Mechanical Insights

Boiler Parts to Order After Winter

Mar 30, 2021 8:30:00 AM / by Tate Engineering

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With spring right around the corner, it can be tempting to look forward to shutting your facility’s boiler down and not think about it again until the fall. Instead, use this time to get ahead on some maintenance so that your boiler will be reliable and ready to go next winter. Your future self will thank you. Let’s look at some of the most common fireside and waterside parts that may need to be replaced, as well as tips for maintenance.

General Maintenance

A little bit of cleaning can go a long way, especially for a boiler that is on the backside of a harsh winter. By doing this maintenance in the spring, minor problems can be addressed when they are still fresh in your mind, and before they become major problems in the middle of an arctic blast.

Boilers can wind up with a lot of soot at the end of the winter. As temperatures in the spring climb and boilers go through cycles of high and low demand, water can condense on the soot accumulation. This “wet soot” is corrosive and can damage boiler tubes, tube sheets, and other fireside components. Removing that soot in the spring can significantly extend the life of your boiler and prevent damage that could impact the safe operation of your boiler.

While cleaning the boiler, inspect the condition of the various parts. Things that are damaged or worn out should be replaced or ordered to make sure replacements are on hand to save valuable time later. During the events of 2020/2021, this has become even more important as parts have extended shipping times.

Fireside Parts

Fireside parts refer to any of the parts that are on the side of the boiler that will burn gas or other combustibles to generate heat. Here are some of the most common parts that fail and need to be replaced. If you don’t want to replace them, at least consider having them on hand or learning how to replace them if you ever need to in the middle of the winter (when the boiler is operational).

Flame Detector

Boilers in commercial and industrial settings use a variety of different technologies to prove flame for safe operation of the burner. This can include a flame rod, which uses the ionizing flame of burning fuel to establish an electrical circuit, a CAD cell, which changes electrical resistance when exposed to the bright light of a flame, a UV Scanner which detected the ultraviolet radiation emitted by the flame, an IR Scanner that detects a narrow optical band of infrared radiation emitted by the flame of carbon fuels, or a thermocouple that generates a small electrical current as it is heated by the flame.

As flame rods are in the flame of the burner, they are very susceptible to damage that inhibits their operation and creates flame failure alarms despite the presence of fire. This is especially true if you are burning propane, but can be just as problematic on natural gas fires as well. CAD cells can be coated with soot that acts as a shade, preventing the cell from fully seeing the flame, and they can also burn out. UV and IR Scanners are susceptible to water intrusion into the eye, soot accumulation, electrical noise, and changes to its view of the flame that make the flame signal unstable. Thermocouples wear out over time.

Ignitor Parts

Ignitors provide the initial heat source to light the fuel. This includes Hot Surface Ignitor ignition of the Main Burner or Pilot Burner, Direct Spark of the Main Burner via electrodes, Spark ignition of an intermittent Pilot, or a Standing Pilot flame. These are parts that can be very helpful to have on hand to get your boiler back online when it's needed most. There is also value in inspecting these parts in the spring and replacing as needed.

Hot Surface Ignitors, or glow coils, eventually wear out and crack due to the intense temperatures they see during an ignition cycle, but they are also exposed to the Main Burner flame during the burn cycle. Spark ignition is dependent upon the correct gap between electrodes and the strength of the Ignition Transformer. The spark gap can change as the electrode is worn away by the high voltage arc it creates. Spark electrodes are also electrically insulated with ceramic. This ceramic can crack, resulting in pathways that don’t allow the arc to ignite the fuel. These electrodes can also be electrically insulated by partially burnt fuel oil, creating intermittent ignition issues. Standing Pilots, while having a long history, are susceptible to soot and dust accumulation that creates a lazy flame, which could lose contact with the thermocouple and drop out.

Gas Pressure Switches

Gas Pressure switches help ensure that fuel pressures stay within ranges for safe and reliable operation of the burner. Depending on the BTU Input of the burner, code may require their presence and correct operation. These simple parts are cheap and easy to replace, but will keep your boiler from running if they fail. In addition to these switches, the Fuel Train should be inspected for damage and fuel leaks, and the Gas Regulator should also be inspected. Most Gas Regulators have a vent to the outside - the vent termination should be inspected to make sure it is clear. As spring temperatures climb, bees, wasps, and hornets can obstruct these vents with their nests.

Fuel Shutoff Valve

Boilers can be very dangerous pieces of equipment if they are not adequately maintained (or if the safety equipment is not inspected). Code requires that all Fuel Burner appliances are equipped with a Fuel Shutoff Valve. If this valve is not operated, it can seize up without your knowledge. This creates a situation where, in an emergency, the fuel must be shut off for safety but your operators cannot operate the valve. It is wise to ensure these valves are clean and operational before you need them.

Related: Must-Have Boiler Tools

Waterside Parts

The term “waterside” refers to parts of the boiler that are exposed to the water, or steam, heated by the burner. These parts are in direct contact with the water on a hydronic boiler, or water below the Normal Operating Water Level or in steam contact above the NOWL in a steam boiler. The tubes and tube sheets separate the waterside from the fireside. These components are susceptible to their own unique challenges and are generally cheap and easy to replace, but their failure can shut down your boiler or create dangerous conditions.

Low Water Cutoff Switch

Every Steam Boiler, regardless of its size or application, is required to have a Low Water Cut-Off device. If the water level falls below an acceptable level, the LWCO senses the condition and turns the burner off. Without this switch, the burner could run with little to no water in the boiler, damaging the boiler and creating a dangerous situation. Boilers above a certain BTU Input are required by code to have two LWCO devices, a primary and an auxiliary.

On steam boilers, LWCO devices are traditionally floats that ride on the surface of the water in a bowl. As water levels change, the float moves up and down. The Primary LWCO can also serve as a Make-Up Water Control, allowing the boiler to fill with water as the level drops, but also shutting the burner off as the water level continues to drop. These float style LWCOs can wear out over time, especially along the linkage that connects the float to the switch. Some steam boilers and water boilers that are equipped use a probe that senses water contact by electrical discharge. These probes can be insulated with scale, preventing them from sensing the water. Additionally, some water boilers confirm correct water flow via a Differential Pressure Switch or Flow Switch to confirm water flow.

Pressure or Temperature Switch

The pressure switch (steam boilers) or the temperature switch (water boilers) are operational controls to allow the burner to cycle as the demand in the building changes. Boilers above a certain BTU Input value are also required to have redundant safeties, shutting the burner off in the event steam pressure or temperature climbs above a safe level. Typically, when used as a safety, these switches require manual resetting to get the boiler back online.

These switches are inexpensive and can be valuable to have on your shelf in the event of a failure. Additionally, pressure or temperature switches used as safeties can sometimes be unused and get stuck in the normal position. In the event that pressure or temperatures rise, they may not operate as intended and no longer function as a safety. They should be inspected and operated to confirm their viability as a safety control.

Pressure Relief Valve

Boilers can develop unsafe conditions due to the high energy potential of pressurized steam. If allowed to develop, this pressure can quickly exceed the operating characteristics of the boiler’s pressure vessel. The Pressure Relief Valve is a safety that is designed to vent steam or water if the pressure becomes unsafe. It is important to keep in mind that these safety valves are designed to protect the integrity of the boiler, and by virtue, the occupants of your building. It is smart to replace these valves annually and, in some cases, their annual replacement is required by code or by your boiler insurance company. At the very least, these safety valves should be inspected for physical damage, evidence of leakage, and confirmation that their vent is free and clear of obstructions.

Level Control

In addition to boilers that use a float style LWCO that also provides make-up water control, modern boilers can also be equipped with a combination of a sensor, loop controller, and modulating feedwater valve to maintain a consistent and reliable water level in the boiler. This is a significant improvement to a boiler, as the on/off operation afforded by the float style control results in a wide swing of water level in the boiler and can result in prolonged make-up water cycles that can collapse the steam pressure in your boiler, requiring additional consumption of fuel beyond the needs of your load. Modulating make-up water control maintains a tighter water level in your boiler without exposing it to prolonged cycles. It can be smart to have a few of these parts on hand, as make-up water system issues can take boilers offline or create unsafe conditions within the boiler.

When reliability and safety are paramount, preventive maintenance can be one of the best ways to address developing problems before they become catastrophic to your operation. The experts at Tate Engineering are ready to help you maintain and service any of your boiler needs.

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Tags: Seasonal, Equipment

Written by Tate Engineering