Solved Sample Problems

Problem No. 6.5.1

A boiler’s tubes have a scale thickness of 1.2mm (3/64 inches). If the boiler consumes 15 GJ/hour and operates 2,500 hours per year, what are the annual savings if you can clean the tubes and get the scale reduced to 0.4mm (1/64 inches) (on average). Assume “normal” scale. Fuel costs PhP 155/GJ.

Solutions:

The savings are approximately 3% minus 1%… So about 2% { 3/64 – 1/64 } = 0.20

Problem No. 6.5.2

If you have 1,500 fixtures operating 3,000 hours per year. The lamps within the fixtures are supposed to last 15,000 hours, but you want to do group relamping at 75% of rated life.

Solution:

The group relamping interval:

Problem No. 6.5.3

You find one 3mm (1/8 inch) compressed air leak on an 8 bar line. If energy cost is PhP 9.55/kWh, approximately what would you save each year if you repaired the leak?

Solution: