thermal oil heating

i worked in a german build vessel which dosent have steam insted it has thermal oil heating system. in which boiler circulating tubes was circulated with thermal oil can any one tell me what are the disadvantages in such type of system

[seasriram]

The main disadvantages are
1. The thermal oil if started leaking, say any l/o heaters, it is difficult to separate thermal oil and l/o.
2 if it mixes with hfo, then it may cause carbonisation and thermal cracking of hfo...
3. This will impair the heat transfer co-efficient of the boiler.