DRYING BANANAS 141 



The amount of warm circulating air can be varied 

 within wide limits, and the direction of the air current 

 can be reversed if required. The trays are interchange- 

 able, so that the material may be moved from one part of 

 the drier to another if desired, or taken elsewhere for the 

 bananas to " cool off " after drying, to prevent it forming 

 mould. Such an installation can easily be erected and 

 looked after by an intelligent person. The building costs 

 270. 



The Wolff system is worked either by live or exhaust 

 steam for drying tropical produce bananas, copra, cocoa, 

 rubber, maize, coffee, ground nuts, &c. from two tons 

 per day and upwards. 



By this system the material to be dried is carried in trays 

 on skeleton trucks running on light steel rails through a 

 long, low, cheaply built shed, in which the air is heated by 

 steam pipes on the ground level. The condensed steam 

 is automatically returned to the boiler. The temperature 

 is lowest at the end where the trucks make their entrance 

 through large doors. The process is thus continuous, 

 beginning with a comparatively low temperature, which 

 gradually increases as the line of trucks is moved forward, 

 and as the front truck containing the fully dried material 

 leaves the building, another is joined to the train at the 

 cool end. 



The temperature is never so high as is necessary when 

 the air has to be introduced so heated that it will be able 

 to traverse the drying house without becoming too cool 

 to be serviceable at a distance from its source. It can be 

 very easily controlled, so that it need never exceed that 

 which is best suited to the material in hand. When the 

 quantity to be dealt with is less than the full capacity of 

 the drier, it is best to reduce the firing and give more time. 



There is no complicated machinery to require the 

 attendance of an engineer. A simple boiler and fixed 

 steam pipes, with no moving parts, can be looked after by 

 an intelligent labourer. 



The trucks have roller bearings, so that a whole train 



