Boiler Basics
Knowing the types of Boiler objects
My Boiler won’t start - what to do first!
Nothing can be more frustrating than a nonfunctioning boiler on a cold
day. Fortunately, noticeable changes in boiler performance precede most
mechanical failures. If you notice a change in boiler performance such
as new noises, smells, rising stack temperatures or continually resetting
safety devices, call your boiler professional for help.
Although unexpected mechanical failures do occur, it is likely that one
of the boiler’s safety or operational devices is preventing your
boiler from starting. Most safety devices have manual reset buttons that
need to be reset before boiler operation can continue. Continual resetting
of safety devices is an indication of unsafe operating conditions.
Prompt attention by your boiler technician is required.
Locate all devices that can prevent your boiler from starting.
They include:
- Burner controller: The controller is usually located in front
of the burner. On a call for heat the controller starts a sequence of
events that ensure safe operation before the burner is allowed to start.
The controller continues to monitor burner operation while the boiler
is running. If for any reason the controller senses an unsafe operating
condition it will shut the burner off. Pushing the manual reset on the
controller will often restart the boiler.
- High pressure or temperature switch: This device is a safety
backup to the “operator” control. It has a manual reset which
when pressed to start the boiler indicates that the “operator” control has failed.
- Gas pressure switches on the fuel train: The natural gas fuel
train usually has two pressure switches. The low pressure switch locks
out the boiler when too little gas is available for operation. The high
pressure switch locks out the boiler when the regulator is allowing
too high a gas pressure. Both switches have a manual reset.
- Low water cutoff: The low water cutoff may have a manual reset.
When reset indicates a low water condition existed in the boiler.
Other devices that may prevent the boiler from starting:
- Time clocks:
Time clocks or other energy management devices may restrict boiler operation
during weekends, evenings or other times of the day. Check their operating
schedule.
- Outdoor temperature limits:
These devices sense outdoor temperatures and prevent boiler operation
above certain outdoor temperatures, usually 65 degrees.
If resetting these devices does not start your boiler call your boiler
professional for assistance.
Reminder: Do not bypass any safety devices in an effort to start your
boiler.
Causes of Boiler Room Accidents
Boiler systems are designed for safety and efficiency. The key to safe
boiler operation is the operator. Armed with some basic knowledge about
boiler systems and maintenance the boiler operator can ensure years of
safe, reliable service.
History has shown that without proper operation and maintenance, boiler
conditions and safety deteriorate, causing potential hazards due to neglect
and misunderstanding.
Routine maintenance is well within the ability of most boiler operators.
Boiler tune up and repairs however are best left to trained professionals.
Understanding when to turn to qualified professionals for assistance is
an operators first responsibility.
Here are some problem areas where trained professionals are needed:
- Leaking pressure relief valves
- Continuous make up water to boiler
- Steam leaks or steam vented from condensate tank (steam systems)
- High stack temperatures (greater than 350 degrees)
- Insufficient heat to building
- Condensate dripping down stack or out the front of the boiler
- Constantly resetting controller, high pressure or temperature limits
or low water cut off switches
Common Boiler Room Accidents
Dry Fire Accidents: Dry fire accidents are also called boiler
meltdowns. These accidents occur when the boiler is allowed to operate
without adequate water in the boiler. Functioning low water cutoffs are
essential to preventing dry fire accidents. Boiler damage can run from
severe buckling and deforming of the boiler to complete meltdown or potential
boiler explosion.
Excessive Pressure Accidents: Excessive pressure is potentially
the most lethal form of boiler accident. These accidents occur when the
boiler can no longer contain the excessive pressure allowed to build in
the boiler. The operator control, high pressure limit, and the pressure
relief valve need to fail before these accidents can occur. Excessive
pressure accidents, even in small boilers, have been known to completely
destroy a building.
Fuel Related Accidents: Fuel related accidents usually occur when
the operator fails to purge combustible gases from the fire box before
ignition is attempted.
Never bypass safety devices with jumper wires to restart your boiler.
Unintended ignition of unburned combustion gases in the fire box is possible.
Leaking fuel valves can also be the cause of these accidents. If the
operator notices any gas odor the boiler should be shut down and the fuel
supplier called immediately.
Water Treatment Basics
Boilers are filled with water that contains naturally occurring impurities.
Common impurities such as calcium, magnesium and oxygen can, if they are
not controlled, effect boiler performance and durability.
All water contains dissolved minerals such as calcium and magnesium.
If these minerals are allowed to reach high enough levels in the boiler
water they will come out of solution and form as a hard shell on the hot
surfaces of the boiler. This hard shell is called scale and is often found
on the outside of the fire tubes. Scale insulates the heating surfaces
reducing the ability of the fire tubes to transfer heat from the hot combustion
to the boiler water. High stack temperatures or ruptured fire tubes are
common problems related to scale build up.
Boiler water also contains dissolved gases such as oxygen or carbon dioxide.
These gases in the presence of water and metal can cause corrosion. Corrosion
eats away the metal effecting the durability of the boiler.
Water treatment strategies:
Boiler heating systems lose water through steam and water leaks. Additional
water called "makeup water" is added to the boiler to replace
these losses. The amount of make up water and the level of naturally occurring
impurities in the water will determine the type of water treatment required.
Boiler heating systems that have very few leaks will require simple water
treatment programs. Your boiler inspector or water treatment professional
can assist you in developing a water treatment program. Steam and hot
water boilers typically require different water treatment programs.
Steam boilers:
Steam boilers are usually treated to prevent scale and corrosion. Scale
producing dissolved minerals accumulate in the boiler water when mineral
rich make up water replaces mineral free steam and condensate leaks. Strategies
to prevent scale attempt to keep the components of scale such as calcium
and magnesium suspended in the boiler water or to reduce their concentrations
in the boiler water. Draining water from the boiler (bottom blowdown)
is a common method for reducing the concentration of solids and to discharge
sludge.
Corrosion is reduced by adding oxygen scavenging chemicals to the boiler
water. Boiler water testing is required to ensure that conditions suitable
for scale and corrosion are not present.
Hot water boilers:
Scale build up is usually not a problem in hot water boilers. Although
make up water contains dissolved minerals, system leaks discharge water
with an equal amount of dissolved minerals. Since as many minerals are
leaving the boiler system as enter it; minerals do not have the opportunity
to accumulate in the boiler water.
Corrosion remains a problem so oxygen scavenging chemicals are added
to address the problem.
Note: Provided and posted with permission
courtesy of State
of Oregon Boiler Program staff.
