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Chapter 4

Chapter 4. Steam and Water Accessories. Feedwater Heaters • Feedwater Pumps • Surge Tank • Condensate Tank and Pump Unit • Main Feedwater Line • Steam Traps • Desuperheating and Pressure-Reducing Station.

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Chapter 4

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  1. Chapter 4 Steam and Water Accessories Feedwater Heaters • Feedwater Pumps • Surge Tank • Condensate Tank and Pump Unit • Main Feedwater Line • Steam Traps • Desuperheating and Pressure-Reducing Station

  2. The open feedwater heater, located above the feedwater pump on its suction side, supplies water to the pump at a slight pressure.

  3. Because of its vent condenser, the deaerating feedwater heater does a more effective job of removing oxygen and other noncondensable gases from the steam than an open feedwater heater.

  4. The horizontal deaerating feedwater heater is used when headroom is a problem.

  5. The closed feedwater heater is located on the discharge side of the feedwater pump. Unlike the open feedwater heater, the closed feedwater heater does not mix steam and water.

  6. In an economizer, gases of combustion are used to raise boiler feedwater temperature. The gases of combustion are then released to the atmosphere.

  7. A two-stage condensing economizer recovers additional heat from the gases of combustion by preheating the incoming makeup water.

  8. In a duplex-reciprocating feedwater pump, the steam piston must be 2 times to 2 1/2 times larger in area than the water piston.

  9. In a centrifugal feedwater pump, the centrifugal force of the impeller produces pressure.

  10. The two most common centrifugal feedwater pumps are the single-stage type and multiple-stage type.

  11. Turbine feedwater pumps are positive-displacement pumps and require an open discharge valve when starting.

  12. A surge tank provides the extra capacity required to handle changing loads and peak flows of condensate in larger steam boiler plants.

  13. Condensate pumps are used to return all possible condensate from various parts of the plant to the open feedwater heater.

  14. The main feedwater line utilizes check and stop valves to control water flow.

  15. When a feedwater pump feeds more than one boiler, each boiler should be isolated with a globe valve.

  16. The thermoexpansion feedwater regulator thermostat is located at the NOWL and is connected to the steam and water side of the boiler.

  17. A two-element feedwater regulator has a diaphragm assembly on the top part of the regulator valve that senses the pressure differential from the superheater.

  18. A three-element feedwater regulator is used for closer control of water level in large watertube boilers with sudden fluctuations in steam load, and/or boilers equipped with economizers.

  19. A thermohydraulic feedwater regulator operates when boiler water level increases or decreases.

  20. Float feedwater regulators may be installed inside or outside the water column, depending on their design.

  21. Steam traps are located in the system wherever steam releases its heat and condenses. Steam strainers are installed before steam traps.

  22. The thermostatic steam trap can be used with both high and low pressure steam.

  23. The float thermostatic trap removes air and other noncombustible gases as well as condensate.

  24. Inverted bucket steam traps are used when large quantities of condensate must be removed.

  25. An impulse steam trap valve opens when condensate or air entering the trap causes a pressure drop above the control disc.

  26. In a thermodynamic steam trap, pressure of the air or condensate enters the inlet port under the center of the disc and lifts the disc from its seat to discharge condensate.

  27. In a variable orifice (labyrinth) steam trap, the steam and condensate enter the body and pass through a series of compartments that reduce the pressure.

  28. Drum desuperheaters are used primarily on marine boilers.

  29. The quantity of steam increases with the use of a line desuperheater.

  30. Plants often require steam at different pressures. Steam at the required pressure is supplied by using pressure-reducing stations

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