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Radio Free Trumpistan @[email protected] · 2026-06-17 · 18:41 UTC

#BoilerManual #ProtectingPressureParts #Section10 #Page5

matched. However, several other factors can effect steam temperature as well as alter the heat distribution pattern within the boiler.

Spray attemperators are used to balance the relationship between main steam and reheat steam temperature. With over-attemperation it is possible to overfire the boiler and still maintain steam temperature. Increased excess air and gas recirculation after the heat distribution within the boiler causing more convection and less radiant heat transfer. Variations in feedwater temperature requires a different firing rate to maintain steam temperature. A 10 F change in FW temperature results in about a 3 F change in main steam temperature.

The ability to alter steam and heat distribution independently of firing rate and steam flow means that fluid temperature throughout the boiler must be closely monitored to prevent overheating tubes in some circuits. While all temperatures are important, furnace tube temperatures are the most critical. The furnace tubes are exposed to the direct radiant heat of the fires, and along with the SSH tubes, are the most affected by errors in the firing rate/steam flow ratio. All tube temperatures must be kept below their alarm limits.

Tube temperatures also provide good indications of firing imbalance. The fluid temperatures in any circuit should be within 80 F of the average temperature of the fluid in the same pass. This is important to prevent both overheat failures and failures due to thermal stress caused by the temperature differentials. Thermal stress failures as well as a failure of attachments to the tubes can be further minimized if the rate of change of the fluid temperature at the convection pass outlet is limited to 100 F/hr. This limit is particularly important during startups and shutdowns.

All cyclone and furnace enclosure circuits are designed to permit a fluid leakage rate of 3% (126,000 lb/hr) of full load flow, over the load range. This built in safety factor insures that the fluid temperature in

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Radio Free Trumpistan @[email protected] · 2026-06-17 · 18:36 UTC

#BoilerManual #ProtectingPressureParts #Section10 #Page4

These same thermocouples are also important for SH protection during normal operation. As mentioned earlier, the primary method of SH protection under normal conditions is to balance steam flow and firing rate. The usual indicator that the two are properly balanced is the main steam temperature. There are, however, other factors such as excess air, gas recirculation, and spray attemperation, which affect main steam temperature. Hence, it is possible to have a proper steam temperature and still overfire the SH. Over attemperation is an excellent example, Main steam temperature would be correct, but SH tube leg temperatures could be dangerously high since firing rate and steam flow would not be properly matched

The outlet leg thermocouples also indicate firing imbalances across the width of the furnace. Tube outlet leg thermocouples can be used to minimize these imbalances and aid in combustion as well as protecting the SH from locally high gas temperature.

The special attention required by the SH's does not lessen the protection required by the rest of the boiler pressure parts and in fact, many of the SH protection measures also protect the furnace enclosure.

BOILER PROTECTION

As with the SH's, the primary method of protecting the boiler pressure parts against overheating is by maintaining the correct firing rate for each flow. This is due to the forced, once-through circulation utilized with the UP boiler. To insure that flow through each tube within each pass is sufficient to protect the tube, minimum flow and pressure requirements must be maintained. MINIMUM FLOW IS 33% OF FULL LOAD FLOW AND MUST BE MAINTAINED AT ANY TIME THE UNIT IS FIRED.

With the proper operating pressure, main steam temperature is usually the primary indication that firing rate and steam flow are

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Radio Free Trumpistan @[email protected] · 2026-06-17 · 18:29 UTC

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SUPERHEATER PROTECTION

Special attention must be given to protecting the superheating surfaces, particularly during startup as they are located in the hottest areas of the convection pass. During operation of the bypass system, fluid flow through the SH's is less than flow through the furnace circuits. The reheater is in effect an additional superheater inserted ahead of the intermediate pressure turbine and is placed in service in tandem with the SH, so it requires the same protection.

The two primary methods of protecting the SH's are to match fluid flow to firing rate during ramping and normal operation, and to limit gas temperature entering the SSH during startup until steam flow through each tube is sufficient for protection.

Gas temperature is limited to 1000 F entering the SSH until all water is removed from each tube and total steam flow is greater than 10% of rated flow. Ten percent flow is required to insure an even distribution of flow to each tube. The 1000 F limit is measured by the thermoprobes.

As previously stated, the superheater loops must be cleared of all condensate. The reason for the water removal requirements is that there can be no steam flow through a partially filled tube. Those portions of the tube not in contact with the water leg will be subject to high temperature and can overheat and fail. Water is removed from drainable SH's and RH's simply by opening all drains and vents. Removal is not as simple with the non-drainable pendant SH's and RH's since the water must be boiled away.

Thermocouples attached to the outlet legs of the SSH tubes will indicate when they have boiled out. The thermocouples will read saturation temperature while water remains in the tube. The reading will rise sharply as the tube is boiled clear and flow is established. SH tubes adjacent to the sidewalls are normally the last to boil out.

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Radio Free Trumpistan @[email protected] · 2026-06-17 · 18:21 UTC

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than 100 ppb. It is also extremely important to keep oxygen out of the system for corrosion prevention, even during the cleanup period. The turbine should be sealed, the condenser under vacuum, and the deaerator pressurized.

The unit must be purged of combustibles before firing is initiated. The purge cycle is extremely important in the prevention of furnace explosions. Most furnace explosions occur during these periods. Large amounts of combustibles may accumulate or pockets of combustible gas may form in almost any part of the boiler. When an ignition source is provided, their rapid ignition can cause an explosion. Purging the unit at a minimum of 25% rated air flow prior to lightoff removes the unburned combustibles and minimizes the possibility of explosions. The purge cycle should extend for at least five minutes with 25-30% of rated air flow.

As an additional precaution, the furnace should be post-purged with 25-30% air flow immediately following the removal of all fires. There is one important exception to this rule. IF ALL FUEL TO THE BURNERS HAS BEEN TRIPPED DUE TO FLAME FAILURE, INCREASING AIR FLOW TO MEET PURGE REQUIREMENTS COULD RESULT IN AN EXPLOSION. IN THIS CASE, THE PURGE PERIOD SHOULD BE EXTENDED BEYOND ITS NORMAL TIME LIMIT WITH EXISTING AIR FLOW. THIS WILL REMOVE THE COMBUSTIBLES WHILE AVOIDING THE DANGEROUS SUDDEN INCREASE IN AIR FLOW.

The frequency of furnace observation should be increased significantly during extended periods of low load operation. Dark and smoky fires indicate that the fuel is not being completely burned and the possibility of an explosion is increased. Burner adjustments may be necessary and excess air levels may have to be increased above normal; CAUTION: sudden changes in air flow should be avoided.

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Radio Free Trumpistan @[email protected] · 2026-06-17 · 18:17 UTC

This is the very last section of the boiler training manual, folks. None of this is light reading, but submitted to the public for mulling over just how intensely complicated these behemoths are, and to recognize the importance of making these things museum pieces so that others may learn from them--rather than demolishing them, for no two boilers are alike, not even the Baldwin Twins Units 1 and 2. Unit 3 was an antique GE drum boiler, which should also be deemed to be a museum piece, as well as its own history of operation.

#BoilerManual #ProtectingPressureParts #Section10 #Page1

Protecting pressure parts

Proper protective care of the boiler is essential to unit reliability. We often think of care of the boiler only in connection with maintenance. However, as an operator there is a great deal that you can do to protect boiler pressure parts and help ensure reliable operation and high availability. The need for these protective procedures is present from the initial filling through startup, during normal operating periods, shutdown and storage. The major concerns which we'll be detailing in this section are those which will protect the boiler against corrosion, overheating and thermal stresses.

GENERAL

High temperature differentials cause thermal stresses which can break studs, lugs and other attachments. Severe stresses limit the life of pressure parts. Therefore, the temperature of the water used to fill the boiler should be regulated to match the temperature of the boiler metals so that these stresses are minimized. Normally, water temperature should be within 100 F of metal temperature, and it should be at least 70 F.

All boiler vents should be open during the filling process so that any air in the boiler tubes is replaced with water. This reduces the possibility of oxygen corrosion while at the same time insuring that all boiler tubes are filled.

High quality water should be used for filling in order to minimize cleanup time and protect the boiler against waterside corrosion and deposition {which is why the facility also had its own complete water treatment plant for processing the lake water, and that even includes chlorination--and they used straight-up chlorine gas for that}. Water quality is no less important during startup than during normal operation, and firing is not permitted until cation conductivity is below one micromho at the economizer inlet. Fluid temperature is limited

to 550 F at the convection pass outlet until iron content is less

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