The main criteria for the selection of the type are as follows, although they can not be listed in order of importance since it varies from application.

Resistance to freezing: Trap should resist to freezing for instance outdoor using in cold countries, body of the trap should not broken because on the difference on temperature when t he s team l ine and/or process shout down. For such applications body should not keep condensate. The ideal traps are thermostatic, thermodynamic and bi-metallic. Inverted bucket and float t raps should not install such processes.

Installation versatility: Traps that should install with certain position should be chosen accordingly to the line. For instance thermodynamic steam traps should be installed on the horizontally otherwise they cannot work properly and have less cycle life, float steam traps should be also installed horizontally otherwise they will be failed as either open or blocked/closed all the time.

Air venting: Traps especially for steam line where lots of air rooms and gas occurs should be able to discharge this gas otherwise they will be failed as either open or blocked:/closed all the time.

Resistance to water hammer: Traps especially for steam line where lots of air rooms and gas occurs and becomes a water hammer should be either able to discharge this gas or have strong mechanism that can resist against water hammer otherwise they will be damaged easily.

Discharging capacity: Traps especially for big sized lines such as 1 ½” and 2” should be able to discharge all the condensate that occurs on the process otherwise accumulated condensate can damage the pipe-line and as well to the equipment, plus it will be a result of losing the heat of steam.

Heat Exchange efficiency: traps such as thermostatic types which are discharging the sub cooled condensate do not allow an efficient heat ex change and should not be installed fo r super-heated steam lines. Otherwise they will be blocked immediately and cause lots of important problems such as damaging turbines.

Sensitivity to back pressure: Traps such as thermodynamic types should not be installed on steam lines where the back is more than 80 % of inlet pressure. In such cases thermodynamic traps failed as either open or blocked / closed all the time.

Resistance to corrosive conditions: The initial parts of all traps should be stainless steel but for such cases where even the outer conditions are corrosive traps should have stainless steel body and cover as well.