QA/QC for Sampling and Analysis
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 for 0.5-inch tubing
Drum boiler water from blowdown lines  or circulation pump manifold
Velocity > 2 ft/s for 0.5-inch tubing
Drum boiler water from a downcomer or blowdown
Isokinetic sampling velocity
Velocity of > 2 ft/s for 0.5 inch tubing if consistent with isokinetic sampling requirements
Isokinetic sampling nozzles
Saturated steam for steam leads
Isokinetic sample velocity
Isokinetic sampling nozzle
Superheated steam
Isokinetic sample velocity
Isokinetic sampling nozzle
Condensate at subatmospheric pressure
Velocity of > 2 ft/s for 0.5-inch tubing
Large diameter sampling nozzles net positive suction head actual (NPSHA) greater than net positive suction head required (NPSHR) at all conditions

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.
Check the sampling system
Once a 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 a 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 a year
7.
Inspect sampling nozzles for deposits
As required
8.
Inspection clean, or replace sample line filters
Every Instrument Calibration
On-Line Analytical Instruments
1.
Consistency of data (pH vs. conductivity vs. NH3, anions vs. cation conductivity, etc.)
Daily
2.
Flow and temperature dependency
Once a year
3.
Effects of sample line filters (total vs. filtered)
Every 2 years
4.
Calibration with Sample Synthesizer or a check against detail grab sample analysis or a check with a quality portable instrument
Once a year
5.
Calibration records (before and after calibration)
Every calibration, review once a year
6.
Effects of sample lines - compare sample at the root valves vs. instrument panel
Every five years
7.
Dissolved oxygen analyzers vs. Chemets
Twice a year
8.
Cation conductivity ion exchange resin
Daily
Grab Sample Analysis
1.
Check the laboratory procedures vs. ASTM or other standards
Every 2 years
2.
Intra-laboratory precision:  duplicate blind samples analyzed by 3 analysts
Once a year
3.
Inter-laboratory precision:  duplicate blind samples analyzed by 2 outside laboratories
Once a year
4.
Laboratory dilution (reagent) water analysis (no storage allowed)
Conductivity continuously
Suspended solids twice a year
5.
Calibration of laboratory instruments
As required by instrument vendor or at least once a month
6.
Check of grab sampling procedures and containers (container materials, preparation, storage, etc.)
Once a year
7.
Laboratory audit
Every 2 years