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Oil refineries


An oil refinery may be considered a factory that converts crude oil into a range of useable products.

Within this environment, multiple processes will involve a large range of hazards; responding fire and rescue service personnel will need to be aware of, and manage, them.

The site management teams and on-site fire teams will be critical in the safe management of any incident, as these sites are complex in design and size and use processes that will need specialist advisers.

Refining is the manufacture of petroleum products from crude oil. Refining involves two major branches:

  1. Separation processes
  2. Conversion processes

For a diagram showing typical refinery processing units, refer to the UKPIA website.

There are many processes available to the refiner and the final processes chosen are determined by the products required (both quantity and quality) and the crude oil available.

Refinery products

The refining process produces a large range of petroleum products, for example:

  • Liquefied petroleum gas (LPG)
  • Propylene
  • Petrol (gasoline)
  • Jet fuel, aviation turbine fuel (ATF or AVTUR)
  • Diesel (gasoil)
  • Sulphur

It also produces a number of petroleum components, which can either be sold or processed in the refinery.

Crude oil

Petroleum products are made from crude oil. There are many types of crude oil that come from many different sources around the world. Selecting the right crude oil is a key part of the refining process.


The first stage of crude processing is known as distillation, or fractionation, and occurs in a column known as a distillation column.

In this process, the crude oil, which is a mixture of many types of hydrocarbons, is boiled and recondensed to separate the crude oil into components, based on a range of boiling points.

Components that are heavier are harder to boil and will collect in the lower part of the column. Lighter components are easier to boil and will be collected in the upper part of the column.

Very heavy components, which cannot be boiled, will leave from the bottom of the column in a stream known as residue, while very light components will leave from the top of the column. This stream is known as liquefied petroleum gas (LPG).


To meet environmental specifications, or to assist in further processing, some components then undergo a process known as hydroprocessing. The objective of this process is to remove sulphur from the component stream.

To assist in removing sulphur, this process will consume hydrogen. The sulphur removed is converted into pure liquid sulphur and is sold to local industry for producing acid and fertiliser.


This process converts a low-value component called naphtha into a product known as reformate or platformate. This reformate has a much higher octane number and is used for gasoline blending. This is achieved using a catalyst that contains platinum.

Thermal cracking

To meet product demand, further refining processes have been introduced. Today, a modern refinery, in addition to atmospheric and vacuum distillation, may also consist of secondary refining processes such as cracking, which may be thermal or with a catalyst.

Thermal cracking is the oldest and, in principle, the simplest refinery conversion process. It is carried out over a wide range of temperatures, between 450 to 750°C, and pressures from atmospheric to 70 bar. The temperature and pressure depends on the type of feedstock and the product requirement.

At these elevated temperatures, the large hydrocarbon molecules become unstable and spontaneously break into smaller molecules

Catalytic cracking

This conversion process involves breaking up large hydrocarbon molecules into smaller molecules using a combination of heat and catalytic action.

Long-residue catalytic cracking (LRCC) takes a heavy hydrocarbon stream, called long residue, and converts it into a number of more valuable components and products, including:

  • LPG
  • Propylene
  • Fuel oil components

However, the main product from LRCC is a gasoline-blending component known as cat-cracked gasoline (CCG). A by-product of this process is coke (carbon), which is burned to generate steam and electricity.

Secondary treating

The refinery also has a number of smaller secondary processes. These are mainly involved with further polishing components and products to remove sulphur and other impurities.


The final stage of the refining process is called blending. This is a crucial step where the various hydrocarbon components manufactured in the refinery are mixed together to make the final products sold by the refinery.

The final blend recipes will depend on the quality of the available components and on the customer's requirements, called specifications. All blended products are tested before they are sold to ensure that they meet the customer's specifications.

Product distribution

Once the petroleum products are blended and tested, they can then be delivered to customers. The main distribution channels following the refining process are:

  • Ship
  • Pipeline
  • Road tanker
  • Rail wagon

The importance of good on-site liaison prior to any incident, with detailed pre-planning, will be key to the successful resolution of an incident. Sites will be run and managed by highly experienced personnel.

Refining sites are covered by the Control of Major Accident Hazards (COMAH) Regulations, which ensure that businesses:

  • Take all necessary measures to prevent major accidents involving dangerous substances
  • Limit the consequences to people and the environment, if any major accidents occur

Under the regulations, there will be internal and external plans, which will have been developed with the local fire and rescue service.


Britain is criss-crossed by a network of pipelines, some of them owned by individual oil companies dedicated to supplying their own terminals, some being joint ventures, for example United Kingdom Oil Pipelines, and others belonging to the government.

For a map showing the UK refineries, pipelines and key product distribution centres, refer to the UKPIA website.

Hazards (for further information refer to National Operational Guidance: Utilities and fuel, National Operational Guidance: Industry and National Operational Guidance: Hazardous materials)

  • Hazards consistent with working at any large commercial processing site
  • Hazardous materials

References and further reading