Steam Tracer Lines and Traps Chemical Engineering
by Scott Jenkins, Department Editor
Steam tracer lines are designed to maintain the fluid in a primary pipe at a designated uniform temperature. In most cases, these tracer lines are used outdoors, which makes ambient weather conditions a critical consideration.
The primary purpose of steam traps on tracer lines is to retain the steam until its latent heat is fully utilized, and then discharge the condensate and non-condensable gases. As is true with any piece of heat transfer equipment, each tracer line should have its own trap. Even though multiple tracer lines may be installed on the same primary fluid line, unit trapping is required to prevent short-circuiting.
In selecting and sizing steam traps, it is important to consider their compatibility with the objectives of the system, as traps must accomplish the following:
2. Provide abrupt periodic discharge in order to purge the condensate and air from the line
3. Operate under light load conditions
4. Resist damage from freezing if the steam is shut off The cost of steam makes wasteful tracer lines an exorbitant overhead that no industry can afford.
Trap selection for steam tracer lines
this formula:
Q = Condensate load in lb/h
L = Length of product pipe between tracer line traps in ft
U = Heat transfer factor in Btu/ft2/°F/h
ΔT = Temperature differential in °F
E = One minus the efficiency of insulation (example: 75% efficient insulation or 1 – 0.75 = 0.25 or E = 0.25)
S = Linear feet of pipe line per ft2 of surface
H = Latent heat of steam in Btu/lb
Safety factor
Do not oversize steam traps or tracer lines. Select a steam trap to conserve energy and to avoid plugging with dirt, scale and metallic oxides.
Installation
To conserve energy, return condensate to the boiler. Freeze-protection drains on trap discharge headers are suggested where freezing conditions prevail.
Example
What is the condensate load?
Using the formula:
On most tracer line applications, the flow to the steam trap is surprisingly low; therefore, the smallest trap is normally adequate. Based on its ability to conserve energy by operating reliably over a long period of time, handle light loads, resist freezing and purge the system, an inverted bucket trap is recommended for tracer line service.
Acknowledgements
Material was supplied by Armstrong International, Three Rivers, Mich.
1 comentario:
Great informative article. Keep sharing such type of informative and useful articles with us. Exciting to read your next blog. Also, check out Steam and Condensate Systems Insulation.
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