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*
What
is Scale Formation ?
*
How
do I stop Scale
Formation from
happening ?
*
What
is corrosion ?
*
How
do I stop Corrosion ?
*
Why
all the concern about
Condensate Treatment
and Monitoring ?
*
How
do I prevent the Most
Common Boiler Problems
?
*
A
More In-depth Look
*
What
is the meaning of
Horse power ?
What
is Scale Formation ?
Scale
formations in boilers
are responsible for lost
efficiency, increased
maintenance and
operating costs not to
mention lost revenue due
to outages and downtime.
Most scale formations in
boilers can be traced to
the presence of hardness
in the make-up water.
This hardness reacts in
the high temperatures
environment within the
boiler to form and
insoluble scale. This
insoluble scale coats
the heat transfer
surfaces, acting as an
insulator to impede heat
transfer.
Hardness
isn't the only cause if
scale formation in
boilers, other
impurities such as iron,
silica, copper, oil,
etc. are often found in
samples of boiler scale.
In fact, it is rare to
find scale which isn't
the result of several of
these impurities.
Normally
pre-softening the water
before feeding it to the
boiler is the first step
in eliminating scale
formations. Even when
the make-up is soft,
there is still a need
for chemical scale
inhibitors inside the
boiler. With proper
treatment the problems
of lost efficiency, tube
damage and lost
production can be
avoided or greatly
reduced. Proper
treatment requires the
right balance of
chemical treatment and
control.
How
do I stop Scale
Formation from happening
?
The
first and foremost
aspect of stopping scale
formation is to have a
good idea of the make-up
water that is feeding
your system. If you
aren't sure, have a
certified laboratory
complete a fully
analysis on this water
so you can make an
informed decision on
what exactly the
potential problems you
may encounter.
After
determining these
specific aspects of your
make-up water then your
water treatment expert
can guide you through a
program that fits your
situation.
Just
a few items that may be
of concern when putting
together a good water
treatment program for
your boiler.
A complete program will
include sludge build-up,
pH levels, oxygen
removal, condensate
treatment, and
alkalinity levels.
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What
is corrosion ?
Corrosion
in boilers can almost
always be traced to one
or both of two problems.
The most common cause is
dissolved oxygen
entering the system via
the feed-water. The
oxygen causes very
localized corrosion to
occur in the form of
pitting. The pits are
small but deep pinpoint
holes which eventually
can penetrate tube walls
and cause their failure.
Another common cause of
corrosion in boiler
systems is low pH within
the boiler. This reduced
pH may result from
carbon dioxide
infiltration or form
contamination by
other chemicals.
Oxygen
corrosion is normally
controlled by driving
the oxygen from the
feed-water in a
deaerating heater or by
chemically removing it
with an oxygen scavenger
such as sodium sulfite.
There
are many contaminates
which can infiltrate a
boiler system and cause
low pH levels to
develop. Manufacturing
wastes such as sugar or
acids from plating
operations which can be
returned to the boiler
with condensate can be a
source of problems
because they concentrate
in the boiler. Oxygen
can infiltrate the
boiler system at
virtually any point.
When dissolved, oxygen
is present in boiler
feed water attach on
feed lines, pumps and
economizers can be
expected. The severity
of the attach depends
upon the concentration
of the oxygen and the
temperature of the
water.
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How
do I stop Corrosion ?
You
can use a deaerator
which is defined as a
piece of equipment which
heats water with steam
to insure essentially
complete removal of
dissolved gases. There
are several types of
deaerator available,
each having its own
advantages and
disadvantages.
Internal
treatment for dissolved
oxygen corrosion is
normally accomplished by
the addition of sodium
sulfite. Most oxygen
scavengers contain a
catalyst which speeds
the reaction of the
sulfite with the oxygen.
In systems equipped with
a deaerator the sulfite
should be fed to the
storage tank of the
deaerator or to either
the suction or pressure
side of the feed water
pump. In systems which
do not have a deaerator,
the sulfite can be fed
at almost any point in
the feed water system,
including the condensate
tank.
Internal
treatment for carbon
dioxide is normally
accomplished by the use
of a volatile amine.
"Amine" refers
to any of a number of
chemicals derived from
ammonia. There are two
major groups of amines
in practice as water
treatment chemicals
today. There are
normally referred to as
"neutralizing
amines" or
"filming
amines" depending
upon whether they
neutralize the acid
formed by carbon dioxide
or form a protective
film on the metal.
Filming
amines do not neutralize
the carbonic acid which
forms in condensate
systems. Instead, they
form a film on the metal
which is non-wettable,
or impervious to water.
this protective film
prevents the corrosive
impurities from
contacting the metal.
Neutralizing
amines function by
increasing the pH of the
condensate. Normally
they are fed at such a
rate that the pH of
the condensate is
maintained slightly
above 7.0. Satisfactory
reduction of carbon
dioxide corrosion is
possible with the use of
a neutralizing amine. it
is necessary to
supplement this type of
condensate protection
with an oxygen scavenger
to remove dissolved
oxygen.
Whether
condensate corrosion is
controlled by chemical
treatment or a
combination of
mechanical and chemical
methods, it is important
that careful checks and
testing be incorporated
as a part of the
treatment program. No
treatment can be better
than the way in which it
is applied. Consult a
water treatment expert
to get you started on
the right foot.
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Why
all the concern about
Condensate Treatment and
Monitoring ?
You Condensate is
very important to your
facilities overall
operation, ignoring this
unseen component will
soon cause failures
costing
bottom-line dollars.
Therefore, condensate
must be treated with the
proper chemistry.
Treating your
plants steam condensate
is critical for several
reason, but these are
the most important two
reasons:
1. To
insure the integrity of
your equipment.
2. To
keep the amount of
condensate corrosion
minerals that are
returned to the boiler's
makeup water in check.
Corrosion in your steam
lines occurs when the
carbonic acid builds up
and begins to breakdown
the metallic surfaces
throughout the system.
When the Carbonic acid
is allowed to build,
localized attacks occur
due to the simple
increase in CO2,
which is the breakdown
product of carbonate
alkalinity in the
boiler, condensing with
water to form H2CO3.
This results in the
"pitting" of
condensate piping, which
usually shows up by
visual leaks at
threaded junctions.
Oxygen pitting occurs as
steam condenses and the
vacuum created pulls air
into the system. Due to
the localized nature of
oxygen pitting, it
can cause relatively
quick failure in a
condensate system.
The most common method
of dealing with this
problem is through the
use of neutralizing
amines. These chemicals,
better known as
morpholine and
cyclohexylamine,
neutralize the carbon
acid, and increase the
pH of the condensate.
Corrosion of mixed
metallurgy condensate
systems is minimized
when the pH is
maintained between 8.8
and 9.0. Due to high
alkalinity in boiler
makeup water elevating
the pH to this level may
not be economical. In
this case the pH should
be maintained at 8.3 or
higher, or a filming
amine applied.
A
filming amine, such as
octyldecylamine,
provides a non-wettable
protective barrier
against both carbonic
acid and oxygen. When
utilizing a filming
amine, the pH is usually
maintained between 6.5
and 7.5, so a
neutralizing amine may
still be required.
In order to minimize
oxygen pitting one can
utilize a filming amine
as previously mentioned,
or a volatile oxygen
scavenger such as DEHA (diethylhydroxyamine.)
DEHA provides better
results as it scavenges
oxygen and passivates or
coats the condensate
system, making it less
susceptible to
corrosion.
Depending
on the treatment method
chosen, condensate
monitoring can vary. In
all cases the following
tests should be
performed.
1.
Soluble and insoluble
iron levels.
2. pH
levels at various points
in your steam condensate
system. It is extremely
important that pH
measurements be made on
cooled samples. If the
sample is taken hot,
carbon dioxide will gas
off, which results in
artificially high pH
measurements.
If a filming amine is
utilized, the residual
should be measured. The
same is true if DEHA is
used as an oxygen
scavenger. In the latter
case, a residual of 100
to 150 ppb is usually
targeted. Note that this
may take time (as much
as 6 months) since much
of the DEHA will be
consumed pasivating the
system.
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How
do I to Prevent the Most
Common Boiler Problems ?
A regular inspection
schedule is critical and
should cover four areas:
boiler, burner,
controls, and system.
Preventive
maintenance
Is
the most widely used
means of minimizing
common problems in
boilers. Unfortunately,
most maintenance
programs do not properly
address the needs of the
boiler and its related
systems. Statistics
indicate about
two-thirds of all boiler
failures and nearly all
unscheduled shutdowns
are caused by poor
maintenance and
operation.
Boiler inspection and
maintenance are critical
It
covers four basic areas:
boiler, burner,
controls, and system.
Regardless of boiler
design, application, or
size, the basic
maintenance criteria
remain the same.
Maintaining the Boiler.
There are eight primary
areas of the boiler
itself that should he
examined or inspected
regularly.
Water level. The
most important
maintenance inspection
is to check the boiler
water level daily.
Insufficient water
causes pressure vessel
damage or failure. At a
minimum, steel in the
pressure vessel could
overheat. The condition
could change the
pressure withholding
capabilities of the
vessel, necessitating
vessel repair or
replacement. More
seriously, a low water
level could damage the
equipment or building.
or even cause personal
injury.
Boiler blow down
Steam
boilers should be blown
down daily to maintain
recommended dissolved
solids levels and to
remove sludge and
sediment. Hot water
boilers generally take
on no makeup water and,
therefore do not need to
be blown down. As the
boiler takes on makeup
water the solids
concentration builds up.
Solids accumulate in
either dissolved or
suspended form. Unless
they are controlled
dissolved solids promote
carryover of water with
the steam causing water
hammer and damaging
piping, valves, or other
equipment. Carryover
also raises the moisture
content in the steam,
affecting proper
operation of equipment
that uses steam.
Suspended solids
Which
cause sludge or sediment
in the boiler, must be
removed because they
affect the heat transfer
capabilities of the
pressure vessel. Sludge
buildup leads to
problems ranging from
poor fuel-to-steam
efficiency to pressure
vessel damage.
Water column blow
down
Water
columns on steam boilers
should be blown down
once each shift or at a
minimum once a day. This
action keeps the column
and piping connections
clean and free of
sediment or sludge. The
water column also must
he kept clean to ensure
the water level in the
gauge glass accurately
represents the water
level in the boiler. The
gauge glass and tricocks
connected to the water
column are the only
means of visually
verifying boiler water
level. The low-water
cutoff should be checked
once a week by shutting
off the feed water pump
and letting the water
evaporate under normal
steam conditions at low
fire. The gauge glass
should he observed and
marked at the exact
point at which the low
water cutoff shuts down
the boiler. The test
verifies operation of
the low-water cutoff
under operating
conditions. The
low-water cutoff also
should the removed and
cleaned every six
months.
Water treatment
Proper
water treatment prolongs
boiler life and ensure
safe and reliable
operation. Treatment
programs are designed
around the quality and
quantity of raw water
makeup and system
design. They should be
directed by a qualified
water management
consultant. Flue gas
temperature. Flue gas
temperature is a good
indicator of boiler
efficiency changes. The
temperature should be
recorded regularly and
compared to those of a
clean boiler under the
same operating
conditions.
Accurately determining
the affect on efficiency
requires that the firing
rate and operating
pressure be the same.
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Rise in flue gas
temperature
Usually
indicates dirt on the
fireside of the boiler
or scale on the
waterside. As a rule of
thumb a 40-deg F rise in
temperature reduces
boiler efficiency 1% The
cost of fireside
cleaning should be
compared to those of
lower operating
efficiencies to
determine the minimum
temperature rise at
which the fireside
should be cleaned. Other
factors also affect flue
gas temperature. For
example, a rise in stack
temperature may indicate
a baffle or seal in one
of the boiler's passes
has failed.
Waterside and
fireside surfaces
Waterside
and fireside surfaces
should be inspected and
cleaned annually. A
visual inspection
provides an early
warning that the vessel
needs repair or water
treatment or that
combustion needs
adjustment. Inspecting
and cleaning
water-column connections
should receive special
attention. Soot in the
breeching is a fire
hazard and can cause
severe
combustion-related
problems.
Safety valves
Safety
valves are the most
important safety devices
on the boiler They are
the last line of defense
for protecting the
pressure vessel from
overpressure. Once a
year. operating pressure
should be tested by
bringing the relief
valve to its setting.
Valves should pop and
reseat according to the
valve stamping.
Refractory
Refractory
protects steel not in
direct contact with the
water from overheating.
It also helps maintain
proper burner flame
patterns and
performance. If the
boiler remains on all
the time, refractory
should be inspected
twice a year. If the
boiler cycles more
frequently or is turned
on and off daily,
refractory should be
inspected more often.
Heating and cooling
refractory
A
lot shortens its life
considerably. It cracks
and eventually fails.
Hot spots on the steel
that the refractory
protects indicate
refractory or gasket
failure. If a hot spot
is found, the cause
should be determined and
repaired immediately to
prevent the steel from
failing.
Maintaining the
Burner
Although
burners vary by design,
application, fuel,
regulations, and
insurance requirements,
the same
basic maintenance
criteria must be
addressed. Burner
maintenance generally
focuses on safety.
efficiency, and
reliability. Adjustments
should be made only by a
trained service
technician using the
proper instrumentation
and tools.
Combustion
Poor
combustion is unsafe and
costly. Changes in
combustion air
temperature and
barometric pressure, for
example, impact burner
performance (see table).
Low excess air levels
result in incomplete
combustion, sooting, and
wasted fuel. High excess
air levels raise stack
temperatures and reduce
boiler efficiency.
Maintaining steady
excess air levels with
an oxygen trim system
helps ensure optimum
efficiency at all times.
Visually inspecting
combustion is the
easiest way to detect
changes that affect
safety and efficiency.
Changes in flame shape,
color, and sound are
among early indicators
of potential
combustion-related
problems. Changes may be
due to:
- Large fluctuations in
ambient temperatures
- Changes in fuel
temperature, pressure,
heating value, or
viscosity
- Linkage movement dirty
or worn nozzle
- Dirty or distorted
diffuser dirty fan
- Dirt on the boiler
fireside
- Furnace refractory
damage.
Visual combustion
inspection should be
compared to flame
characteristics observed
at similar firing rates
with efficient
combustion. However,
combustion efficiency is
verifiable only with a
flue gas analyzer. Even
if a flame appears to be
good, it should be
checked with an analyzer
and adjusted once a
month.
Fuel and air linkage
Changes
in fuel and air linkage
affect the combustion
fuel-to-air ratio. Flame
failure or a hazardous
fuel rich condition may
result. Proper linkage
settings should be
physically marked or
pinned together. Linkage
should be checked for
positioning, tightness,
and binding. Any
noticeable changes
should be remedied
immediately.
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Oil pressure and
temperature
Pressure
and temperature directly
affect the ability of
oil to properly atomize
and burn completely and
efficiently. Changes
promote flame failure,
fuel-rich combustion,
sooting, oil buildup in
the furnace, and visible
stack emissions. Causes
include a dirty
strainer, worn pump,
faulty relief valve, or
movement in linkage or
pressure-regulating
valve set point. Oil
temperature changes
typically are caused by
a dirty heat exchanger
or a misadjusted or
defective
temperature control.
Gas pressure
Gas
pressure is critical to
proper burner operation
and efficient
combustion. Irregular
pressure leads to flame
failure or high amounts
of carbon monoxide. It
may even cause over or
under firing, affecting
the boiler's ability to
carry the load. Gas
pressure should be
constant at steady
loads, and should not
oscillate during firing
rate changes. Usually,
pressure varies between
low and high fire.
Therefore, readings
should be compared to
those taken at
equivalent firing rates
to determine if
adjustments are needed
or a problem exists. Gas
pressure irregularities
are typically caused by
fluctuations in supply
pressure to the boiler
regulator or a dirty or
defective boiler gas
pressure regulator.
Atomizing media
pressure
When
oil is burned, an
atomizing medium, either
air or steam, is needed
for proper, efficient
combustion. Changes in
atomizing media pressure
cause sooting, oil
buildup in the furnace,
or flame failure.
Changes result from a
regulator or air
compressor problem or a
dirty oil nozzle.
Fuel valve closing
If
a fuel valve leaks,
after burn may occur
when the burner is
turned off, or raw fuel
could leak into a hot
boiler and cause an
explosion. When the
burner is turned off,
the flame should
extinguish immediately.
Prolonged burning is a
hazard and demands
immediate action.
Maintaining the
Controls
Controls are often used
to protect the boiler
against unsafe
operation. Flame
safeguard, operating,
limit, and safety
interlock controls are
among the most common.
Of course, controls only
protect the boiler if
they are maintained and
adjusted properly.
Flame safeguard
control
Also
called the primary
control or the
programmer, the flame
safeguard control
ensures safe light-off,
operation, and shutdown
of the burner. The
control regulates
purging the boiler of
all gases prior to trial
for ignition. It also
verifies that there is
no flame in the boiler
prior to light-off, and
checks for a pilot
before allowing the main
flame to light. The
control provides proof
that the main flame has
ignited before releasing
the boiler to the run
(modulation) mode. Most
importantly it does not
allow any action to
occur if operating
controls, limits, or
safety interlocks are
open. In addition, this
control initiates a post
purge upon shutdown to
remove all gases from
the boiler. And it often
provides a means for
detecting a problem
elsewhere in the system.
Although the flame
safeguard is designed
for fail-safe operation
and is quite reliable, a
faulty device can be
catastrophic and should
not be ignored.
Operating and limit
controls
These
controls tell the boiler
at what temperature and
pressure to operate.
Proper settings minimize
boiler cycling, maintain
proper limits for
efficient system
operation, and ensure
the boiler shuts down
when predetermined
limits are reached.
Improperly set operating
controls cause the
burner to operate
erratically and stress
the pressure vessel. All
these controls should be
checked weekly. The
scale of the control for
temperature or pressure
settings should not be
relied upon. Settings
should be verified with
the actual operating
temperatures and
pressures on the boiler
gauges.
Safety and interlock
controls
Safety
and interlock controls
vary with state, local,
and federal codes and
insurance requirements.
They must be operational
at all times. Among the
consequences of
inoperable safety
interlocks are personal
injury, equipment or
property damage, and
liability for losses or
damages. All interlocks
should be checked weekly
for proper operation. A
defective control should
be replaced immediately.
A control should never
be bypassed to make a
boiler run.
Indicating lights and
alarms
Indicating
lights and alarms are
part of the control
circuit. They alert the
operator to specific
boiler conditions.
Unfortunately, they are
often neglected and do
not provide the intended
information. Many
control circuits have
test buttons to verify
proper operation.
Circuits that do not
should be checked by
simulating conditions
that activate a light or
alarm.
Maintaining the
System
All too often, when a
boiler problem occurs,
the system is
overlooked. The emphasis
falls on the equipment
and not the equipment's
function in the overall
system. An effective
maintenance program must
be based on an
understanding of the
entire system and the
function of each piece
of equipment. Only an
understanding of the
system provides the
means for preventing the
causes of system-related
problems and reducing
the time spent on the
symptoms.
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Operating conditions
Operating
parameters of the boiler
room system should be
recorded daily. The data
provide a means for
evaluating boiler
operation trends that
affect efficiency,
downtime, and
maintenance planning.
The following data
should be recorded.
Feed water
pressure/temperature
Changes
in feed water pressure
affect the system's
ability to maintain
proper boiler water
levels. A pressure drop
may be caused by a leaky
check valve on a standby
pump or a worn pump
impeller. Changes in
feed water temperature
are indicative of a
problem in the
deaerator, potential
pump seal damage, loss
in efficiency, dirty
economizer, dirty blow
down heat recovery
exchanger, or excessive
or insufficient
condensate returns.
Boiler water
supply/return
temperatures
On
hot water systems,
supply and return
temperatures to the
boiler are a means for
evaluating the system's
effect on the boiler and
vice versa. The desired
operating temperature
set point and
temperature differential
across the boiler should
be evaluated
against the system
design to determine if a
potential problem
exists. High temperature
differentials caused by
excessive load or a
control malfunction
could cause thermal
shock and subsequently
pressure vessel damage.
Makeup water use
Records
of the amount of makeup
water used help
determine the presence
of leaks or losses in
the system. They also
assist in developing a
more effective chemical
treatment program.
Excessive water use
indicates a change in
system operation and,
therefore, a change in
efficiency.
Steam pressure
Steam
pressure operating set
points usually are based
on system design and
type of steam use.
Pressure changes are
typically caused by
problems with control
settings, burner
operation, boiler
efficiency, or, most
commonly, changes in
steam demand.
Leaks, noise,
vibration, and unusual
conditions
Checking
for leaks, noise,
vibration, and the like
is a cost-effective way
to detect system
operational changes. For
example, a small leak is
repaired by tightening
connections. By the time
a leak becomes large,
sealing surfaces usually
are worn and
major repairs are
needed.
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A
More In-depth Look
A
maintenance program
Must
focus on prevention to
be an effective tool.
Whether the maintenance
program is motivated by
safety, cost, reliable
operation, or all of
these, it is the best
means of
preventing common,
boiler-related problems.
Automatic
low-high
Water
control equipment must
be serviced on a daily
basis when the boiler is
in operation. A high
frequency of boiler
failures is the result
of low water, and can be
attributed to a careless
boiler operator. A
procedure must be
established at your
school to regularly
clean the glass gauge
column by "blowing
down" the column at
the start of the school
day, during non-peak
operating periods, and
at the conclusion of the
school day or shift.
This ensures ability to
determine the level of
water in the boiler.
Low Water
A major reason for
damages incurred to low
pressure steam boilers
is the low water within
the boiler. If the
condition of low water
exists it can seriously
weaken the structural
members of the boiler,
and result in needless
inconvenience and cost.
Low pressure boilers can
be protected by
installing an automatic
water level control
device.
Steam boilers are
usually equipped with
automatic water level
control devices
It
must be noted, however,
that most failures occur
due to low water on
boilers equipped with
automatic control
devices. The water
control device will
activate water supply or
feed water pumps to
introduce water at the
proper level, interrupt
the gas chain and
ignition process when
the water reaches the
lowest permissible
level, or perform both
functions depending on
design and interlocking
systems. No matter how
automatic a water
control device may be,
it is unable to operate
properly if sediment
scale and sludge are
allowed to accumulate in
the float chamber.
Accumulations of
matter
Will
obstruct and interfere
with the proper
operation of the float
device, if not properly
maintained. To ensure
for the reliability of
the device, procedures
must be established in
your daily preventive
maintenance program to
allow
"blow-down"
the float chamber at
least once a day. Simply
open the drain for 3 to
5 seconds making certain
that the water drain
piping is properly
connected to a discharge
line in accordance with
local Codes. This
brief drainage process
will remove loose
sediment deposits, and
at the same time, test
the operation of the
water level control
device. If the water
level control device
does not function
properly it must be
inspected, repaired and
retested to guarantee
proper operation.
Low Water Cutoff -
Tests and Maintenance
There are two very
effective tests for low
water controls on steam
boilers.
The
first, is the quick
drain. or blow down
test, which should be
performed at a time
other than a peak steam
generating period. As
the water is drained
from the column the
firing sequence is
interrupted, the low
water alarm signal
activates and the boiler
operation shuts down.
The second, and
more costly method is
the slow-drain test. By
opening the blow down
valves the water level
can be checked to
determine the water
level in the column, the
gauge glass, and the
boiler. The boiler
should shut down while
you determine the level
in the gauge glass.
As a safety precaution,
the low water float
chamber of hot water
boilers should be tested
daily, at the beginning
of the shift, at the end
of the shift, and once
during non-peak firing
periods. Time of tests
and the boiler controls
tested should be
recorded on your Boiler
Room Log.
Annually, or as
required, a thorough
inspection of all low
water control parts
shall be performed. The
annual inspection should
include opening and
cleaning the water
chamber.
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Feed
Water Pumps
Old, worn and obsolete
feed water pumps are
sometimes overlooked as
potential problems. A
centrifugal pump may
have worn seal rings
that allow the water to
chum between the suction
and discharge openings.
low
pressure discharge
An indicator of the
latter problem is low
pressure discharge.
Also, by comparing the
time it takes to raise
the boiler water level
to a predetermined level
or the time to empty the
condensate tank to the
time it formerly
required, it is possible
to determine if a pump
is operating properly.
Also, a pump that
operates quietly does
not mean it is
functioning properly.
Overpressure
Safe operation of a
boiler is dependent on a
vital accessory, the
safety valve. Failure to
test the safety valve on
a regular basis or to
open it manually
periodically can result
in heavy accumulations
of scale, deposits of
sediment or sludge near
the valve. These
conditions can cause the
safety valve spring to
solidify or the disc to
seal, ultimately
rendering the safety
valve inoperative. A
constantly simmering
safety valve is a danger
sign and must not be
neglected. Your
preventive maintenance
program includes the
documentation and
inspection of the safety
valve. A daily test must
be performed when the
boiler is in operation
Simply raise the hand
operating lever quickly
to its limit and allow
it to snap closed. Any
tendency of a sticking,
binding or leaking of
the safety valve must be
corrected immediately.
Steam Traps - Care
and Maintenance
Steam traps have play a
very important role in
steam distribution
systems. The service
performed by steam traps
is primarily to
discharge condensate.
Normally a steam trap
can be easily and
quickly selected by
considering only the
average operating
conditions. However, an
exact analysis of these
conditions will give the
proper data necessary
for selecting the type
and size for greater
savings and proper plant
operation. After the
careful selection of the
steam trap, it must be
properly installed,
tested, periodically
inspected, cleaned and
maintained to keep it
operating efficiently.
Traps need cleaning
periodically. A simple
way to prevent dirt from
entering is to drop a
short length of pipe
vertically below the
supply to the trap
(called a dirt leg)
which can be cleaned
easily and frequently.
Traps can be seriously
damaged by scale or pipe
comings in lines. A good
practice is to install
strainers ahead of the
traps which should be
inspected and cleaned
frequently.
Traps are subject to
severe wear if steam
blows through
continuously. They
should be inspected for
worn valve parts or a
change in operating
conditions.
When a steam trap fails
to discharge, inspect
the heating system and
be certain that all
units are drained with
separate traps, thus
guarding against short
circuiting, loss of
energy, and reduction of
operating efficiency.
Traps operating under
high pressure or
superheated steam are
often insulated in a
manner similar to
adjacent pipe lines. In
such instances, they
shall be fitted with
dirt pockets, test
valves, and drains.
Steam traps installed in
areas exposed to
climatic conditions will
lose heat if not
insulated and may freeze
unless adequately
protected. Discharge
lines should be short
and self draining and
traps should be fitted
with a drain tapping and
valves.
Steam traps handling
large volumes of air
require more frequent
inspection and proper
venting for efficient
operation. Vents shall
be used to avoid air
binding and ensure
positive drainage. Gauge
glasses shall be kept in
proper repair, for they
indicate whether or not
the trap is working.
Periodic cleaning and
gauge glass replacement
shall be considered as a
high priority in the
maintenance of steam
traps.
All steam traps require
protection from
corrosion to prevent
unnecessary
deterioration. All
valves, joints, and
gaskets should be kept
tight to avoid steam
leakage and ultimate
energy losses. For
continuous and efficient
operation. steam traps
require periodic
inspection and
maintenance for purposes
of eliminating foreign
matter and obstructions
in supply and discharge
lines. Each steam trap
at an assigned work
station should be
inspected as specified
by the preventive
maintenance program.
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Steam
Trap - Troubleshooting
It is important to
inspect the operation of
steam traps frequently.
There are many
conditions under which
traps may fail to
operate property. The
following are some of
the most common reasons
for trap failures:
1. Condensate does
not flow into the trap:
A.
Obstruction in line to
trap inlet.
B.
Valves leading to trap
are closed.
C.
Bypass open or leaking.
D.
Trap may be air bound.
E.
Insufficient pressure to
blow condensate through
orifice.
F.
Improper installation of
trap.
G.
Accumulation of foreign
matter within the trap.
H.
Trap held closed by
defective mechanism.
I.
Strainer may be blocked.
2. Condensate fails
to drain from trap.
A.
Discharge valve may be
closed.
B.
Trap may not be large
enough to handle
condensate.
C.
Pressure may be too low
to blow the condensate
through.
D.
Improper installation
for draining.
E.
Check valve may not be
holding.
F.
Obstruction in return
line or the line may
simply be too small.
3. Trap does not shut
off.
A.
Trap is too small for
the condensate load.
B.
Trap held open by
defective mechanism,
C.
Overload due to
excessive boiler foaming
or priming.
D.
Submerged steam coils
leaking.
E.
Differential pressure
exceeds design of trap.
F.
Scale or foreign matter
lodged in orifice.
4. Steam blows
through trap.
A.
Valve mechanism does not
close due to wear or
defective valve.
B.
Mechanism is held open
by foreign matter.
C.
Trap has not been
properly primed or reprimand
after clean-out
or blow-off.
D.
Bypass is open or
leaking.
E.
Excessive pressure for
design of trap.
What
is the meaning of Horse
Power ?
Horse
Power is a unit of
measurement of the
ability of a boiler to
evaporate water, usually
given as
the ability to evaporate
34¸ lb. (15.6 kg) of
water an hour, into dry
saturated steam
from and at 212¡F (100¡C).
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