STEAM TRAPS Introduction Steam Trap Selection Guidelines
Steam Trap Selection Guidelines
Steam Traps for Drip Applications: “ Drip traps “ Drip applications refer to draining condensate that forms in distribution piping as steam is transported from the boiler to where it is to be used. Eliminating this condensate protects valves and piping from wiredrawing and water hammer Because condensate loads tend to be low, steam traps with smaller orifices are typically select- ed for extended service life. It is reasonable to consider a single trap that can operate over a wide pressure range in order to simplify selection and reduce inventory. Other factors to consider when selecting drip traps: materials, repairability, efficiency, reliability, installation orientation, personal preference/experience, as well as the trap’s ability to handle freezing climates, superheated steam, or pipe scale and debris. Steam Traps for Tracing Applications: “ Tracing Traps “ Tracing Applications refer to using steam to elevate the temperature of a product, process, or piece of equipment by using tubing or some type of jacketing device filled with steam. These applications are commonly used to promote flow of heavy fluids or prevent pipelines and equipment from freezing. The relatively small traps used for these applications are referred to as “Tracing traps”. A Non-Critical Tracing application may benefit from a thermostatic steam trap which sub-cools and backs up some condensate - an adjustable bimetal trap offers additional temperature control. Thermodynamic traps are ideal for critical tracing applications where condensate back-up is not permitted. Steam Traps for Process Applications: “ Process Traps “ Process applications refer to draining condensate from the actual process using the steam. These require steam traps with relatively high condensate capacity. In the majority of process applications, it is important to discharge air present in the system during start-up so the steam can quickly enter the system. Although separate air vents can be used for this purpose, it makes sense to select a trap which has air venting capability, in addition to discharging varying condensate loads. The trap must have enough capacity to discharge the condensate even when the differential pressure across the trap is low. These low pressure conditions commonly occur in process heating applications where control valves are used to regulate the flow of steam into the equip- ment. However, if the trap is significantly oversized it may cause it to wear out more quickly and allow steam to pass into the condensate return. The most common trap type for process applications is the Float & Thermostatic style.
Most Common Types of Steam Traps
F&T (Float & Thermostatic) Traps: Float & Thermostatic Steam Traps contain a float-operated valve to continually discharge condensate and a thermostatic air vent which discharges air. Body materials available are Cast Iron, Ductile Iron, Cast Steel, & Stainless Steel for pressures up to 450 psig. (F&T traps are referred to as mechanical traps.) Typical Applications: F&Ts are the most commonly used trap for both batch type processes and continuous process applications with rapidly changing pressures and loads. Advantages: F&Ts quickly respond to load and pressure changes, discharge large amounts of air present at start-up which allow steam to quickly enter the system, continuously discharge condensate as it forms and offer a wide range of capacities for any process application. Other Factors to Consider: F&Ts narrow operating pressure ranges require more care during selection. They are not self- draining, therefore, are subject to freezing. Trap body must be installed vertically for proper operation.
Most Common Use: Process Applications from low pressure HVAC models for residential heating to Industrial cast steel and stainless steel models for Chemical and Petro-Chemical plants up to 450 PSI. Suitable alternative for drip applications to 200 psig.
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