The 1988 Piper Alpha disaster killed 167 people, making it the world's deadliest oil rig accident in history. 

Situated just off the coast of Aberdeen, a city famous for its oil rigs and production, the oil platform exploded on July 6 1988. 

But what exactly happened, and how does the city commemorate those who died? 

What was the Piper Alpha? 

The Piper Alpha was an oil platform in the North Sea, 120 miles from Aberdeen. 

It originally just produced oil before expanding to include gas production. 

This meant that the platform was built with oil safety, rather than gas safety, in mind, which contributed to the 1988 explosion. 

At the time of the explosion, Piper Alpha was Britain's biggest platform, accounting for around 10% of the North Sea's total oil and gas production. 

What happened on July 6 1988?

The first explosion occurred at 9:55pm on July 6. 

The fire should have been contained as soon as the emergency button to stop the flow of gas and oil was activated. 

However, because the platform was originally built for oil rather than gas, the firewalls were designed only to withstand fire and not explosions. 

There was no call for an emergency evacuation, a factor which was later investigated in the inquest.

Search and Rescue was first notified of a potential emergency 10 minutes later. 

A second explosion occurred  at 10:20pm and a third at 10:50pm, both which proved catastrophic.

The final explosion occurred at 11.18pm. 

How many workers survived the disaster? 

Of the 226 people on board the platform, 165 were killed with only 61 surviving. 

There were also another two casulties from one of the rescue vessels. 

What happened in the aftermath of the Piper Alpha disaster? 

It took three weeks to eventually extinguish the flames. 

The gulley where around 100 victims had sheltered for protection was discovered on the seabed in late 1988, with 87 bodies found inside. 

Following the disaster there was controversy over why there had not been a more effective emergency evacuation. 

This was because the only person with the authority to instruct such an evacuation was killed in the initial explosion. 

A report published following the inquiry into the Piper Alpha disaster made 106 recommendations for changes to North Sea safety procedures, which then led to the introduction of the Offshore Safety Act 1992. 

What is the Piper Alpha legacy?  

The Piper Alpha Families and Survivors' association was formed following the tragedy by relatives of victims as well as survivors.

The group campaigns on North Sea safety issues. 

There are various memorials throughout the city, including a sculpture in Hazelhead Park and a chapel on Union Street which is dedicated to those who died and contains a remembrance book listing their names.