Depending on the application, a process steam trap will probably have to handle heavy startup loads, often followed by smaller running loads. Equipment is generally protected from the weather and typically features a single coil. Heavy startup loads, followed by smaller running loads are to be expected, but without the extreme swings of weather-exposed equipment.
Adequate air venting is most important as the equipment is often run on daily or weekly schedules.
Tendency is for total shutdown of equipment following completion of run or batch. Air in a heating system significantly reduces its efficiency. Also, steam mixed with air contains fewer BTUs at a given pressure than steam alone. It is the function of a steam trap to aid in venting air from a steam system, but auxiliary thermostatic air vents are often required. Open to cooler air and closed to hotter steam they greatly speed up the air purging process.