Connecting tubing into a junction box requires what?

The correct choice is bulkhead fittings because they are specifically designed to provide a secure and effective means of connecting tubing to a junction box. These fittings create a sealed connection that helps prevent environmental contaminants from entering the junction box, which is particularly important in instrumentation and electrical applications where the integrity of the connection is crucial for function and safety.

Bulkhead fittings also allow for the passage of the tubing while maintaining a level of strain relief, reducing stress on the tubing and ensuring that it stays properly in place. They can accommodate various sizes of tubing and provide versatility across different applications.

In contrast, oversized holes could lead to loose connections or difficulties with securing the tubing. Tubing unions are generally used to connect two pieces of tubing together rather than to a junction box. Internal clamps may help secure components within the junction box but do not serve the primary purpose of creating a sealed entry point for tubing.

Using bulkhead fittings is the best practice for ensuring a reliable, safe, and durable connection between tubing and a junction box in instrumentation work.