Centrifugal fans are commonly used in fertilizer and chemical plants. They can be designed for many and different sizes.

3D model of a steam turbine driven centrifugal fan 3D model of a steam turbine driven centrifugal fan

Large size fans, usually designed according to API standards, require the highest skill and they are adopted for the following services:

  • steam reformer forced draft fan;
  • steam reformer induced draft fan;
  • steam boiler fans;
  • fluidization air fans in urea plant.

After some years of continuous operation, for several reasons, centrifugal fans can face a reduction of their performances. On short term, Customer can manage the situation by increasing fan speed or damper opening, thus reducing flexibility in operation. However, after a certain time, performance can drop beyond an acceptable limit, and fans can become the bottleneck of the plant section.

In all those situations of underperforming machines, Casale is able to provide:

  • a full comprehensive investigation of all the issues that are badly affecting the performance of the fan, including an analysis of other connected equipment (like steam reformer o steam boiler);
  • the technical solution most fitting to Customer needs, from the revamping to the substitution of one or all components of the machinery train.

In all the below-mentioned cases, Casale can become the focal point for the Customer, and deal on his behalf with original or new manufacturers for centrifugal fan, drivers, and other main components.

In addition to the specific machine analysis, Casale is therefore able to provide an overall assessment of a part of the plant, that allows to specify the new conditions for the centrifugal fan that guarantee the perfect balance among investment cost, service life and process flexibility.

Case History 1

Sequence of installation activities at site


Site survey during revamping of a methanol plant.


The induced draft fan of the steam reformer (a centrifugal DWDI fan driven by a steam turbine) was not performing according to the design curves, running above the rated speed and facing vibration problems.


  • Space: new machine, even if bigger, needed to be placed in the existing building and match with existing suction and discharge connections.
  • Time: fan train replacement had to be performed during plant shutdown, in a short time frame.
Positioning of steam turbine driver in the buildingPositioning of steam turbine driver in the building


Completely substitute the centrifugal fan train with a new one of larger performances.


Fan replacement was successfully achieved respecting the schedule.

Case History 2


Ammonia plant revamping.


Two induced draft fans of a steam reformer installed in an ammonia plant were not operating according to the conditions required to cope with new process needs.

3D model of the revamped part of the plant 3D model of the revamped part of the plant


  • Activities to be performed during plant SD;
  • Turbine foundations to be reused;
  • No modifications to be done on fans;
  • One common lube oil system to be foreseen, due to space limitations;
  • State-of-the-art control and monitoring systems to be implemented;
  • New turbine manufacturer to be selected by Customer.


Replacement of the steam turbine drivers, taking in charge all the activities, from purchase to testing and commissioning on site.


Existing machine successfully tailored to the Customer requirements.

Steam turbine mechanical running test at Supplier’s workshop Steam turbine mechanical running test at Supplier’s workshop