© 2019 Department of Petroleum Resources. All rights reserved Department of Petroleum Resources (DPR) PROCEDURE GUIDE

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2.4.3.3 For tank with petroleum and petroleum products content of between 10ft - 15ft
(3.048m-4.572m) in depth, two samples are withdrawn as upper and lower samples from
which a composite is made.

Upper Sample: this is taken from the middle of the upper third of the level of petroleum or
petroleum products that is 1/6th point from the top of the oil level.
Lower Sample: This is taken from the level of the fixed tank outlet or the middle of the lower
top portion of the tank for tanks with sump outlets.

2.4.3.4 For tank with petroleum and petroleum products content above 15ft (4.572m) in
depth, three samples are withdrawn as upper, middle and lower samples from which a
composite is made.
Upper Sample: This is taken from the middle of the upper third of the level of petroleum or
petroleum product, that is, 1/6th of the point from the top of the petroleum or petroleum
product’s level.
Middle Sample: This is taken from the middle of the tank content which is 3/6th of the point
from the top of the petroleum or Petroleum product level.
Lower Sample: This is taken from the middle of the lower third portion of the fixed tank
which is 5/6th of the point from the top of the petroleum or Petroleum product level. 2.5.3.3
Where the petroleum or petroleum product’s level in the tank is above 15ft (or 4.572m)
three samples are withdrawn from the following points from which the composite sample
is blended.

2.4.4 General Precautions
2.4.4.1 The following precautions shall be taken when carrying out a sampling exercise:
2.4.4.2 The exercise shall be conducted immediately after gauging the tank.
2.4.4.3 The sampling apparatus, including the cord, shall be clean and free of any
contaminant; also, the “thief-can” shall be cleaned with standard solvent and thoroughly
rinsed with petroleum or petroleum product being sampled before it is lowered into the
tank to withdraw the sample.
2.4.4.4 The cord of the “thief-can” shall be made of material that does not accumulate static
electricity.
2.4.4.5 The sample container shall be closed immediately it has been withdrawn from the
tank to prevent entry of water from external sources (for example, when the exercise is
being conducted in a wet weather).
2.4.4.6 It is very essential to ensure that the can is full at the desired depth before
withdrawing it to the surface.
2.4.4.7 When samples are required from more than one level in a tank, the order of
sampling shall be from the top downwards so that each sample will be obtained before the
liquid at that level is disturbed.