Steam and Water Accessories

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