4-Step Method For Sizing - Xylem Bell & Gossett Hoffman Speciality Series Engineering Data Manual

Step 1:
Collect All Required Information.
A. Determine maximum condensate load in
Lbs./Hr. (Pounds per Hour). See "Helpful
Hints—Approximating Condensate Loads"
on page 12.
B. Inlet pressure at steam trap. It could be
different than supply pressure at boiler.
Heat exchanger applications with modulat-
ing control valves are good examples.
C. Back-pressure at steam trap. Pressure
against outlet can be due to static pres-
sure in return line or due to lifting to
overhead return.
D. Determine Pressure Differential.
Inlet pressure (B) - Back-pressure (C)
= Differential Pressure.
Step 2:
Select Proper Type ot Trap.
A. Other Things to Consider.
1. Condensate Flow—Fluctuate?
1. Continuous?
2. Large Amount of Air?
3. Pressure—Constant? Fluctuate?
B. Application.
1. Main.
2. Drip Leg.
3. Process Heat Exchanger.
4. Other.
C. Critical Process.
1. Fail Cold.
2. Fail Hot.
Step 3:
Apply Safety Factor.
A. SFA Recommended.
1. Float & Thermostatic Trap 1.5 to 2.5.
2. Bucket Trap 2 to 4.
3. Thermostatic 2 to 4.
4. Disc Traps 1 to 1.2.
See specific applications.
B. The SFA Will Depend On Degree of
Accuracy at Step 1.
1. Estimated Flow.
2. Estimated Pressure—Inlet.
3. Estimated Pressure—Back.
Step 4:
Select Correct Trap Size.
A. Use manufacturer's capacity table to size
trap. Capacity tables should be based on
hot condensate (some specified tempera-
ture below saturation) rather than cold
water rating. Hoffman Specialty published
actual test data, unless stated, is 10°F.
below saturation.
B. The trap seat rating must always be
higher than the maximum inlet pressure
specified.
C. When inlet to equipment is controlled by a
modulating control valve, the trap size
should be selected with a pressure rating
greater than the maximum inlet pressure
at the trap. The capacity should be
checked at the minimum differential pres-
sure to assure complete condensate
removal under all possible conditions.
4 Step Method
for Sizing
11