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Steam and Water Sampling

Steam and Water Sampling. “Sampling 101” and Sample System Components. Utility Market Components. Back Pressure/Relief Valve - BPRV ™. Sample Coolers. Cation Resin Columns. Thermal Shut Off Valve - TSV ™. Variable Pressure Reducing Elements VREL ™. Steam and Water Sampling. Why sample?

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Steam and Water Sampling

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  1. Steam and Water Sampling

  2. “Sampling 101” and Sample System Components

  3. Utility Market Components Back Pressure/Relief Valve - BPRV™ Sample Coolers Cation Resin Columns Thermal Shut Off Valve - TSV™ Variable Pressure Reducing Elements VREL™

  4. Steam and Water Sampling • Why sample? • Monitor/adjust water chemistry to: • Maximize heat transfer efficiency • Maximize time between chemical cleanings • Maximize boiler life and turbine life • Minimize operating & maintenance costs

  5. Typical Plant Diagram

  6. Typical Plant Diagram

  7. Important Sample Conditioning Parameters “The Primary objective of any sampling system is to transport and condition a sample without altering the characteristics of interest. The system parameters which need to be controlled are velocity, pressure and temperature.” Source: EPRI CS-5164, April 1987

  8. Sample Point Selection, CC System • Gas Turbine • Generators • Steam Turbine – Main Steam SiO2, Na, CC • HRSG – Boiler Drum - pH, SC, PO4, SiO2, Na, Chloride • Condenser – pH, SC, CC, Na, SiO2, DO • Feed water – SC, CC, Na, pH, SiO2 • Boiler Feed Pump • Not shown: • Deaerator – DO, pH, SC, CC • Economizer – pH, CC

  9. Sample Point Selection Based on: • System design • Subject constituents • Chemical treatment • System specific problems

  10. Sample Velocity • Velocity should be 5-6 ft/sec (1.8 m/sec) to maintain equilibrium of ionic and particulate components • Ideally, sample lines in sample system should be 1/4” (6.35mm) tube; flow rate at of about 1200 cc/min and velocity at 6 fps (1.8 m/s). • Flow rate of 3300 cc/min in a 3/8” (9.5mm) tube with .065” (1.65mm) wall is 6 fps

  11. Erosion/Deposition and Equilibrium

  12. Velocity –vs- Deposition

  13. Deposition –vs- Time

  14. Sample Lag Time Flow rate Velocity Tube Size cc/min Ft/sec Lag Time/1000’ 1/4”x.042” wall 500 2.5 6.5 min 12006.02.8 min 3/8”x.065”wall 500 0.9 18.7 min 1200 2.2 7.6 min 16663.05.6 min Theoretically correct > 3300 6.0 2.8 min But not practical 1/2”x.125 wall essentially equal to 3/8”x.065 wall 6.0 ft/sec is approximately 1.8 m/sec

  15. P&ID – Complete System

  16. Temperature Control – Primary Coolers • Primary sample cooler approach temperature: 5 ºF (2.8 ºC) of coolant temperature • Corrosion resistant tubing (18% Cr, 8% Ni), 316 SS, internal baffles • Coil tubing to meet velocity requirements (1/4”, 3/8” O.D.) (6.35mm, 9.5mm)

  17. Sample Coolers

  18. Sample Coolers

  19. Sample Coolers • High Efficiency, Counter Flow Design • All Stainless Steel Construction • Single Gasket Design • 100% Hydrostatic Testing, Tube and Shell • Variety of Shell and Tube Materials Available

  20. Standard Shellside Materials: • 316/316L Stainless Steel • 304 Stainless Steel • 90/10 CuproNickel Sample Coolers - Materials Standard Tubeside Materials: • 316/316L Stainless Steel • Alloy 625 (Inconel 625)

  21. Special Sample Coolers • Special sample coolers • Cooling water with elevated chlorides and DO such as cooling tower water or potable water sources • High temperature samples • Use Inconel 625 coils, CuNi shells

  22. Sample Coolers - Materials Optional Tubeside Materials, short coil only: • Alloy C-276 (Hastelloy) • Alloy 200 (Nickel) • Alloy 400 (Monel) • Titanium • Zirconium • 310SS Optional Shellside Materials: • 316/316L SS Additional materials may be possible. Orbitally welded long coils currently available in Zirconium

  23. Sample Coolers

  24. Competitive Products • Waters Equipment – USA • Dr Thedig - Germany • Forbes Marshall – India • Lowe – U.K. • DKK – Japan • Nikkiso – Japan/Taiwan • Eurosysteme • Watcom • Westhoff

  25. Competitive Products • Analyzer manufacturers • ABB • Yokagawa • Emerson • Swan • Others –local

  26. Competitive Products • May not offer performance calculations • Carbon steel shells • Thin wall shells (drawn) • May not offer dual baffle • Tie-rod designs • May offer dual-tube units which don’t work for ASTM recommended flows

  27. Important Sample Conditioning Parameters – Secondary Cooling • Secondary cooling • Recommended to control sample temperature to 77 °F +/- 1 °F (25 °C +/- .5 °C) • Analyzer temperature correction algorithms should be evaluated for: • Suitability given the expected sample matrix • Sample temperature range • Sensitivity • Potential correction factor error

  28. Important Sample Conditioning Parameters – Secondary Cooling • Isothermal Bath • Coils in chilled water bath • Chiller with hot gas bypass • Thermal bypass valves • Must have good mixing in bath • Bypass valves can be problematic

  29. Important Sample Conditioning Parameters – Secondary Cooling • Individual sample coolers • Individual, high efficiency coolers for each sample stream • Chilled water supply with hot gas bypass 75-76 °F +/- 1 °F (23.9 –24.4 °C) • Hot gas bypass can add heat into system if samples are sub cooled

  30. Important Sample Conditioning Parameters – Secondary Cooling • Field Study • 19 Fossil and Nuclear plants • 11 isothermal bath systems • 8 individual cooler systems • Isothermal baths averaged 77 °F +/- 5 °F ( 25 °C +/- 2.7 °C) • Max deviation 28 °F (15.6 °C) • Individual secondary coolers averaged 77 °F +/- 2 °F ( 25 °C +/- 1 °C) • Max deviation 5 °F (2.7 °C)

  31. Important Sample Conditioning Parameters • Pressure Reduction • All Wetted Parts Stainless Steel • Needle valves for 500 psig and less • Rod-in-tube for pressures greater than 500 psig • Drag valves and capillary tubes are prone to plugging • Adjustable rod-in-tube preferable • Cleanable in place • Adjust to proper flow

  32. Pressure ReductionVREL™ (Variable Pressure Reducing Element)

  33. VREL™

  34. VREL™

  35. Competitive Products • Look alike or similar rod-in-tube designs – may or may not operate well • Capillary tubes - plug • Drag valves – plug - expensive • Multiple needle valves – wear – same price as VREL

  36. Important Sample Conditioning Parameters • Flow Control • EPRI/ASTM recommends a Rod-in-tube pressure reducing device and backpressure valve combination • Constant sample velocity/flow • Reduced possibility of crud bursts • Constant flow to on-line analyzers for repeatable analysis results • BP/RV acts as a “shock absorber”

  37. Back Pressure Regulator/Relief Valve

  38. BP/RV • Assures Constant Pressure/Flow to Analyzers • Protects System From Over Pressurization • Large Orifice Won’t Plug or Stick • Constant Pressure Over Wide Flow Range • Regulates to 20 psi (standard) • Metallic Wetted Parts – Stainless Steel • Elastomer – Viton • Seat – PEEK • Optional pressure settings: 5 psig (0.3 barg), 7 psig (0.5 barg), 12 psig (0.8 barg), 28 psig (1.9 barg), 42 psig (2.9 barg), 60 psig (4.1 barg)

  39. BP/RV

  40. Back Pressure Regulator/Relief Valve

  41. Competitive Products • Tescom • Go • Coniflo • Not designed specifically for the application

  42. TSV(Thermal Shut Off Valve)

  43. Thermal Shut Off Valve (TSV) • Protects analyzer cells • Protects operators • Mechanically Actuated, Automatic Shut-Off for Thermal Protection • Visual Trip Indication • Optional Switch for Remote Indication • Requires Manual Reset • Latching Design • No Pneumatic or Electrical Power Required

  44. Competitive Products • Wax valves – automatically reset or are one use • Sensor, controller and solenoid valve – expensive – problematic • Bi-metal, mechanical or electro-mechanical – trip point is not accurate, prone to failure

  45. Thermal Shut Off Valve (TSV) • Standard Wetted Materials • 316 Stainlesss Steel, Viton, PEEK • Optional Elastomer • Kalrez • Standard Temperature Set Point = 120° F (49° C) • Optional Temperature Set Points = 104° F (40° C), 140° F (60° C), 160° F (71° C), 153° F (67° C), 194° F (90° C), 203° F (95° C), 210° F (99° C)

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