What Material Should I Choose?

Selecting the right material for your heat exchanger is important and involves finding a good balance between the following:

  • thermal conductivity of the material
  • mechanical properties of the material
  • corrosion resistance of the material
  • cost of the material

These factors should be balanced with how the unit will be used when selecting the material to ensure the optimum life of the heat exchanger.

Some products such as saturated salt brines, sweet chilli sauce and sports drinks all offer challenges in material selection.  High levels of acidity or alkalinity often call for materials with different properties to the conventional austenitic stainless steels (304 or 316) that are suitable for many other “typical” applications.

 The photo above shows a Double Tube cooler for 25% salt brine.  The brine solution flows within the 1 inch SAF2507 inner tube with cooling water chilling it from 65 deg C to 20 deg C.
Hipex keep in stock a number of corrosion-resistant materials based on stainless steel. Having Duplex options available in-house, and combined with the ability to fabricate with these materials means that we can offer fast turn around on many Hipex models when others can’t. 

Selecting the correct material isn’t the last or only step in ensuring the long and happy life of the heat exchanger.  Factors such as correct installation, proper operation, effective cleaning and draining during downtime all combine to keep things under control.  The instruction manual included with your Hipex heat exchanger includes detailed information about all of these factors.  If you have any further questions, please contact one of the experienced team at Hipex and we will be happy to point you in the right way.

Care needs to be taken in regards to chloride levels in water.  High levels of chloride combined with elevated temperatures can lead to stress corrosion cracking in stainless steels.  Chlorides are (unfortunately) increasing in our water supplies, particularly those based on country river waters.  The water supply should be analysed and if necessary treated before use in the process.  Treatment is cheaper than damaged product and corroded equipment.

 The unit above is a hot fill pasteuriser for Sports Drink.  It can process a maximum of 11,000 l/h of Sports Drink.  The system uses two hot water sets to give more stable temperature control.  Low chloride potable water can (and should) be used to heat and cool the product prior to filling.  The regen section of this system utilises Double Tube heat exchangers with SAF2507 on both shell and tube sides in order to cope with the Sports Drink.
 
This large Polytube unit has SAF2205 tubes, tubeplate and multi-pass end caps and is suitable for cooling 40 l/sec of glycol at -5°C to approximately -6.5°C using a saturated calcium chloride brine  at -15°C.  The unit should be kept cold (below ambient temperature) and not allowed to become acid in pH otherwise corrosion can occur.  Duplex 2205 is more resistant than 316 stainless steel to stress corrosion cracking