Steam heat exchanger assemblies

Heat exchangers are a key part of steam and condensate systems. Our range consists mainly of plate heat exchangers, owing to their good pressure and temperature resistance, heat exchange efficiency, and compact dimensions. Typical applications include, for example, heating of process or addition water, condensation of saturated steam from turbines, and boiler blowdown, exhaust steam and flue gas heat recovery systems (economisers).

Heat exchanger manufacturing materials and the sealing method can be selected from a variety of alternatives depending on the target system’s operating values such as the medium, pressure, and temperature. Our heat exchanger modules are always dimensioned in a system-specific manner. The pre-contemplated module serves as a starting point for dimensioning, accelerating the design work and limiting the number of product variations. All of the components of our exchanger module are replaceable and have been chosen from our extensive range of suppliers to fit the purpose as exactly as possible.

Among the partners we represent, Gestra has launched its own range of ready-made heat exchanger modules, which mainly consists of larger tube heat exchangers. The water space in tube heat exchangers is larger, which means that the adjustment behaviour of exchangers heated by process steam is calmer.

The following process source data are required from the customer for module dimensioning: thermal input, flow rate, pressure and temperature, medium used, permissible pressure drop, expected contamination factor, and the over- dimensioning possibly required.

In modules produced by Konwell, high-quality Finnish plate heat exchangers by Vahterus are employed, the properties of which have been optimised with consideration given to the plant conditions. Extensive practical experience and ongoing product development have made Vahterus one of the best-known and high-quality heat exchanger manufacturers in the world, which is also demonstrated by several patents and awards for innovative solutions.

Heat exchanger control circuits, shut-off valves and steam traps have been chosen from the range of German manufacturers Gestra and ARI Armaturen, the quality of whose products has been established during Konwell’s decades-long representation.

Depending on the process, in connection with the heat exchanger, a heating steam dryer or special exchanger overheating protection may be required. We also deliver such special solutions according to the customer’s needs.


In general, the exchanger’s shell side functions as a steam space into which process steam is fed based on the set target temperature of the medium output line. The amount of steam released into the exchanger is controlled by a special control valve on the steam inlet side. The valve types used include self-operated temperature control valves or electric/pneumatic control valves. In the heat exchanger modules of building heating systems, a control valve is sometimes used on the heat exchanger’s condensate side as well. As regards safety arrangements, self-operated control circuits can be equipped with a self-guarding temperature limiter, but in electric/pneumatic systems, the range of available security and safety features is naturally more extensive. The correct selection and dimensioning of control valves is an extremely important part of a functional heat exchanger module.

Especially when starting the process and during substantial load variations, water hammer in the exchanger must be avoided – in other words, sufficient condensate discharge must be ensured.

Depending on site conditions, a steam trap or a steam trap with an integrated condensate lifter is installed at the heat exchanger’s discharge side, which is to direct the condensed steam that has ceded its energy in the exchanger into the installation’s condensate discharge line. A condensate lifter is needed if the differential pressure between the steam and the condensate line is so small that when the exchanger is at partial load the differential pressure fails to discharge the condensate from the exchanger. When the need for heat transfer decreases and the control valve starts to throttle the steam flow, the differential pressure inside the exchanger decreases as well. This leads to the reduction of condensate discharge; this response takes place in all heat exchangers irrespective of the exchanger over- dimensioning. As a consequence of the decrease in condensate discharge, the condensate level in the exchanger begins to rise, which leads to so-called heat exchanger stall.

Some heat exchangers are equipped with a vacuum relief valve to prevent vacuum generation and improve poor condensate discharge. However, through the vacuum relief valve, atmospheric gases can enter the system, which function as insulation in a heat exchange event. If a vacuum relief valve is not used, the condensate gas content and temperature variations are lower, which leads to improved heat exchange efficiency. Exchanger module corrosion problems and water hammer are eliminated as well, which means a reduction in maintenance costs. In addition, the need for process water chemical treatment is reduced. Plate heat exchangers by Vahterus are designed to be vacuum-resistant