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Mossmorran has been flaring for months to burn off gas which can't be processed while two boilers are being repaired.

There have been a growing number of complaints over excessive flaring at the Fife Ethylene Plant (FEP), which some residents say even causes vibrations throughout their homes and results in sleepless nights.

The plant will be restarted soon, with a date yet to be confirmed, but here's how Exxon Mobil - who run the plant jointly with Shell - say it will happen.

The plant has seen a great deal of flaring.

STEP 1: ETHANE GAS ARRIVES

• The ethane is needed to begin sequence of generating steam and starting major machines.

• There will be a 3-4 day journey for natural gas from the North Sea via St Fergus near Peterhead.

• The ethane gas will be separated at the Shell plant next door and sent to FEP,

• As major process machinery not yet started, some gas is diverted to flare.

STEP 3: BOILER AND FURNACE OUTPUT INCREASED

• Both combine to generate the steam needed to start major machines

• Steam and water vapour will be visible from the plant

STEP 2: FLARE SIZE MANAGED

• Some of ethane gas sent to furnaces and some to ground flare

• Remainder sent to elevated flare

• These steps combine to reduce elevated flare size

• Steam will be added to ensure the flare burns clean

STEP 4: MAJOR PROCESS MACHINERY STARTED

• Three major compressors started

• Each started individually in sequence

• Visible steam will start to reduce as it is consumed by the machines

STEP 5: DISTILLING TOWERS STARTED

• Final stage of start up

• Three distilling towers brought online

• Elevated flare will fluctuate but will not increase

STEP 6: SAFE RE-START COMPLETE

• Ethane gas now being turned into on-spec ethylene

• No longer in elevated flare

• On-spec ethylene piped to Braefoot Bay terminal

• Total time for safe re-start around 6 days

Mossmorran is going to restart soon: Here's what's going to happen