body.

Thermostatic Steam Traps

Typical characteristics of thermostatic steam traps is to operate according to the difference in temperature of steam and condensate. As the condensate cool, the liquid condenses lowers the internal pressure of the membrane. The resultant pressure differential will favor the external pressure acting on the membrane to retract and open the orifice, permitting the condensate discharge.

Thermodynamic Steam Traps

Thermodynamic steam traps operate periodically according to the difference in dynamic pressure of steam and condensate and discharge the condensate at the same temperature of the steam. Steam entering the trap expands suddenly as it reaches the backside of the disc. The resulting high flow velocity causes a decrease in pressure under the disk. Steam above the disc gets high pressure force and this pressure balance forces the disc onto the seat to close the orifice in other words to trap the steam.

When condensate appears at the trap inlet under and above the disc the pressure force above the disc disappears and allows the condensate discharge.