ANSI FCI 13-1 pdf free download

ANSI FCI 13-1 pdf free download.Determining Condensate Loads to Size Steam Traps.
Steam mains in various applications may operate in saturated or superheat conditions. When the steam main is superheated, the start-up load may be high to bring the pipe to temperature, but then very little or no condensate is generated when operating at full superheat. In low steam velocity conditions, such as very low demand or in a (stagnant flow) collecting leg, flow reduces to the threshold where the heat loss of the main exceeds the BTU’s of superheat available. Then, condensate will again be created and must be removed from the system. In instances where the superheated steam flow is stopped, the main or collecting leg can revert first to saturated steam, and then to wet steam, depending upon the amount of time for the flow cessation. For that reason, a steam trap is required at the drip points along the pipe with either saturated or superheated steam. Steam mains generally operate more than 90% of the time in the full operational mode. The condensate load produced during normal operation is known as“Running Load”, whereas the condensate load generated during the time when the main is brought up to full operation is known as“Start-up Load”. Start-up times of the main should not be so short as to generate large amounts of condensate that could cause water hammer. Another issue with short start-up times is that large steam traps need to be used to handle the over-large start-up load, and then those traps could be grossly oversized in the normal operating mode. It is important that both Start-up Load and Running Load are calculated to help properly size the steam trap for both conditions. In some instances, steam traps can even be selected to support automatic start-up of the main, provided the steam is applied in a slow, controlled manner. Slow starting is needed so as to not create water hammer conditions or to overwhelm the steam trap’s capacity at the available pressure differential while the steam pressure builds in the line (Both Start-up Load and Running Load calculations are needed to properly select and size the trap).
Steam traps require sufficient differential pressure from the inlet to outlet side to discharge flow against the return line backpressure. When traps are located on equipment with inlet-side, modulating steam control; both the lowest and highest trap inlet pressure must be evaluated for sufficient differential pressure. This range of consideration is required due to the resultant pressure fluctuation from modulation and to enable discharge without condensate back-up into the equipment.
To evaluate further, under certain reduced-demand conditions, it is possible that supply steam modulates to a lower pressure than the return line backpressure and, in some instances, vacuum conditions inside the equipment can occur. In such cases, the simplest solution is to install a vacuum breaker to restore the steam space to atmosphere conditions and enable free drainage through a steam trap if sufficient head pressure is available. When backpressure is present and does not allow gravity drainage, a secondary pressure drainer, SPD Type I or II, is required to discharge condensate.ANSI FCI 13-1 pdf download.