A fuel test is only as useful as the sample tested. A clean instrument and correct procedure cannot compensate for a sample that does not represent the delivery, tank, container or batch under investigation.
Representative sampling and evidence preservation are particularly important where abnormal fuel is suspected, equipment has been affected or a commercial dispute may follow.
Define the purpose before sampling
Ask what decision the sample must support:
- Routine delivery screening
- Density measurement
- Marker testing
- Water or sediment investigation
- Suspected product mixing
- Vehicle or equipment failure investigation
- Supplier or transporter dispute
- Laboratory analysis
The purpose affects where, when and how many samples should be taken.
Understand the product location
Fuel may be sampled from:
- Road tanker or compartment
- Storage tank
- Drum or intermediate container
- Dispensing pump
- Vehicle tank
- Delivery line
- Retained supplier sample
Contamination, water or sediment may not be evenly distributed. A sample from the top of a tank may not represent material concentrated at the bottom.
Use suitable sampling equipment
Sampling equipment and containers should be clean, compatible with the product and appropriate for the intended test.
Consider:
- Container material
- Cleanliness and dryness
- Secure closure
- Required sample volume
- Space for thermal expansion where applicable
- Tamper-evident sealing
- Suitability for transport to a laboratory
Do not use an unidentified household container that may contain residues or react with the sample.
Avoid cross-contamination
Cross-contamination can occur through containers, funnels, sampling devices, gloves or surfaces.
Good practice includes:
- Using dedicated or properly cleaned equipment
- Avoiding contact with water, dirt, cleaning products or other fuels
- Keeping lids and closures clean
- Not returning tested fuel to the original tank
- Separating samples from different products and locations
Record the sample identity immediately
Label the sample at the point of collection. Do not rely on memory later.
The label and sample record should include:
- Unique sample number
- Date and time
- Location
- Fuel type
- Tank, compartment, pump or vehicle reference
- Supplier
- Transporter
- Delivery-note, invoice or batch number
- Sampling point and method
- Name and signature of sampler
Photograph the context
Photographs can support the written record. Capture:
- Delivery vehicle and registration where relevant
- Compartment or tank identification
- Seals
- Delivery documentation
- Sampling point
- Sample containers and labels
- Field-test setup and result
- Visible water, sediment, colour or separation
Photographs should supplement, not replace, a written chain of evidence.
Take duplicate or split samples where appropriate
Where a dispute is possible, consider collecting enough product for:
- Immediate field screening
- Retained control sample
- Supplier or counterparty sample
- Independent laboratory sample
Each sample should be separately sealed, labelled and recorded. The exact process should be appropriate to the seriousness of the matter and any contractual or laboratory requirements.
Preserve chain of custody
Chain of custody records who collected, held, transferred, opened and tested the sample.
Record:
- Sample number
- Seal number
- Person releasing the sample
- Person receiving it
- Date and time of each transfer
- Purpose of transfer
- Condition of seal
- Storage conditions
Unexplained gaps can weaken the evidential value of the sample.
Store and transport samples correctly
Fuel samples are flammable and must be handled, stored and transported safely and lawfully. Protect samples from heat, ignition sources, contamination and unauthorised access.
For laboratory submission, follow the laboratory’s instructions regarding:
- Container type
- Minimum volume
- Labelling
- Preservation
- Packaging
- Transport
- Requested analytical methods
Do not delay material investigations
If abnormal fuel may damage vehicles, equipment or storage infrastructure, isolate the affected product where safe and obtain appropriate technical advice. Continuing to use or mix the product may make it harder to determine the cause.
Preserve relevant records such as:
- Purchase orders
- Supplier invoices
- Loading and delivery notes
- Tank readings
- Vehicle or equipment records
- Maintenance reports
- Customer complaints
- Communication with supplier and transporter
Match the test to the question
Density, marker screening, water checks and laboratory analysis answer different questions. Select the method after defining the suspected issue and consequence.
UFuel’s fuel-testing centre explains available field products and their limitations. For help selecting a test, contact UFuel.