Shutdown is a term often used in Oil & Gas to conduct planned maintenance on process equipment for which normal routine operations have to be suspended / stopped.

The maintenance can be predictive or breakdown maintenance.

Preliminary planning activity, wherein To do list is prepared, material is procured, human resources is planned & lined up, time & motion studies are done to calculate time required to do & accomplish a unit work.

Shutdowns are planned and executed either as part of maintenance or it could be enhance operational efficiency or doing reengineering of processes for more production & profitability It is war like scenario where materials are drawn, workers are on the job, doing repair or maintenance or both or equipment is replaced or serviced in a systematic manner.

Shutdown normally planned for a 30–45 days on average. Initially when the ZERO day starts, all the operations are closed, equipments are internally cleaned with steam, then allowed to cool, manholes are opened, preliminary equipment internal & external inspections carried out then in addition to other sundry list, some additions are made after internal / external inspection, welders do some repair works, quality team evaluates the work using non-destructive testing then on everything being checked & re-verified, the box-up activity starts, safety ensures that NO worker is left behind or alone in the pressure vessels or columns or tanks.

As the country’s economy depends upon the Oil & Gas so it is well planned, executed clinically in least possible time and this continues year after year considering the age of the plant, engineering process design - old or new technology etc.

Engineers & Technicians plan the jobs; which are then built & go thru a commissioning program to prove out all the installations & production programs.

The post shutdown time is the period where procedures are carried out to make the refinery operational.

An equipment item is normally shut down manually when it is no longer required for duty or during inspection or maintenance. A shutdown can also occur in an emergency when:

Item Shutdown
An item shutdown will shut down only the equipment item, without shutting down the entire process or plant.
In some cases, two equipment items are connected in parallel to prevent the need for a process shutdown:

Maintenance Shutdown
A maintenance shutdown will consist of shutting down, then fully isolating, draining and purging an equipment item to make it safe for maintenance work.

Unit Shutdown
A unit shutdown will shutdown only the process unit in a plant, but will not shutdown the entire plant. Many units will feed to storage tanks so that downstream processes can take their feed from the storage and continue to operate when another unit is offline.

Total Shutdown
A total shutdown will shutdown an entire plant.

Emergency Shutdown
An emergency shutdown due to fire, major spills or gas release, will shutdown an equipment item as quickly as possible, then depressurise and drain equipment and lines to leave them in the safest possible condition. Emergency shutdowns can create extra wear and tear on machinery, as the shutdown time is shorter than for a normal shutdown.

An emergency shutdown is usually required for:
Major spills and gas leaks.
Serious oil fire.

Where a shutdown will affect upstream or downstream process units, advance warning must be given to appropriate personnel to allow them to prepare for and react to, changing conditions. This would generally include suppliers of utilities and feed stocks and the receivers of the product downstream(s).