Information for Storage Tank Manufacturers – HSE Circular

Fuel Oils – Information – HSE Circular

Explosions in Fuel Oil Storage Tanks
Local Authority Circular – Revised March 2000

The circular referred to is paraphrased below and concerns explosions in fuel oil storage tanks caused by overheating of their contents.

Background : Heavy Fuel oils are normally heated in storage tanks by steam coils and / or electric heaters.

Storage Temperatures : BS5410 Pt.2:1978 Sec. 6 gives a table of minimum storage temperatures (see “Fuel Oils – Information”) A set of figures are derived in the report with respect to the BS and information provided by SHELL to give maximum storage temperatures as follows :

Class of Fuel Oil

Max. Storage Temp.

Max. T for Outflow & Handling

E (light)

27 C

20 C

F (medium)

28 C

40 C

G (heavy)

57 C

60 C

H (bunker)

62 C

65 C

It is stated that the flashpoints of these oil classes is normally at least 66 C and assuming that the temperature remains below this value these oils will not be readily ignited.

Dangers : If the oil heating system becomes faulty then the temperature can rise above the flashpoint, and once this occurs it is able to produce flammable vapour /air mixtures which can be ignited either inside or outside the tank or the pipework.

External Ignition : An example of an accident with this ignition source is given

Internal Ignition : An argument is led that several explosions have been the result of electric heaters being exposed to the air, in which some may reach temperatures up to 800 C. This would of course indicate poor system design, since the heater should never be uncovered.

Stock Management : Discusses incorrect fuel for tank heater settings.

Reviewed 03.06.16

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