Oil Acid Tester

 

What is Oil Acid Tester?

An oleic acid tester is an automated chemical analyzer used to precisely measure the acid content in petroleum products, such as transformer oil and lubricating oil. Its primary function is to monitor the degree of oil degradation and determine whether the oil has deteriorated, thereby ensuring the safety of industrial equipment.

 

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The instrument is based on the acid-base neutralization titration method and is fully controlled by a microcomputer:

1. Extraction: The oil sample is mixed with the extraction solvent and heated to ensure complete dissolution of acidic substances.

2. Titration: Standard alkaline titrant (such as an ethanol solution of KOH) is automatically injected to initiate the neutralization reaction.

3. End-point Detection: The reaction end-point is automatically detected using a color sensor (colorimetric method) or a pH electrode (potentiometric method).

4. Calculation: The acid value is automatically calculated and displayed based on the volume of alkaline solution consumed.

1. Fully Automated Potentiometric Titration

• Principle: This method relies on a pH electrode or ion-selective electrode to monitor changes in the solution’s potential in real time. During titration, as KOH is added, the solution’s potential changes gradually. When all acidic substances are completely neutralized, the potential undergoes a sudden change, and the instrument automatically detects this “inflection point” as the titration endpoint.
• Features: Highly automated, precise, and reliable; not affected by the color of the oil sample itself; ideal for dark-colored oils or laboratory analyses with stringent requirements for results.

2. Colorimetric Method / Color Indicator Method

• Principle: An indicator (such as phenolphthalein or thymol blue) is added to the oil sample solution; this indicator changes color at a specific pH value. During titration, the solution’s color gradually changes. Once all acidic substances are neutralized, the solution changes color and stabilizes, marking the endpoint.
• Manual/Semi-automatic: The color change is observed visually, suitable for educational settings or situations with limited budgets.
• Automatic: Utilizes an RGB color sensor to detect subtle color changes—such as a shift from yellow to blue or pink—to automatically determine the endpoint, thereby eliminating human error.

3. Coulometric Titration: Portable and Rapid Testing

• Principle: This method does not use an external titrant but instead generates a “titrant” (typically hydroxide ions, OH⁻) directly in the solution through electrolysis. The generated base immediately reacts with the acid in the oil sample.
• Features: Extremely fast reaction speed and high detection efficiency. Based on Faraday’s law, the instrument converts the electrical energy consumed during electrolysis into acid value and displays it directly. The entire process is clean and rapid, making it commonly used in handheld or portable rapid analyzers.

4. Sensor Method

• Principle: This is a relatively new cutting-edge technology that does not rely on titration.
• Examples: Interdigitated electrode sensors: Determine acid value by measuring the dielectric constant of the oil.
• Triboelectric/thick-film sensors: Generate electrical signals through the reaction of special materials with acidic substances.
• Features: The greatest advantage of this technology is that it requires no chemical reagents and enables non-destructive, in-situ, and continuous online monitoring. It represents an important future direction for intelligent monitoring of industrial oils. However, the maturity of these technologies varies, and most are still in the early stages of research and application.

 

Main Functions of the Oleic Acid Tester

1.Fully Automatic Acid Value Determination

Automatically completes the entire process—including sampling, liquid addition, stirring, heating extraction, titration, endpoint detection, calculation, and result printing—in accordance with national standards.

2.Parallel Testing of Multiple Samples

Supports simultaneous testing of 3, 5, or 6 samples, allowing multiple oil samples to be tested at once and significantly improving testing efficiency.

3.Automatic Data Calculation and Display

Directly displays acid value (mgKOH/g) and automatically calculates averages and deviations, eliminating the need for manual conversion.

4.Data Storage and Traceability

Can store hundreds to thousands of test data sets, supports querying and printing of historical records, and meets testing archiving requirements.

5.Automatic Cleaning and Waste Liquid Disposal

Automatically cleans tubing and cups after testing, reducing manual operations and preventing cross-contamination.

6.Printing and Communication Interfaces

Equipped with a built-in printer or supports data export via USB/serial port, facilitating the generation of test reports.

7.Suitable for Multiple Oil Types

Can test various petroleum products, including transformer oil, turbine oil, lubricating oil, fire-resistant oil, and insulating oil.

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Product Features

1.High Testing Accuracy and Good Repeatability

Utilizes a high-precision titration system with a resolution of up to 0.001 mgKOH/g, ensuring stable and reliable results.

2.Intelligent End-Point Detection to Minimize Human Error

Utilizes potentiometric titration as the primary method, detecting the end-point through sudden changes in electrode potential, which is more objective and accurate than manual colorimetry.

3.Simple Operation with Touchscreen Control

Features a large English-language touchscreen with one-touch startup, requiring no specialized chemical laboratory experience.

4.Safe and Eco-Friendly, Fully Enclosed Testing

A fully enclosed piping system minimizes the volatilization of toxic organic solvents, ensuring the safety of laboratory personnel.

5.Precise Heating and Temperature Control

Automatic temperature-controlled extraction ensures complete reactions, meeting the requirements of standards such as GB/T 264, GB/T 7599, and GB/T 28552.

6.High Interference Resistance and Stable Operation

Suitable for various environments, including substations, laboratories, and maintenance sites.

7.Compact Design and Easy Maintenance

Integrated design, low reagent consumption, low failure rate, and low long-term operating costs.

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1.Instructions for Using the Laboratory Fully Automatic/Semi-Automatic Oleic Acid Titrator

I. Pre-Test Preparation

Place the instrument on a stable surface, connect it to a power source, turn it on, and enter the main interface.

Check the reagents:

Standard titrant (KOH ethanol solution)

Extraction solvent (anhydrous ethanol, etc.)

Ensure there is an adequate supply of reagents and that there are no air bubbles in the tubing.

Prepare the oil sample: Shake thoroughly to remove impurities.

Place a clean, dry sample cup into the instrument’s sample station.

II. Sampling and Parameter Settings

Select the test method on the touchscreen: Acid Value Determination.

Enter information such as the sample number and oil sample weight.

Set test parameters (number of cups, whether to use heated extraction, etc.).

After confirming all settings are correct, pour the oil sample into the sample cup.

III. Start Automatic Testing

Click “Start” to initiate fully automatic operation:

Automatic addition of extraction solvent

Stirring and heated extraction

Automatic titration

Automatic endpoint detection

No manual supervision is required throughout the process; simply wait for the test to complete.

IV. Viewing and Recording Results

Upon completion of the test, the acid value (mg KOH/g) is displayed directly on the screen.

You can view individual cup results, the average value, and repeatability.

Click “Print” to generate a report directly, or save the data to a USB drive.

V. Post-Test Procedures

The instrument automatically discharges waste liquid and cleans the tubing and titration cups.

Remove the sample cup and clean the work surface.

Turn off the instrument, cover it with the dust cover, and organize the reagents.

VI. Precautions

Reagents are volatile; ensure adequate ventilation during operation.

Ensure the oil sample is homogeneous to prevent sedimentation from affecting the results.

Electrodes require regular maintenance and calibration to ensure accuracy.

If the instrument will not be used for an extended period, drain the reagents from the tubing to prevent crystallization and blockages.

2. Operating Procedures for Portable Rapid Test Kits

These devices are primarily used for rapid screening and are easier to operate.

• Sample Preparation and Reaction: Take a small amount of oil sample (approximately 1 drop) and add an extraction agent (e.g., 2 mL) and other reagents to initiate the reaction. Some devices come with pre-calibrated reagents.
• Instrument Testing: Place the reacted sample solution and the blank control solution into the corresponding test channels. Select the “Acid Value” or similar test item on the instrument, click the “Test” button, and wait for the results.
• Precautions Before Use: To ensure accuracy, check that the test kit is within its expiration date before use. If the device supports it, it is recommended to perform regular calibration using a standard oil sample to ensure the error is ≤±5%.

3. Traditional Manual Titration Procedure

This is the most basic method, with the core focus on precise control of the titration process and end-point determination.

• Solution Preparation: Weigh 2–3 g of oil sample and dissolve it in 50 mL of a mixed solvent (e.g., diethyl ether–ethanol 2:1).
• Start Titration: Add 1–2 drops of phenolphthalein indicator, then add KOH solution drop by drop using a burette.
• Determining the End Point: At the end point, the solution turns pink and does not fade within 30 seconds. Record the volume of KOH consumed.
• Manual Calculation: Record the volume of KOH consumed and substitute it into the formula AV (mg KOH/g) = (V × C × 56.1) / m to perform the calculation.

I. Classification by Level of Automation

1. Manual Titrators

• Key Features: All operational steps—including titration, shaking, and reading results—are performed entirely by hand.
• Advantages: Affordable, simple design, and low maintenance costs.
• Disadvantages: Low accuracy and high error rates; inefficient; endpoint determination relies on visual observation, making it highly subjective.
• Suitable Applications: Educational demonstrations and settings with extremely limited budgets.

2. Semi-automatic Titrators

• Key Features: Typically equipped with auxiliary tools such as magnetic stirrers, but endpoint determination still requires manual intervention.
• Advantages: Slightly more convenient to operate compared to fully manual models.
• Disadvantages: Still cannot avoid the subjective errors associated with visual endpoint determination.
• Suitable Applications: Preliminary screening where high precision is not required.

3. Fully Automatic Titrators

• Key Features: Highly automated, capable of automatically completing the entire process, including liquid dispensing, titration, stirring, calculation, and printing.
• Advantages: High precision, good reproducibility, high testing efficiency, and significantly reduced human error.
• Disadvantages: Expensive, complex maintenance, and requires operators with certain technical skills.
• Suitable Applications: Laboratories and quality inspection agencies with stringent requirements for data accuracy.

II. Classification by Detection Principle

1. Color Indicator Method

• Working Principle: Determines the titration endpoint by visually observing color changes in an indicator (e.g., phenolphthalein).
• Advantages: Low cost and simple instrument design.
• Disadvantages: Highly subjective; not suitable for dark-colored oil samples (e.g., waste lubricating oil, heavy oil); prone to errors.

2. Potentiometric Titration

• Principle: Utilizes a pH electrode or specialized electrode to monitor changes in solution potential in real time, automatically determining the endpoint based on a potential “jump point.”
• Advantages: Unaffected by oil sample color or turbidity; high precision (up to ±0.01 mgKOH/g); compliant with multiple international and national standards.
• Disadvantages: Relatively high instrument cost.

III. Classification by Usage Method (Testing Scenarios)

1. Laboratory Benchtop

• Features: Powerful functionality and precise measurements, but bulky and requiring fixed installation.
• Applicable Scenarios: Centralized testing at fixed locations, such as central laboratories and quality inspection centers.

2. Portable/Handheld

• Features: Compact size, simple operation, fast testing speed, and typically battery-powered.
• Applicable scenarios: Rapid on-site screening, field inspections, and testing alongside production lines.

3. In-line

• Features: Permanently installed on equipment or pipelines, enabling real-time, continuous, and automatic in-line monitoring of oil quality.
• Applicable scenarios: Intelligent monitoring of industrial equipment and unattended continuous operation systems.

Domestic Brands

1. Golldhome(Wuhan)

• Core Focus: Specializes in power testing equipment; offers both potentiometric titration and colorimetric methods; high cost-effectiveness and comprehensive after-sales support
• HM703 Three-Cup Fully Automatic Oleic Acid Value Tester
• Principle: Colorimetric indicator method / Potentiometric method
• Cup Capacity: 3 cups
• Suitable for: Small to medium-sized laboratories, moderate budgets
• Price: 25,000–32,000 RMB
• Advantages

1. Highly compatible with the power industry, compliant with GB/T 264/7599/28552
2. High efficiency with 3/6-cup capacity, automatic cleaning, simple operation
3. Nationwide after-sales service, complete spare parts, export-ready

2. Delite (Beijing)

• Model: A1041 Fully Automatic Acid Value Analyzer
• Principle: Potentiometric titration
• Features: PC connectivity, curve display, stable accuracy
• Applications: Petrochemical, research, universities
• Price: 10,000–15,000

3. Yuntang (Shandong)

• Model: YT-YSZ Fully Automatic Acid Value Tester
• Features: Touchscreen, high cost-performance ratio
• Price: Around 22,000

4. Chengdu Ruice

• Model: RCYS-006 Six-Cup
• Features: Approx. 2 minutes per sample, automatic calibration
• Price: 30,000–38,000

Imported High-End Brands：

1. Metrohm (Switzerland)

• Model: 888 Titrando Potentiometric Titrator
• Advantages: World-class precision, ASTM/ISO standards, durable electrodes
• Applications: Multinational corporations, third-party testing labs, research institutes
• Price: 100,000–200,000

2. Mettler Toledo

• Model: DL55 EasyTitr Series
• Advantages: Stability, high automation, powerful software
• Price: 80,000–150,000

3. Shimadzu

• Model: TITREX Series
• Suitable for: Petrochemical industry, precision testing
• Price: 90,000–180,000

 

Alternative Name

· Acid Value Tester

· Acid Number Tester

· Automatic Acid Value Analyzer

· Oil Acid Value Tester

· Transformer Oil Acid Tester

· Insulating Oil Acid Value Tester

· Acid Number Analyzer

· Acid Value Test Equipment

· Potentiometric Acid Value Tester

· Colorimetric Acid Value Tester

· Oil Acid Number Test Apparatus

· Fully Automatic Acid Value Tester

· 6 Cups Acid Value Tester

· Lab Acid Value Analyzer

· Portable Acid Value Tester

· Acid Value Tester with Printer

· Acid Value Tester ISO Standard

· Portable oil acidity meter

· Transformer oil acid value tester

· Insulating oil acid number analyzer

· Automatic Acid Value Tester

· Transformer Oil Acid Value Analyzer

· Acid Number Tester for Insulating Oil

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