Common use of Feedwater System Clause in Contracts

Feedwater System. Function The Feedwater System transfers heated feedwater from the heat recovery steam generator (HRSG) low pressure (LP) drums to the respective HRSG high pressure (HP) and intermediate pressure (IP) drums and also maintains the correct HP and IP drum water level over a wide range of steam demands. The Feedwater System also provides feedwater to various desuperheaters, and hot water to the fuel gas heater. The Feedwater System shall consist of the following major components: o One (per HRSG) 100 percent capacity horizontal multistage feedwater pumps with interstage takeoff. (These will be either split-case or segmented ring section design.) o Piping, valves, piping specialties and instrumentation System Description The feedwater pumps take suction from their respective HRSG low pressure drums. The feedwater pumps provide the necessary pumping head to supply feedwater to the HRSG IP and HP steam drums including piping friction losses and differential static head. An automatic recirculation control valve shall be provided for minimum flow recirculation of the feedwater pumps to prevent overheating and cavitation during startup and low load operation. Due to the configuration of the interstage takeoff, minimum flow through the high pressure discharge of the pump satisfies the minimum flow requirements of the interstage bleed and recirculation flow shall be required at the HP discharge only. The minimum flow recirculation valve shall be provided with anti-cavitation trim to accommodate the high pressure drop. Pump runout shall be prevented during initial fill of the HP feedwater system by a flow restricting orifice in parallel with a full flow manual isolation valve. When the HP feedwater -------------------------------------------------------------------------------- Proprietary Information Page 22 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- system is filled, the full flow isolation valve shall be opened, and flow shall be unrestricted. The IP feedwater runout is limited by a back pressure control valve which maintains a minimum backpressure on the interstage bleed during HRSG filling and plant startup. This valve prevents the high pressure stages of the feedwater pump from being starved by the IP interstage takeoff during initial system fill. The feedwater pumps shall be supplied with instrumentation to monitor and alarm on high bearing temperature. Feedwater pump suction pressure and temperature shall be monitored and the control system calculates available NPSH. The available NPSH shall be compared against the manufacturer's required NPSH and an alarm shall be actuated if measured available NPSH drops below pump required NPSH for more than 5 seconds. The pump shall be automatically tripped if the condition persists for more than 30 seconds. Also, the feedwater pump shall be tripped if the LP drum water level drops below the low-low level set point. The IP and HP feedwater flows shall be monitored. These measurements along with drum level and steam flow shall be used in a three element drum level control algorithm. The feedwater pumps shall be started by the operator from the central control room. They shall operate continuously unless shutdown by the operator or tripped by the distributed control system (DCS). The DCS will alarm and automatically trip the feedwater pump on the following conditions: High pump vibration Low LP drum level Low pump NPSH available -------------------------------------------------------------------------------- Proprietary Information Page 23 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- The DCS will alarm only on the following conditions: Low pump flow Low pump discharge pressure High bearing temperature Design Basis The design capacity of each boiler feedwater pump will be based on supplying 100% of the maximum feedwater flow to be encountered in operation including turbine bypass. The boiler feed pumps shall have 5% flow and head margin above the maximum design condition. Each pump shall be designed such that the best efficiency point lies in the flow range between normal and maximum flow conditions. Modes of Operation During normal operation water is pumped to the IP & HP economizers. During operation with the steam turbine bypassed, desuperheating water is sent to the HP bypass steam line. -------------------------------------------------------------------------------- Proprietary Information Page 24 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- TYPICAL HORIZONTAL SPLIT CASE BOILER FEEDWATER PUMP DESIGN FEATURES Motor Driver Speed Increaser, if required Three Element Grouted Steel Baseplate 12% Chrome Casing 12% Chrome Impellers 420 SS Shaft Carbon Steel Pressure Studs & Nuts Cast Iron Inboard & Outboard Bearing Housing High Pressure Casing 316L SS Dual Take-off RF Flanged Suction Connection RF Flanged Discharge Connection Masonite Flange Covers Sleeve / Sleeve KTB Bearings Tri-Land Bearings Forced Feed Lube Oil System Vent & Drain Connections Gib Block Vibrometer Pad Bearing Temperature Detector Taps BSTFM Mechanical Seals 316 SS Pumping Rings 316 SS Flush, Vent, & Drain Glands 1/2" 316 SS Tubing w/ Xxxx Fittings Xxxxxx Cooler 4x4C-10/CI CSG/304 Tube Non-cooled Bearing Housing Non-cooled Stuffing Box Coupling - Pump/Speed Increaser -------------------------------------------------------------------------------- Proprietary Information Page 25 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- Coupling - Motor/Speed Increaser PMC Beta 440DR Vibration Sensor/Switch Type K Thermocouple Temperature Sensors -------------------------------------------------------------------------------- Proprietary Information Page 26 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- TYPICAL SEGMENTED RING SECTION BOILER FEEDWATER PUMP DESIGN FEATURES Baseplate for pump, gear increaser/lube system, and motor Spacer, gear coupling and disc coupling between motor and gear Steel coupling guards 12% chrome stage casing 12% chrome impeller and diffusor 12% chrome shaft Carbon steel pressure studs and nuts Carbon steel suction and discharge casings clad with 316 SS Balance water NPT connection (balance line to be returned to the suction source

Feedwater System. Function The Feedwater System transfers heated Two 100% feedwater from pumps for each pressure level shall be provided for each HRSG. All pumps shall be driven by either variable-speed motors or variable-speed fluid couplings, with the heat recovery steam generator (HRSG) low pressure (LP) drums capability to operate at minimum load without requiring recirculation. These pumps shall be horizontal, volute, and multiple-stage ring-section pumps in accordance with Hydraulic Institute Standards. Double-bearing design shall be used with bearings on either side of the respective HRSG high pressure (HP) impellers. Impellers shall be stainless steel. A multistage feedwater pump may also be used for HP and intermediate intermediate-pressure (IP) drums and also maintains the correct HP and IP drum water level over a wide range of steam demandssupply. The Feedwater System also provides feedwater to various desuperheaters, and hot water to the fuel gas heater. The Feedwater System pump shall consist of the following major components: o One (per HRSG) 100 percent capacity horizontal multistage feedwater pumps with interstage takeoff. (These will be either split-case or segmented ring section design.) o Piping, valves, piping specialties and instrumentation System Description The feedwater pumps take suction from their respective HRSG low pressure drumsthe deaerator and/or feedwater storage tank. The HP feedwater pumps provide the necessary pumping head to supply feedwater shall be piped to the HRSG IP HP economizer inlet. The system shall be designed for continuous operation at flows ranging from manufacturer’s minimum recirculation to 100% of design capacity. At a minimum, a 5% margin on capacity and HP steam drums including piping friction losses and differential static head10% margin on total head shall be added for pump wear. An automatic recirculation control The available net positive suction head (NPSH) shall be at least two times the required NPSH of the purchased pumps. A manual stop-check valve arranged in series shall be provided on each boiler feed pump discharge. A warm-up line tapped off each discharge line, downstream of the stop-check valve, for warming the boiler feed pump while in a standby mode of operation shall also be provided. A pressure breakdown orifice shall be provided in each warming line to help match the internal pressure in the pump casing while isolated from the feedwater discharge header. Each pump shall be provided with a minimum flow recirculation of the feedwater pumps control system to prevent overheating and cavitation during startup and low load operation. Due to the configuration of the interstage takeoff, minimum flow through the high pressure discharge of the pump satisfies meet the minimum flow requirements of the interstage bleed and recirculation flow pump. Chemicals shall be required at injected into the HP discharge onlyfeedwater and HRSG to maintain water and steam chemistry within HRSG and steam turbine manufacturer limits. The minimum flow recirculation valve chemical injection points and blowdown drains shall be provided with anti-cavitation trim configured to accommodate the high pressure dropallow control of steam and boiler water chemistry within HRSG and steam turbine OEM specifications and within EPRI guidelines. Pump runout All chemical injection, sampling, and monitoring points shall be prevented during initial fill easily accessible for routine maintenance. Each feedwater and condensate chemical addition/injections systems shall include two 100% chemical injection pumps and chemical storage adequate for 7 days of the HP feedwater system by a flow restricting orifice operation for each type of chemical. Centralized sampling location with remote readout in parallel with a full flow manual isolation valve. When the HP feedwater -------------------------------------------------------------------------------- Proprietary Information Page 22 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- system is filled, the full flow isolation valve control room shall be opened, and flow provided. Motors shall be unrestrictedfurnished and mounted by the driven-equipment supplier on a common base plate. The IP feedwater runout is limited by a back pressure control valve which maintains a minimum backpressure on the interstage bleed during HRSG filling and plant startup. This valve prevents the high pressure stages of the feedwater pump from being starved by the IP interstage takeoff during initial system fill. The feedwater pumps shall be supplied with instrumentation to monitor and alarm on high bearing temperature. Feedwater pump suction pressure and temperature shall be monitored and the control system calculates available NPSH. The available NPSH shall be compared against the manufacturer's required NPSH and an alarm shall be actuated if measured available NPSH drops below pump required NPSH for more than 5 seconds. The pump shall be automatically tripped if the condition persists for more than 30 seconds. Also, the feedwater pump shall be tripped if the LP drum water level drops below the low-low level set point. The IP and HP feedwater flows shall be monitored. These measurements along with drum level and steam flow shall be used in a three element drum level control algorithm. The feedwater pumps shall be started by the operator from the central control room. They shall operate continuously unless shutdown by the operator or tripped by the distributed control system (DCS). The DCS will alarm and automatically trip the feedwater pump on the following conditions: High pump vibration Low LP drum level Low pump NPSH available -------------------------------------------------------------------------------- Proprietary Information Page 23 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- The DCS will alarm only on the following conditions: Low pump flow Low pump discharge pressure High bearing temperature Design Basis The design capacity of each boiler feedwater pump will be based on supplying 100% of the maximum feedwater flow to be encountered in operation including turbine bypass. The boiler feed pumps shall have 5% flow and head margin above the maximum design condition. Each pump shall be designed such that to automatically start the best efficiency point lies in standby pump when the flow range between normal and maximum flow conditions. Modes of Operation During normal operation water is pumped to the IP & HP economizers. During operation with the steam turbine bypassed, desuperheating water is sent to the HP bypass steam line. -------------------------------------------------------------------------------- Proprietary Information Page 24 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- TYPICAL HORIZONTAL SPLIT CASE BOILER FEEDWATER PUMP DESIGN FEATURES Motor Driver Speed Increaser, if required Three Element Grouted Steel Baseplate 12% Chrome Casing 12% Chrome Impellers 420 SS Shaft Carbon Steel Pressure Studs & Nuts Cast Iron Inboard & Outboard Bearing Housing High Pressure Casing 316L SS Dual Take-off RF Flanged Suction Connection RF Flanged Discharge Connection Masonite Flange Covers Sleeve / Sleeve KTB Bearings Tri-Land Bearings Forced Feed Lube Oil System Vent & Drain Connections Gib Block Vibrometer Pad Bearing Temperature Detector Taps BSTFM Mechanical Seals 316 SS Pumping Rings 316 SS Flush, Vent, & Drain Glands 1/2" 316 SS Tubing w/ Xxxx Fittings Xxxxxx Cooler 4x4C-10/CI CSG/304 Tube Non-cooled Bearing Housing Non-cooled Stuffing Box Coupling - Pump/Speed Increaser -------------------------------------------------------------------------------- Proprietary Information Page 25 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- Coupling - Motor/Speed Increaser PMC Beta 440DR Vibration Sensor/Switch Type K Thermocouple Temperature Sensors -------------------------------------------------------------------------------- Proprietary Information Page 26 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 -------------------------------------------------------------------------------- TYPICAL SEGMENTED RING SECTION BOILER FEEDWATER PUMP DESIGN FEATURES Baseplate for pump, gear increaser/lube system, and motor Spacer, gear coupling and disc coupling between motor and gear Steel coupling guards 12% chrome stage casing 12% chrome impeller and diffusor 12% chrome shaft Carbon steel pressure studs and nuts Carbon steel suction and discharge casings clad with 316 SS Balance water NPT connection (balance line to be returned to the suction sourceoperating pump fails.