and covering, to be sure that setting is free of air
placed. A disorderly, cluttered boiler room consti-
leaks, and in good structural condition. Inspect ex-
tutes a definite hazard to personnel safety and is a
posed surfaces, particularly the crownsheet and in-
detriment to proper maintenance and operating ef-
terior surfaces of the combustion chamber, and the
ficiency. The floor should be clean at all times and
lower areas at the mud ring for water leaks and
kept clear of water and loose tools and materials.
corrosion. The surfaces on the fire side should be
Accumulated material is a serious fire hazard.
Section XVII. TYPICAL STEAM HEATING OPERATING DIFFICULTIES
4-77.
Water level fluctuation.
result in instantaneous make-up water demand
a. Rapid fluctuation. Rapid cycles of water level
beyond the capacity of the feeder. When low water
rise and fall or a bouncing water level, is usually
level is detected, shut off automatic firing equip-
caused by grease and oil in the boiler. The grease
ment immediately or open firing doors and shut off
and oil form a film on the surface of the water and
draft of hand fired boilers to cool the boiler
cause rolling of water which is released in slugs
gradually. Do not open cold water make up lines.
with the steam. Excessive firing rates cause high
After the boiler has cooled, proceed to determine
steam release rate with entrained moisture or ex-
the cause of water loss. Low water level indication
cessive steam velocity through boiler outlets which
may be due to any of the following causes:
may siphon water from the surface and produce a
a. Water-gauge glass either shut off manually or
bouncing water level. Gauge glass connections
water drained from the glass.
placed at very active circulating points of the boiler
b. Broken boiler sections or excessive leak in
result in siphonic or forced flow action in the water
steel boiler.
column; this gives the appearance of fluctuating
c. Pump failure or broken return main from
water level, though the actual boiler water level is
system to pump or valve at pump inlet shut-off.
satisfactory. The water level may be too high,
d. Broken or stopped up pump discharge line to
causing siphon action or carry-over of boiler water.
boiler or return valve at boiler shut-off.
b. Slow fluctuation. Slow rise and fall of the
e. Excessive oil, grease, and foreign matter in
water level in single boiler installations is usually
boiler water resulting in excessive priming.
due to a vacuum or condensate pump returning
condensate in excessive quantity at each feeding
4-79.
Loss of pressure.
cycle. This occurs when the distance between re-
a. If pressure fails, check for the following
ceiver water levels at pump cut-in and cut-out is
possible causes:
too great. This condition can also be caused by
(1) Inadequate firing rate or poor combustion
water which is forced out through return connec-
condition, insufficient draft, soot clogged boiler
tions of gravity systems owing to failure to equalize
passages and breeching, or inadequate air supply to
as the result of long runs of mains or by an ex-
the boiler room.
cessive initial steaming rate. In multiple boiler in-
(2) Dirty boiler including either scale on water
stallations, water may be higher in one boiler be-
side, soot on fire side, or both.
cause of an uneven firing rate.
(3) Broken main causing excessive loss of
steam.
4-78.
Low water level.
(4) Steam load in excess of boiler capacity.
Low water level is the most serious situation that
(5) Oil or grease in boiler water.
may occur in a boiler plant. Automatic water feed-
(6) Steam gauge may be defective, not properly
ers should not be depended upon for assurance of
indicating actual pressure conditions. Open test
proper water level, as accidents to piping may
4-49
TM 5-642
cocks and note if steam pressure is available re-
4-82.
Failure of space to heat.
gardless of gauge indication.
If space heating units such as unit heaters or blast
b. Do not confuse pressure failure with a condi-
systems are filled with steam, the ductwork and
tion under which closed vapor or vacuum systems
fans should be checked for air delivery and distri-
may be circulated under negative pressure or
bution. Lack of heat may be caused by fan motors
vacuum because of temperature or other controls
which are running under speed or by reduction of
which cause a low firing rate, balanced with low
duct capacity due to closed or partially closed
space heat demand. Induced vacuums will occur
dampers. Heating failure and lack of proper distri-
when the radiator condensing rate exceeds the
bution often occurs in large spaces such as aircraft
boiler evaporation rate.
hangers and work shops, caused by the inability of
unit heaters located too high above the floor, to
4-80.
Pounding in the system.
force air to the work space. Stratification of heated
air at ceilings in such installations may be overcome
This should not be confused with snapping which
by use of recirculation ducts which have floor inlets
occurs when expansion takes place at initial heating
and which connect to the inlet side of the unit
up of systems. Pounding or water hammer is caused
heaters. Also, check the heat loss of the space; be
by slugs of water which are carried at high velocity
sure to include the load imposed by an exhaust air
with steam and which may have sufficient force to
system and compare the load with the capacity of
break piping, in addition to creating excessive
installed heating units.
noise. Existence of water slugs in steam piping is
the result of:
4-83.
Pump venting steam.
a. Carry-over through the boiler nozzle due to
Do not confuse this with low temperature vapor or
excessive steaming rates, priming due to grease and
moist air discharged from pump vent. Steam vent-
oil in water, or the water level being too high.
ing from condensate or vacuum pumps is caused by
b. Condensate trapped in piping system because
leaking traps, open bypasses around traps, or
of sagging mains and pockets; plugged and faulty
backup of high temperature boiler water into the
steam main drip connections.
pump due to leaking check valves in the pump dis-
c. Air bound mains due to defective vents which
charge line. High temperature water is present in
trap condensate behind the air pocket.
the pump when steam is observed to be venting
from the pump. This may result in vapor binding of
4-81.
Heating unit malfunction.
the pump. If the pump is a vacuum type it will fail
to create a vacuum at excessive condensate
This is basically a failure of the steam space of the
temperatures. When steam discharges from vents of
radiator, coil, or steam chest to fill with steam and
vacuum pumps or high condensate temperatures
is due to:
exist, the pump should be placed on float control.
a. Inadequate steam pressure.
If allowed to remain on vacuum control, the pump
b. Defective valve (in which the disc may have
will run continuously and will accomplish no useful
fallen onto the valve seat), valve plugged with
purpose. If check valves in the pump discharge line
scale, or failure to open.
leak, the pumping units will cut in frequently and
c. Air bound radiator caused by defective air
cut out for relatively short periods, depending on
vent or trap.
the rate of boiler water backflow into the pumps.
d. Water logged radiator caused by defective
trap.
4-84.
Pump venting water.
e. Discharge connection pocketed or rising from
If water is venting from the pump check, consider
unit causing flooding of unit.
the following possible causes:
f Traps of inadequate capacity.
a. Pump capacity, volume or discharge pressure
g
Heating coils of excessive length and height
of pump, is inadequate. Determine the discharge
may fail because of air binding and should be pro-
pressure at the pump outlet by installing a pressure
vided with vent connections and/or vacuum break-
gauge at this point and checking with manu-
ers in accordance with the manufacturer*s recom-
facturer*s performance and capacity charts or
mendations.
curves. Open the return connection to the pump
h. Inadequate pitch of the heating element or
and measure the rate of condensate flow to deter-
radiator will cause faulty ‘drainage and failure to
mine the quantity to be pumped.
heat. This is particularly marked in small horizontal
b. Pump may be rotating in wrong direction.
extended surface, fin-tube radiation.
This can be readily determined by touching a rubber
4-50
TM 5-642
tipped pencil to the shaft. Note the direction of
a. Check water line conditions.
rotation and compare with manufacturer s drawing
b. Excessive firing rates may cause “dry spots”
or, if present, the direction arrow mark placed on
in the water side of the boiler, particularly if water
pump casing.
contains oil, grease, and other foreign matter.
c. Pump control may be failing to cut in pump at
Check for faulty circulation in narrowed drop
proper receiver level.
sections or baffles at the rear of the combustion
d. Pump impeller may be worn or clearances
space.
may be too great, reducing discharge capacity of
c. Header connection may not be properly ar-
the pump.
ranged to permit expansion and contraction of
e. Outlet valve of pump or discharge line may be
clogged.
header and system connections. This usually results
f.
If the pump is controlled by a float controller
in fractures in the area of the header connections.
at the boiler line and equipped with a float con-
d. Staybolts too tight to permit expansion and
trolled makeup water valve at pump receiver, the
contraction of sections.
makeup valve may be leaking or set too high.
e. Accumulation of soot and scale which work
Under these conditions the pump may cut in and
into the space between sections and result in
satisfy the boiler water level with makeup water,
growth and expansion, which may break sections.
followed by condensate returning to the pump in
f.
Excessive feed of cold water to a hot water
large volume with no demand for boiler water level
boiler may cause failure.
replacement, which results in overflow of the
receiver. This can be corrected by adding an auxil-
4-87.
Boiler room smoke.
iary receiver above the pump receiver to take care
Presence of smoke and combustion gases in the
of overflow, or by changing the control system to
boiler room is a serious condition. Combustion
a standard pump receiver level control in place of
the boiler water level control.
gases such as carbon monoxide may be created
wherever there is incomplete combustion of gas
4-85.
Steel boiler failure.
fuel, generally, because of inadequate draft in a gas
appliance or a leak in the furnace*s heat exchanger.
If a steel boiler burns out or leaks, check for the
following possible causes:
When such conditions exist, corrective measures
a. Low water level, particularly if the failure is in
should be taken immediately. Check for the
the area of the crown sheet.
following possible causes:
b. Failure in lower area of combustion chamber.
a. Check for a closed boiler outlet damper or
This is usually caused by accumulation of mud,
stoppage of the breeching or stack.
scale and other foreign matter in the mud ring area
b. Check to see that the tube or gas passages of
which results from improper cleaning and
the boiler are not closed by an accumulation of ex-
blowndown.
cessive soot and fly ash.
c. Corrosion on the fire side of the boiler caused
c. Determine that sufficient door, window, or
by improper layup or cleaning.
other openings are in use to permit air necessary for
d. Interior corrosion caused by improper layup
combustion to enter boiler room.
or water conditions.
d. Leaky settings or breechings will permit gas
e. Leaks at tube ends, drain openings, and man-
leakage to the boiler room during periods of posi-
holes will, if not corrected immediately, result in
tive pressure in the combustion chamber. Check the
corrosion of adjoining plates.
boiler settings for leaks by using a candle to note
f.
Improper suspension or expansion provisions
suction at surface cracks and joints when the boiler
of headers and piping if leaks or fracture occur in
the area of boiler connections.
is under negative pressure.
e. Stack or breeching may be inadequate.
4-86.
Cast iron boiler failure.
f.
Breeching may have too many sharp turns, or
may pitch downward and reduce the effective area.
If a cast iron boiler cracks, check for the following
causes:
4-51
TM 5-642
Section XVIII. SUMMER LAY-UP PROCEDURES
4-88.
General.
a. Cast iron boilers.
Most damage to and deterioration of heating
(1) Clean boiler thoroughly and remove grates,
equipment occurs during summer and other lay-up
if applicable, to facilitate access and inspection. Use
periods because of careless or inadequate proce-
wire brushes to remove all soot, dirt, and scale
dures in placing equipment on inactive basis.
from flues and firebox surfaces. Open boiler drain
During these periods excessive rusting, corrosion,
plugs at the front and rear of boiler. If drain is not
and grease clogging occurs. If the idle period in-
present, open the return header and thoroughly
cludes periods of freezing temperature, incomplete
wash out the boiler using a hose with water at suf-
drainage will result in damage from freezing. Well
ficient pressure to loosen mud and accumulated
planned procedures must be followed in placing
sludge. Complete removal of accumulated foreign
heating systems in proper condition for standby.
material in the lower sections of the boiler or mud
ring is of extreme importance.
4-89.
Draining system.
(2) Spray flue surface with light lubricating oil,
Drain all steam and return lines of condensate
using an oil gun with an extended stem and bend
completely by opening drain valves at pumps or
end, so as to reach all corners and crevices. Used
return connections in the boiler room, and by
crankcase oil is unsatisfactory for this purpose.
opening the drain or dirt pockets located at ends of
(3) Remove all ashes and unburned fuel from
mains and at other drip points in the building piping
the grates and ashpit of hand fired coal burning
system. Particular care must be taken to assure
boilers.
proper draining of wet returns and loops under
(4) Clean the smokepipe and remove it during
doorways. During draining operations, it is
the summer, if feasible. If controls are mounted in
important to determine that piping is properly
the smokepipe be careful not to disturb them.
pitched and that no low points or pockets which
(5) Leave boiler doors and dampers open
can accumulate water are present. This is particu-
during the lay-up period. This will permit air
larly important in servicing wet return lines. Mains
movement through the setting and will help prevent
under basement floors should be opened at both
sweating on the inside of the boiler while not in use.
ends and blown out with compressed air. Leave
drain points open during lay-up to permit air
(6) Oil hinges of all doors and moving parts of
movement and reduction of sweating. Threads of
regulators.
drain plugs, caps and other similar pieces of
(7) On hand fired boilers replace warped,
equipment should be carefully brushed clean of rust
broken, or worn out grates which, if not serviced,
and other debris, thoroughly coated with oil and
would permit unburned coal to drop into ashpit and
tied to the drain point to be readily available for
would also affect proper combustion during the
reinstallation at the start of the heating season.
heating season.
Drain openings should be covered with a single
(8) Tie rod nuts should be removed and re-
layer of cloth to prevent entrance of rodents and
placed with spring washers and safety nuts to
foreign matter. If drainage through available drain
permit safe expansion conditions.
points is inadequate, disconnect intermediate unions
(9) Cast iron steam boilers, following cleanup
to assure drainage of piping. Also note condition
of the boiler at the end of heating season, should be
and exposure of outdoor mains to assure that they
completely filled until the start of next heating
will not be damaged by outside weather conditions
season.
or by accumulated water in pits, conduits, and
(10) If an automatically fired steam boiler is
tunnels.
operated during summer months for operation of
submerged type domestic water supply heaters,
4-90.
Boiler cleaning and lay-up.
maintain the water line above normal for steaming.
At the end of the heating season, boilers should be
Improved circulation to the heater will result.
opened, thoroughly washed internally, and laid up
(11) Brush exterior exposed iron work with a
so that the water side and fire side are free of cor-
wire brush, and, after removing all rust, paint with
rosive material. All personnel engaged in boiler
rust proof heat resisting paint.
cleaning and spraying should be provided with
b. Steel boilers (dry method)
proper respiratory and eye protection, and suitable
(1) Do all lay-up work for steel boilers immedi-
protective clothing. The following methods are rec-
ately after the close of the heating season.
ommended for lay-up of boilers.
4-52
TM 5-642
(2) Draw the fires, remove all combustibles,
through all parts of boiler by keeping all doors and
and drain the boiler while still warm. This pre-
wash-out openings open.
vents drying of loose mud, rust, and some types of
(16) If the boiler room is damp or air circula-
scale.
tion is poor, moisture may be absorbed by placing
(3) Open valves to all radiators and all other
pans of unslaked lime in the boiler. Replace lime
heating elements wide to permit condensate to
when necessary.
drain back to the boiler, boiler feed pump, or
(17) For coal fired boilers, clean the grate as-
opened piping drain points.
sembly and inspect thoroughly. Replace any parts
(4) Remove all manhole plates and washout
that are burned or even slightly warped.
plugs from the boiler and set to one side.
(18) Make every effort to clean the boiler
(5) Wash the water side boiler surfaces clean
properly. A thorough cleaning is good assurance of
and remove all loose scale and sediment by flushing
freedom from boiler trouble throughout the next
thoroughly with water pressure from a hose.
heating season.
(6) Use all washout openings, starting at the
c. Steel boilers (wet method). If a boiler is on
lowest point in the boiler and working toward the
standby service, the following wet method of boiler
top. Then repeat the washing by flushing from top
lay-up is recommended:
down to lower openings.
(1) Drain the boiler completely. Check to be
(7) Open the city water or makeup water valve
certain that water walls and gauge columns are not
to flush the bottom of the boiler. When the boiler
overlooked. Next, open the boiler and wash clean
has been flushed, make certain this valve is closed
and free from all loose scale and sediment by
tightly and does not leak.
flushing thoroughly with strong water pressure. Use
(8) Flush out all boiler accessories such as
a stiff brush to clean all internal surfaces of the
water column piping, water column, gauge glass,
boiler that can be reached. Break the feed-water
pressure damper regulator, and steam gauge thor-
and steam connections to the boiler and blank the
oughly. All automatic controls on mechanically
connections if other boilers are operating.
fired boilers should also be cleaned thoroughly.
(2) Fill the boiler with either feedwater, return
(9) It is important to clean the fire surfaces of