Why Choose L&L Industrial Box Furnaces?

L&L Special Furnace Co., Inc. industrial box furnaces are a cut above the competition because we go the extra mile to do things that other furnace companies do not.

Our goal is to provide our customers with a variety of quality-critical features, from our sturdy exteriors to our robust, easy-to-maintain heating elements. We understand that our customers’ needs can change throughout the lifetime of their furnace. With these needs in mind, L&L not only focuses on features such as uniform heating and precise temperature control, but we pay careful attention to maintenance issues, as well. The result is an industrial box furnace that isn’t just a good fit on day one, but extends throughout the furnace’s useful life. Easy to use, easy to maintain, dependable, and precise are just a few of the words we hear from our customers time and time again when describing our furnaces in general and our industrial box furnaces in particular.

Sturdy Yet Attractive Exterior

Our focus on quality and performance begins with the exterior of our box furnaces. We start with a stiff, heavy outer shell and, in most cases, we use steel with a minimum .125 gauge thickness. To provide even more robust support for the outer case of our furnaces, we also employ case stiffeners. External bracing angles are welded to the entire case and base assembly, and the main seams are continuously welded for an attractive appearance. The entire case is primed inside and out with a high temperature (800°F) coat. The final coat for our furnaces is a heat-resistant enamel either in our attractive blue color, or optionally in custom colors as needed.

Easy to Maintain Refractory Panels

Maintenance is a crucial factor in extending the lifespan of a heat treatment furnace and optimizing the level of customer satisfaction. After several years of service, or if a new need arises, we also realize that the need for a rebuild is not uncommon. Many of our customers prefer to complete such rebuilds using their in-house maintenance teams, and we take that into account in the design of our furnaces. Ease of maintenance and straightforward rebuilds are some of the reasons why we use easy-to-remove insulating refractory panels for our brick-lined Box Furnace Series, which are commonly replaced during a standard rebuild. The brick sections are easy to install, too, and there is no need to employ expensive bricklayer specialists – we’ve designed them so that our customers’ maintenance departments can easily handle the removal and installation. In addition, all of the refractory panel sections fit together tightly with engineered heat locks. These heat locks serve to improve the insulating integrity of our furnaces even after many years of service, which is another benefit of our refractory panel design. L&L’s customer support is available for telephone consultation, and for on-site maintenance if desired.

Quality Insulation

Our medium-sized industrial box furnaces are insulated with 4-1/2” of low K factor refractory firebrick backed up by 2” of very low K factor mineral wool board on all surfaces except the bottom. The bottom has 2″ of hard calcium silicate backup for solid hearth support. Also layered on the bottom is low-density fiber back-up insulation. This combined layering yields an excellent combination of strength, insulating quality, as well as the fast heat-up and cooldown times which we discuss in a moment. The roof of all insulating firebrick-lined models that are 24″ wide or above is made from 2,600°F ceramic fiber modules to prevent roof failure. L&L’s larger models and most roofs use ceramic fiber insulation modules, either 2300F or 2600F grade, which usually never have to be replaced.

Precision, Dependable Temperature Control

L&L offers many options for temperature control, from simple, single set point controls to multiple program controls or PLC based. Your heat treatment process — no matter how complex — can have an L&L control system designed and suited to fit your specific needs. L&L uses solid state relays and multiple zone control with digital biasing for stabilizing and minimizing temperature gradients. A separate overtemperature system prevents the furnace from over firing.

Fast Heat Up and Cool Down

At L&L, we also understand that time is of the essence in heat treating. There are some things you just can’t speed up, but you can speed up the initial heat up and the final cooldown of the oven. An empty L&L industrial box furnace heats up to 2,000°F (1,093°C) in about 90 minutes. The high K.W. (superpower) option can reduce this to just one hour. As far as a cooldown, our industrial box furnaces take about five hours to reach 500°F (260°C). Cooling time can be further reduced by adding a venturi.

Element System

L&L’s element system is second to none when it comes to heating elements. Coil design is given our highest priority, and all considerations of watt density, stretch ratio and mechanical strength under heat load are evaluated. It’s just a fact that heating elements must be replaced from time to time. Most competitor furnaces require multiple steps just to gain access to the elements. However, our element system is unique in that all the elements can be easily accessed with the simple removal of an external cover panel.

We also use ceramic element terminal blocks that allow the element ends to be clamped without twisting the whole end around a terminal bolt, making it easy to remove an element. In fact, an element in an L&L furnace can usually be changed in less than 5 minutes. Also, the connection wires can be easily removed without disturbing the element termination. This design also allows you to isolate an element for a resistance check very quickly. In addition, L&L’s proprietary element terminal block features sturdy element posts with excellent electrical isolation characteristics.

Element Placement

Element placement is also key when it comes to superior performance. L&L’s element placement includes elements in all the sides as well as the back and door of the furnace. This type of element placement promotes excellent uniformity for heat coverage. In fact, this approach to element placement is the best method of distributing radiant heat energy at high temperatures – and is unique to L&L furnaces. Many furnace companies only provide heat from each side, which doesn’t provide anywhere near the same level of radiant uniformity.

XLE Series Furnace

If you need a precise, powerful, reliable industrial heat treatment furnace, allow us to introduce our XLE series. The XLE series furnaces are insulating firebrick lined, 2350°F electric box furnaces. They are unique in the furnace market because we have paid great attention to small details, interchangeable parts, serviceability, reliability, adjustments, documentation, and instructions. From the blueprints to the final assembly, we focus on what our customers need in a heat treatment furnace.

There are many models that are available in various sizes. While we offer standard configurations, each furnace in the XLE series has an entirely customizable feature list. This list includes options such as different hearth configurations, multiple heating zones, fans, cooling devices, door configurations, inert atmosphere control, racks, baskets, and loading devices. You can view some of our XLE options here. At L&L, our technical sales team will work with you to configure a box furnace to suit your specific heat treatment needs.

Note that we also offer a three-day, all-inclusive startup service as an option with each system within the continental US and Canada. For international customers, startup and training service is available by factory quote. All of our furnaces come with extensive instructions and documentation, also.

XLE Series Applications

The XLE series will most likely fit your application for processes such as general heat treatment, annealing, tempering, hardening, stress relieving, preheat, and other thermal processes. This series of furnaces also works exceptionally well in tasks such as thin film processing, glazing, ceramic bisque firing, and decorating. It can be used for everything from brazing, calcining, and drying, to the melting of glass and metals, glass annealing and bending, enameling, and sintering. Please see L&L’s resource page for a list of typical applications that the XLE furnace can be used for.

L&L services many markets and industries, including aerospace, medical, automotive, research and development, technical ceramics, and other fields. In addition, L&L’s XLE furnaces are all available with a pyrometry package for specialized aerospace, automotive and medical applications. This allows the furnace to conform to AMS2750E and soon-to-be-certified MedAccred guidelines, as well as many other pyrometry specifications.

L&L Furnaces – Your Best Choice for Industrial Furnaces!

L&L has been in the heat treatment furnace business for decades. We take pride in the precise temperature control and uniformity of our industrial furnaces, as well as their ease of maintenance and reliability. Quality, durability, and precision are built into our industrial furnaces as we consider our customer’s requirements all the way through the life of the furnace. Our XLE series of industrial box furnaces are a source of pride for our company. Our knowledgeable staff can help you customize an industrial box furnace to fit your specific needs, and we can provide the training and instruction required for you to get the most out of your furnace.

No matter what your heat treatment tasks may be, L&L has a furnace for you! Please contact L&L direct or via email to discuss your thermal needs.