"Dampers." Guillotine dampers shall have bonnets over the top frame if
required to prevent flue gas leakage to the atmosphere. Bonnet assembly
shall be of carbon steel and shall have easily removable side plates for
inspection of the damper drive assembly. Bonnet shall be designed for
continuous-seal air purge. Guillotine dampers shall have a removable plate
for access to the bottom frame seal. Damper blade shall be fabricated of
plate, and shall be as rigid as necessary to withstand the maximum
differential pressures specified. Provide blade with sealing strips around
the periphery of the blade and on the seating surfaces of the frame. Local
seals on both the upstream and downstream sides of the blade. Sealing
strips, seal strip bolting materials and backing strips shall be as
specified for louver dampers. Blade shall be designed to include
provisions for thermal expansion such that the blade will not bind.
Bearings shall be permanently lubricated, self-aligning type. Design shall
be such that thermal gradients and long periods of time between damper
operation will not cause bearings to bind or seize. Damper drive shall be
designed to lift the damper blade evenly on both sides. Each drive, tie
rod, and bearing, shall be designed to withstand three times the load
caused by the damper blade plus the operator output torque, at worst-case
pressure and flow conditions. Upper frame shall be designed to support the
blade, drive mechanisms, and attachments. Frame shall not sway and cause
binding of the blade when operating at worst-case flow and pressure
conditions. Pressures and flows provided to the damper manufacturers shall
be approved by the Contracting Officer in advance. Damper shall include a
mechanical crank for manual operation.
2.11.4
Mechanical Draft Equipment
Mechanical draft equipment and appurtenances shall have an acceptable
history of satisfactory reliable service in industrial steam plant use for
a period of a least three years at comparable temperature, pressure,
voltage, and design stress levels. Newly developed equipment with less
than three years actual service may be considered from established
manufacturers, only if it has been adequately tested, at an approved lab
meeting AMCA standards, meets the requirements of this Contract, and is
approved by the Contracting Officer. Prior to shipment, the manufacturer
shall thoroughly inspect parts of the equipment furnished to ensure sound
material and first class workmanship. Rivets shall be tight and welds
shall be full thickness and without undercutting. Keys shall fit snugly
and rotors shall be secured firmly to the shafts. Welding on rotors for
fans shall be examined by magnetic particle inspection. Magnetic particle
inspection shall be performed on the root pass and the finished surfaces of
all welds. On full-penetration welds, the backside of the root base shall
be examined by magnetic particle inspection before depositing weld from the
backside. Welds shall be free from undercutting in excess of 0.40 mm 1/64
inch in depth and free of cracks and fissures in excess of 6 mm 1/4 inch in
length. Inspection of the fans for compliance may be made by the
Contracting Officer. Notify the Contracting Officer, in writing, at least
45 days prior to start of assembly and welding of fan rotors so that he may
have a representative present to inspect fan rotors during fabrication, if
desired. This inspection of the fan rotors will include an examination of
the weld grooves preparations on the material being joined in the assembly
of the fan wheels, witnessing the actual welding being performed on the fan
wheels, a visitation to the manufacturer's nondestructive testing facility,
witnessing the nondestructive testing being performed on welds and base
material of the fan wheel, and verifying that subassemblies are fabricated
properly and in accordance with the manufacturer's drawings and
specifications. Fans shall be designed and constructed to ensure
reliability with a minimum number of scheduled outages for repairs and
SECTION 15864N
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