Spare Boiler Parts To Keep on Hand

Are you feeling the impact of supply chain issues? These days who isn’t?? Do you have spare boiler parts on hand in case your boiler goes down? Do you know lead times for critical parts in an emergency downtime situation? Check out this article to learn what you can do now to be ready…. starting with 23 Spare Boiler Parts to consider having readily available now.


23 Spare Boiler Room Parts to Keep on Hand

An important part of maintaining your critical infrastructure is ensuring you have parts on hand in the event of an unexpected failure of your critical equipment. Having spare parts for your boiler’s mission critical components is a great way to avoid costly downtime when something fails. You will also potentially save money on emergency calls, expedited shipping, and extended unplanned downtime. But, what parts should you keep on hand and how many do you need? In this article we break down 23 key boiler spare parts and suggested quantities every boiler operator should consider keeping on hand.

Note: This is a general list. You should check with your service provider about any specific long lead or hard to procure items that might also be beneficial to have available.  Do you want a custom list based on your specific equipment? Click Here to claim it.

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Boiler Spare Parts List (Alphabetical)


The Boiler Level sight Glass helps in identifying the actual water level in the steam boiler. It is critically important that your sight glass is clear and clean, not leaking and there is no evidence of thinning on the glass. You should never let the sight glass get to a point where it becomes hard to read. If it’s so dirty you can’t blow it down, then it’s time to replace. Even a small leak from the boiler sight glass or packing will affect the water level reading, leading to a very unsafe operating condition.

Keeping a spare part in your boiler room makes switching it out easier if a problem arises. Reusing worn-out components isn’t worth the risk. Your sight glass and packing should also be replaced annually as part of your annual preventative maintenance services.


Does your boiler have a standalone combustion air switch? Have you ever tried to light the boiler but the fan doesn’t spin? What happens? If you haven’t had this happen to you, the answer is nothing. Nothing happens. If the boiler goes to light but the fan doesn’t spin due to some failure, it’s because the combustion air switch prevents a burner from opening the fuel valves if there is no air flow. Why wouldn’t you keep a spare? If you don’t have a standalone combustion air flow switch, your equipment may have other sensors that serve this purpose.


A flame detector is a crucial control and safety boiler part that detects the absence or presence of flame within the boiler. Flame scanners are necessary when running fired equipment. You will need a replacement ready in case of part default. This critical device is known to be troublesome and one of the most common parts to keep on hand.

Industrial manufacturers use a variety of flame detection technology. For instance, there are UV (Ultraviolet) scanners, IR (Infrared) scanners Near IR (Near Infrared), Flame Rods, Thermocouples and more.  Some use a “self-check” feature to verify the operation of the scanner.  The choice of the scanner is dictated based on the fuel being burned, and the furnace construction and position of the scanner. 

So how does a flame scanner work? Regardless of the type of scanner used, the primary function is to “look” to see if a flame is present. The scanner is an integral part of the boiler’s flame safeguard system. If the flame goes out, or if a flame is detected during part of the boiler cycle when it should not be present, the boiler will shut down to avoid an explosive environment when raw fuel builds up.


(Main, Secondary Valve, Fail Open Vent, Pilot)

Main valve, secondary valve, and for large gas fired equipment, a fail open vent valve. Don’t forget the pilot safety shutoff valves too. These valves ensure that fuel doesn’t slowly leak into the boiler when it is off. Imagine lighting a boiler that has had gas slowly leaking into it for hours. . The outcome would be hazardous, either an explosion or fire.  When these critical valves fail or leak, you’ll want to replace them ASAP.

For some larger valves, you may just keep extra proof of closure switches and a valve rebuild kit on hand. This prevents you from needing a full assembly. However, be aware that some of these valves have extremely long lead times. It isn’t common for these valves to be irreparable, but if it happens, that boiler could be out of service for a long time. Confirm that your trusted service provider includes bubble testing these valves for tightness in your annual preventative maintenance service plan.


We suggest you keep a complete rebuild kit for your gas pressure regulator plus a manual. Otherwise, you may struggle to get one quickly when your system is down. It’s also good practice to inspect the vent lines regularly to confirm that they are free from any blockages.

9-13.     GASKETS

Over time, with heating and cooling cycles gaskets can fail and allow leaks. Gaskets are generally replaced every 12 months or during any inspections done on the boiler. Because they are cheap and frequently replaced, keeping a few extra sets on hand is a no brainer. This will also shorten downtime should a leak occur.  Suggested Gaskets to keep on hand are: handhole gaskets, manway gaskets, LWCO gaskets, Full Fireside and waterside gasket kits.

Be sure to swap these at every annual inspection. The lost time cooling, draining, and refilling alone pays for storing a few new gaskets in the boiler room. Keep a couple full sets of the suggested gaskets/gasket kits on hand for outages or leaks.


High and low gas pressure switches monitor for “out of range” gas pressure being delivered to your boiler’s burner. These 2 pressure switches are critical to ensuring that the boiler isn’t getting too much or too little gas. Without these switches, your boiler could go too lean or rich and cause major damage or an explosion. Keep one handy and have a qualified technician set your spares during your next burner tune so that the switches are ready when you need them. Keep in mind, the switch set point is likely boiler specific, so presetting them may require a spare high and low for each boiler.


This simple pressure switch (for steam boilers) or temperature switch (hot water boilers) can put your boiler out of commission. Combustion safety codes require this safety switch on all installations. Even if you can get it shipped to you quickly, don’t let this relatively inexpensive part be responsible for production loss.


Ignitors and flame rods (fancy spark plugs). These are cheap and easy to keep on hand.  Don’t be down and out because you can’t light the pilot


Low water cut-off is arguably the most crucial safety device of a boiler. You can find it on any steam or hot water boilers to ensure safety if the water level goes down. They can be mechanical (float-type) or electrical devices (probe-type).

The type of LWCO used is determined by code. A mechanical low water cut-off device using a float mechanism is the most common for the Primary LWCO. These rely on a float with an arm connected to a switch tied to a burner circuit.

These devices play a critical role in detecting low water conditions in the boiler. Low Water Cutoffs generally have a ten-year expected life if they are thoroughly cleaned on an annual basis. If maintenance is neglected, low water devices will need to be replaced much sooner, and they will be significantly less reliable in operation.


Observation port glass and packing are cheap and easy parts to replace. Therefore, plan to keep a spare on hand. You want to avoid having observation port glass and packing that is broken, sooty, hot, or leaking. Damaged or dirty observation glass makes it impossible to have a clear view and puts you at unnecessary risk. Stay on top of this simple part so that you can spot leaks, cracked refractory, and damaged burner heads while they are still minor issues! It just makes sense to have a spare on hand.


Without this device, an operator would have to watch the boiler pressure gauge and manually adjust the boiler firing rate to maintain system pressure. Depending on the installation, this can be a difficult task and certainly not a reliable method of fine pressure control. In large systems, this is a part of the PLC based controller. In smaller systems, this may be a stand alone ‘pressure controller’. Keeping a spare pressure sensor and loop controller or a spare PLC on hand, preloaded with the required software can be a life saver.


A boiler safety valve limits the amount of steam pressure within a boiler to prevent over-pressurization that could damage the equipment or even cause harm to people inside the boiler room. Excess pressure pushes the valve seat, forcing it to open against spring tension. The relief valve closes when steam flows out of the boiler, and the pressure falls.

Did you know that safety relief valves are required by code to be tested annually? Some companies instead choose to have a spare set of valves that can be rotated in at the scheduled annual outage. This allows the valves that were in operation to be sent out for certification and testing. Getting new valves sized for your boiler at your set points can take days even if expedited. Plan to do it now and have the spare valves on hand in case of an emergency and to swap out at your annual inspection so that you can stay in compliance without any unnecessary downtime.


While it’s possible to run your boiler with leaking valve packing, it’s not ideal. Some operators tighten the packing to reduce leakage. Unfortunately, valves don’t work well when the packing is overtightened. Therefore, it’s reasonable to have extra packing sets for your valves.


A water-level device controls the water volume inside the boiler. If it fails, you will need an operator to regulate a manual valve when necessary to keep the boiler close to its Normal Water Level (NWL). As we know, most boiler rooms don’t have operators standing around with nothing to do. Therefore, the best option is to have a spare water level sensing device on hand. There are many different types of water level controls, the specific devices that are on your boiler will determine the appropriate spare parts (a spare level sensing device, loop control device, etc.) to have on hand should something fail.


Before making a purchase decision on any boiler spare parts to keep on hand, consider the cost to carry vs the cost of downtime. While downtime is generally very expensive, this should still be considered on a case by case and equipment specific basis. If, for example, your facility has full boiler redundancy, this could reduce the need to keep all manner of spares on hand. Likewise, if your facility is very near suppliers who regularly carry these parts, this may be less of an issue under normal circumstances. Ensure your facility has a contingency plan with contingency boiler connections and you will have a robust set of options when problems occur.

One good way to approach this is to first identify the most critical components of your system. Then determine the associated costs of carrying that component. Finally, consider the space available to store that item verses the lead time required to obtain that item should an emergency arise. If the item has a long lead time and you have the storage capabilities, you should carry the spare part. These days, even seemingly easy to acquire parts with shipping time of a few days can cause an unnecessary prolonged outage.


When it comes to deciding which boiler spare parts to keep on hand, the quantity and type of replacement parts you need will vary depending on the application. For instance, critical facilities like hospitals or manufacturing plants that cannot afford a boiler to be down require a large in-house spare part stock of fuses, selected controls, heating elements, and gaskets.

Additionally, it is best to consider the cost of downtime, storage space, the shelf life of the parts, and storage cost before purchasing boiler spare parts. Also consider redundancy and the critical aspects of your operations before investing I a large stockpile of spare parts. Finally, develop a relationship with your local service provider. Work with your trusted service provider to establish a regularly scheduled maintenance plan and ensure that you have a trusted partner in the event of an emergency.

avoid critical failures -keep these boiler spare parts on hand


Are you unsure which spare boiler parts to keep on hand for your specific situation? Do you know which boiler spare parts have longer lead times than others? Not sure what parts are critical for your mechanical equipment? Are you in need of boiler parts or repair? Contact the Powerhouse Combustion & Mechanical Corporation team and our boiler room experts to find the best solution.  Do you want a specific list tailored for your equipment? Claim it here

Reach out to the experts at Powerhouse Combustion & Mechanical Corporation to ensure your facility is ready should an emergency arise. Call us at 1-800-707.9242, email, or contact us online at www.powerhouse-combustion/contact.

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23 Spare Boiler Room Parts to Keep on Hand