Jonas, Inc.
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309 Highland Terrace
Prince Frederick, MD 20678
USA
Phone:  (410) 535-6851
Fax: (410) 535-6846
Email:
Specializing in Sampling and Instrumentation, Corrosion,
Water and Steam Chemistry, and Failure Analysis
jonasinc@steamcycle.com
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Serving the power industry since 1983
QA/QC for Sampling and Analysis
Copyright (c) 2009  Jonas, Inc.  All Rights Reserved
Common Errors in Laboratory Analyses:
-  Incorrect analytical procedure
-  Analytical interferences
-  Poor technique
-  Degradation of reagents utilized in analyses
-  Improper sampling procedures
-  Contamination of the sample during collection and storage
-  Reaction of the sample with the sample container
-  Chemical reactions during sample storage
-  Organic growth of bacteria and algae in sample container

Typical Sampling Errors:
-  Sample withdrawal (not representing the sampled steam, not representing all phases)
-  Deposition in sample tubing
-  Chemical reactions in sample tubing or cooler
-  Deposition in the pressure reducing device
-  Dissociation of water in the pressure reducing device
-  Leakage of cooling water into the sample in the cooler
-  Corrosion of the sampling system - generation of corrosion products
 
Summary of Criteria for Sampling:
Sample Criteria
 
 Pressurized Condensate and Feedwater with
 representative sampling of particulates
  Isokinetic Sampling Velocity
 
 Isokinetic Sampling Nozzle
 
 Velocity > 2 ft/s
 Drum Boiler Water from Blowdown Lines or
 Circulation Pump Manifold
  Velocity > 2 ft/s
 Drum Boiler Water from Blowdown or Downcomer  Isokinetic Sampling Velocity
 
 Isokinetic Sampling Nozzle
 
 Velocity > 2 ft/s
 Saturated Steam  Isokinetic Sampling Velocity
 
 Isokinetic Sampling Nozzle
 Superheated Steam  Isokinetic Sampling Velocity
 
 Isokinetic Sampling Nozzle
The following is a checklist for QA/QC procedures and the recommended times for their periodic application.  In new units or when the sampling and analytical systems are upgraded, all the checks should be covered during commissioning:
 
Sampling System
 1.  Inspect the Sampling System  Once per Year
 2.  Check the Sampling System for Deposits  Every 3 Years
 3.  Chemically Clean Sample Tubing  As Needed
 4.  Check Sample Coolers for Leaks  Once per Year
 5.  Check Sample Coolers for Deposits
 When Sample Temperature or
 Flow Indicate a Problem
 6.
 Inspect Sampling Nozzles and Valves for
 Integrity and Leaks
  Once Per Year
 7.  Inspect Sampling Nozzles for Deposits  As Needed
 8.  Inspect, Clean or Replace Sample Line Filters  Every Instrument Calibration
On-Line Analytical Instruments
 1.
 Consistancy of Data (pH vs ammonia vs conductivity,
 anions vs cation conductivity, etc.)
  Daily
 2.  Flow and Temperature Dependancy  Once per Year
 3.  Effects of Sample Line Filters (total vs filtered)  Every 2 years
 4.
 Calibration with Sample Synthesizer or check with
 detailed grab sample analysis or check with quality
 portable analyzer
  Once per Year
 5.  Calibration Records (before and after calibration)
 Every Calibration,
 Review Once per Year
 6.
 Effects of Sample Lines (compare sample at root valve
 to sample panel)
  Every 5 Years
 7.  Dissolved Oxygen Analyzer vs Chemets  Twice per Year
 8.  Cation Conductivity Ion Exchange Resin  Daily
Grab Sample Analysis
 1.
 Check Laboratory Procedures vs ASTM or other
Standards
  Every 2 years
 2.
 Intra-Laboratory Precision: Duplicate Blind Samples
 Analyzed by 3 Analysts
  Once per Year
 3.
 Inter-Laboratory Precision:  Duplicate Blind Samples
 Analyzed by 2 Outside Laboratories
  Once per Year
 4.
 Laboratory Dilution (Reagent) Water Analysis
 (no storage allowed)
 Conductivity Continuously,
 Suspended Solids Twice per Year
 5.  Calibration of Laboratory Instruments
 As Recommended by Manufaturer,
 At Least once per Month
 6.
 Check of Grab Sampling Procedures and Containers
 (container materials, storage, preparation, etc.)
  Once per Year
 7.  Laboratory Audit  Every 2 Years