FOR MECHANICAL SYSTEMS. All wiring incidental to the operation of controls
and instrumentation shall be provided. All piping to connect to the tank
for accessories shall be provided.
2.5
HEAT EXCHANGERS
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NOTE: If the bulk of the condensate return is at a
high temperature, as from a laundry, a heat
exchanger will be used. If the bulk of the
condensate is returned to a heating pump unit, a
heat exchanger will not be required for that
application. Heat exchangers can be used for either
heating or cooling the condensate.
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Heat exchangers shall be designed, fabricated, tested, and stamped in
accordance with ASME BPVC SEC VIII D1. Additionally, heat exchanger
designs shall meet the requirements of HEI 2623. Closed feedwater heater
designs shall meet the requirements of HEI 2622. All heat exchangers shall
be provided with relief valves as required by ASME BPVC SEC VIII D1 and HEI
2623 and shall be designed for a working steam pressure of [586] [_____]
kPa [85] [_____] psig. [Heat exchangers using service water shall be
designed to have the service water inside the tubes.] [The exchangers
shall be of straight tube design with bolted full diameter access channel
covers to facilitate tube maintenance as required.] Return bonnets are
acceptable when there are no tubeside connections at the far end.
Materials of construction shall be all carbon steel, except the service
water side which shall reflect the service water available. When the water
quality permits, 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 111MAlloy 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,
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 holes so that a
shell hydro test may be applied without the channel in place. Materials of
construction shall be 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
SECTION 15846A
Page 41
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