Thermal technology

Designing your boiler room, installing your steam, thermal oil, hot water or central heating boiler, organising the heat transport to your users via pipes... we bring your production process or plant to the right temperature.

Thermal engineering

Our team of concept and sales engineers, project managers, project leaders and draughtsmen invariably manage to come up with the ideal technical solution for your heating needs or issues and are always happy to work it out for you in detail. On the basis thereof, you will receive a competitive quotation.

Our technology engineers keep a watchful eye on the technical standards and a keen eye on any innovations our R&D department comes up with.

Warmtetechnieken Engineering Callens


Our skilled, experienced pipefitters, installers, welders and electricians see to the qualitative and timely installation of your system.

Our commissioning engineers, for their part, ensure your system is commissioned and set correctly, and for its visualisation. Our 125-strong crew enables us to complete the most complex, time-critical projects, to your satisfaction.

Installatie warmtetechnieken Callens

Thermal system servicing

Technical problem or scheduled maintenance?

Our team of 21 skilled service engineers and burner technicians and 12 highly-trained maintenance technicians are at your beck and call seven days a week, 24 hours a day. Add to that our large stock of spare parts and its little wonder that you'll find a Callens team knocking at your door within 2 hours of your call, anywhere in Belgium.

We are proud to be able to offer you the most secure and reliable service in our sector.

Technologie thermique - service et entretien Callens

Working with Callens stands for... strength, reliability and safety!

Personal approach to customers and staff
In-house engineering department, staffed by experienced engineers
A-Z integration & total solutions
Unique service & intervention team


Steam boilers

Engineering, installation & service for all kinds of steam boilers.

  • Output: 25 kg/h - 55,000kg/h
  • Operating pressure: 0.5-30 bar
  • (Bio)gas – heating oil – biochemical fuel - electricity
  • Fire-tube boilers – coil boilers – waste gas boilers

Thermal oil boilers

More than 1,000 references

  • Output: 100,000-12,500,000kcal/h
  • Vertical and horizontal
  • (Bio)gas – heating oil – dual fuel
  • Emissions in accordance with Vlarem II

Energy recovery systems

  • Economisers
  • Condensers
  • Thermal degassing units
  • Heat exchangers
  • Waste heat recovery boilers
  • Deodorisation
  • ...

Industrial pipework

  • Steel
  • Stainless
  • DN10-DN1000
  • Fittings

Hot water boiler

We design hot water systems for specific circumstances:

  • for plants where they are the only option of connection
  • on request

Industrial central heating boilers

Smart, inspection-free option for processing temperatures of up to 110 °C:

  • Up to 8 MW
  • Low medium temperature
  • Direct fired
  • Can be combined with a thermal oil process for cooling

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