Function and Types

PurposeSteam traps exist to discharge air and condensate while

not permitting the escape of live steamTheir goal is to ‘purify’ the steam of excess air and water

(condensate) to :Improve efficiency (Excess water or air in the system prevents it

from reaching operating temperature quickly during start-up)Protect system (Inadequate steam trapping can lead to

waterhammer, corrosion, leakage, and high maintenance costs)Provide maximum heat transfer (‘dry’ steam has best heat

transfer properties in equipment like a heat exchanger)

Types1. Mechanical steam traps - Have a float that rises

and falls in relation to condensate level and this usually has a mechanical linkage attached that opens and closes the valve. Operate in direct relationship to condensate levels present in the body of the steam trap.

Click link below to view mechanical steam trap with animation:

[www.tlv.com/global/US/product-operation/free-float-steam-trap-jx.html]

Types2. Temperature steam traps - Have a valve that moves

in/out of position by either expansion/contraction caused by temperature change. Some condensate builds up as it cools sufficiently to allow the valve to open. In most circumstances this is not desirable as condensate needs to be removed as soon as it is formed.

Click link below to view temperature steam trap with animation:[http://www.tlv.com/global/US/product-operation/temperature-control-steam-trap-lex.html]

Types3. Thermodynamic steam traps - Work on the

difference in response to velocity change in flow of compressible and incompressible fluids. As steam enters, static pressure above the disk forces the disk against the valve seat. The static pressure over a large area overcomes the high inlet pressure of the steam. As the steam starts to condense, the pressure against the disk lessens and the trap opens to allow condensate out.

Click link below to view thermodynamic steam trap with animation:

[http://www.tlv.com/global/US/product-operation/thermodynamic-steam-trap-a3n.html]

ComparisonMechanical

continuous operation no action at no load,

continuous at full load good energy

conservation good resistance to wear good corrosion

resistance excellent ability to vent

air at very low pressure excellent operation

against back pressure poor resistance to

damage from freezing fair ability to purge

system excellent performance

on very light loads poor ability to handle

dirt large comparative

physical size closed at mechanical

failure

Temperature intermittent

operation fair energy

conservation fair resistance to

wear good corrosion

resistance good abilities at low

pressures excellent operation

against back pressure good resistance to

damage from freezing

excellent ability to handle start-up

fair ability to handle dirt

small comparative size

open or closed at mechanical failure (depending on design)

Thermodynamic

intermittent operation

poor energy conservation

poor resistance to wear

excellent corrosion resistance

poor abilities at low pressures

poor operation against back pressure

good resistance to damage from freezing

excellent ability to purge system

poor ability to handle dirt

poor ability to handle flash steam

open at mechanical failure