2.5.2
Furnace and Boiler
The boiler shall be of the water-tube welded-wall type, having in-bed tube
surface for AFB offerings with natural and/or forced circulation. Tubes
shall be seamless and all connections shall be welded. Tubes of the
electric resistance welding process, where used, shall be identified by the
Contractor and shall be ultrasonically tested along their entire length by
the Contractor. The Contractor shall provide permanent thermocouples, as
required, run to a terminal box outside the boiler casing. As a minimum,
these thermocouples shall indicate:
a.
Water wall temperature in critical locations (risers, etc.).
b.
Heat absorption rates (cordial type t/c).
c.
Air and gas temperatures.
d.
Water and steam temperatures.
Drums shall be fusion welded throughout and fitted with manholes and hinged
covers at both ends. The hydrostatic test temperature shall be carefully
monitored, as indicated in paragraph "TESTS," to avoid brittle failure.
Boiler drains shall be furnished sufficient in size and number to
completely drain the water from the entire unit in not more than 1 hour at
0 kPa psig pressure. The drum shall be equipped with internals for steam
separation.
2.5.3
Forced Circulation System
Boiler designs utilizing horizontal in-bed evaporating surfaces shall be
provided with a forced circulation system. The number and capacity of the
pumps installed shall be such that with one pump out of service, the
maximum rating of the boiler can be carried with complete safety. In
addition, loss of all pumps, with the unit at MCR, shall allow for a safe
and orderly shutdown (without fans) without damage to the boiler. The
pumps shall be single stage, centrifugal, driven by constant speed motors.
Pumps shall be complete with all necessary accessories, including welded
suction and discharge connections, lubrication system, casing drain valves
in duplicate, and any necessary auxiliary pumps, heat exchangers, or other
equipment. The pumps shall withstand the boiler test pressure and all
operating pressures and temperatures without distortion, binding, or other
effects. The casings shall withstand the forces and moments imposed upon
them by the connecting piping without disturbing the alignment or
successful operation of the pumping units. The construction shall be such
as to permit inspection of the rotating parts without dismantling the
suction and discharge piping. The pumps shall operate satisfactorily at
all loads, either by themselves or in parallel with the other pumps
furnished. The pump suction valves shall be motor operated. Bypasses with
valves shall be furnished around the pump isolating valves to maintain
operating temperature in the idle pumps and piping. The discharge valves
shall have impactor handwheels and lugs for air motor drive. Orifices,
with protecting strainers as required, shall be provided to assure adequate
circulation to all parts of the boiler circuits. All materials that may
come in contact therewith shall be suitable to withstand acid and caustic
boiler cleaning solutions. Connecting lines with stop valves shall be
provided between the main distributing header and the economizer inlet
header for use as a circulating line to the economizer when the boiler is
acid cleaned.
SECTION 15559A
Page 41
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