Cast iron gilled surface was one of the first type of extended surface utilised in the economisers with steel tubes.


The purposes of the cast iron protection are :

1) Provide surface extension
2) Provide protection to the inner steel tubes against corrosion and/or erosion.


1. Checking of tube diameter; sometimes the tube must be machined (grinded) in order to obtain a precision of the diameter up to 1/100 mm;
2. cast iron sleeves are machined on the extremities to realise between one sleeve and the other a spigot and socket connection;
3. inside machining of cast iron sleeves, to obtain a regular surface on the internal diameter of the sleeve machined in the order of 1/100 mm, note that the internal diameter of the sleeve is lower than the outer diameter of the tube;
4. Fitting of the cast iron sleeves on the tube : this is the final step of the manufacturing; the shrinking is obtained heating the cast iron sleeves in a specific heater and then fitting them one by one or in couples on the tubes;

At the end of manufacturing the cast iron gilled sleeves are in intimate contact on 100% of the tube surface, thus ensuring a very performant heat transfer.

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