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Removable Insulation for Boiler Doors & Drum Covers

Thermaxx Removable Insulation Jackets are an excellent solution for improving boiler energy efficiency and safety.

Un-insulated boiler door

Uninsulated Scotch Marine Boiler – Before

Insulated boiler door

Insulated  Boiler – After







It is common knowledge that boiler rooms are uncomfortably hot year round, and that is a fact of life if you have steam boilers, right? Not at all! If your boiler room is hot it simply means that your system is not adequately insulated. And one of the largest culprits, literally, can be the boiler’s doors and drums.

About Boiler Doors and Drum Covers

Boilers are large closed containers where liquids, commonly water, are heated for industrial use, generating power and various heating purposes. Each boiler is made of high-grade metal, often steel, iron, copper or brass. Most hot water and steam boilers for central heating in medium and large facilities have one or more doors. The doors on a boiler need to be accessed so that the boiler can be inspected and serviced not only for maintenance but for insurance requirements as well. Based on what boilers you may have, the unit could have anything from very large hinged doors down to manholes just large enough for a person to fit inside The job of boiler doors is to allow access inside the boiler, while still maintaining an airtight seal and full structural integrity of the boiler. Some boiler doors may also require openings or ports for ventilation, observation, or other needs. Types of boiler doors and covers we regularly encounter include: access doors, steam drum covers, and mud drum covers.

Access doors are located in the front and/or rear of the boiler, access doors are typically fire doors which allow personnel to access the interior of the boiler for inspection and maintenance.

Steam drum covers are located at the top of a water-tube boiler, the steam drum is where dry, pure steam collects and is drawn off while the remaining water is passed back to the heat source. Problems with the steam drum causes, at the least, inefficient heat distribution and can also result in corrosion of the steam system or boiler malfunction. The steam drum cover allows inspection and maintenance for this vital component.

Mud drum covers are located at the bottom of some boilers, the mud drum (sometimes called a “bottom drum”) captures impurities and sediment from the boiler water. The mud drum cover enables removal of this sludge.

Insulating Boiler Doors and Drums

ThermaXX Removable Insulation Jackets can be designed to fit any style and configuration of boiler. Due to the size and temperature, insulating the boiler drums and doors offers the fastest return on your investment, economically speaking. Also, due to the large surface area and amount of wasted energy, this is the biggest contributor to greenhouse gas emissions on a steam system.

Boilers walls and ends are insulated by their manufacturers in order to keep the heat in the intended areas and maximize efficiency. By not sharing the same level of internal insulation like the rest of the unit, doors and drums can easily reach external temperatures of 350°F or more, and have a surface area of several square feet.  While the exact statistics vary by unit and system, the constant remains that you’re left with a large, hot surface that not only creates an uncomfortable ambient environment, but wastes energy while exposing personnel to unnecessary burn hazards.  

Boiler doors and covers all can reach rather hot surface temperatures. Surface temperatures may reach around 350°F in fire doors, 200°F in mud drum covers, and, for steam drums covers, the temperature of the pressurized steam which the drum contains. This presents a safety hazard for the workers at risk for coming into contact with these surfaces. In addition, a great deal of heat can radiate from boiler doors and cover, resulting in wasted energy.

Boiler access doors and drum covers all require regular use, making permanent insulation that would extend past these components unrealistic. Fire doors often have fire brick or other insulation in the interior but may still have unacceptable surface temperatures.

In our experience, boiler drum covers are typically not insulated at all. Some covers utilize cementitious insulation. Many applications of cement insulation from the 1970s or earlier contain asbestos and are not safe. In addition, cementitious insulation cracks and deteriorates over time, and is especially prone to damage when workman open and close the covers for maintenance.

Thermaxx creates custom jackets to fit your exact boiler door and drum, taking into account any additional piping, sight glasses, etc that was added during the unit installation. Creating a custom jacket ensures a great fit that will keep all heat where it should be and not leeching into your mechanical room. The good people doing inspections and maintenance will certainly appreciate the decreased touch and ambient temperatures.

Thermaxx has strong capabilities insulating the doors and drum covers of many boilers including sectional cast iron boilers, scotch marine boilers, shell boilers, fire tube boilers, and water tube boilers.

Your Thermaxx Jacket will be manufactured specifically for your boiler and made of high quality materials chosen to offer the best results, high durability and cost effectiveness. Attachments methods that are secure, yet easy to use such as Velcro, straps and D-rings will not only contribute to the performance of the jacket, but aid your staff by being easy to work with.

Custom insulated jackets for your boiler drums and doors will make your mechanical rooms more comfortable, safer, and more efficient. This step can forever vanquish the myth that boiler rooms are hot and scary; at least with the hot part!

Our capabilities in removable insulation are diverse, but our products have a few things in common:

  • The right fit: We produce covers to exact fit for your specific boiler door and cover needs. In addition, we can design custom boiler insulation “panels” for many applications.
  • Convenient: Our insulation jackets are designed to be able to be removed and replaced easily and quickly by any personnel. They typically use a simple closure system of velcro and D-rings.
  • Cost effective: We’ll provide the jackets that are compatible with your needs and device. We typically utilize 1” fiberglass for boiler insulation, but we can tailor design, materials, and thickness to your needs. Being able to buy exactly the jacket you need means you don’t have to pay for un-needed insulation.
  • High quality: Our jackets are painstakingly designed and crafted to remain effective under harsh conditions for extended periods of time. As with all Thermaxx Jackets, we stand behind our removable boiler insulation with a 5 year guarantee.

Got questions? We’re happy to answer any questions you have about our boiler insulation or any of our other removable insulation solutions for your facility. Fill out the form below or give us a call today at (866) 993-6299!


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