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Why is the coulometric method for Oil Moisture Tester in oil products the gold standard?
The Karl Fischer titration method was first published by the German chemist Karl Fischer in 1935. The original method used volumetric titration until the coulometric version was developed in 1959, specifically for the determination of trace moisture.
The core hardware includes a microprocessor, a dual-circuit balanced titration system, and an anti-leakage electrolytic cell. It integrates automatic calibration, data storage (more than 1000 entries), display of electrolytic curves, and thermal printing functions. Through automatic adjustment of the electrolytic current (0-430mA) and real-time monitoring technology, it enables rapid determination of sample moisture content, and supports solid, liquid, and gaseous sample compatibility.
What are the precautions to be observed during use?
1) Samples must be drawn using a dry syringe to prevent moisture absorption from the air (the coulometric method is sensitive to ambient humidity).
2) Ketone- and aldehyde-containing oils react with methanol, leading to falsely high readings; specialized Karl Fischer (KF) reagents or the oven method should be used instead.
3) Perform a blank drift compensation (taking less than 10 minutes) each time the instrument is powered on to ensure a stable baseline.
What data is used to verify the accuracy of Oil Moisture Tester?
1. Titration method: Coulometric titration (coulometric analysis)
2. Display: 5-inch 800*480 capacitive touch screen
3. Electrolysis current control: 0~400mA automatic control
4. Measuring range: 3ug~100mg
5. Resolution: 0.1µg
6. Accuracy: (10µg~1000µg)±3µg; no more than 0.3% above 1000µg
7. Printer: micro thermal printer
8. Power supply voltage: 220×(1±10%)V
9. Power supply frequency: 50×(1±5%)Hz
What are the specific challenges and solutions associated with testing for water content in oil products?
Oil sample insoluble in reagent
Oil is a non-polar organic substance and is immiscible with Karl Fischer reagents (polar solvents)
Use oil-specific reagents containing chloroform, hexane, or xylene; increase stirring intensity
Difficulty injecting high-viscosity oil samples
Viscosity of gear oils, greases, etc., can reach up to 100,000
Heat the sample inlet (60°C) to reduce viscosity; use a wide-bore syringe; dilute with solvent before injection
Interference from oil additives
Certain antioxidants and detergents may undergo side reactions with Karl Fischer reagents
Use ketone-based reagents (pyridine-free formulations) to minimize side reactions; optimize the endpoint determination algorithm
Is the maintenance performed just once to reduce costs?
Daily: Replace the molecular sieve drying tube; check the electrolyte color (replace if it darkens).
Weekly: Calibrate using a 10 μg water standard; clean the electrode if the error exceeds 2 μg.
Monthly: Calibrate using a sodium tartrate dihydrate standard reference material to ensure ISO 17025 traceability.
After-sales Service
Warranty Policy: 24-month warranty on the entire machine (excluding damage caused by human error and consumables).
Lifetime Maintenance: Lifetime paid repair service provided after the warranty period, charging only the cost of materials.
Rapid Response: 24/7 technical support hotline, fault response time < 2 hours.
Where do users employ Oil Moisture Tester?
1) Power companies/substations: Excessive moisture in transformer oil is a primary cause of dielectric breakdown; ASTM D1533 is a mandatory test.
2) Oil manufacturers/lubricant distributors: ASTM D6304 requires lubricant moisture content to be <200–500 ppm.
3) Petrochemical/Pharmaceutical industries: Moisture content in solvents, esters, and lithium-ion battery electrolytes must be <30–100 ppm.
4) Third-party testing laboratories: Used for ISO 17025 accreditation; requires traceable calibration data.
FAQ
Q1: What is the difference between the coulometric and volumetric methods?
A: The coulometric method generates iodine via in-situ electrolysis and is suitable for trace water levels ranging from 1 ppm to 0.1%; the volumetric method relies on a burette and is suitable for moisture content >0.1% . Transformer oil analysis must use the coulometric method (ASTM D1533).
Q2: What level of precision (in ppm) can be achieved?
A: The instrument has a sensitivity of 0.1 μg , allowing for a detection limit of 0.1 ppm for a 1 mL oil sample. Actual measurements of water samples in the 10–100 μg range show a deviation of ≤±1 μg , meeting the standard of ≤10 ppm for new oil .
Q3: Does it comply with international standards?
A: It fully complies with ASTM D1533 (insulating oil), ASTM D6304 (petroleum products), IEC 60814, GB/T 7600, and SH/T 0246 .
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