A boiler is a very large vessel that is designed to heat up water or create steam by heating water.
In a commercial building, the heat generated from the hot water or steam provides heat and comfort to the occupants, living or working there.
The source of heating is mostly a burner that uses natural gas as fuel.
Other heating sources used in boiler systems are oil burners or electric heating coils.
Boilers usually enjoy a long operational life and are an efficient means of heating.
Nonetheless, fuel costs can prove to be substantial, and repairs can be expensive if they are not maintained properly.
For boiler maintenance, you may consider working with Comfort Heating, Inc.
Comfort Heating boilers are a reliable option, whether you want a new installation or boiler care.
What is a Boiler?
A commercial boiler is a high-pressure system that uses fuel or electricity to heat water.
Some boilers use heat from the hot water to supply heating in a building. Others first produce steam by heating the water and then use the heat from the steam.
Understanding Boiler Operation
Typically, a boiler system consists of a pressure vessel for holding water heated by fuel or electricity.
The walls of this container can endure high pressures that build up during the heating process.
A fuel storage tank supplies the fuel to a burner, which mixes the fuel with oxygen and ignites it, with an ignition device.
The combustion takes place in a chamber, which transmits heat to the water through a heat exchanger.
The hot water or steam generated by the boiler circulates through a distribution network of pipes and radiators in the building.
Key Components of Boilers
Each of these elements of a boiler system plays a crucial part in the process of heat transfer:
Boiler tank
A closed tank used to heat up the water.
Its design can withstand the pressure that builds up during the water heating process.
The manufacturing of these tanks must consider parameters like temperature, pressure, and corrosion.
The construction and design of these pressure tanks must follow regulations laid down by the ASME Boiler and Pressure Vessel Code (BPVC).
Burner
The burner receives an electronic signal from the thermostat when the system needs to deliver heat.
An outside source, mostly an adjoining fuel tank, pumps fuel into the boiler.
The burner nozzle ignites it, triggering a combustion reaction in the combustion chamber.
Gas-fired boilers work with one of two kinds of burners:
- The more traditional atmospheric burner that utilizes atmospheric air for combustion.
- Power burner, which uses a mechanical blower to force the air in, thus attaining higher efficiencies.
Pre-mix and low NOx burners are gaining usage on account of stricter air quality controls.
These burners ensure an optimum mix of fuel and air, resulting in reduced emissions.
Combustion chamber
Mostly built out of cast iron or steel, the combustion chamber houses the burners, and is the part of the boiler which burns the fuel.
Achieving very high temperatures, of up to hundreds of degrees, is possible in a very short span of time in the chamber.
The boiler’s heat exchanger transfers the heat generated in the chamber to the boiler water.
Heat exchanger
The primary function of an exchanger is to transfer the heat created from the combustion process to the boiler water in the tank.
Heat exchangers are generally made from cast iron, steel tubes, or even copper.
Pump
A pump is a part of the boiler distribution system.
Water drains into the boiler tank and out of it, with the help of a pump.
Steam boilers do not need a pump as the steam moves through the distribution pipes from high-pressure areas to low-pressure areas.
Expansion tank
The expansion tank prevents the buildup of excessive pressure in the boiler.
Pressurized air in a partitioned part of the expansion tank absorbs the surplus water pressure created by thermal expansion.
Pressure reducer valve
The heated water distribution loop requires a low-pressure water supply.
The water supply originating from the city water source is mostly 40 psi or higher.
A Pressure Reducer Valve (PRV) helps reduce the water pressure, which is set at 12 psi for most boilers.
Boiler flue
The flue or the exhaust stack is a pipe that expels gases and hot air from the boiler.
It mostly emits water vapor, carbon dioxide, and sometimes, very small traces of unwanted substances like carbon monoxide and nitrous oxide.
Heating
Hey everybody. Eric Sorensen with Servi-Tek Engineering and Facility Solutions. We're standing in one of
our buildings. We're talking about central plant systems, heating and cooling. We've kind of gone over
some of the chilled water side. Now we're going to talk about the heating. We're in a very quiet boiler
room. It's the middle of the summer here in Southern California, so none of the pumps nor the boilers
are running. These particular boilers are Cleaver-Brooks. Often we'll see Laars Lochinvar, we'll see
Raypak or even P-K's. Pretty much they're all doing the same thing. They're creating comfort hot water.
We're running that comfort hot water anywhere between 175 and 190 degrees Fahrenheit. That hot
water is being circulated by these hot water pumps down through a closed loop that's running inside the
air handlers or straight to the VAVs depending on the type of system that you have.
Then that air handler or that fan unit is blowing air, the return air, across the coils, picking up the
warmer air and then moving it down to the conditioned space. Much like the cooling towers, much like
the chillers and one of these smarter newer energy management system controlled boilers and pumps,
everything is being controlled by sensors. Again, on your hot water loop you're talking about closed
loop. You're talking about chemicals that stay in the loop. Unless you have a leak, there's no need for
makeup, there's no need to add more chemicals. Once in a while during cleaning, during repair and
maintenance, you're going to lose some nitrates. But other than that, you want to make sure that you
keep your loop tight and you keep your chemical levels at the right level so that we reduce oxygen in our
system, so that we reduce the amount of potential corrosion that's touching our capital equipment.
Boiler System Controls and Distribution Network
Boiler Controls
Various boiler system controls monitor functions like ignition, firing rate, water temperature, steam pressure, and boiler pressure. These include:
- Thermostats that govern the delivery of heat by signaling the boiler to generate more heat or shut off, as it gets too cold or too hot, respectively.
- Combustion and operating controls readjust the rate of use of fuel to match the demand.
- The main operating control regulates the water temperature or steam pressure by transmitting signals to govern the firing rate, the rate at which fuel and air enter the burner.
- Safety controls breach the circuit to prevent conditions like high temperature, high pressure, high or low water level, high or low fuel pressure, the firing of the boiler, and others. For example, if the boiler pressure tops the limit setting, the fuel valve shuts down to protect the boiler from an unsafe condition.
Distribution system
Apart from the boiler, a distribution network for heat circulation within the building is required, which includes:
- Feedwater supply to compensate for any loss of water in the boiler’s system and pumps that circulate the water.
- A loop of pipes within the building, originating from the outlet and going back to the boiler inlet. This pipework distributes steam or heated water and restores it after having radiated heat in the premises, and has cooled down.
- A fuel tank or local utility connection.
- A backflow preventer.
Types of Boilers
There are many types of boilers in the market, based on varied parameters like size, application, fuel type, etc.
Here are a few types of boilers that are in use currently:
Fire-tube boiler
In a fire-tube boiler, hot combustion gases move through a set of tubes encircled by water.
Facilities with applications that require hot water, or steam at low pressure, mostly use fire-tube boilers.
Fire-tube boilers come in either a wetback or a dry back design.
Water-tube boiler
In a water-tube boiler, hot combustion gases surround the set of tubes filled with water.
Buildings with high-pressure steam utilization favor the usage of water-tube boilers.
Cast-iron boilers
Cast-iron boilers comprise sections of cast-iron with water and gas pathways, instead of tubes.
Bolts secure the castings together and gaskets seal the gaps in the sections.
An advantage of cast-iron boilers is the ease of assembly on site.
But they are also more liable to leak because the gaskets wear down with age.
Condensing Boilers
Condensing boilers function at a lower return water temperature than conventional boilers.
The condensation of exhaust gases because of the lower temperature results in the formation of water vapor.
The boiler extracts heat from the change of phase from water vapor to liquid. This enhances boiler efficiency.
Electric Boilers
Because electric boilers do not use combustible fuels, these are much simpler machines, with no exhaust stack or fuel handling equipment.
Because they run purely on electricity, electric boilers are compact, noiseless, and easy to install.
Buildings that do not need large amounts of steam or where natural gas is not available, prefer to use electric boilers.
Hot Water
So remember, we have two types of hot water running through our typical office building, right? We've
got our domestic hot water. That's what we're going to see at the sink, in the bathroom, or in the
kitchens or those kinds of things. That's just regular potable water, city water that's coming through,
going through a hot water heater and then being pushed out at the sink level. Then, of course, we have
high-temperature hot water that's running at about 175 to 190 degrees versus about 120 degrees on
the domestic side for comfort heating. Those pumps that we just showed you earlier are typically being
controlled by these variable frequency drives.
We talked about that with the cooling towers, and then it's sensed load. How much hot water is really
being demanded at this moment? How many valves are open and calling for hot water flow? These will
sense that demand and send a signal to those hot water pumps to pump that amount of water. When
the demand goes down, these will ramp those motors back down and we won't pump as much hot
water. So again, two types of hot water in buildings, domestic and high-temperature hot water. One
running about 115 to 130 degrees, one running about 175 to 190 degrees Fahrenheit.
Steam and Hot Water Boilers
A hot water boiler system pumps heated water into the building’s heat distribution system.
This results in more uniform heat distribution.
But it takes a longer time for a hot water boiler system to deliver the heat.
Given the limitations of the circulating pumps, this system is not productive in buildings higher than six floors.
But the general effectiveness of this boiler system makes it a preferable option for buildings that are not too tall.
On the other hand, a steam heating system does not rely on circulating pumps.
Because of the additional pressure, steam delivers heat at a faster rate but not as evenly as heated water.
The heat distribution system also needs larger radiators to effectively extract heat, but steam heating systems work better for tall buildings.
Preventive and Routine Maintenance
Preventive maintenance involves regular checks on your boiler system to help you spot any minor faults that might turn into larger issues.
If you identify a potentially major problem, waste no time in scheduling repair services with a qualified technician.
Here is a checklist we have prepared to help you with the routine maintenance of your boiler system:
- Check all gas pressure safety controls.
- Examine and purge all burners.
- Check all gaskets for leaks.
- Examine refractory systems.
- Scrutinize and test safety valves.
- Clean low water cut-off.
- Review all operating controls.
- Check and secure electrical terminals.
- Inspect flue chimneys and check the flue gases.
- Check the vent pipe.
- Check all fans and blowers for dirt.
- Examine all electricals and electrical connections.
- Check for leakages in the block and bleed valves.
- Review oxygen, carbon monoxide, and carbon dioxide levels.
This list shows the need for preventive maintenance of commercial boilers to help enhance their life and safety and reduce repair costs as well.
This is not a comprehensive list and we will discuss boiler maintenance in length, later in this article.
Benefits of Preventive Maintenance
Safety
Boiler mishaps can cause serious damage to human lives as well as property.
A potent combination of heated water, high-pressure steam, and combustible fuel can prove dangerous.
Regular maintenance of your boiler system is of paramount importance for the safety of your employees.
Compliance
Periodic inspection and assessment of boilers are mandatory under the National Boiler Codes.
A licensed boiler contractor must check commercial and industrial boilers at least once a year.
Insurance
Because of the hazardous nature of boiler systems, there are potential dangers to employees and property.
Insurance companies also require code compliances, apart from any extra checks in their policy conditions.
Energy efficiency
The annual preventative maintenance checks go a long way in saving costly repairs and increasing boiler efficiencies.
Prevention
The money spent on regular preventive maintenance of your boiler system is worth the safety of your employees, and of the commercial facility, apart from savings on costly repairs.
Boiler Maintenance and Inspection
A basic boiler system has several parts that are bound to incur wear with usage and over time.
Regular inspections and maintenance are the key to efficient operation and long life of your boiler.
Keep a detailed history of all the maintenance work.
Choose a trusted service provider, such as Comfort Heating boilers for professional care and maintenance as well as for installation of new boilers.
Here is a list of things you need to do on a daily, weekly, or periodic basis as part of the basic maintenance of your boiler system:
Daily Maintenance
- Water levels: Check the level of water in the boiler, the feed tank, and the exchanger. Since water is the sole working fluid, its low levels can cause a failure to transfer or dissipate heat in the system. Maintain a record of the amount of water infused into the structure to retain optimum balance.
- Water temperature: Continuous daily checking of water temperature to maintain the minimum stipulated system temperature is essential.
- System pressure: Daily appraisal of pressure, along with the monitoring of the temperature.
- Fuel levels: Fuel usage can vary daily, depending upon the weather. It is imperative to check the fuel levels in the boiler as well as the storage tanks. This helps in avoiding a shortage of fuel and ensures smooth, continuous operation of your boiler system.
- Lubrication oil: Inspect the lubrication oil levels in compressors and pumps. A damaged pump can bring the whole system to a grinding halt and can cause a long shutdown.
- Oil pressure: Observe and record the oil pressure generated by the pumps.
- Combustion flame: Visually inspect to check the flame length and burning of combustion feeds.
Weekly Maintenance
- Pressure gauges: Verify if the pressure gauges show error-free readings.
- Thermometers: Check if the temperature readings on water and stack thermometers are precise.
- Oil pre-heater: Check the oil pre-heater once a week, if your boiler’s system has one.
- Safety switches: Test low-water safety switches, at least once every week.
- Valves: List all the valves in the system and carry out a weekly inspection of all the valves.
- Oil filters: Clean all the filters and strainers. Replace the filters if required.
Monthly Maintenance
- Combustion chamber: Inspect the chamber for leftover oil and clean it if required.
- Burner assembly: Clean the assembly thoroughly, once a month.
- Safety valve: Inspect pressure regulating valves and inspect the connected pressure gauge.
- Steam valves: Adjust the control valves according to the specifications in the instruction manual.
- Water quality: Maintain water pH levels and chemical balance to avoid corrosion. Impurities in the pipe network affect the boiler water’s ability to transfer heat. Supervise and improve water quality on a regular basis.
- Combustion air supply: Make sure of adequate delivery of oxygen to the combustion compartment. Check air passages to the boiler and the boiler room. This is necessary to avoid the build-up of noxious exhaust gases.
- Blowers: Check blowers and their belts, for any signs of wear and tear, slack, or slippage.
- Air leaks: Check for leakages in the combustion chamber and near the openings. Inspect the gasket seals and ensure there is no leakage on account of wear and tear.
- Boiler tank: Perform a thorough visual inspection, inside and out, once a month. Look for rust and insulation wear that could lead to the deterioration of the tank.
Annual Maintenance
- Burner overhaul: Remove and re-assemble the burner.
- Efficiency test: Check and find out ways to improve the Annual Fuel Utilization Efficiency rating.
- Exhaust stacks: Sweep all exhaust chimneys, stacks, and outlets.
- Relief valve: Recondition the valve.
- Fuel tank: Inspect and clean the fuel storage tank.
- Water pumps: Purge the feedwater pumps.
- Deaeration system: Cleanse the system and clean condensate receivers.
- Apparatus: Clean and readjust the pumps and components like filters, heaters, and oil tanks.
- Exposed surfaces: All uncovered areas need cleaning annually. Surface dirt and grime can damage unprotected seams, intakes, and outlets.
- Refractory lining: The brick liner needs an annual inspection to see if it needs repair or even replacement.
Boiler Blowoff and Blowdown
A boiler receives water with various impurities in it.
Over a period, these impurities entering the boiler with the feed water accumulate at the bottom of the pressure vessel and form sludge.
This adversely affects the performance of a boiler.
In an electric boiler, the accumulated sludge can impede the heating elements and cause them to fail prematurely.
Blowoff and blowdown are the two ways to get rid of the impurities that build up in a boiler.
The main purpose of a blowoff is to remove the accumulated solids from the bottom of the boiler.
It usually has two valves (one of them, slow-acting) in series, and is located very low in the boiler.
Blowdown, on the other hand, is not mandatory by ASME or by the NBIC.
Boiler manufacturers often add a blowdown as an accessory.
It makes use of the larger quantities of impurities at the water-steam interface.
One blowdown method uses a perforated pipe just below the water level in the boiler.
A blowdown maintains water chemistry in the boiler in a more gradual and controlled manner than a blowoff.
Safety and Operating Boiler Equipment
The main aim of the National Board of Boiler and Pressure Vessel Inspectors is boiler safety.
The board reports and records mishaps related to boiler heating systems, each year.
According to their data, the primary reason behind incidents causing injury was the lack of proper maintenance and operating mistakes.
This clearly demonstrates the significance of regular maintenance and proper operator training.
All combustion equipment needs proper handling to prevent hazardous conditions or mishaps that can cause grievous injury and extensive property damage.
Accumulated gases in the boiler cause the most boiler mishaps and explosions.
The main reason for the accumulation of gases is ignition failure or delay.
Boiler systems have an enormous quantity of stored energy.
Change of state of the superheated water into vapor inside a boiler releases tremendous amounts of energy.
While useful for our needs, this energy can also prove to be a hazard, if not controlled properly.
Following proper maintenance and safety measures goes a long way to ensure efficiency without compromising on safety.
Routine Boiler Inspection
The National Boiler Codes stipulate that a licensed boiler contractor needs to inspect and certify all commercial boilers at least once a year.
But some of the higher efficiency boiler systems in use today (such as condensing boilers) may need more maintenance checks in a year.
Apart from the routine maintenance of your boiler, it may be a good idea to have an annual inspection by a certified member of the NBBI (National Board of Boiler and Pressure Vessel Inspectors).
You will need a lot of time to prepare for this inspection, as it involves a complete shutdown and disassembling of your boiler by the inspection agency.
Reliable Boiler Heating System Maintenance for Your Building
Servi-Tek provides customizable engineering and facility maintenance solutions for commercial buildings.
Our experienced teams provide best in class commercial boiler maintenance, including boiler service, repairs, and preventive maintenance.
We adhere closely to manufacturer recommendations, industry standards, and best practices.
We schedule all preventive maintenance tasks on a defined frequency to ensure optimum levels of performance.
If you have concerns about your boiler’s heating capability or energy efficiency, contact us online or call us at (866) 454-6185 today.
