Transcript Seminar on Sample Conditioning for Steam & Water Sampling
Steam and Water Sampling
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Sampling Solutions • Specialty Heat Exchangers
“Sampling 101” and Sample System Components
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Sampling Solutions • Specialty Heat Exchangers
Utility Market Components
Back Pressure/Relief Valve - BPRV ™ Thermal Shut Off Valve TSV ™
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Sampling Solutions • Specialty Heat Exchangers Sample Coolers Cation Resin Columns Variable Pressure Reducing Elements VREL ™
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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Sampling Solutions • Specialty Heat Exchangers
Typical Plant Diagram
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Sampling Solutions • Specialty Heat Exchangers
Typical Plant Diagram
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Sampling Solutions • Specialty Heat Exchangers
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 temperature .” and
Source: EPRI CS-5164, April 1987
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Sample Point Selection, CC System
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6.
7.
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
Tube Size 1/4”x.042” wall Flow rate Velocity cc/min Ft/sec 500
1200
2.5
6.0
Lag Time/1000’ 6.5 min
2.8 min
3/8”x.065”wall Theoretically correct
>
But not practical 500 1200
1666
3300 1/2”x.125 wall essentially equal to 3/8”x.065 wall 6.0 ft/sec is approximately 1.8 m/sec 0.9
2.2
3.0
6.0
18.7 min 7.6 min
5.6 min
2.8 min
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P&ID – Complete System
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Sampling Solutions • Specialty Heat Exchangers
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Sampling Solutions • Specialty Heat Exchangers
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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Sampling Solutions • Specialty Heat Exchangers
Sample Coolers
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Sampling Solutions • Specialty Heat Exchangers
Sample Coolers
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Sampling Solutions • Specialty Heat Exchangers
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)
Standard Shellside Materials:
316/316L Stainless Steel 304 Stainless Steel 90/10 CuproNickel
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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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Sampling Solutions • Specialty Heat Exchangers
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.
Sampling Solutions • Specialty Heat Exchangers
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 don’t 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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Sampling Solutions • Specialty Heat Exchangers
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Sampling Solutions • Specialty Heat Exchangers
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 Reduction
VREL ™ (Variable Pressure Reducing Element)
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Sampling Solutions • Specialty Heat Exchangers
VREL ™
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VREL ™
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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Sampling Solutions • Specialty Heat Exchangers
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Sampling Solutions • Specialty Heat Exchangers
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 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: 60 psig (4.1 barg) 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),
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Sampling Solutions • Specialty Heat Exchangers
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Sampling Solutions • Specialty Heat Exchangers
BP/RV
Back Pressure Regulator/Relief Valve
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Sampling Solutions • Specialty Heat Exchangers
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 ° C), 160 ° F (71 ° C), 153 ° F (67 ° C), 194 ° C), 210 ° F (99 ° C) F (40 ° F (90 ° C), 140 ° C), 203 ° F (60 ° F (95 °
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Sampling Solutions • Specialty Heat Exchangers
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Sampling Solutions • Specialty Heat Exchangers
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 +Ca +2 <=> 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 – Ca +2 – Mg +2 – Na + – Fe +2 – Cr +6 – Ni +3 – Cu +2 – Zn +2 – NH 4 +
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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 – closed conduits Standard Practices for sampling water from 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
Strainer, high pressure and temperature Sentry Equipment Corp
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Traditional sintered element filter, low temperature
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
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Sampling Solutions • Specialty Heat Exchangers