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Steam Traps

Steam Traps

Steam Traps

Hi all,

Is someone out there able to give a list of applications in which thermodynamic traps are used over float, vice versa and why?


RE: Steam Traps

Thermodynamic traps are typically a good choice for high pressure steam main condensate removal, including superheat conditions. Not so good for low pressure or high back pressure. They can also be used on steam tracing.

Float traps are the first choice for draining of most heating and process equipment and can vent a lot of air at startup.

Check out engineering tutorials at the Spriax Sarco website:

RE: Steam Traps

Hey Jonathan,

To give you a straightforward simple way of looking at steam trap applications without being force fed Spirax-Sarco literature; Thermodynamic traps are always the most cost effective trap initially to install, however require the most maintenance and are the first to require repair. The nature of their design (a pressure differential across a disc mechanically closing and opening it) make these traps constantly cycle even when the application is not creating condensate.

To answer your question regarding thermodynamic versus float & thermostatic, that is an easy one. F&T traps = modulating condensate applications. Thermodynamic = constant condensate discharge applications (either on or off).

There are many reasons why, however in a nut shell when for example an exchanger is modulating its set point via a control valve on steam inlet, the rate at which condensate forms varies and the float within the F&T is able to rise and fall accordingly to accommodate this drainage (it will still discharge at very light loads). The thermostatic element within the F&T trap is for venting air and non-condensables upon exchanger startup when it goes straight into full load. This is also why you mainly can have Float and Thermostatic traps with the option for an integral vacuum breaker. Reason being for the Vacuum Breaker is that when you are modulating, a control valve can be sending an exchanger steam, than reach it's set point, and go straight to shut-off. That means, you have an exchanger full of live steam that's stuck inside it that will quickly overtime naturally condense, and turn into condensate as the temperature drops. A certain volume of gas (steam) is much larger than that same amount of gas in liquid form. I have seen massive heat exchangers which were literally imploded due to being under vacuum.

Thermodynamic traps have a fixed maximum rate at which they can cycle to discharge, and light condensate loads will cause unnecessary sub-cooling of condensate if you do not need. If you were to put a thermodynamic trap and a modulating coil, it would at the very least be flooded and not meet the intended capacity. Water hammer and errosion follow.

Hope that helps :)

« Rien ne se perd, rien ne se crée : tout se transforme ».
— Antoine Laurent de Lavoisier (1743-1794)

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