Steam and Water Sampling

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

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Typical Plant Diagram
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Typical Plant Diagram
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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

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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

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Sample Point Selection

• Based on
• System design
• Subject constituents
• Chemical treatment
• System specific problems

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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

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Erosion/Deposition and Equilibrium
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Velocity vs- Deposition
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Deposition vs- Time
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Sample Lag Time

• Flow rate
  Velocity
• Tube Size cc/min Ft/sec Lag Time/1000
• 1/4x.042 wall 500 2.5 6.5 min
• 1200 6.0 2.8 min
• 3/8x.065wall 500 0.9 18.7 min
• 1200 2.2 7.6 min
• 1666 3.0 5.6 min
• Theoretically correct gt 3300 6.0 2.8 min
• But not practical
• 1/2x.125 wall essentially equal to 3/8x.065
  wall
• 6.0 ft/sec is approximately 1.8 m/sec

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PID Complete System
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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)

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Sample Coolers
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Sample Coolers
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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

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Sample Coolers - Materials
Standard Tubeside Materials

• 316/316L Stainless Steel
• Alloy 625 (Inconel 625)

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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

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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
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Sample Coolers
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Competitive Products

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

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Competitive Products

• Analyzer manufacturers
• ABB
• Yokagawa
• Emerson
• Swan
• Others local

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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 dont work for
  ASTM recommended flows

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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

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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

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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

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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)

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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

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Pressure ReductionVREL (Variable Pressure
Reducing Element)
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VREL
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VREL
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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

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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

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Back Pressure Regulator/Relief Valve
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BP/RV

• Assures Constant Pressure/Flow to Analyzers
• Protects System From Over Pressurization
• Large Orifice Wont 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)

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BP/RV
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Back Pressure Regulator/Relief Valve
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Competitive Products

• Tescom
• Go
• Coniflo
• Not designed specifically for the application

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TSV(Thermal Shut Off Valve)
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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

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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

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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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Cation Resin Column
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Cation Resin Column

• Ion exchange resin uses porous beads that have a
  Hydrogen ion that can be exchanged for a cation.
• R the resin and H hydrogen ion
• 2R-H Ca2 ltgt R2-Ca 2H
• The Resin column acts somewhat like a filter
• Reduces the masking effect of ammonia
• Proper length dia. Ratio for good ion exchange
• Prevents channeling
• Refillable

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Cation Resin Column

• Major Cations in water
• Ca2
• Mg2
• Na
• Fe2
• Cr6
• Ni3
• Cu2
• Zn2
• NH4

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Competitive Products

• Many, varied
• Resin is mostly the same but length to diameter
  ratio is key to proper ion exchange
• A larger column may offer more resin but poorer
  ion exchange
• Tubes are usually thinner, poor quality

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ASTM Standards

• ASTM 3370 Standard Practices for sampling water
  from closed conduits
• ASTM 5540 - Standard Practices for flow control
  and temperature control for On-Line water
  sampling and analysis
• Shortcut to ASTMD5540.pdf
• ASTM 1066 Standard practices for sampling steam
• Note
• ASTM 1192 Similar to D5540 - suspended

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Conclusion

• A properly designed sample system transports
  and conditions samples from the point of
  extraction to analysis points without altering
  the characteristics of interest

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End Of Sampling Components
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Sample Line Fouling Solutions
Traditional sintered element filter, low
temperature
Strainer, high pressure and temperature
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Sample Line Fouling Solutions

• Sludge trap
• Designed to drop out particles rather than trap
  them and hold them in the flow stream.
• Installed upstream of primary sample cooler
• Usually limited to boiler drum or similar samples
• Requires periodic flush to drain and piping to
  safe location (HP header, blow down tank)

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Sample Line Fouling Solutions