Transcript Developments In Corrosion Monitoring

ER & LPR Monitoring Systems
Popular Corrosion Monitoring
Techniques
• Weight Loss Coupons
• Linear Polarisation Resistance Probes (LPR)
• Electrical Resistance Probes (ER)
• CEION Probes
• Hydrogen Probes
• Biofilm probes
Weight Loss Coupons
Weight Loss Coupons
3 inch strip coupons before cleaning
3 inch strip coupons after cleaning
Flush Disc
Top of line
Middle of Line
3” Strip (pair)
Multi –disc
Ladder Strip (pairs)
6” Strip (pair)
Bottom of Line
ER: The Ratiometric
Principle
SAMPLE
REFERENCE
The ratio of sample & reference elements resistance is a
measure of the corrosion affecting the exposed sample
element by a reduction in its surface area and therefore
increase in its resistance. The ratio Rs/Rr is converted to
metal loss in the measuring instrument. The slope of the
metal loss curve is the corrosion rate
ER Probes
Can be used in all systems
(Gas, Water, Oil)
Can measure erosion
Low sensitivity
Thinner elements improve sensitivity
At the cost of probe life.
Typical Flush Probe (High Pressure
System) showing F20 (0.5mm thick
element) Lifetime ½ element
thickness
•ELECTRICAL RESISTANCE (ER)
•ELECTRICAL RESISTANCE (ER)
Wire Loop Probe 1.0mm (40 thou’) element
Lifetime ¼ of probe thickness
ER Wire loop probe
with velocity shield
in 2” HP access
fitting
Tubular ER Probe
(left) in retractable
assembly. Max
pressure 1000 psi
•DCU3 Data Logger ER
or LPR Configurations
•4000 readings storage
•ATEX/CSA approval
•Also transmitter
capability
•Probe mounted for HP
applications, panel
mounted for LP
(retractable) assemblies
Linear Polarisation Resistance
(LPR)
Theory of Operation
The theoretical basis of the LPR technique was founded in a publication
dating back to 1957.
In the LPR technique, a potential (typically of the order of 10-20 mV) is
applied to a freely corroding sensor element and the resulting ("linear")
current response is measured.
The current measured in a conductive solution ie., a continuous phase of
water is proportional to the ‘corrosion’ current and is converted to
corrosion rate by multiplying the measured value by a conversion factor
depending on electrode size and electrode material
Probes
Linear Polarisation Resistance (LPR)
• Instant corrosion rates
• Used in conductive systems
• Can’t be used where oil is present
• Can’t be used in gas systems
Typical flush mounted 3-electrode
probe
•ACCESS SYSTEMS
RETRACTABLE
Flanged LPR assembly with protruding electrodes
LINEAR POLARISATION RESISTANCE (LPR)
Multi-Function instrument HHU-M for upload from data loggers (ER
& LPR configurations) and reading ER & LPR probes directly
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