supplied with fuel. It is kept at a value that has Information of importance in the operation of boilers must be recorded. This section provides information concerning the type of data that should be recorded in logs.
1. Steam pressures. Steam pressure is recorded by the operator from steam gauges and shows performance of automatic or 'manual control.
2. Steam flow. Actual output of the plant is recorded by the operator in pounds per hour to obtain steam flow. This record determines the number of boilers to operate for greatest efficiency.
3. Feedwater heater. Feedwater-heater pressure indicates whether proper deaerating temperature can be maintained in the heater. Feedwater-heater temperature shows the effectiveness of the feedwater heater. A drop in steam supply pressure or insufficient venting may cause low heater temperature.
4. Feed-pump pressure. Feed-pump pressure indicates effectiveness of the boiler feed pumps. If feedwater supply fails, the pressure reading enables the operator to determine whether or not the difficulty is in the feed pumps. The pumps are defective when the feed-pump pressure reading is below normal.
5. Forced draft. Forced draft is an indication of thickness of the fuel bed. The most satisfactory value varies with different installations and fuels and is determined by actual trial.
6. Furnace draft. Furnace draft, when used in connection with forced draft, should be slightly less than atmospheric pressure to prevent smoke from leaking into the boiler room and overheating the furnace lining. If only an induced or natural draft is used, furnace draft must be sufficient to cause the quantity of air required for combustion to flow into the furnace. Operating with a furnace draft higher than actually required results in excessive air leakage into the setting with an accompanying loss in efficiency.
7. Last - pass draft. Last-pass draft shows actual draft produced by a stack or an induced- draft fan. Fireman should become familiar with last-pass draft at various ratings when the boiler is operating satisfactorily. A decrease in last-pass draft with other conditions constant indicates leaking baffles. An increase in last-pass draft shows that gas passes are becoming clogged.
8. Percent CO2 flue gas. Percent CO2 flue gas is a measure of relative quantities of air been established as most satisfactory for the plant, fuel, rating, and like factors. In plants not equipped with CO2 recording meters, this value is determined with a hand gas analyzer. With experience, you can determine the correct amount of air supplied for a furnace by checking the draft gauges and from personal observation. In all cases, you should check values by use of a hand gas analyzer.
9. Flue-gas temperature. Flue-gas temperature is an indication "of the portion of heat "leaving the boiler with the flue gases. This heat represents a direct energy loss in fuel. Abnormally high flue-gas temperatures at a given boiler rating are caused by dirty heating surfaces or leakage of baffles. If the heating surface has a coating of soot and ash, heat that cannot escape is discharged to the stack. Leakage through baffles allows the gases to take a shorter path than intended and reduces contact of gases with the entire heating surface. Excessive fouling of the boiler's firesides increases the draft loss while leaking baffles decreases the draft loss. Either condition raises the temperature of flue gases above normal.
10. Fuel. Always determine the quality of fuel being used as this represents a major operating cost.
a. Pounds of coal. Procedures for determining the quantity of coal burned depends upon the means available. You may use scales that automatically dump weighed quantities of coal into the stoker or pulverizer hoppers. A register indicates the number of "dumps" that, multiplied by the weight of coal discharged per dump, gives the total. Another weighing method uses traveling larries equipped with scales so that the weight of each load can be recorded before it is dumped into the boiler hopper. In the absence of a weighing device, the quantity of coal consumed can be determined by filling and leveling bunkers at given intervals and recording the coal used from the report of coal received during a given interval. Methods for approximating coal burned by counting stoker revolutions are only estimates and are subject to considerable error when the size of coal changes.
b. Cubic feet of gas. The quantity of gas used is indicated on a meter. The readings can be direct or they may necessitate calculation by use of a meter factor.
c. Gallons of oil. Fuel oil quantities are determined by use of a measuring stick. Tables supplied with a given tank are then used to determine quantity from level of fuel. Tanks may also be supplied with gauges that can be read directly.Continue Reading