container equipment through clean-air supply, pressure monitoring and defined safety responses.
Positive pressure ventilation maintains a slightly higher air pressure inside an offshore container than outside. A controlled supply of clean air creates this pressure difference, helping reduce the risk of a surrounding hazardous atmosphere entering the enclosure.
In electrical shelters and control cabins, the protection depends on the complete arrangement: the air supply, enclosure, access doors, monitoring and protective controls must work together.
Why Do Offshore Equipment Containers Use Positive Pressure?
Offshore containers may house motor controls, switchgear, monitoring instruments and other electrical equipment near areas where flammable gases could be present.
A suitable pressurisation system helps separate that equipment from the surrounding atmosphere. Its effectiveness depends on maintaining the specified conditions and responding when those conditions are lost.
Positive pressure is one part of the container’s protection strategy. The required arrangement depends on the installation location, equipment and applicable project requirements.
What Happens Before and During Operation?
A pressurised container follows a defined operating sequence.
Before startup: Where purging is required, clean air passes through the room and associated ducts to reduce the concentration of flammable gases to the specified level before the protected equipment is switched on.
During operation: The air supply maintains the required pressure while compensating for expected leakage through the enclosure.
If protection conditions are lost: Monitoring and controls initiate the alarm or protective response specified for the system.
Purging prepares the space, while positive pressure helps maintain protection during use. IEC 60079-13 addresses pressurised rooms and the related controls needed to establish and maintain their protection conditions. IEC guidance on pressurised rooms
How Is Positive Pressure Different from Air Conditioning?
Positive pressure controls the pressure difference between the inside and outside of the container. Air conditioning controls temperature.
A container can feel cool while failing to maintain the required positive pressure. Temperature alone therefore does not demonstrate that pressurisation is working.
Equipment cabins may need both functions: cooling to manage equipment heat, and pressurisation to help limit outside atmosphere entry.
What Can Affect the Pressure Inside?
Personnel access and changes to the enclosure can affect internal pressure.
Opening a door changes airflow. A damaged door seal or an inadequately sealed cable opening can increase leakage. These everyday conditions explain why doors, seals and service openings form part of the protection arrangement.
Depending on the design, the container may use self-closing doors, an airlock or other access measures. Personnel should follow the operating procedure supplied for the installed system.
After maintenance or modifications, affected parts of the enclosure and protection system should be checked before returning to service.
What Happens if Positive Pressure Is Lost?
Loss of the required pressure means the specified protection conditions are no longer being maintained.
The response may involve an alarm, automatic protective action or a combination of measures, according to the system design. Equipment restart may require pressure restoration and completion of a defined recovery sequence.
The response must be established for the application; it should not be assumed that every pressurised container follows the same shutdown or restart logic. Pepperl+Fuchs explanation of purging and pressurisation
How Does TLS Apply Pressurisation to Equipment Cabins?
TLS provides pressurised containers for applications including MCC electrical shelters, switchgear enclosures and control cabins. MCC means Motor Control Centre, which controls and protects electric motors.
TLS can configure the enclosure, pressurisation, HVAC, fire and gas detection, and associated controls around the project’s equipment and operating environment. The supplied features and certification scope are confirmed for each project. TLS pressurised container solutions
For an enquiry, provide the intended application, equipment details, installation location and hazardous-area requirements.
FAQ
Does a running fan prove that a container is pressurised correctly?
No. The required pressure and other specified protection conditions must be established and monitored.
Does positive pressure make every electrical device suitable for a hazardous area?
No. Equipment suitability depends on the complete protection arrangement, assessment and approval scope.
Can positive pressure control a gas release inside the container?
An internal release needs a separate assessment and may require additional ventilation or other measures. Positive pressure alone should not be assumed sufficient.
