the tubes shall be stainless steel in accordance with ASTM A 249/A 249M,
Grade TP 304, the remainder of the tube side shall be all carbon steel.
When the service water is known to contain chloride levels harmful to
stainless steels, the tubes shall be 90-10 Copper-Nickel in accordance with
ASTM B 111/B 111M Alloy 706; the remainder of the service water side shall
be as follows: tubesheets, monel-clad steel; channel covers, carbon steel
lined with monel; channels and bonnets, monel. Fixed tubesheet designs are
preferred when operating conditions do not impose a large differential
movement that cannot be readily accommodated with a simple thin-wall metal
bellows expansion joint. For larger differentials, a packed floating
tubesheet with lantern ring is acceptable up to 1.03 MPa 150 psig design
pressure. For pressures above 1.03 MPa 150 psig, a split ring floating
head design shall be used. Heat exchangers using steam to heat domestic
water or other fluids such as glycol-water mixtures or fuel oil shall have
the steam in the shell side. The exchangers shall be of U-tube designs
with bolted full diameter channel covers to facilitate tube maintenance as
required. The tubesheet shall be the full diameter to match the shell
flange and shall have sufficient threaded bolt holes so that a shell hydro
test may be applied without the channel in place. Materials of
construction shall be of all carbon steel with the exception of the tubes
which should typically be specified as stainless steel in accordance with
ASTM A 688/A 688M, Grade TP 304, stress relief annealed temper with the
U-bends stress relieved after bending. Fuel oil heaters shall have carbon
steel tubes in accordance with ASTM A 179/A 179M and be furnished in the
stress relief annealed temper with the U-bends stress relieved after
bending. Feedwater heaters shall be of all welded construction with bolted
full diameter channel covers to facilitate tube maintenance as required.
The channel barrel shall be integral with the tubesheet and have an
internal pass partition bolted cover design that shall be readily removable
when the channel cover is removed. Pass partitions that are sealed with a
gasketed groove in the channel cover are prohibited. Materials of
construction shall be all carbon steel except the tubes. Pressure boundary
material shall be in accordance with ASTM A 516/A 516M, Grade C, when plate
material is required, or ASTM A 350/A 350M when forging material is
required. Shroud plate material for desuperheating and subcooling zones
shall be in accordance with ASTM A 285/A 285M, Grade C. Tubes shall be
stainless steel in accordance with ASTM A 688/A 688M, Grade TP 304, stress
relief annealed temper with the U-bends stress relieved after bending.
2.18
DEAERATING FEEDWATER HEATER
**************************************************************************
NOTE: Economizer or preheater will be selected to
be compatible with pollution control equipment being
utilized.
**************************************************************************
Deaerating feedwater heater shall be installed where indicated and shall be
size and capacity indicated. Shell shall be [cast iron] [steel plate].
[Tray system for unit shall be [cast-iron] [corrosion-resistant steel.]
Floats shall be of [copper] controlled overflow-trap] type. Heater shall
be provided with [a pressure relief valve,] [thermometers,] [pressure
gauge,] [and] [oil separator]. [A combination temperature-pressure
recorder shall be installed for each feedwater heater.] [Steam pressure
readings shall be taken from the shell, and the temperature bulb shall be
so placed as to [indicate] [record] the temperature of the feedwater after
it passes over the trays and sprays.] An alarm shall be provided to turn
on a red pilot signal lamp and to sound a bell gong in the event that water
level in the feedwater heater storage tank falls to 300 mm 12 inches above
SECTION 15559A
Page 63
Previous Page
