Brazed Aluminum Heat Exchangers

Chart’s Brazed Aluminum Heat Exchangers (also known as a Plate Fin Heat Exchanger) and Cold Boxes are at the heart of low temperature natural gas, air separation and petrochemical processes worldwide.

Chart Industries pioneered the use of BAHX for cryogenic gas processing in the 1950s and we’ve produced over 13,000 units since. A Chart BAHX is a highly efficient, all brazed and welded compact heat exchange device that offers distinct advantages versus other heat exchanger types. They are designed in accordance with the world’s pressure vessel codes and deployed globally. Our principal design and manufacturing facility is in La Crosse, Wisconsin. Notable Chart firsts include the introduction of vacuum brazing, Core-in-Kettle®, mercury tolerant construction and Smart Layer®. 

Plate fin heat exchangers are essential for cryogenic gas processing applications including LNG liquefaction, Nitrogen Rejection, Natural Gas Liquids (NGL) Recovery, Propane Dehydrogenation, Hydrogen Recovery and other low temperature natural gas and petrochemical processes. In addition to stand-alone units Chart offers fully assembled and tested battery assemblies and Cold Boxes.

Brazed Aluminum Heat Exchanger
BAHX Nomenclature

BAHX Footprint Comparison
BAHX Footprint vs. Shell and Tube Heat Exchanger

BAHX are at the center of these applications

Industrial Gas Production

  • Air Separation
  • Nitrogen Liquefaction
  • Helium Liquefaction
  • Argon Recovery

Petrochemical Processing

  • Ammonia Purification
  • Ethylene
  • Hydrogen Recovery (HYCO)
  • Propane Dehydrogenation (PDH)

Natural Gas Processing

  • Nitrogen Rejection
  • Helium Recovery
  • Natural Gas Liquids (NGL) Recovery
  • Ethane Recovery

Liquid Natural Gas

  • Peak Shaving
  • Small & Mid-scale Liquefaction
  • Baseload
  • Floating LNG

Cold Box

Cold box Phases

Single plate fin heat exchangers can be supplied pedestal mounted and insulated locally in the field. However, when the service requires multiple units assembled in series and/or parallel and ancillary process equipment such as vessels and drums, a cold box is the most efficient solution.

Externally, a Cold Box is a carbon steel enclosure with flanged terminations to facilitate simple on-site connection to plant process pipework. It's best described as a process module incorporating all the following:

  • Supports and houses
    • heat exchangers
    • piping
    • other related cryogenic equipment
    • insulation material
  • Provides inert atmosphere
  • Modular assembly, includes instrumentation
  • Multiple services in a single piece of hardware
  • Complete, compact package

Chart’s primary Cold Box fabrication location is a 40-acre coastal facility in New Iberia, Louisiana, USA, providing direct access to the US inter-coastal waterway and the Gulf of Mexico.

New Iberia Cold Box Facility

Cold box manufacturing is supported by design and engineering from La Crosse, Wisconsin, and The Woodlands, Texas, USA.


Chart’s patented Core-in-Kettle®, introduced in 1989, further extends the use of Plate Fin technology in a range of petrochemical and natural gas processes as an alternative to traditional shell and tube kettle reboilers. Instead of a tube bundle, the external vessel houses one or more plate fin heat exchangers and provides around 10 times more heat transfer surface area and up to 20 times more ‘UA’ than the equivalent tube and shell unit.

The superior heat transfer performance can be utilized to produce a significantly more compact unit for new installations, or considerably more performance can be provided to existing installations by replacing the tube bundle with a BAHX retro-fitted into the same shell. This is a particularly useful solution for process plant debottlenecking.

Plate fin heat exchanger construction permits close temperature approaches down to 2°F (1°C), resulting in significant power savings and reduced compressor horsepower.

How does Core-in-Kettle® work?

  1. The warm process stream fluid enters the heat exchanger through steel inlet nozzle(s) on the vessel shell. The inlet nozzles are connected to the aluminum inlet pipes of the exchanger by an aluminum to stainless steel transition coupling.
  2. Inside the BAHX the warm stream cools as it flows against a cold stream.
  3. The cold stream enters the vessel either as a liquid or 2-phase fluid directly from a distillation column (or expansion valve in the case of a refrigerant).
  4. A liquid level is formed outside the BAHX core to create a liquid head that drives the cold stream liquid through the core
  5. A disengagement space above the core causes the liquid and vapour to separate.
  6. The cooled warm stream leaves the BAHX and vessel.
  7. The cold stream vapour exits the vessel through the outlet nozzles while the liquid falls back to be recirculated.
  8. A manway is provided in the vessel shell.

Core In Kettle

Continuous Innovation

We continually innovate to enable our customers to meet their challenges and to further optimize the performance and longevity of our equipment. Before you purchase your next BAHX, ask us about the following design and construction features:

Mercury Tolerant Construction - under certain conditions liquid elemental mercury can have a detrimental effect on unprotected BAHX. Chart’s proprietary solution combines multiple design, material selection and fabrication features that work in tandem with guard beds to protect against attack. Since pioneering the technology in the 1980s Chart has supplied >800 mercury tolerant units with no reported field failures.

Smart Layer® is a predictive maintenance solution intended to provide prior warning when a critical threshold in the operational life of a BAHX has been reached and where continued mal-operation is likely to result in loss of containment. The vast majority of BAHX provide trouble-free operation for 20 years+ when operated in accordance with industry guidelines. However, excessive thermal gradients will weaken the unit’s integrity and can lead to external leaks developing. Typically, because these operating upsets go un-noticed, the leaks manifest without warning. With Smart Layer the leak path is contained and an emergency plant shutdown is avoided.

Continuous innovation and investment in our technology and capacity enables our customers to maximize their opportunities.

Installation, Operation, Maintenance - Service & Support

Chart Lifecycle is dedicated to keeping your BAHX fleets operating with maximum efficiency and longevity. Of course, we’re there for you if things go wrong, but ultimately our focus is a proactive approach to improved plant safety and reliability through increased awareness of best practice, process control, effective personnel training and attention to operating data. Learn more at

You can also download our Installation, Operation & Maintenance manual and BAHX Product Bulletin from the literature section below.

BAHX Maintenance and Repair Services