- Myth of density variation 3.0 kg/m3 in Petroleum Industry , (a Scholarly article)

- Myth of density variation 3.0  kg/m3 in Petroleum Industry 

Globally Oil industry Quality Manuals specify certain tolerance density variation for petroleum products like Gasoline,  Diesel fuels,  Aviation fuels etc, between density of dispatched products and density of received product. As long as this density difference remains less than permitted variation, the product is accepted in the system.

Particularly in field operations and market have notion that as long as density variation of petroleum products remains less than +/- 3.0 kg/m³  compared to parent density,  quality of product is OK ie. product meets specification requirements.

The above may be grossly wrong and consequence of practice of such error may result into a great loss financially as well as fetal if  Kerosene contamination with highly volatile fuel like gasoline or Naphtha.

Let us study following examples of  product blend prepared and tested for key parameters.

Table 1  -  Density variation is 2.0 kg/m³   however,  2 % HSD in MS  fails in Distillation Final Boiling Point  ( limit for MS FBP is 210 C max)  and  Residue on Evaporation tests ( Limit 5 units).

   

   Table 1.

Product	Density at 15C,  Kg/m3	FBP  Deg C	ROE
MS  (Gasoline)	734	192	1
HSD (Gasoil)	832	372	-
2%  HSD  in   MS	736	232	758

Table 2 below -  Density variation is 2.0 kg/m³ however,  2 %  MS in HSD fails in Flash Point for HSD, though Sulphur content remain with Specification limit of 50 ppm.

   Table 2.

Product	Density at 15C	Total Sulphur  ppm	Flash Point  C
MS	734	24	--
HSD	832	45	42
2%  MS  in HSD	830	42	28

Table 3 below -  Density variation is 2.0     however,  3 %  MS in kerosene fails in Flash Point for Kerosene, though Sulphur content remain with Specification limit of 50 ppm.   Using Such kerosene of 5 deg C flash Point against specification limit of min 35 deg C is highly dangerous when used in stoves,  causing fires resulting into fetal injuries.

  Table 3. 

Product	Density at 15C	Total Sulphur  ppm	Flash Point  C
MS	734	24	--
Kerosene	800	360	41
3%  MS  in Kerosene	798	345	22

Table 4 below -  Density variation is 4.0     however, 4 %  Kerosene  in MS  does not fail in Distillation FBP and ROE tests.

  Table 4.

Product	Density at 15C,  Kg/m3	FBP  Deg C	ROE
MS  (Gasoline)	734	173	1
SKO (Kerosene)	802	256	-
4%  SKO  in   MS	738	204	3

From above tables it is clear that

1.  Density difference is less than 3 kg/m³ still product fails in table 1, 2 and 3

2.  Density difference is more than 3 kg/m³ still product passes in table 4.

Lessons can be learnt:

1.  Density variation of less than 3 kg/m³ usually means product pass specification,  if there is no or very little contamination.   Further detail lab testing  can confirm.

2.  Density variation more than  3 kg/m³ usually means the product quality is suspected,  and may pass or fail specification.   Further detail lab testing  can confirm.

3.  Since density of petroleum product is only means available in field,  it helps if along with density difference, other parameters like sample appearance, visual colour etc also critically looked into to get indications of suspected contamination. 

4. For comparing densities, it is must that in the field, observed densities are converted to 15 deg C first. Many a times, density conversion not done in the field due to ASTM conversion tables are not handy in field.  ( Note - One can find easy way of converting density to 15 deg C without ASTM tables in the field  - in this blog)

Hope, above brings clarity in prevailing Myth of  density variation number 3.0 kg/m³ petroleum products.

Keywords :  Hydrocarbon blends,  Gasoline, Gasoil, Kerosene, ASTM Density

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