cale removal time varies with the type of boiler, operating time, kind of feed water, operating condition and working temperatures. Boilers with excessive scale should be inspected every two weeks during the first month and cleaned with pressure water to remove chunks, scale and muddy sediment leached from boiler surfaces and accumulated on the bottom of boiler. Generally, most scale removal is completed in 60 days, except for iron/silica scale which may take up to two or three months longer for total removal. |
| Boiler Scale Insulating Properties | ||||
|---|---|---|---|---|
| Scale Thickness In Inches | Average Efficiency Loss | Oil Wasted Per 1000 Gallons | Coal Wasted Per Ton | Gas Wasted Per 1000 Cubic Feet |
| 1/64 | 4% | 40 | 80 lbs. | 40 |
| 1/32 | 7% | 70 | 140 lbs. | 70 |
| 1/16 | 11% | 110 | 220 lbs. | 110 |
| 1/8 | 18% | 180 | 360 lbs. | 180 |
| 3/16 | 27% | 270 | 540 lbs. | 270 |
| 1/4 | 38% | 380 | 760 lbs. | 380 |
| 3/8 | 48% | 480 | 960 lbs. | 480 |
| 1/2 | 60% | 600 | 1200 lbs. | 600 |
| 5/8 | 74% | 740 | 1480 lbs. | 740 |
| 3/4 | 90% | 900 | 1800 lbs. | 900 |
The insulating properties of boiler scale vary with the chemical/mineral composition of different waters. Therefore, it is difficult to quote the heat insulation value of any thickness of scale. The efficiency loss can be as high as 15% for each 1/16" of normal calcium-magnesium scale and over twice as high with iron/silica scale. However, the average heat loss caused by scale of various types can be summarized as shown in the above table. |