What is a Junction Box Used For?

Junction boxes are an integral part of every electrical, control, and instrumentation installation.

For control and instrumentation, it is an enclosure used for interconnection between field devices (i.e., instruments) in the process/production areas and control/monitoring equipment typically located in the control room.

Junction Box

The junction box is typically used for terminating multiple field devices of common systems in a general area.

Instrument junction boxes should be designed to suit the environmental conditions of the intended locations. It should have certification to demonstrate proper ingress protection (IP) and hazardous area protection.

The specifications for instrument junction boxes covered in these Guidance Notes address the following items:

• Materials
• Degree of protection
• Type of terminal
• Cable entry direction and devices
• Earthing
• Temperature class and gas group
• Breather/drain plug
• Enclosure size
• Labels
• Terminal block back plate
• Doors
• Ambient temperature

Instrument junction boxes are required for many systems and can be in a variety of work locations (e.g., in wet or dry conditions and safe or hazardous areas) onboard offshore structures and units.

Generally, instrument junction boxes should be maintained at safe and efficient conditions. Because typically many junction boxes are required on offshore structures and units, it is recommended that the requirements and specifications be standardized.