Steam Heating System

1. Steam Heating System DU-101-PP

2. 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

3. 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.

4. 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

5. 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

6. 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.

7. 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.

8. STEAM HEATING SYSTEM • QUESTION • Why is condensate returned to the plant? • For disposal • To preheat feed water • To fill the water towers • To absorb steam

9. STEAM HEATING SYSTEM • ANSWER • To preheat feed water

10. STEAM HEATING SYSTEM • QUESTION • How does heat flow? • Lower temperature to higher temperature • Higher temperature to lower temperature • Heat does not flow • Downhill

11. STEAM HEATING SYSTEM • ANSWER • Higher temperature to lower temperature

12. STEAM HEATING SYSTEM • QUESTION • How 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

13. STEAM HEATING SYSTEM • ANSWER • Water is heated enough above the boiling point to produce steam

14. 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.

15. 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.

16. 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

17. STEAM HEATING SYSTEM • HIGH PRESSURE STEAM HEADER • Sensors at the HPS Header send data on the steam to the Control Room.

18. STEAM HEATING SYSTEM • EAST CAMPUS STEAM PLANT

19. STEAM HEATING SYSTEM • WEST CAMPUS STEAM PLANT

20. STEAM HEATING SYSTEM • QUESTION • Where 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

21. STEAM HEATING SYSTEM • Answer • East Campus and West Campus Steam Plants

22. STEAM HEATING SYSTEM • QUESTION • What is the nominal pressure of steam leaving the HPS Header? • 75 psig • Less than 16 psig • 125 psig • 170 psig

23. STEAM HEATING SYSTEM • ANSWER • 125 psig

24. STEAM HEATING SYSTEM • QUESTION • Which 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

25. STEAM HEATING SYSTEM • ANSWER • All boilers that are on line

26. 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

27. 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.

28. 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

29. 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

30. 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.

31. STEAM HEATING SYSTEM • PIPING • Three Pipe System • High Pressure Steam (HPS Supply) • High Pressure Condensate (HPC Return) • Pumped Condensate (PC Return) DRIP LEG STATION MANHOLE

32. STEAM HEATING SYSTEM • THREE PIPE SYSTEM • HPS Supply carries steam from the plant to Campus and Medical Center buildings. DRIP LEG STATION MANHOLE HPS SUPPLY

33. STEAM HEATING SYSTEM • THREE PIPE SYSTEM • Condensate 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

34. STEAM HEATING SYSTEM • THREE PIPE SYSTEM • Condensate from air handlers is pumped from buildings to the Steam Plant through the PC Return piping PC RETURN DRIP LEG STATION MANHOLE

35. STEAM HEATING SYSTEM • QUESTION • What 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

36. STEAM HEATING SYSTEM • ANSWER • 35 miles

37. STEAM HEATING SYSTEM • QUESTION • Approximately how much piping is in the Underground Steam and Condensate Distribution System? • 300 feet • 50 miles • 35 miles • 900 yards

38. STEAM HEATING SYSTEM • ANSWER • HPS Supply, HPC Return, PC Return

39. STEAM HEATING SYSTEM • QUESTION • What is carried in PC Return piping? • Condensate from building • Steam from Plant • Condensate from Drip Leg Station • LPS from PRV Station

40. STEAM HEATING SYSTEM • ANSWER • HPS Supply, HPC Return, PC Return

41. STEAM HEATING SYSTEM • TUNNELS • Provide easy access to the Underground Steam and Condensate Distribution System to personnel • Maintaining piping, valves, sensors, and controls • Isolating segments of the system

42. STEAM HEATING SYSTEM • UNDERGROUND PIPING • The majority of piping is buried. • Steam Vaults (manholes) provide access and junction points

43. STEAM HEATING SYSTEM • STEAM VAULTS • HPS supply side of the vault • 36 inch Manhole provides access for maintenance • Drip Leg Station drains and cleans condensate from HPS • PC return side of the vault • 24 inch Manhole provides access for maintenance of condensate return piping • Sump 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

44. STEAM HEATING STATION • STEAM VAULT • HPS Supply Side • Drip Leg Station • 36 inch Manhole for maintenance access MANHOLE HIGH PRESSURE STEAM DRIP LEG STATION

45. STEAM HEATING SYSTEM MANHOLE • STEAM VAULT • PC Return Side • 24 inch manhole lid for maintenance access • Sump with Pump MAIN PC RETURN SUMP PUMP SUMP

46. STEAM HEATING SYSTEM • STEAM VAULT • Top View of Junction HPS SUPPLY BRANCH PC RETURN BRANCH HPS MANHOLE MAIN HPS SUPPLY MAIN PC RETURN PC MANHOLE

47. STEAM HEATING SYSTEM • STEAM VAULT DRIP LEG STATION • Drip Pocket • Strainer • Steam Trap HPS SUPPLY ISOLATION VALVES DRIP POCKET TO HPC RETURN BLOWDOWN TEST TEE STRAINER STEAM TRAP BLOWDOWN DRAIN

48. 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. HPS SUPPLY DRIP POCKET CONDENSATE

49. STEAM HEATING SYSTEM • STEAM VAULT DRIP LEG STATION • Strainer • Condensate from the drip pocket passes through the strainer • Fine mesh screen collects dirt and particulates DRIP POCKET SCREEN STRAINER

50. 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. VALVE INVERTED BUCKET CONDENSATE FROM STRAINER TO HPC RETURN STEAM TRAP