Types of Samples. A sample is a small portion of a substance used to inspect or to determine the
quality of the total substance. The various types of samples of petroleum products are listed below:
Top Sample. A sample taken with a weighted bottle or beaker sampler from a depth of about 6 inches
below the surface of the tank's contents.
Upper Sample. A sample taken with a weighted bottle or beaker sampler from the middle of the top third
of the tank's contents.
Middle Sample. A sample taken with a weighted bottle or beaker sampler from the middle of the tank's
Lower Sample. A sample taken with a weighted bottle or beaker sampler from the middle of the bottom
third of the tank's contents.
Bottom Sample. A sample taken with a bacon bomb or thief sampler from material present on the
bottom of a tank.
All-Levels Sample. A sample taken by submerging a stoppered, weighted bottle or beaker sampler to a
point as near as possible to the tank draw off point, opening the sampler, and raising it at a constant rate
so that it is 75 to 85% full when it emerges from the liquid.
Average Sample. A sample that consists of proportionate parts from all levels of the container. For
example, an average sample from a horizontal, cylindrical tank or from a spherical tank should contain
more material from the middle of the tank where the diameter is greatest.
Composite Sample. A sample combining individual samples that represents the bulk of the product from
which it was taken.
- Single tank composite sample. A sample that is a blend of the upper, middle, and lower samples
from a tank's contents.
- Multiple tank composite sample. A sample that is a proportionate blend of individual, all-levels
samples taken from compartments containing the same grade of product. The sample consists of
parts in proportion to the volume of product in each compartment sampled.
Outlet Sample. A sample taken with a weighted bottle or beaker sampler at the level of a tank outlet,
whether fixed or swing line.
Drain Sample. A sample taken from the water drain-off or discharge valve.
Continuous Sample. A sample taken from a flowing pipeline in such a manner that the sample is a
representative average of the stream during the period of sampling.
On-Line Sample. A sample taken from a flowing pipeline by opening a valve and collecting the sample
during the flow of the product.
Sampling Procedures. A simple set of sampling procedures cannot be given because products are
different; the method of transportation and storage are different. Sampling requirements of many tests are
different. A few important sampling points are as follows:
Representative Sample. A sample must represent the entire quantity of product sampled. Otherwise,
the resulting analysis can only reflect the quality of a portion of the whole substance and the quality
reflected may be better or worse than the true quality.
Size of Sample. The normal size of a sample is 1 gallon for liquids and 5 pounds for semisolids. Special
samples and gasoline samples for testing performance number by the super charger method should be 5
gallons. Samples of jet fuel to be tested for thermal stability should be 5 gallons.
Standard Sampler. The sampler should be one of the standard types (ASTM D270) and the one best
suited to the product and to the carrier or container. However, in situations where a standard sampler is
not suitable because of the small opening through which the sample must be taken, an improvised
sampler can be used. In any case, the sampler must be clean and made of a material that will not
contaminate the sample.
Cleaning the Sampler. Rinse sampler and container with the product being sampled.
Protecting Samples. All sample containers should be protected for shipment. Samples of gasoline, jet
fuel, and kerosene should be protected from direct sunlight by using brown bottles or cans or by covering
clear bottles with paper or foil. Samples of gasoline and JP-4 should be kept cool (30 to 40F) if
possible to prevent loss of light ends. Samples of product containing lead additives must be protected
Sample Numbers. A sample number should be assigned to each sample and entered on the sample tag.
This number is made up of the last two digits of the calendar year and the sample number for that year.