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CAN CGSB 3.0 No. 140.1-2017: Standard Test Method for Water Separation Characteristics of Aviation Turbine Fuels (Portable Separometer Method)
Essential Guidance on Scope, Procedure, and Compliance for the Canadian National Standard for Aviation Fuel Testing
Introduction and Scope
CAN CGSB 3.0 No. 140.1-2017, part of the CGSB 3.0 series of test methods for petroleum and associated products, specifies a procedure for determining the water separation characteristics of aviation turbine fuels using a portable separometer. This method is essential for evaluating whether a fuel can rapidly separate from emulsified or free water under controlled conditions—a critical property for safe engine operation and fuel system reliability.
The standard applies primarily to kerosene-type aviation turbine fuels (e.g., Jet A-1 as specified in CAN/CGSB-3.23 or ASTM D1655) and can be used for fuels containing additives such as corrosion inhibitors, static dissipaters, antioxidants, and metal deactivators. It is intended for fuels produced from conventional petroleum refining processes and may also cover synthetic and blended turbine fuels where approved.
The method is not suitable for fuels containing alcohols, high concentrations of water-miscible additives, or fuels that have been treated with electrostatic separators or other conditioning processes that artificially alter the natural water separation behavior. The test provides a rapid, field-deployable means of assessing the presence of surface-active substances that inhibit water coalescence and separation.
Important: Results from this test are qualitative indicators of water separation ability. They must be interpreted in conjunction with other fuel property tests and specification limits. The method does not directly simulate dynamic fuel system conditions, but it correlates well with the fuel’s tendency to form hazy or water-contaminated mixtures in storage and handling.
Technical Requirements and Test Procedure
Principle of the Method
A fuel sample is first filtered to remove any free water and particulate matter. A precisely measured volume of fuel is mixed with a small volume of distilled water in a glass syringe. The mixture is agitated for a defined period to create an emulsion, then allowed to settle. The emulsified mixture is then forced through a coalescer element (a standardized fibrous pad) at a constant flow rate. The optical transmittance of the effluent stream is measured by a photocell as a function of volume or time, producing a transmittance vs. volume curve. The area under the curve is converted into a water separation index (WSI) value, typically ranging from 0 to 100.
Key Procedural Steps
| Step | Parameter | Requirement |
|---|---|---|
| Sample conditioning | Temperature | 20 ± 5 °C (unless otherwise specified in the fuel specification) |
| Fuel volume | Syringe capacity | 20 mL (or as specified by the instrument design) |
| Water addition | Volume of distilled water | 0.5 mL or 1.0 mL depending on the method variant |
| Agitation | Mechanical shaking | 60 seconds at a fixed frequency and amplitude defined by the instrument manufacturer |
| Settling time | After agitation | 30 seconds |
| Coalescer pad | Medium | Fiberglass, specific pore size and density per annex A of the standard |
| Flow rate | Through coalescer | Constant rate defined by the apparatus (typically 27 mL/min) |
| Detection | Optical transmittance | Wavelength ~780 nm (near-infrared), reference measurement with clean fuel |
Interpretation of Results
The reported value is the Water Separation Index (WSI). A higher WSI indicates better water separation characteristics (less interference from surface-active materials). Typical thresholds:
- WSI ≥ 90: Excellent separation ability; fuel has low surfactant content.
- WSI between 75 and 90: Acceptable for most applications.
- WSI below 75: Potential degradation in separation performance; may require further investigation or additive adjustment.
Tip: Always run a control sample of known WSI (e.g., a reference fuel with WSI between 85 and 95) during each test batch to verify instrument performance. Inconsistent temperatures or worn coalescer pads are the most common sources of error.
Apparatus and Instrumentation Requirements
The portable separometer specified in CAN CGSB 3.0 No. 140.1-2017 must meet the following design criteria:
- Syringe: Borosilicate glass, opaque or shielded to keep out ambient light, with a capacity of 20 mL ± 1 mL.
- Agitator: Motor-driven mechanism that produces a consistent back-and-forth motion with a stroke length of 50 mm and frequency of 300 oscillations per minute.
- Coalescer assembly: Spring-loaded holder ensuring uniform compression of the coalescer pad. The pad must be replaced after each test or as per the instrument manual.
- Optical system: A light-emitting diode (LED) source with peak emission close to 780 nm, and a photodetector that measures transmitted light through a 1 cm path length cell. The system must be calibrated using a neutral density filter or a certified reference fluid.
- Data acquisition: Microprocessor-controlled unit that records transmittance at a frequency of at least 10 samples per second and calculates the WSI automatically.
- Temperature conditioning: The entire test cell area must be enclosed in a temperature-controlled chamber that maintains 20 ± 5 °C.
Advantage: One of the main benefits of the portable separometer method is its speed (≈10 minutes per test) and portability. It can be used in field laboratories, refueling depots, and even on board aircraft carriers or remote airstrips to verify fuel quality prior to use.
Implementation Highlights and Quality Control
Adoption of CAN CGSB 3.0 No. 140.1-2017 in a testing laboratory requires careful attention to the following:
- Operator training: Personnel must be familiar with the instrument’s operation, especially the importance of using distilled water that is free of organic contaminants, and the need to handle coalescer pads with gloved hands to avoid transferring oils or moisture.
- Calibration and verification: The instrument must be verified each day of use by testing a certified reference fluid (e.g., ASTM WSI standard) or by running a control fuel with a known WSI obtained through interlaboratory studies. Weekly calibration checks are recommended.
- Coalescer pad management: Store pads in a sealed container away from solvents and excessive humidity. Do not reuse pads. Some instruments recommend conditioning the pad with a small volume of test fuel before the actual measurement.
- Sample handling: Collect fuel samples in clean glass containers, protect from direct sunlight, and test within 4 hours of collection if possible. If storage is necessary, keep at <10 °C and warm to test temperature before analysis.
- Interlaboratory precision: The standard provides repeatability (within-laboratory) and reproducibility (between-laboratory) limits based on round-robin tests. For WSI values near 85, repeatability is approximately ±3 and reproducibility ±6.
| Quality Control Activity | Frequency | Acceptance Criterion |
|---|---|---|
| Blank test (clean fuel) | Daily or before sample analysis | WSI ≥ 95 |
| Reference fluid check | Weekly | Within ±2 of certified value |
| Coalescer pad verification flow test | With each new lot of pads | Flow resistance within manufacturer’s specifications |
| Interlaboratory proficiency program | Quarterly | Z-score ≤ 2 |
Non-compliance risk: Failure to follow the calibration and verification procedures can lead to undetected instrument drift, resulting in incorrect WSI values. This could allow out-of-specification fuel to be accepted, posing a real risk to aircraft fuel systems, including filter plugging, icing, and microbial growth. Laboratories must ensure their quality management system covers all equipment and consumables.
Compliance and Regulatory Integration
CAN CGSB 3.0 No. 140.1-2017 is referenced directly or indirectly by several Canadian and international fuel specifications:
- CAN/CGSB-3.23-2019 – Aviation Turbine Fuel (Jet A-1) includes a mandatory requirement for water separation characteristics tested in accordance with No. 140.1.
- MIL-PRF-83133A (JP-8) – The U.S. military specification references the equivalent ASTM D3948; however, for fuels delivered in Canada, the CGSB method is often contractually required.
- DefStan 91-091 (UK) and NATO F-35 fuel specifications – While these refer to ASTM D3948, CAN CGSB 3.0 No. 140.1-2017 is considered technically equivalent and may be used with customer approval.
Laboratories seeking accreditation to ISO/IEC 17025 for this test must include the standard in their scope of accreditation. The CGSB standard is published in English and French, and amendments are issued periodically. Users should confirm they hold the latest version (2017 edition with any subsequent amendments).
Note: Although CAN CGSB 3.0 No. 140.1-2017 is based largely on ASTM D3948, there are minor procedural differences (e.g., specific temperature range, coalescer pad description). Always use the exact version referenced by the applicable fuel specification to avoid non-conformities. Some purchasers may require a statement of equivalency if using the CGSB method instead of ASTM.
Frequently Asked Questions
Q: What is the difference between CAN CGSB 3.0 No. 140.1-2017 and ASTM D3948?
A: Both standards use the same portable separometer principle and produce comparable results (WSI). The CGSB version is the Canadian national adoption of the method and includes specific references to Canadian fuel specifications, a tighter temperature control range (20 ± 5 °C vs. 20 ± 15 °C in some editions of ASTM D3948), and distinct packaging/formatting requirements. In practice, a fuel meeting either method is generally acceptable, but the governing specification should be consulted.
A: Both standards use the same portable separometer principle and produce comparable results (WSI). The CGSB version is the Canadian national adoption of the method and includes specific references to Canadian fuel specifications, a tighter temperature control range (20 ± 5 °C vs. 20 ± 15 °C in some editions of ASTM D3948), and distinct packaging/formatting requirements. In practice, a fuel meeting either method is generally acceptable, but the governing specification should be consulted.
Q: Can I use tap water or distilled water that is not freshly boiled?
A: No. Only freshly distilled water that has been boiled and cooled to remove dissolved gases and CO₂ is acceptable. Contaminants in the water can introduce surfactants or change the emulsion behavior, leading to erroneous WSI values. Water quality must be verified periodically by measuring its surface tension.
A: No. Only freshly distilled water that has been boiled and cooled to remove dissolved gases and CO₂ is acceptable. Contaminants in the water can introduce surfactants or change the emulsion behavior, leading to erroneous WSI values. Water quality must be verified periodically by measuring its surface tension.
Q: How long does it take to obtain a result?
A: The entire procedure from sample receipt to final WSI printout typically takes 10–12 minutes. This speed makes the method ideal for high-volume screening and field use.
A: The entire procedure from sample receipt to final WSI printout typically takes 10–12 minutes. This speed makes the method ideal for high-volume screening and field use.
Q: Are there any limitations for fuels containing synthetic components?
A: The standard was developed for conventional petroleum-derived fuels. For blends containing synthetic paraffinic kerosene (SPK) or hydroprocessed esters and fatty acids (HEFA), the method may still be applied if the fuel meets the specification density and viscosity ranges. However, the correlation of WSI to actual water separation performance may differ; users are advised to perform additional testing (e.g., high-pressure filter clogging tests) if the fuel is borderline.
A: The standard was developed for conventional petroleum-derived fuels. For blends containing synthetic paraffinic kerosene (SPK) or hydroprocessed esters and fatty acids (HEFA), the method may still be applied if the fuel meets the specification density and viscosity ranges. However, the correlation of WSI to actual water separation performance may differ; users are advised to perform additional testing (e.g., high-pressure filter clogging tests) if the fuel is borderline.
© Canadian General Standards Board 2026. This article provides an overview of CAN CGSB 3.0 No. 140.1-2017 and is intended for informational purposes. For official compliance, always refer to the current published edition of the standard.