Evaporators - Trap

Trap Requirements

Traps servicing evaporators are subject to continuous large loads and may be subject to significant quantities of flash steam and air as well. Because of this, traps that drain evaporators should:

drain the heat exchanger continuously
vent air and CO₂at steam temperature
vent air at low (1/4 psi/0.02 bar) differential pressure
handle start-up air loads well when the evaporators are used for batch processing
be able to purge the system
respond immediately to slugs of condensate without creating service problems
handle flash steam

The best trap selection to meet all of these requirements is the differential condensate controller (DC). Suitable alternatives would be an inverted bucket (IB) with a large vent or a float and thermostatic (F&T) trap.

	Characteristic	Inverted Bucket	F&T	Disc	Thermostatic	Differential Controller
A	Method of Operation	Intermittent	Continuous	Intermittent	Intermittent	Continuous
B	Energy Conservation (Time in Service)	Excellent	Good	Poor	Fair	Excellent
C	Resists Wear	Excellent	Good	Poor	Fair	Excellent
D	Resists Corrosion	Excellent	Good	Excellent	Good	Excellent
E	Resists Hydraulic Shock	Excellent	Poor	Excellent	Poor	Excellent
F	Vents Air and CO₂ at Steam Temperature	Yes	No	No	No	Yes
G	Vents Air at Very Low Pressure (1/4 psig)(.02 bar)	Poor	Excellent	NR	Good	Excellent
H	Handles Start-up Air Loads	Fair	Excellent	Poor	Excellent	Excellent
I	Operates Against Back Pressure	Excellent	Excellent	Poor	Excellent	Excellent
J	Resists Damage from Freezing	Good	Poor	Good	Good	Good
K	Can Purge System	Excellent	Fair	Excellent	Good	Excellent
L	Performs on Very Light Loads	Excellent	Excellent	Poor	Excellent	Excellent
M	Responds to Slugs of Condensate	Immediate	Immediate	Delayed	Delayed	Immediate
N	Handles Dirt	Excellent	Poor	Poor	Fair	Excellent
O	Comparative Physical Size	Large	Large	Small	Small	Large
P	Handles "Flash Steam"	Fair	Poor	Poor	Poor	Excellent
Q	Mechanical Failure (Open -- Closed)	Open	Closed	Open	Open, Closed	Open


First Choice				Alternative				Overriding condition