Boiler Protection in Dairy Sector

Reduce the risk of corrosion

Executive Summary

Reducing the risk of unexpected downtime is crucial for one of New Zealand’s leading dairy producers. Therefore equipment such as boilers need to be protected from corrosion when not in use. Accordingly, Humiscope have supplied Fisair desiccant dehumidifiers to control humidity levels inside of power generating boilers.



  • Reducedthe risk of corrosion inside the boiler (water side)
  • Lowered relative humidity to below 40% RH
  • Supplied small portable units that can be connected easily during down time.
  • 27 dehumidifiers supplied to 14 different sites around New Zealand


Challenge: Minimising the risk of corrosion

Dairy producers run and maintain their own boilers for onsite power generation. These boilers are taken ‘on-line’ and off-line’ on an as needs basis, dependant on site requirements. During these shut down periods a major challenge is keeping equipment in an ‘as left’ condition till there is a need to reactivate them.
When a boiler-plant is taken out of operation for shorter or longer period of time, equipment is at risk of corrosion occurring. This is due to the presence of moisture in the air. Moisture accelerates the rate of corrosion leading to malfunctions and the deterioration of parts and components in the boiler. Our client could not afford this to happen as any down time not only results in greater maintenance costs but the loss of production can be crippling to operations.  It was for this reason that the Reliability Engineer contacted Humiscope’s New Zealand office in order to minimise the risk of corrosion inside the water circuit of the boilers.


Solution: Control relative humidity levels with dehumidification

Rate of corrosion accelerates, when Relative Humidity crosses the critical level of 40%. Above this level industrial pollutants, like Sulphur-Di-Oxide, also, enhance the corrosion rate as the corrosion is faster when surfaces are exposed to polluted air in combination with high relative humidity. Hence, if the relative humidity of boiler’s pipes can be restricted to below 40% then a well-preserved condition can be maintained for immediate activation, whenever required.

We achieve this using Fisair desiccant dehumidifiers. Fisair desiccant dehumidifiers remove moisture from the air using a rotating desiccant wheel. The large surface area of this honey comb like structure absorbs moisture from the air, lowering the absolute humidity level of the air pumped into the boilers. These units have a robust construction, easy and simple maintenance, with a very long operating life.


Advantages of Desiccant system:

  • The dry air forced through the tubes carries off the remainder of water left after water purge. This protects the internal surfaces from corrosion and reducing the potential for tube fraction on restart.
  • It is easy to check whether there are corrosion risks by simply measuring the humidity at the air outlets
  • Less energy is required than the heating method and no dangerous and expensive chemical compounds are required for humidity conservation.


Results and Return on Investment

After a few site visits and discussions with our technical experts, the company decided to hire some of dehumidifiers from our rental fleet. This was to prove the technology and make a case study for management approval. After the successful installation of 5 hire units, management gave the approval for the purchase of 27 Fisair desiccant dehumidifiers to be used over 14 different sites in New Zealand. The equipment was slightly modified and sent with ducting ready to be used straight away by the end user.
The dairy company now has a reduced risk of corrosion inside the boiler resulting in worry free shut down periods. When the boilers are taken off-line and purged of water, our Fisair dehumidifiers are connected to an air inlet and blow air through the pipes. The dehumidifiers supplied are transportable and are easily connected with ducting when required.