How-To-Size
Drip applications refer to the removal of condensate formed in steam lines due to the radiant heat loss of the hot steam pipes to surrounding air
and are required for the protection of the steam system. (Drip Traps remove the condensate from the steam lines where the process traps remove
condensate being generated by the actual process.) Drip traps should be placed 150 to 300 feet apart on straight runs of piping, before elevation
changes, and before critical equipment such as Regulators and Control Valves.
Why Condensate Safety Load Factors and Warm-up Loads need to be considered:
During start-up, when the piping system is cold and steam begins to flow thru the pipes, steam is condensing very quickly because of the energy
required to heat all the cold surfaces. Furthermore, the steam pressure in the system which is required to push the condensate through the steam
trap into the return line, is low before the system comes up to full pressure. Therefore, condensate is being generated at a maximum rate and the
steam pressure used to push the condensate out of the system is at a minimum. If the traps are sized for the normal running loads and normal
system pressures, then they would be undersized for the start-up condition. In a supervised start-up, condensate drain valves located throughout
the system, are manually opened to drain excessive condensate generated by the cold piping system; relying less on the steam traps. Therefore, the
steam traps selected for a system with a supervised start-up can be more closely sized for the actual normal running load.
Sizing Example: Size a drip trap for an 8” steam main with 100 psig steam pressure. Traps should be placed every 200 ft. A 2x safety factor based on
Warm-Up load will be used.
• Based on Warm-Up Load Chart: 100 lbs/hr of condensate is generated per 100 feet length of pipe.
• Warm up load for 200 ft. length is therefore, 200 lbs/hr (2 x 100 lbs/hr)
• If a 2x safety factor based on warm-up load is used, we require a trap with a capacity of 400 lbs/hr
• Actual running load for 100 ft. length = 41 lbs/hr
• Actual running load for 200 ft. length = 82 lbs/hr
Warm-Up Loads in Pounds of Condensate per hour per 100 ft. of Steam Main
Running Loads in Pounds of Condensate per hour per 100 ft. of Steam Main
Trap Selection: Reference the TD600S Series Capacity Chart below based on inlet steam pressure. Enter the chart under 100 psig inlet pressure to
compare the capacities of different models.
The 1/2” TD600LS will be capable of discharging 375 lbs/hr of condensate at 100 psig steam pressure. The capacity is slightly less than the load
calculated based on warm-up load with 2x safety factor, however, this trap selection would be a suitable choice since its capacity is well in excess of
what is actually required. These loads are indicative of drip applications and lend support as to why only reduced capacity 1/2" TD600L or 3/4" TD600L
traps are required for the majority of drip applications.