2.9.3.4
Steam Turbines
Single stage, rated at not less than [_____] kW hp, with inlet steam
pressure of [_____] kPa (gage) psig and [_____] degrees C F and normal
exhaust back pressure of 34 kPa (gage) 5 psig or a maximum back pressure of
103 kPa (gage) 15 psig. Water rate at full load and normal steam
conditions shall not exceed [_____] kg per BkW per second pounds per BHP
per hour. Provide a stainless steel steam strainer, sentinel relief valve,
sight oil level indicator and one hand valve. [Variable speed] turbines
direct connected to respective pumps with a gear type, forged steel,
flexible coupling. Provide a shaft and coupling guard.
a.
Turbine Construction: Turbine casing split on the horizontal
centerline constructed of ASTM A 48M ASTM A 48cast iron, with a
design pressure rating of 1724 kpa (gage) 250 psig at 232 degrees C
450 degrees F at inlet, and 379 kpa (gage) 55 psig at 232 degrees
C 450 degrees F at the outlet.
b.
Turbine Bearings and Shaft: Horizontal split, ring oiled, sleeve
type, water cooled. The shaft shall be stainless steel or chrome
plated under the packing glands. The shaft seals shall be
segmented carbon rings with springs and stops.
c.
Speed Governor: Variable speed oil relay, NEMA Class D governor
for speed control and pneumatic operator to maintain an
adjustable, preset pump discharge header pressure by variation of
turbine speed. Input to the operator shall be a 20 to 103 kPa
(gage) 3 to 15 psig pneumatic signal. Provide an
electro-pneumatic transducer to accept the 4 to 20 mA signal from
the control system controller specified in VAMS Section 15901N
CONTROLS AND INSTRUMENTATIONS BOILER PLANT.
d.
Emergency Overspeed Governor: Completely independent of the speed
governor and shall operate trip valve.
e.
Insulation: Turbine shall be insulated and lagged by the
manufacturer as specified in Section 15080N MECHCANICAL INSULATION.
2.9.3.5
Minimum Flow Protection for Boiler Feed Water Pumps
a.
Automatic Flow Control Valve: Provide with each pump an automatic
bypass valve. Valve shall automatically program the recirculation
flow, the detection of low flow, the cycling of control valve and
pressure letdown for high pressure boiler feedwater return to the
feedwater heater. Bypass valve shall be cast steel with stainless
steel internals, and shall have a rating of not less than 2068 kpa
(gage) 300 psig at 204 degrees C 400 degrees F. Valve shall have
a line size body with a 25 mm one inch recirculation connection.
b.
Boiler Feedwater Automatic Recirculation System: (Option to
Automatic Valve). Provide a boiler feedwater automatic
recirculation system to protect the feedwater pumps at low flow
conditions. System shall be capable of recirculating the minimum
flow recommended by the pump manufacturer. The system shall be an
engineered system consisting of the various functional components
specified or shall be a self-contained and self-powered mechanical
system. Components of the engineered system shall include a flow
transmitter with orifice in feedwater line, bypass flow controller
with bypass flow control valve, and a bypass pressure reducing
SECTION 15511N
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