BOILER RATING

Rating of boiler can be specified as:

1) F& A 100˚C – From and at 100 Deg Celsius

2) kW Rating

3) Boiler Horsepower (BoHP)

4) MCR – Maximum Continuous Rating

F & A 100 ˚C

F & A is the measure of the maximum quantity of steam in kilogram per hour (kg/h) or (lb/hr) that the boiler may generate at atmospheric pressure when supplied with feed water at 1000C.

For example: If a boiler is rated as 2 TPH, F & A 100; it means the boiler can deliver 2 TPH steam at atmospheric pressure provided the feed water is supplied at 100˚C.

The actual operating conditions, the pressure of steam generation, and feedwater will change based on the configuration of the boiler and the need of the process application.

Therefore, we apply a de-rating factor,

Consider a 2 TPH, F & A boiler which generates steam at 10 Kg/sq.cm and the

feed water temp is 30˚C. Therefore,

 

De-rating factor =  540 / 663-30= 0.85

 

Where, 

Sp. Enthalpy of evaporation at atmospheric pressure = 540 Kcal/Kg

Sp. enthalpy of steam at operating pressure = 663 Kcal/Kg

Sp. Enthalpy of feed water temperature = 30 Kcal/Kg

 Therefore,

Actual Capacity: 2000 x 0.85= 1700 Kg/hr.

This can be understood from the graph below.

kW Rating

kW rating is the actual evaporation by mass. It can be determined by the amount of energy put to one kg of water.

Boiler rating with kW form can be calculated by using the following equation:

Boiler Horsepower (BoHP)

Boiler horsepower (BoHP) is one unit to show boiler rating, BoHP is commonly applied exclusively in New Zealand, Australia, and the USA. In New Zealand, BoHP rating is the formula of area of heat transfer and applies to heating surface of 17 ft2 in the boiler, seeing that shown in the following equation:

Boiler Horsepower (BoHP) = area of heat transfer (ft2) x (1/17)

Boiler horsepower (BoHP) isn't normally acknowledged conversion component of 1 horsepower = 746 Watts and also the frequently recognized 550 ft lbf/s.

Larger boiler capacity is generally given in lbs of steam evaporated per hour, under specified steam conditions.

 

MCR

Maximum continuous rating (MCR) is the capability of steam boiler to produce and provide the stated quantity of steam continually and easily with no all kinds of deficit or unwanted effects (for example overloading, slagging, or overheating) upon the principal steam boiler and its components.

Maximum continuous rating specifies the maximum output of the boiler at the specified operating pressure. I.e. if the rating specifies 2TPH at 10 kg/sq.cm it would deliver 2TPH at 10 kg/sq.cm.