How to choose the ideal steam trap for your specific applications
It is crucial to understand an application’s characteristics, such as pressure fluctuations, temperature ranges, condensate flow rates, and the presence of non- condensable gases, in determining the best-fit steam trap. The rate and quantum of condensation of steam differs across different applications.
Discharge temperatures of steam traps
Table: Selecting the right type of steam trap
| Trap Type | Float | Inverted Bucket | Thermostatic | Thermodynamic |
|---|---|---|---|---|
| Response | Fast | Moderate | Moderate | Slow |
| Air Venting | Medium/High | Low | High | Low |
| Capacity | High | High | Low | Low |
| Maintenance | Moderate | Moderate | Easy | Easy |
| Relative Cost | Medium/High | Medium/Low | Low | Low |
| Failure Mode | Closed | Open | Open, Closed | Open |
Likewise the discharge pattern for different types of steam traps also varies. Considering both these aspects, there is only one type of trap which is the best fit for a given application.
In addition to selecting the right type of steam trap, selecting the right size is also critical. In order to size the trap correctly, calculate the condensate load to be handled, allow for a safety factor and based on the upstream pressure and back pressure, follow the typical capacity curve chart provided by the trap manufacturer.
Because plant operating conditions can vary, it is important to add a safety factor to the calculated condensate load before selecting a steam trap. This enhances the steam trap’s ability to handle changes in operating conditions, including changes in process parameters, equipment/system start-up conditions, etc. Moreover, the safety factor also serves as buffer to accommodate factors such as wear and tear on the trap, deterioration of insulation health, or other unexpected conditions that can impact trap performance. Incorporating a safety factor, minimises the likelihood of the trap operating beyond its designed range, thereby preventing premature failure.
The recommended safety factor to consider for different types of steam traps is illustrated below.
Table : Safety factors to consider while sizing steam traps.
| Trap Type | Safety Factor |
|---|---|
| Thermodynamic Trap | 1.2 |
| Float Trap | 1.5 |
| Thermostatic Trap | 2 |
| Inverted Bucket Trap | 2-3 |
Steam traps are available in various materials of construction (MoC), including cast iron, stainless steel, carbon steel and alloy steel. Based on where a steam trap is installed, it can be subject to varying steam pressures and temperatures. It is imperative to make sure that the MoC of the steam trap selected, is suitable to withstand the pressure and temperature it will be subjected to ensure its longevity and safe operations.
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