Facilities Management Utilities & Engineering Services Duk e Steam Heating System DU-101-PP
Jan 12, 2016
Facilities ManagementUtilities & Engineering ServicesDuk
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Steam Heating System
DU-101-PP
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STEAM HEATING SYSTEM
PURPOSE The purpose of the Operations and Maintenance Training Program is to
train Operations and Maintenance Technicians in the operation of the Duke University Chiller and Steam Systems.
OBJECTIVES Trainees will demonstrate knowledge of
– Steam Heating System Components– Steam Heating System Components Operation– Steam Heating System Configuration– Steam Heating System Controls and Instrumentation
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STEAM HEATING SYSTEM
PURPOSE The purpose of the Steam Heating System is to provide climate control for
all East Campus, West Campus, and Duke Medical Center buildings.
STEAM HEATING SYSTEM Boilers in the East Campus Steam Plant and the West Campus
Steam Plant supply steam to the Underground Seat and Condensate Distribution System.
The Control Room assures a steady supply of steam to all facilities, bringing boilers online as they are needed and taking boilers offline to accommodate pressure requirements and equipment maintenance.
In the campus buildings, a Pressure Reduction Valve (PRV) Station reduces steam pressure to levels suitable for heating and other services.
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STEAM HEATING SYSTEM
WHY STEAM? Steam is an efficient and easily controlled heat transfer medium. Heat from the boilers is stored in the steam until it is processed in the
building air handlers. Steam transports energy from the boilers to any number of remote
locations with minimal loss of energy. Both steam plants serve a common distribution system, which ensures a
steady supply of steam to all facilities while boilers and other equipment are taken offline:– To provide access for maintenance without interrupting service– To improve equipment life– To enable the most efficient use of resources
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STEAM HEATING SYSTEM
HEAT TRANSFER PRINCIPLES Boilers raise water temperature enough above the boiling point to
produce ‘saturated’ steam. The temperature of latent heat in the saturated steam is maintained until
the steam releases its latent heat into the coils of a heat exchanger.
LATENT HEAT
SATURATED STEAM
CONDENSATE
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STEAM HEATING SYSTEM
Heat naturally flows from a higher temperature level to a lower temperature level. This is known as heat transfer.
The purpose of the distribution system is to convey steam from the boilers to the heat exchange with minimal loss of latent heat along the way.
Pipe walls, condensate film, condensate drops, air film, scaling, and even the insulation on the outside of the pipe all cause some heat loss and condensation. To maintain necessary pressure, the boiler has to work harder.
The effects of these factors on heat transfer can be minimized by:– Drip Leg Stations at regular intervals to remove condensate from the piping.– Monitoring pressure.– Regular maintenance to remove scale and other damage to the pipes.– Conditioning feed water used in the boiler to ensure the steam generated in
the boiler is as pure as possible.
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STEAM HEATING SYSTEM
CONDENSATE RETURN PRINCIPLES Condensate is the byproduct of heat transfer in the Steam Heating System. Condensation forms in distribution piping and heating equipment. As condensation forms in the underground piping, it is separated from the
steam in drip leg stations and returned to the plant where it will be used to preheat feed water.
At a campus building, after steam has condensed and given up its valuable heat in the air handler’s heat exchanger, the hot condensate is pumped back to the boiler before it can cool.
The hot condensate is used to preheat feed water before it enters the boiler, which helps the boiler run efficiently.
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STEAM HEATING SYSTEM
QUESTIONWhy is condensate returned to the plant?
– For disposal– To preheat feed water– To fill the water towers– To absorb steam
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STEAM HEATING SYSTEM
ANSWERTo preheat feed water
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STEAM HEATING SYSTEM
QUESTIONHow does heat flow?
– Lower temperature to higher temperature– Higher temperature to lower temperature– Heat does not flow– Downhill
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ANSWERHigher temperature to lower temperature
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STEAM HEATING SYSTEM
QUESTIONHow is saturated steam made?
– Water is heated enough above the boiling point to produce steam
– Water is heated to boiling– Steam is mixed with hot water– Steam is cooled slowly to remove water
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ANSWERWater is heated enough above the boiling point to produce
steam
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STEAM HEATING SYSTEM
PURPOSE The systems that make up the Steam Heating System work together to
provide a reliable and and efficient heat source for the East and West Campuses and Medical Center.
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STEAM HEATING SYSTEM
SYSTEMS The Duke University Steam Heating System includes the following
equipment and locations:– High Pressure Steam System
• East Campus Steam Plant • West Campus Steam Plant
– Underground Steam and Condensate Distribution System • Steam from the East Campus Steam Plant and West Campus Steam Plant
is fed into the Underground Steam and Condensate Distribution System• Reaches all Duke University facilities
– Medium Pressure and Low Pressure Steam System• Located inside all Campus and Medical Center buildings • Converts high pressure steam to medium pressure steam for services and
low pressure steam for heating.
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STEAM HEATING SYSTEM
HIGH PRESSURE STEAM SYSTEM High Pressure Steam Headers are located in the East Campus Steam Plant
and the West Campus Steam Plant.
EAST CAMPUS STEAM PLANT
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HIGH PRESSURE STEAM HEADER Sensors at the HPS Header send data on the steam to the Control Room.
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STEAM HEATING SYSTEM
EAST CAMPUS STEAM PLANT
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STEAM HEATING SYSTEM
WEST CAMPUS STEAM PLANT
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STEAM HEATING SYSTEM
QUESTIONWhere are HPS Headers located?
– East Campus and West Campus Steam Plants– All steam and chiller plants– Campus and Medical Center buildings– Chiller Plants 1 and 2
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STEAM HEATING SYSTEM
AnswerEast Campus and West Campus Steam Plants
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STEAM HEATING SYSTEM
QUESTIONWhat is the nominal pressure of steam leaving the HPS
Header?– 75 psig– Less than 16 psig– 125 psig– 170 psig
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ANSWER125 psig
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STEAM HEATING SYSTEM
QUESTIONWhich boilers in a Steam Plant supply the High Pressure
Steam Header?– All boilers all the time– Each boiler has its own HPS Header– All boilers that are on line– All boilers that are offline
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ANSWERAll boilers that are on line
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STEAM HEATING SYSTEM
UNDERGROUND STEAM AND CONDENSATE DISTRIBUTION SYSTEM
PURPOSE– The Underground Steam and Condensate Distribution System
conveys high pressure saturated steam to buildings throughout the Duke University Campus and Medical Center
– The nominal steam pressure is 125 psig
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STEAM HEATING SYSTEM
UNDERGROUND STEAM AND CONDENSATE DISTRIBUTION SYSTEM
COMPONENTS– Underground Piping
• The majority of piping is buried.• Steam Vaults (manholes provide access points and junctions for
buried pipes.• There are approximately 35 miles of underground piping.
– Three-pipe design• High Pressure Steam (HPS) supply piping delivers steam to
buildings.• Pumped Condensate (PC) return piping conveys hot
condensate drained from air handlers back to the plant.• High Pressure Condensate (HPC) return piping sends
condensate removed from the High Pressure Steam piping to the plant to be used as make-up feed water.
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STEAM HEATING SYSTEM
COMPONENTS– Tunnels provide access to piping that is not buried
• Tunnels are tall enough to allow personnel to walk upright• Access is provided for maintenance of piping, valves, and
instrumentation• Valves are provided to isolate segments of the system
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STEAM HEATING SYSTEM
COMPONENTS– Steam Vaults (Manholes)
• Steam Vaults are located at no more than 300-foot intervals in underground piping
• HPS Supply side of Steam Vault– 36 inch manhole lid– Drip Leg Station drains and cleans condensate from HPS Supply
• PC Return side of Steam Vault– 24 inch manhole lid– Sump pit provides drainage (with an electric sump pump, when
gravity drainage is not adequate• Junction(s)
– Steam Vaults can contain junctions to connect branches of piping
– HPS Supply and PC Return lines can be joined in a Steam Vault in various configurations
– Not all Steam Vaults contain junctions
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STEAM HEATING SYSTEM
COMPONENTS– Drip Leg Stations
• Drip Pocket drains condensate from steam lines.• Strainer removes dirt and particulates from condensate.
– Steam Entry Pits • Located beneath each Campus and Medical Center building.• HPS Supply enters from the Underground Steam and Condensate
Distribution System.• Steam pressure is reduced at the PRV Station.• Condensate from air handlers drains by gravity into the sump in
the Steam Entry Pit.• Condensate in the sump pit is returned to the Underground Steam
and Condensate Distribution System by the sump pump.
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STEAM HEATING SYSTEM
PIPINGThree Pipe System
– High Pressure Steam (HPS Supply)– High Pressure Condensate (HPC Return)– Pumped Condensate (PC Return)
DRIP LEG STATION
MANHOLE
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STEAM HEATING SYSTEM
THREE PIPE SYSTEMHPS Supply carries steam from the plant to
Campus and Medical Center buildings.
HPS SUPPLY
DRIP LEG STATION
MANHOLE
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STEAM HEATING SYSTEM
THREE PIPE SYSTEMCondensate removed from HSP Supply at the Drip
Leg Station is returned to the Steam Plant in the HPC Return piping.
HPC RETURN
DRIP LEG STATION MANHOLE
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STEAM HEATING SYSTEM
THREE PIPE SYSTEMCondensate from air handlers is pumped from
buildings to the Steam Plant through the PC Return piping
PC RETURN
DRIP LEG STATION
MANHOLE
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STEAM HEATING SYSTEM
QUESTIONWhat are the three pipes in the three pipe design?
– HPS Supply, HPC Return, PC Return– HPS Return, HPC Supply, PC Return– LPS Supply, HPS Supply, PC Return– PC Supply, PRV Return, HPS Supply
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ANSWER35 miles
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QUESTIONApproximately how much piping is in the Underground Steam
and Condensate Distribution System?– 300 feet– 50 miles– 35 miles– 900 yards
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ANSWERHPS Supply, HPC Return, PC Return
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STEAM HEATING SYSTEM
QUESTIONWhat is carried in PC Return piping?
– Condensate from building– Steam from Plant– Condensate from Drip Leg Station– LPS from PRV Station
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ANSWERHPS Supply, HPC Return, PC Return
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STEAM HEATING SYSTEM
TUNNELSProvide easy access to the Underground Steam and
Condensate Distribution System to personnel– Maintaining piping, valves, sensors, and controls– Isolating segments of the system
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STEAM HEATING SYSTEM
UNDERGROUND PIPINGThe majority of piping is buried.Steam Vaults (manholes) provide access and junction points
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STEAM HEATING SYSTEM
STEAM VAULTSHPS supply side of the vault
36 inch Manhole provides access for maintenanceDrip Leg Station drains and cleans condensate from HPS
PC return side of the vault24 inch Manhole provides access for maintenance of
condensate return pipingSump pit provides drainage of condensate lost from the the
system Junction
HPS supply and PC return from various lines can come together in a steam vault
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STEAM HEATING STATION
MANHOLE
HIGH PRESSURE STEAM
DRIP LEG STATION
STEAM VAULT HPS Supply Side
Drip Leg Station 36 inch Manhole for maintenance
access
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STEAM HEATING SYSTEM
MAIN PC RETURN
SUMP PUMP
SUMP
STEAM VAULT PC Return Side
24 inch manhole lid for maintenance access
Sump with Pump
MANHOLE
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STEAM HEATING SYSTEM
MAIN HPS SUPPLY
HPS SUPPLY BRANCH
MAIN PC RETURN
PC RETURN BRANCH
PC MANHOLE
STEAM VAULT Top View of Junction
HPS MANHOLE
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STEAM HEATING SYSTEM
STEAM VAULT DRIP LEG STATION Drip Pocket Strainer Steam Trap HPS SUPPLY
DRIP POCKETISOLATION VALVES
STEAM TRAP STRAINER
BLOWDOWN DRAIN
BLOWDOWN TEST TEE
TO HPC RETURN
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STEAM HEATING STATION
STEAM VAULT DRIP LEG STATION Drip Pocket
– Condensate forming as steam cools can cause water hammer, erosion and scaling of pipe, and pipe and equipment failure
– Condensate drops out of the stream as steam passes over the drip pocket.
DRIP POCKET
HPS SUPPLY
CONDENSATE
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STEAM HEATING SYSTEM
STEAM VAULT DRIP LEG STATION Strainer
Condensate from the drip pocket passes through the strainerFine mesh screen collects dirt and particulates
SCREEN
DRIP POCKET
STRAINER
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STEAM HEATING SYSTEM
STEAM VAULT DRIP LEG STATION Stream Trap
Air and CO2 separate from the condensate and collect in the inverted bucket. When the inverted bucket becomes buoyant, the bucket rises, triggers the valve
above the bucket, and the gases vent out the top of the Steam Trap.
INVERTED BUCKET
STEAM TRAP
VALVE
CONDENSATE FROM STRAINER
TO HPC RETURN
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STEAM HEATING SYSTEM
QUESTIONWhat does a Drip Leg do?
– Removes gases from HPS Supply– Drains and cleans condensate from HPS Supply– Pumps condensate from the Steam Pit Entry– Detects leaks in underground piping
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STEAM HEATING SYSTEM
ANSWERDrains and cleans condensate from HPS Supply
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STEAM HEATING SYSTEM
QUESTIONThe majority of piping is where?
– In tunnels– Buried– Overhead– Underwater
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ANSWERBuried
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STEAM HEATING SYSTEM
QUESTIONHPS supply is connected to HPS Return by what?
– PRV Station– Junction– Drip Leg Station– Steam Vault
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ANSWERDrip Leg Station
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STEAM HEATING SYSTEM
QUESTIONWhat are Steam Vaults also known as?
– Steam Entry Pits– Manholes– Deaerators– Steam Traps
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ANSWERManholes
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STEAM HEATING SYSTEM
QUESTIONWhat does a Steam Trap do?
– Reduces steam pressure– Captures steam for testing– Removes air and CO2 from condensate
– Removes dirt and particles from steam
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STEAM HEATING SYSTEM
ANSWERRemoves air and CO2 from condensate
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STEAM HEATING SYSTEM
QUESTIONWhat does a Steam Vault do?
– Holds steam until it is needed– Provides access to underground piping– Serves as an entry point for HPS Supply into a building– Removes steam from condensate lines
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STEAM HEATING SYSTEM
ANSWERProvides access to underground piping
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STEAM HEATING SYSTEM
LOW PRESSURE AND MEDIUM PRESSURE STEAM SYSTEM– Steam Pit Entry is the vault beneath each building where HPS Supply
enters the building and PC Return leaves.– The PRV Station in each building reduces high pressure steam (125
psig) to medium pressure steam\ (75 to 16 psig, and medium pressure steam to low pressure steam (less than 16 psig).
– Medium pressure steam is used for building services washing hot water, and other services).
– Low pressure steam is used by air handlers to heat the building.– Condensate from the air handlers flows to the sump pit by gravity. The
condensate pump sends condensate to the plan through the PC Return piping.
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STEAM HEATING SYSTEM
STEAM PIT ENTRY– Entry point for Buildings– Maintenance access– Drip Leg removes
condensate– Condensate Pump
returns condensate to Steam Plant
CONDENSATE PUMP
DRIP LEG
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STEAM HEATING SYSTEM
PRV Station Reduces pressure in buildings in two stages
– HPS Supply to Medium Pressure Steam (MPS) for services– MPS to Low Pressure Steam (LPS) for heating
HPS FROM STEAM PLANT
MPS TO SERVICES
LPS TO HEATING
PRV
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STEAM HEATING SYSTEM
PRV STATIONPRV
– PRV uses adjustable spring and diaphragm design to reduce steam pressure.
– The PRVs in the first stage of the PRV Station reduce steam pressure from 125 psig (HPS) to 75 to 16 psig (MPS)
– The PRVs in the second stage of the PRV Station reduce steam pressure from 75 to 16 psig to less than 16 psig (LPS).
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STEAM HEATING SYSTEM
QUESTIONWhat does a PVR Station do?
– Reduces pressure so steam can be used for services and heating – Pumps condensate from the air handlers– Increases steam pressure so steam can reach the most remote air
handlers– Converts steam to hot condensate
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STEAM HEATING SYSTEM
ANSWERReduces pressure so steam can be used for services
and heating
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STEAM HEATING SYSTEM
QUESTIONWhat is LPS used for?
– Reducing pressure from HPS Supply– Heating– Hot water– Pumping condensate back to the plant
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ANSWERHeating
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STEAM HEATING SYSTEM
QUESTIONWhich of these is MPS used for?
– Reducing pressure from HPS Supply– Heating– Hot water– Pumping condensate back to the plant
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ANSWERHot water
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STEAM HEATING SYSTEM
QUESTIONWhat does a PRV do?
– Reduces voltage to the condensate pumps– Reduces steam pressure– Converts condensate to steam– Removes air and CO2 from steam
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STEAM HEATING SYSTEM
ANSWERReduces steam pressure
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STEAM HEATING SYSTEM
STEAM HEATING SYSTEM CONFIGURATION AND PROCESS FLOW
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HPS HEADERS, EAST AND WEST STEAM PLANTS Steam from boilers is regulated in HPS Header Header supplies HPS to Underground Steam and Condensate Distribution
System Steam pressure exiting plant is 125 psig
HPS HEADER
BOILERS
UNDERGROUND PIPING
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STEAM HEATING SYSTEM
STEAM VAULT HPS steam enters Steam Vault Condensate drains into Drip Pocket Steam Trap removes air and CO2
Strainer removes dirt and particulates
STEAM VAULT
DRIP LEG STATION
STEAM TRAP
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STEAM ENTRY PIT HPS enters Campus and Medical Center buildings at Steam Entry Pit Drip Leg removes condensate
STEAM ENTRY PIT
DRIP LEG
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PRV STATION HPS is reduced to MPS, 75 to 16 psig MPS is reduces to LPS, less than 16 psig LPS is sent to the building heating system
PRV STATION
75-16 psig
> 16 psig
125 psig
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STEAM ENTRY PIT Condensate from heat heating goes to the Condensate Pump Condensate is returned to the Steam Plant
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QUESTIONWhat is the function of the Steam Pit Entry?
– Where HPS Supply enters a building– Entrance to Steam Vault– Contains the LPS Station– Contains air handlers
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ANSWERWhere HPS Supply enters a building
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STEAM HEATING SYSTEM
QUESTIONSteam from boilers enters the distribution system where?
– PRV Station– HPS Header– Steam Pit Entry– Steam Vault
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ANSWERHPS Header
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QUESTIONWhat is the pressure of low pressure steam?
– Below 16 psig– 16 psig– 75 psig– 24 psig
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ANSWERBelow 16 psig
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QUESTION In what part does the Drip Leg Station collect condensate
from HPS Supply?– The Drip Leg Station does not collect condensate– Steam Trap– Strainer– Drip Pocket
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ANSWERDrip Pocket
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STEAM HEATING SYSTEM
QUESTIONWhat does the strainer do?
– Removes air and CO2 from condensate– Removes LPS from HPS Supply– Removes dirt and particulates from condensates– Removes latent energy from HPS Supply
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ANSWERRemoves dirt and particulates from condensate
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STEAM HEATING SYSTEM
OPERATIONS MONITORING– Operation of the Steam Heating System at Duke University is
monitored through the Control Room, at West Campus Chilled Water Plant #2.
– The Digital Control System (DCS) provides operators with information on system operation and control over system parameters.
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PLANT ROUNDS– During an Operator’s routine shift, Rounds are accomplished to record
key information and visually assess Steam Heating System operation, as well as other systems in the Steam Plants.
– Each Steam Plant has a Round Sheet to be filled out by the Operator.– Each plant has different requirements for plant rounds.– The information is recorded, not only for the current status, but also
to record system trends.
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STEAM HEATING SYSTEM
WEST PLANT– The following is recorded, during operator rounds, for the West Plant, at 0800,
1600, 2000, and 0400 hours:• Steam header PSI• DA steam PSI/water temperature• Steam flow, drum PSI, and gas/fuel Oil PSI to Boilers 1, 2, 3, 6• Steam flow, drum PSI, fuel oil PSI to BLR, and atomizing steam for boilers 4
and 5• City water PSI• C/W booster pump online, and pump outlet PSI• Softeners online• FWP online, and discharge PSI• Plaint air PSI• Air storage tank PSI
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WEST PLANT– The following is recorded, during operator rounds, for the West Plant, at 0800,
1600, 2000, and 0400 hours:• Air compressor online, PSI, and temp• Generator (volts/temp)• Condensate pumps online, and discharge PSI• Tunnel condensate pumps leaking• Cond economizer rounds• Fan status, pump online, water level, flue gas temp in/out, makeup temp
to V01, makeup temp to HA-02, condensate temp leaving HA-01• Glycol system• Pump online, inlet/outlet PSI, glycol inlet/outlet temp, CHW inlet/outlet
temp• Chemical pumps rounds (day shift only)• Softeners rounds (day shift only)• Fuel oil/SPCC rounds day shift only
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EAST PLANT– The following is recorded, during operator rounds, once on dayshift, and once on
nightshift:• Deaerators• Pressure, steam temp, water temp, PC bypass closed• Heating water pumps• Suction/discharge PSI• HP steam to DA• Top/bottom PSI• Steam letdown• Top/bottom PSI, SF#1 breaker on/off• Rooftop• Breakers• Operating Floor• Leak detector, NG/propane valve, HRS inlet/outlet water temp, HRS drain
water temp, HRS soft water inlet/outlet PSI, blowoff tank outlet temp• Rooftop
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EAST PLANT– The following is recorded, during operator rounds, once on dayshift, and once
on nightshift:• Breakers• Basement area• Steam header PSI, city water inlet PSI, city water PSI after strainer, vacuum
skid sight glass, pumps 5-8, booster pumps 1 and 2, HP drip station, fire water system, sump pump station, AHU-1 breaker
• Fan room• SF-2-SF-4 breakers: valves open, AHU-2 breakers: valves open• Outside building• Condensate tank levels, natural gas piping, propane skid, vaporizer,
emergency generator, propane unloading area• Night Shift Only: Softeners online, GMPs, polishers online, boiler 1-15,
chemical pump, softeners, and brine tank
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STEAM HEATING SYSTEM
EXAMPLE WEST PLANT ROUNDS SHEET (front and back)
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STEAM HEATING SYSTEM
EXAMPLE EAST PLANT ROUNDS SHEET (front and back)
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STEAM HEATING SYSTEM
TYPICAL PROBLEMS ASSOCIATED WITH THE STEAM HEATING SYSTEM– Clogged Strainer
• Most likely cause is mesh strainer is full of debris.– Failed Steam Trap
• Most likely cause is failure or clogging of vent.– Flooding of Steam Vault or Steam Entry Pit
• Most likely cause is sump pump has failed or drain is clogged.
– Failed PRV• Most likely cause is clogged valve, degraded diaphragm, or spring
requires adjustment
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QUESTIONWhere does Operations Monitoring take place?
– Control Room in each steam plant– Control Room in West Campus Steam Plant– Control Room in Chiller Plant #2– Control Room in Chiller Plant #1
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ANSWERControl Room in Chiller Plant #2