Boiler performance statements: identify the incorrect statement among the following. Context: Factor of evaporation (FE), equivalent evaporation, and boiler efficiency are standard boiler performance terms. Select the statement that is wrong.

Difficulty: Medium

The factor of evaporation for all boilers is always greater than unity.
The amount of water evaporated in kg per kg of fuel burnt can be expressed as equivalent evaporation from and at 100°C.
The ratio of heat actually used in producing the steam to the heat liberated in the furnace is called boiler efficiency.
None of the above

Correct Answer: The factor of evaporation for all boilers is always greater than unity.

Explanation:

Concept check

Factor of evaporation (FE) adjusts actual evaporation to an equivalent basis (from and at 100°C). It is not necessarily always > 1. FE can be less than, equal to, or greater than 1 depending on feedwater temperature and final steam state.
Equivalent evaporation expresses evaporation on the standard basis “from and at 100°C”. It may be reported per hour or per kg of fuel (i.e., equivalent evaporation per kg fuel).
Boiler efficiency is correctly defined as useful heat to steam / heat released in the furnace.

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