Steam Radiators - Xylem Bell & Gossett Hoffman Speciality Series Engineering Data Manual

Steam
Radiators
32
Radiators
Radiators normally use Thermostatic Traps to
drain condensate. The Thermostatic Trap is a
pressure balanced device that will open usual-
ly 10° to 30° F. below saturation temperature.
A Thermostatic Trap on a low pressure 3 psi
system will open at approximately 190° to
200°F. A 10° to 30° F. drop in condensate
temperature normally occurs in the return pip-
ing in a low pressure heating system. This
controls the return condensate at about
160°F. and simplifies the selection of conden-
sate return units.
Low pressure Thermostatic Traps are normally
rated in sq. ft. E.D.R. heating load and have a
SHEMA rating which allows the proper safety
factor.
Thermostatic Traps are inexpensive in relation
to other types of traps. This makes them
attractive for heating systems where many
large numbers of traps are required.
SUPPLY VALVE
SUPPLY VALVE
Trap Damage from Water Hammer
When automatic temperature controlled sup-
ply valves are used, water hammer may occur
when the valve closes. This occurs due to the
condensing of steam in the radiator causing
an induced vacuum. The induced vacuum may
pull in flash steam from the return line. As
this steam enters the condensate in the bot-
tom of the radiator, steam pockets form and
implode as they lose their heat. The forces of
water hammer (cavitation), can quickly
destroy bellows or diaphragm type radiator
traps. A solid fill Hoffman Specialty 17K is
designed to withstand this service.
Water hammer may also occur during start-up
when lifts are present in the discharge piping
after the trap.
RETURN MAIN
RETURN MAIN
SUPPLY MAIN
SUPPLY MAIN
TRAP
TRAP