EAR TEST METHOD.Hold one end of a metal
rod to the trap body and place the other end in the ear, or
use an engineer's stethoscope. If the trap is operating
properly, you will hear the regular opening and closing
of the valve. If operation is defective, you will hear
considerable rattling or the continuous flow of steam.
PROTECTION AGAINST FREEZING.Pro-
tect traps from freezing in cold weather. If the steam is
shut off during freezing weather, drain the traps and
piping of all condensate. Make certain insulation is in
good condition. The inverted bucket is especially prone
to freezing because, in normal operation, it is half filled
Figure 3-19.A typical unit heater installation.
A boiler plant and heating system cannot be
operated so the flow of water and the flow of steam are
always in balance. The demand for water by the boiler
may exceed the rate at which water is being returned
from the heating system, or the water may be returning
at a rate that is greater than the requirements of the
boiler. One or more tanks can be installed to
compensate for uneven flows and for differences
between the demand and supply of water. These vessels
are called surge tanks.
Sudden reductions in pressure may lead to violent
steam formation. Flash tanks help eliminate
disturbances in the piping system caused by this
process. These tanks are usually small and are located
near the traps where the pressure release occurs.
Unit steam heaters are convection heaters in which
the air is circulated by means of a fan. The unit heater is
similar to an automobile radiator. It is enclosed in a
sheet metal case with the fan mounted at the rear. A
typical unit heater is shown in figure 3-19. The steam
enters the unit at the top and the heat is transferred to the
fins of the heater. The fan blows the air over the fins and
out into the space to be heated. When the steam
condenses, the steam trap, usually a float thermostatic
type, allows the condensate to drain into the condensate
return line. A strainer is installed just ahead of the trap to
help keep foreign matter out of the trap.
Unit heaters are usually suspended from the
ceilings of shops, offices, dining halls, and warehouses.
This type of installation saves on floor space, provides
for rapid heating, and gives wide distribution of heat.
Unit heaters should be taken down periodically and
cleaned, because dust and lint collect between the fins
and reduce the flow of air.
Steam-operated water heaters are used to supply hot
water for laundries, dining halls, latrines, and other
facilities. There are two general types of these heaters:
storage and instantaneous.
The storage type of water heater is used to provide
potable (drinking) water. The steam-operated storage
type of water heater consists of a steel tank that contains
a steam-heating coil like that shown in figure 3-20. The
hot-water tank is connected to the base water supply
system and remains full of water at all times.
The steam is circulated through the heating coil or
"bundle," as it is sometimes called. The heat from the
steam is transferred through the walls of the coil to the
water in the tank. Because of the difference in weight
between hot and cold water, the hot water rises and the
cold water goes to the bottom of the tank where the
Figure 3-20.The storage-type water heater.