Leseprobe_Berichte_363

2021 

DVS-BERICHTE 

1 st Digital International 

Congress on Aluminium 

Brazing 

and 

Aluminium Heat Exchanger 

Technologies for HVAC&R

® 

® 

Pioneered Flux Technology – 

Connected Thinking. 

www.ahlersheinel.de 

NOCOLOK ® – 

Pioneered Flux Technology – 

Connected Thinking. 

With NOCOLOK ® , Solvay Fluor has been the pioneer for aluminium 

brazing for many years. NOCOLOK ® is the world market leader and 

trendsetter and customers know: “NOCOLOK ® is more than just a flux”. 

An extended global network of specialists locally assist clients in all matters. 

Research on new fluxes is continuously carried out in the development 

and production hubs. 

Respectful partnership, achieving success together through innovation, 

global thinking and local support – NOCOLOK ® is limitless. 

www.nocolok.com

Heat Exchanger 

material 

Global capabilities 

We offer: 

• Experience, quality and 

a global footprint 

• Long-term customer partnerships 

• Collaborative material development 

together with our customers and 

expert research centers 

• Technical support from all of our plants 

• Unique solutions 

Aleris Rolled Products Germany GmbH 

Carl-Spaeter-Straße 10 · 56070 Koblenz · Germany 

Tel. +49 (0) 261 891 0 

info.heatexchanger@novelis.adityabirla.com

1 st Digital International 

Congress on Aluminium 

Brazing 

and 

Aluminium Heat Exchanger 

Technologies for HVAC&R 

Lectures of the digital event carried out from 

4 th to 5 th May 2021 

Organiser: 

DVS – German Welding Society, Düsseldorf

Bibliographic information published by the Deutsche Nationalbibliothek 

The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; 

detailed bibliographic data are available in the Internet at http://dnb.dnb.de. 

DVS-Berichte Band 363 

ISBN 978-3-96144-087-0 

The lectures are printed in form of manuscripts. 

All rights, also for translation, are reserved. The reproduction of this volume or of parts of it only 

with approval of the DVS Media GmbH, Düsseldorf. 

© DVS Media GmbH, Düsseldorf 2021 

Printing: Print Media Group GmbH & Co. KG, Hamm

May 4 – 5 2021 – Online 

1st Digital International Congress 2021 on Aluminium Brazing 

and 

Aluminium Heat Exchanger Technologies for HVAC&R 

together with a Digital Exhibition 

Dear Ladies and Gentlemen, dear colleagues, 

We warmly welcome you to the 1st Digital International Congress on Aluminium Brazing in combination with 

Aluminium Heat Exchanger Technologies for HVAC&R. 

Many things in our life have changed dramatically since the last congresses in 2018 and 2019. The Covid19-virus 

has taken a firm grip on the whole world. Production in a lot of companies was affected and global supply chains 

were interrupted. In 2020, the Aluminium Brazing event had to be cancelled - and this year we are moving the 

International Conference Heat Exchanger Technologies for HVAC&R into the virtual world. 

For this reason, we brought together the best of both special fields and we look forward to welcoming you to the 

first Digital Congress on these two topics. A Digital Exhibition will complement the congress. This event will unite 

scientists, engineers and technical personnel from all over the world, who are involved in the research, development 

and application of aluminium brazing technology. 

Even in these times the technical developments are progressing. Everywhere digitalization has advanced, business 

processes have been optimized and customer relationships were strengthened. Joining and brazing as well 

as heat exchangers production are complex technologies that need to be continuously developed. They are based 

on current research results, applicable standards and guidelines as well as adapted training methods. 

DVS is pleased and proud to meet the attendees on this international virtual platform. We would particularly like to 

thank the presenting authors for their valuable contributions. We thank all participants for their interest and we wish 

everyone an interesting congress. 

Dr.-Ing. Roland Boecking 

General Manager of DVS 

German Welding Society

Table of contents 

Preface 

Opening Presentation (First Day) 

Kent Schölin, Sofia Hedevåg 

Carbon footprint study of aluminium brazing sheet ............................................................................................... 1 

Equipment 

R. Hodgkinson, J. Jarman, L. Sansby 

Skin Test – Helium/Hydrogen Leak Testing by Vacuum Engineering Services / 

A theoretical analysis of the Vacuum Technology and related leak detection equipment...................................... 6 

A. Bielewicz, M. Stempniewicz 

SECO/WARWICK Active Only CAB furnace - the smart solution for brazing of diverse alu-minum 

heat exchangers .................................................................................................................................................... 8 

Applications 

Dr. Alexander Rehmer, Dr. Andreas Haas, Dr. Jurgen de Kimpe, Dr. Serge Lievens and Dr. Hans-W. Swidersky 

Project Study of Gel Formation in Engine Coolants - and Considerations for the Development 

of Further Improved Coolant Compositions .......................................................................................................... 15 

M. Ranger 

Assessment of Interactions Between Post-Braze Nocolok Flux and Engine Coolant in the Field 

and Several Means to Reproduce in the Laboratory ............................................................................................ 22 

Process & Quality Control 

H. Zhao, S. Elbel, P. Hrnjak 

Impact of substrate surface features on brazing of microchannel heat exchangers ............................................. 48 

A.-G. Villemiane, L. Pasquet, D. Douksouna, J.-S. Lecomte, E. Fleury, C. Schuman 

Brazing cycle influence on the brazing joint microstructure and nanohardness – 

Behaviour law of the header-joint tube assembly for thermal shock heat exchanger simulation optimization ..... 56 

A. Siggel 

Development of a partial flux application system to reduce post-braze flux residue ............................................ 70 

D. Davies 

Quality Matters-Quality standards are there to be used not abused! ................................................................... 74 

Heat Exchanger Products for HVAC&R 

R. Beckert, P. Kazanowski, J. Maier 

High-Performance Multi-Micro-Port Extruded Tubes ........................................................................................... 75 

A. Große, R. Hermann, U. Wittstadt, B. Nitsch, A. Strehlow 

Multifunctional Heat Exchangers for Thermal Energy Storage ............................................................................. 83

Opening Presentation (Second Day) 

S. Jahn, F. Gemse, M. Matthes 

Recent developments in additive manufacturing of metallic materials .................................................................. 90 

Materials 

T. Suzuki, T. Yamayoshi, Y. Yanagawa 

In-situ brazing observation of removal behaviour of oxide film from Al-Si filler surface by 

brazing flux ............................................................................................................................................................ 100 

V. Saß, G. Bermig, N. Eigen, M. Lentz, M. Mrotzek, C. Wiens 

Heat Exchanger Materials for E-Mobility ............................................................................................................... 106 

P. Morak, G. Hanko, A. Trier, S. Hainthaler 

AMAG TopClad®PURE for improved brazeability ................................................................................................ 112 

Research and Development 

M. Türpe, B. Grünenwald, A. Sommer 

Contribution on New Results of Investigations of Aluminium Vacuum Brazing .................................................... 116 

L. Wojarski; H. Ulitzka; W. Tillmann; I. J. Rass 

Flux-free approaches for brazing aluminum alloys ............................................................................................... 122 

M. Sababi, L. Ahl, D. Abrahamsson 

Effect of the flux on the reactivity of cooling systems aluminum alloys with Ethylene Glycol-based Coolants ..... 130 

Testing and Design 

L. Orman, H. Swidersky 

Analysis of Brazing Imperfections by Metallographic Investigation/Optical Microscopy ....................................... 131 

L. Peguet, H. Noui, F. Raffin 

A SWAAT procedure based on time to perforation and its use for studying the effect 

of metallurgical and process parameters on corrosion resistance of automotive brazing sheets ........................ 141 

M. Cornejo, F. Ritz, B. Jacoby, S. Kirkham, A. Smeyers 

Corrosion in brazed heat exchanger materials: Measurement techniques for optimised 

and application specific material designs .............................................................................................................. 147 

List of authors ................................................................................................................................................ 156 

Index to Advertiser ....................................................................................................................................... 158

Carbon footprint study of aluminium brazing sheet 

K. Schölin, Finspång/Sweden 

S. Hedevåg, Stockholm/Sweden 

Aluminium is generally regarded as a green material based on its recyclability, light-weight, corrosion resistance, 

barrier properties etc. However, the production of primary aluminium is energy intensive due to aluminium’s strong 

affinity to oxygen and the process required to split aluminium from said oxygen. Re-melting recycled aluminium 

saves up to 95 % of the energy required to produce primary aluminium, but to maximize value of the aluminium, good 

sorting of different aluminium alloys is required. 

Determining the carbon footprint of an aluminium brazing sheet requires a decision of system boundaries and a set 

of allocation principles to be put in place. It also requires a set of choices to be made regarding data and data 

sources. The choice of raw material will have a fundamental impact on the carbon footprint for an aluminium product, 

which is of course also valid for an aluminium brazing sheet. 

This paper introduces the concepts of carbon footprint calculations for aluminium brazing sheet products and the 

importance of raw material choice. 

1 Introduction 

Life Cycle Assessment (LCA), as a method to assess the environmental impacts of products in a life-cycle perspective, 

has been around for many years. In the aluminium industry it has also been used for quite a long time, but it is 

only recently that structured and transparent data have become available for a wider variety of aluminium products. 

So-called Environmental Product Declarations (EPDs) according to ISO 14025/14067 are for example available for 

slabs (example from Alcoa) [1] and building sheet [2-4]. No such declarations are available for aluminium brazing 

sheet. 

The carbon footprint for an aluminium product (which can be expressed as tonnes CO 2 

equivalents generated per 

tonne aluminium produced) can be presented according to some different standards. The standards referred to above 

(ISO 14025/14067) which result in a third-party verified EPD, requires that so called Product Category Rules 

(PCR) are established. This in turn requires an industry-wide effort where rules for how to calculate the carbon footprint 

as well as other environmentally important factors are agreed. ISO 14025 is an extension of the standards for 

life-cycle assessments (ISO 14040/14044), where the latter allows for a wider flexibility in how to calculate the footprint. 

The rules for how to calculate are decided by the reporting company, but they must still be transparent and 

verifiable by a third party. 

Gränges has chosen to report in line with the ISO 14040/14044. Several environmental factors have been calculated 

on a product level, but only the carbon footprint results are presented here. 

2 Scope and calculation method 

The first step is to select the system boundaries. Gränges has chosen to calculate and report a cradle-to-gate scope, 

which means that all carbon generation from mining up to delivery out of Gränges’ premises is included, see Figure 1. 

Figure 2 illustrates, in some more detail, the relevant processes upstream (blue) and within Gränges’ operations (red). 

The goal of Gränges’ carbon footprint study is to have third-party verified carbon footprint data available for all products 

delivered, but for the sake of simplicity and clarity a few selected products are presented in this paper. The 

choice of products was done to illustrate the variety in carbon footprint that results from selecting different raw materials 

and processing. 

The three chosen products are characterised as follows: 

1. Unclad fin material, high share of purchased recycled material used as raw material 

2. Clad tube material, high share of internally recycled material used as raw material for core alloy 

3. Clad tube material, high share of primary metal used as raw material for core alloy 

DVS 363 1

4. The generic process routes at Gränges’ premises are shown in Figures 3. For each process route the energy 

con-sumption was considered and used for carbon footprint calculation. “Common processes” include internal 

trans-ports, heating of buildings, packaging materials and rolling oils/emulsions based on annual environmental 

data. Allocation to each product is based on production volume. Recycled material from external sources has 

been calculated as “cut-off ”, i.e. the original production of the primary aluminium has been excluded, only the 

processing of the recycled material and inbound transport are included. For internally recycled material, a carbon 

footprint equal to the average of all purchased material has been allocated. 

Figure 1. 

System boundary for cradle-to-gate calculations 

Figure 2. 

Generic fl ow chart for upstream (blue) and core (red) processes. 

2 

DVS 363

Figure 3. 

Generic process routes of materials for three selected products 

The next step is to make decisions concerning upstream data sources. For production of raw materials and energy 

there are multiple data sources available, such as global averages, regional averages, country averages and in some 

cases supplier specifi c data. Supplier specifi c data should be used to the extent possible as that will provide the most 

representative result for the product. For raw materials contributing with small carbon footprints, average data is 

however adequate. The carbon footprint presented in this paper is based on upstream data ac-cording to Table 1. 

The calculation method and allocation principles used to determine the carbon footprint infl uence the results. The 

choice of upstream data will affect the total result for the whole system (in this case cradle-to-gate). The allocation 

principles applied will only impact the result per product, not the total result. 

Material that leave the system boundaries as scrap, and not as products, does not carry a carbon footprint. It means 

that the carbon footprint of such scrap must be allocated back to products that are sold. This allocation is done 

equally to all sold product as a so-called virtual yield. 

Table 1. 

Upstream data sources for main materials, energy and consumables 

Sourced slabs 

Primary ingots 

Alloying elements 

Externally recycled material 

Electricity 

Liquefi ed petroleum gas 

Transports 

Consumables 

Supplier specifi c data 


Global industry average data 

Supplier specifi c and internal data 



Average data for different transport modes 


3 Results 

The product carbon footprint results are shown in Figure 4. It is clear that the majority of the carbon footprint is generated 

in the primary aluminium production. Alloying elements are primarily manganese and silicon, and their contribution 

is quite small in comparison. The contribution from inbound transports is hardly noticeable. 

Gränges’ share of the total carbon footprint is also small in comparison, however it is clear that products 1 and 2 have 

a larger contribution compared to material 3. The reason is that material 3 uses a sourced slab as core material and 

there is thus no casting done internally at Gränges for this core material. 


Figure 4. 

Carbon footprint calculation results 

Figure 5 illustrates the detailed breakdown of the carbon footprint from Gränges’ operations. It shows clearly the 

dominating infl uence of re-melting and casting compared to other processes. Hot rolling, cold rolling and heat treatments 

require quite signifi cant amounts of energy but as electricity from low-carbon sources is used, the additional 

carbon footprint contribution is still very small. Common processes have a signifi cant infl uence on the carbon footprint 

and especially so when sourced slabs are used. 

Figure 5. 

Carbon footprint calculation results from Gränges’ operations 

4 


4 Discussion and conclusions 

The focus on sustainability in all areas of society has increased dramatically during the last decade and is expected 

to continue to increase, for example due to ever more apparent consequences of global warming. Aluminium can 

play an important role in the strive towards sustainable solutions, but this will require clear and transparent reporting 

of the environmental impact of the aluminium material on a product level. 

As primary aluminium production is very energy intensive, the value of secondary aluminium as a raw material cannot 

be underestimated to reduce environmental impact. On a practical note it is however important to understand that 

primary aluminium is and will be required as a large part of the aluminium products remain in service for a very long 

time. In addition, the use of aluminium continues to grow thanks to aluminium’s “green” profile, manifested by for 

example light-weight, corrosion resistance and barrier properties. 

Positive environmental impact, where the carbon footprint is a prominent part, will thus require both increased use 

of secondary aluminium and a reduced carbon footprint from primary aluminium production. 

As Gränges is a semi-fabrication manufacturer in the value chain, the company needs to identify low-carbon primary 

aluminium smelters for sourcing of primary slabs and ingots. By collaborating with these suppliers, Gränges is 

pushing for more low-carbon primary aluminium production. 

An increased use of secondary aluminium requires efficient recycling in every step of the product manufacturing as 

well as at the product’s end-of-life. Efficient recycling basically entails efficient sorting of alloys to be recycled to be 

able to keep the value of a specific alloy. Brazing sheet, being a composite material where a core is clad with functional 

layers, poses a specific challenge in this respect. Sorting needs to be done in a manageable number of groups 

but also dynamically, taking changes in product portfolio into consideration. Maximizing the recycling of clad material 

also requires a dynamic approach when making the recipes for each alloy to be cast. 

The following conclusions can be drawn from the results: 

• The method for calculating carbon footprint must be thoroughly defined on a product level. 

• Primary aluminium accounts for the largest effect on the product’s carbon footprint. 

• For Gränges’ operations, re-melting and casting have the biggest effect on carbon footprint. 

• Carbon footprint calculation on product level is a powerful tool to understand and improve sustainability performance 

and trigger product development geared at sustainable and circular aluminium alloys. 

More details regarding the carbon footprint calculation principles can be found on Gränges’ website [5]. 

Literature 

[1] https://www.alcoa.com/global/en/what-we-do/aluminum/cast-products/pdfs/Alcoa-EPD-Cast-Products. 

pdf 

[2] https://www.european-aluminium.eu/resource-hub/building-products-epd-programme/ 

[3] https://www.environdec.com/Detail/?Epd=11457 

[4] https://www.environdec.com/Detail/?Epd=9898 

[5] https://www.granges.com/sustainability/sustainable-product-offerings/ 


Skin Test – Helium/Hydrogen Leak Testing by Vacuum Engineering Services / 

A theoretical analysis of the Vacuum Technology and related leak detection 

equipment 

Redfern, J; Hodgkinson, R; Sansby L - Vacuum Engineering Services, (UK, Manchester, USA.) 

Begun in 1994, Vacuum Engineering Services have been at the front end of design and manufacturing of Helium/ 

Hydrogen Leak Detection Equipment. The Skin Test Project is for leak testing all brazed products for many different 

industries. Vacuum Engineering Services undertook initial concept and design in early 2017, where the goal was to 

revolutionise the market. There were two main aims: 1) Faster Cycle Time and 2) Smaller Footprint. This paper highlights 

the results of a three-year study, that found a 60% reduction in pump time, reducing the cycle time by up to a 

quarter and 3-time smaller footprint. Other results achieved were a potential lower service cost, lower running cost 

and faster lead time. The theoretical analysis by the USA technical centre, which has been backed up by hardware 

testing in the UK can conclude the skin test method has achieved the results it set out to accomplish. Further testing 

is required to determine the protection of the surrounding area due to part rupturing at different pressures and volumes. 

1 Title of chapter 

Skin Test – Helium/Hydrogen Leak Testing by Vacuum Engineering Services / A theoretical analysis of the Vacuum 

Technology and related leak detection equipment 

6 


Literature 

[1] Chen D, Nan L, Yuryev D, Baldwin K, Wang Y, Demkowicz M. (2017) Self-organization of helium precipitates 

into elongated channels with metal nanolayers. Science Advances, Vol 3 no 11. 

[2] Hoffman D, Singh B. (1998) Handbook of Vauum Science and Technology. Academic Press, San Deigo 

[3] Protolabs. (2019). Thermoplastic Material Selection for Injection Molding. https://www.protolabs.com/resources/white-papers/thermoplastic-material-selection-for-injection-molding/. 

[2019] 

[4] Rottlander H, Umrath W, Voss G. (2016) Fundamentals of leak detection. Leybolb GmbH Vacuum Engineering 

Services. (1994). www.vac-eng.com. [2016-2019] 

[5] Wei H. (2017) Mechanical properties of carbon fiber paper reinforced thermoplastics using mixed discontinuous 

recycled carbon fibers. Advanced Composite Materials. Volume 27 – Issue 1. 

[6] Zhai H, Euler A. (2005) Materials Challenges for lighter-than-air systems in high altitude applciations. ATIO 

5th. Virginia Arlington. 

Advertisement 


SECO/WARWICK Active Only CAB furnace - the smart solution for brazing 

of diverse aluminum heat exchangers 

A. Bielewicz, M. Stempniewicz, SECO/WARWICK, Poland 

Controlled Atmosphere Brazing is the basic process for manufacturing automotive heat exchangers and many other 

applications such as HVAC, industrial cooling, power generation, household equipment, etc. The first series of brazing 

systems took place in continuous mesh belt lines. Since the 1980s, when SECO/WARWICK delivered one of the 

first CAB furnaces in the world, the CAB continuous furnaces are still the basic equipment / solution for mass production. 

Heat exchangers manufactures are not only OEMs which use high output CAB lines for mass production of similar 

sized products, but also smaller companies including the aftermarket sector which has significant diversity in size 

and type in their manufacturing programFor over 20 years SECO/WARWICK has been providing the market a 

semi-continuous Active Only® CAB furnace, which is the right solution for this demanding market. In the last few 

years, the Active Only® line has seen increased application in the HVAC sector for large size industrial condenser 

brazing and in the automotive sector for special products such as battery coolers or WCAC. 


The standard CAB process in a continuous CAB furnace line is done under protective atmosphere (nitrogen) at atmospheric 

pressure. The aluminum heat exchanger is brazed by way of molten filler metal and Nocolok® flux. On 

melting, the filler metal spreads between the fitted surfaces and forms a fillet around the joint, and during cooling 

forms a metallurgical bond. The filler metal melting temperature is under the melting point of the metals to be joined. 

In the continuous furnace the belt moves at constant speed and operator places the product on the belt with required 

spacing between the parts. This solution yields the highest production efficiency in numbers and cost per piece. The 

belt speed is a basic parameter which determines the output of the furnace. 

Fig.1. 

Radiation continuous CAB furnace 

However, the continuous furnace has limitations in flexibility because at the same belt and temperature settings only 

products of similar size and type can be intermixed. 

Upgrading of the radiation continuous CAB line (Fig. 1.) by adding a convection preheating chamber (Fig. 2.) improves 

the flexibility of the CAB line and allows the user to braze more demanding cores; however, this will still not 

satisfy clients regarding short series brazing with a high intermixing brazing program. 

Fig.2. 

Radiation continuous CAB furnace with convection preheating chamber. 

8 


Due to technological limitations of the continuous CAB furnaces, the operator requires additional time to change the 

brazing profi le for a dedicated heat exchanger, for example, switching to a truck radiator brazing after condenser 

brazing cycle. Additionally, before new parts are introduced, dummy parts are placed down for stabilization the furnace 

which also takes additional time. In total, the production breaks for process conversion are about 30-60 minutes. 

From a production planning point of view, power consumption and labour cost for any brazing program infl u- 

ences the fi nal production output and as well as the single unit cost. 

2 Active Only ® CAB furnace. 

The equipment which allows the user to eliminate the need for the production break to change process settings is 

the Active Only® CAB furnace (Fig. 3.). The heart of this equipment is the convection brazing chamber (Fig. 5.). 

When the load is moved into the chamber the process begins. After the brazing process is fi nished the door opens 

and the load is moved to the following atmosphere (indirect) cooling section. This indexing movement of the products 

from one section to the following one is called semi-continuous mode. 

Fig.3. 

Active Only ® CAB furnace 

The load area is custom designed to meet the particular requirements of each customer. The entire useful area can 

be covered by heat exchangers (Fig. 4.) for processing and brazing. In contrast to the continuous type CAB lines, the 

Active Only® CAB furnace does not require the operator to maintain any spacing between the parts. The load area 

could be covered by as much as the size of products allow for it. Also, the orientation of the parts to the belt movement 

direction is not important. So, it allows the possibility for the most effective utilisation of the load area. 

Also, light heat exchangers can be stacked on two or more layers, providing an even denser, more effi cient production 

cycle. 

Fig. 4. 

Load tray with products 


The semi-continuous system can be provided as a fully integrated production configuration including Thermal 

Degreaser with Afterburner, Fluxer Unit, unloading table after Fluxer unit and the Drying Oven in the front of Active 

Only® CAB furnace. The Thermal Degreaser and Fluxer operate in continuous mode to assure work safety of the 

degreaser and stability of the fluxing process parameters (identical to the continuous CAB equipment). Every process 

step before the Dryer, starting with the CAB line loading table, works in semi-continuous mode. A common 

mesh belt for the Dryer and Active Only® furnace indexes at a time interval which is based on data feedback from 

the control system of the furnace. 

After the drying/debinding process, the load is conveyed into an insulated entrance purging chamber. The entrance 

chamber maintains the load temperature and removes oxygen from the chamber and product by purging it with nitrogen. 

This ensures that the atmosphere in the brazing chamber will not be contaminated with oxygen once the load 

is moved into it. In the brazing chamber the load is heated to the pre-determined recipe brazing temperature. 

Total brazing time in brazing chamber consists of the time for heating the parts to brazing temperature and soak time 

at brazing temperature (also defined in recipe). 

The brazing chamber utilizes a set of thermocouples. An overtemperature thermocouple is located outside the muffle to 

prevent the heating chamber from exceeding a preset temperature setpoint. A process control thermocouple is placed 

directly inside the muffle, in the nitrogen stream between the muffle and recirculation baffle. This thermocouple provides 

setpoint temperature control data for the ACCUBRAZE® computer control system. Load thermocouples – one directly 

above the load and one beneath the load – read the nitrogen temperatures near the load area. When the load is moved 

into the brazing chamber, the bottom load thermocouple senses the temperature of the atmosphere before the product. 

The top thermocouple senses the temperature of the recirculated atmosphere after passing through the load. At the 

beginning of the heating process the top thermocouple records a lower temperature than the bottom one. 

Fig. 5. 

Convection brazing chamber cross section 

The greater the load mass, the greater will be the temperature deviation between top and bottom load thermocouples. 

When the average temperature recorded by load thermocouples reaches the brazing temperature, the control 

system starts counting the soak time. Reaching the brazing temperature indicated by the load thermocouples means 

that the load is not absorbing the energy from the circulating nitrogen anymore. It is a signal that the load has 

reached the brazing temperature. 

When the brazing temperature is achieved and the preset soak time has elapsed, the load is moved into an atmosphere 

cooling chamber to solidify the braze joints. 

The functionality of the load thermocouples as described above allows the operator to reduce the main recipe parameters 

in the Active Only® CAB furnace to only the two mentioned before: brazing temperature and soak time. 

Regardless of the type, mass, or design of the brazed heat exchangers, the time needed to heat up the part is determined 

by its energy absorption. It is one of the main advantages compared with any type of continuous CAB line. 

Considering the time required to heat up the parts, an Active Only® production rate of two to five loads per hour can 

be achieved, depending on the mass and type of heat exchangers. 

10 


In comparison to continuous CAB furnaces, there are no re-tuning times between individual trays (i.e., different types 

of heat exchangers). 

Because of this ability to accommodate an intermixed manufacturing program, the Active Only® furnace produces 

higher output than continuous furnaces. It also achieves shorter heating times (Fig 6.) due to convection heating. 

Fig. 6. 

Temperature profiles: 1 – Active Only ® ; 2 – Continuous CAB line 

The most common sizes of the Active Only® semi-continuous controlled atmosphere aluminium brazing furnace are 

presented below: 

• 1200 mm x 1800 mm x 200 mm 

• 1500 mm x 2500 mm x 400 mm 

• 1400 mm x 4000 mm x 300 mm 

• 1200 mm x 6000 mm x 400 mm 

3 Special types of Active Only ® furnace 

Core types such as Plate and Bar in most cases require vertical positioning during the brazing process. SECO/ 

WARWICK offers a special design of Active Only® furnace with vertical loading. As for plate and bar products, it is 

common to use the paint fluxing method, so dedicated vertical Active Only® furnace for such applications is equipped 

with vacuum purging in the loading and atmosphere cooling chamber. 

For special applications SECO/WARWIC also provides standard horizontal loaded Active Only® furnaces with vacuum 

purging. It guarantees quality of the surface and brazing joints with low nitrogen consumption. This solution is 

especially recommended for plate design parts which are paint fluxed. 

Despite a wide range of available useful sizes of Active Only® furnaces, furnace output does not always meet user 

expectations. In response to our clients’ needs SECO/WARWICK provides an Active Only® furnace with double 

brazing chamber. The first chamber works as preheating section, and the second chamber is the brazing section. 

This solution allows the operator to reduce total cycle time while increasing output of the equipment. 

4 AccuBraze Control System 

The Active Only® brazing furnace system is controlled by a PLC-based system utilizing ACCUBRAZE® software 

developed by SECO/WARWICK, and hosted on an industrial PC as an HMI with touch screen (Fig. 8.). 


Fig. 8. 

ACCUBRAZE ® Control Screen 

The main features of the AccuBraze Control System are: 

• HMI interface with touch screen, 

• dedicated screens for each subsystem, 

• recipe manager for recipe creation, 

• protection of interface by access levels with password, 

• visual presentation of the electric and mechanical components on the screen, e.g., flow sensors, position sensors, 

valves, gas burners, fans, oxygen level etc. 

• visual presentation of the setpoint and real values, e.g., belt speed, temperature setpoints, real value, status of 

the units (ON, OFF, Alarm), 

• presentation of the actual position of the load in each section, 

• presentation of actual and historical alarms, 

• sending SMS to selected phone numbers with alarms, 

• maintenance screen including working hours for critical components and information, 

• I/O status screen. 

A SECO/WARWICK Active Only® CAB furnace provides the possibility of extended utilisation of the control system. 

Each process for each individual load can be fully described by the process parameters, not only by the data of the 

selected recipe but also by the list of alarms and all other information collected by the control system. Each load can 

be assigned an individual number which can be linked with the external central database system. The stored data 

can be exported or presented in the required form by SECO/WARWICK Data Portal system (Fig. 9.). 

The individual trays/loads can be processed on the same or a different recipe. In the Active Only® CAB furnace 

control system, users can create a list of recipes according to the production plan. The control system will automatically 

change the recipe following the order of the loads. 

Fig. 9. 

Example of Data Portal report. 

12 


Data Portal allows the operator to collect data and present it as a detailed report for each load as defined by the 

user’s individual method. 

The main features of the Data Portal are: 

General data: 

• access via web browser, 

• easy configuration using the configuration console, 

• user authorization system, 

• report generation in PDF format, 

• data export to CSV files, 

• making and restoring backups. 

Processes history: 

• displaying history of the processes, 

• processes list archive for a specified period of time, 

• statistics of quantity batches of the past 12 months, 

• statistics of batches according to a recipe, 

• a detailed report of the process, including a chart of process parameters, recipe, alarm list and 

• the parameters entered by the operator for each sections of the CAB line. 

Alarms and events: 

• display of alarm and events history, 

• alarms and events list archive for a specified period of time, 

• alarm filtering by group, 

• list of all instances of the selected alarm, 

• statistics of the most common alarms, 

• statistics of the longer alarms. 

5 Other CAB solutions 

The Active Only® CAB furnace is the most flexible solution among all types of CAB furnaces offered. However, it 

only allows the operator to braze the products in horizontal or vertical position, depending on the type of equipment. 

For some heat exchanger manufacturers, it is still not enough. They are looking not only for flexible but also for a 

universal CAB system which allows for both horizontal and vertical position of the load during brazing in the same 

CAB furnace. For them SECO/WARWICK provides the Universal CAB Batch Furnace which combines high brazing 

quality, universality and flexibility, all in one system. 

Fig. 10. 

Universal CAB Batch Furnace. 


In the basic configuration, the Universal CAB Batch furnace has a square working chamber, with a size determined 

by the dimensions of the products placed vertically or horizontally. It is composed of two sections: a loading-purging/ 

atmosphere cooling vestibule and a convection heated brazing chamber. It works in in/out mode but can be upgraded 

to semi-continuous system for increasing output. 

The SECO/WARWICK Universal CAB Batch furnace is also: 

• adaptable with additional upgrades (by adding / replacing modules) – e.g. Vacuum purging, a third chamber, 

etc. 

• optionally equipped with degreaser, fluxer, dryer, and final cooling, 

• a lower investment cost compering with the continuous or Active Only® CAB systems. 

• compact design, 

• easy to install and use. 

6 Conclusions 

Thanks to its specific features, the Active Only® CAB furnace is a very popular solution for aftermarket but also OEM 

heat exchanger manufactures. The flexibility of the load area, the benefits of the convection heating during the entire 

heating and brazing process and most of all, the sequencing process for each load to be carried out one after the 

other makes Active Only® CAB furnace a smart solution for brazing of diverse aluminium heat exchangers. In many 

cases it is a cost-effective alternative for continuous CAB lines. 

The Active Only® solution has been on the market for over 20 years. During those years SECO/WARWICK has 

continuously developed and modernized the concept to improve its effectiveness and reliability. 

The Active Only® CAB furnace was also chosen as the most suitable solution for SECO/WARWICK’s R&D CAB 

center to support clients in their brazing trials and to be a home base for continuous improvement of CAB equipment 

and technology. 

14 


Project Study of Gel Formation in Engine Coolants - and Considerations for 

the Development of Further Improved Coolant Compositions 

A. Rehmer (Solvay), A. Haas (Arteco NV), J. de Kimpe (Arteco NV), S. Lievens (Arteco NV) and H.-W. Swidersky 

(Solvay) 

During recent years, gel blockage in engine coolant systems with aluminum heat exchangers produced by CAB 

(controlled atmosphere brazing - using non-corrosive flux) has gotten more and more attention in the automotive 

industry. A general understanding of gel formation processes in engine coolants and the role that flux residues on 

internal surfaces of brazed heat exchangers may or may not have is of significant interest. 


The phenomenon of gel deposition in water-based automotive cooling systems such as radiators, heater cores, oil 

condensers, charge air coolers and oil coolers is well known in the industry. In the past, the stability of engine coolants 

was a challenge due to the high silicate level of the corrosion inhibitor. Silicates are one of the best-known 

protection against aluminum corrosion as they form a thin protective layer on the metal surfaces of the engine coolant 

system. Most of the commercially feasible soluble silicates in engine coolants are sodium or potassium silicates. 

However, the stability of such silicates under certain circumstances can deteriorate. Different key contributors 

can affect the stability of silicates in solution. These include high Si concentration (1400 ppm)[1], pH value below 10, 

presence of acidic compounds, high temperature and reaction with polyvalent ions such as Ca 2+ , Mg 2+ and Al 3+ to 

form insoluble species of silicates.[2] 

Today, the instability of such silicate corrosion inhibitors is mitigated by adding appropriate stabilizers into the engine 

coolant. Common stabilizers can be either silicon-based molecules such as substituted organosilicon car-boxylates 

or other derivatives such as polymers of acrylic acid with alkali metal or alkaline earth metals salts thereof.[3] A variety 

of silicate stabilizers exist with similar or different compositions which are used in today’s commercially available 

engine coolants. 

Despite the addition of silicate stabilizers, the risk for gel formation cannot be totally ruled out as long as silicates will 

be used as a corrosion inhibitor in the engine coolant formulation. Improvements of engine coolant formulations are 

necessary to reduce further any kind of gel deposition. In this paper, the role of flux residue and the use of silicate 

based engine coolants with respect to the gel formation process will be presented. Furthermore, a plausible mechanism 

of gel formation in engine coolants will be disclosed. 

2 Literature description of gel formation 

The IUPAC defines the term ‘gel’ as a “Nonfluid colloidal network or polymer network that is expanded throughout its 

whole volume by a fluid”.[4, 5] In other words, gel can be described as a solid three-dimensional network with a 

specific porosity. This porosity can be filled with a liquid (wet gel) or with a gas (xerogel or dried gel). A well-known 

gel is silica gel (SiO 2 

). The general gel mechanism in case of silica gel can be explained by a two-step process, 

which contains the hydrolysis of silicate (Na 2 

SiO 3 

) to silicic acid Si(OH) 4 

and the polymerization of polysilicic acid 

[SiO x 

(OH) 4−2x 

] n 

with the formation of siloxane bonds (-Si-O-Si-). Parameters affecting gel formation are pH, temperature, 

time and concentration. Due to the fact that aluminum heat exchangers are widely used in the automotive field, 

the following section in this paper focuses on gel formation of aluminum in solution and the link to silicate stability. 

When aluminum is dissolved in water under acidic or alkaline conditions, the formation of aluminum hydroxidegel is 

initiated. Two different types of aluminum hydroxide gels can form, depending on pH of the environment. In figure 1, 

the two different types of gel are shown. On the one hand, formation of pseudo-boehmite (AlOOH) will take place 

in alkaline conditions, which can crystallize rapidly to bayerite (α-Al(OH) 3 

). On the other hand, the formation of pregibbsite 

will occur in acidic conditions, which crystallizes slowly to gibbsite (γ-Al(OH) 3 

.[6] It should be noted that 

small changes in a medium with alkaline pH has a significant effect on the ratio of bayerite to boehmite at the beginning 

of the precipitation process. Hence, small changes in alkaline pH can cause a significant difference in the phase 

composition of the precipitates.[7] Furthermore, the presence of Al 3+ ions in aqueous silicate solution will promote 

gel formation. S. Sasahara and S. Ozeki[8] have investigated the effect of introduction of Al 3 

+ ions to silicate 

solution. The formation of four- and six-coordinated aluminum sites (Al IV , Al VI ) could be detected as a function of time. 

In the early stages of silicate reaction with Al 3+ ions a four-coordinated aluminum complex forms. These four-coordi-

Leseprobe_Berichte_363

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