To remove condensate from piping to prevent damage to the piping and control valves, while assuring that production steam users receive dry steam.
Steam Trap Requirement
Adequately sized drip pockets on the bottom of piping or upstream of heat exchanges, collect condensate which then flows to the steam trap. The trap should discharge the condensate quickly.
Steam Pressures and Temperatures
Generally constant, with some seasonal variation. Of all industrial steam trapping applications, these are the higher pressures often exceeding 600 psi. Design pressures and operating pressures can be different and superheat is frequently encountered.
Relatively small and constant while in normal operation, typically to 50 or 100 lb/hr. Startup loads can be heavier. Boiler carry-over produces slugs of condensate which are unpredictable in magnitude and frequency. Desuperheaters that are malfunctioning can produce unexpectedly high loads.
Drainage to Trap
Usually by gravity with the steam trap installed below the steam line. Occasionally piping in trenches or underground have steam traps installed above the pipe, but the condensate collecting point is below the pipe. This is called lift drainage and requires a lift fitting.
Variable. Freezing is the more common concern.
Need is minimal. Pipe lines frequently have separate vents. Startup may present the most common need. Under running conditions, CO2 may be a problem.
Shock, Vibration, Water Hammer
Generally from inadequate drainage of condensate, which moves at high velocity (5,000-10,000 fpm). Thermal ratcheting may also occur at startup.
Dirt and Corrosion
If dirt and corrosion exist at the steam trap, consider what may be happening at the equipment being protected. A common source of foreign matter is packing used to seal leaks. The use of some amines and hydrazine can present "dirt" problems.
Steam Trap Installation
If bypasses around a trap station are installed and utilized during warm-up, consider installing a trap downstream of the bypass valve to reduce the risk of steam blow if the bypass is left open.