Allen-Bradley 1797-TB3 FLEX Ex Terminal Base Units

Description

The 1797-TB3 is an intrinsically safe mounting and wiring component functioning within the FLEX Ex distributed input/output platform. This structural device provides the physical termination points for field instrumentation cabling while anchoring individual electronic application modules to a unified backplane cluster. By containing terminal termination paths away from active logic chips, the assembly allows engineers to run physical electrical connections directly within classified process zones without exposing the primary system bus to signal faults.

Equipped with three-tier screw-clamp termination blocks, the unit distributes power, common grounding, and discrete or analog field lines through independent internal channels. The 1797-TB3 links structurally to adjacent base assemblies via an integrated male/female FlexBus backplane connector, passing data and intrinsically safe power from primary power supplies through the complete multi-module array. It is utilized in heavy extraction and treatment environments—such as marine gas rings, onshore wellheads, chemical storage systems, and grain processing silos—requiring robust mechanical foundations that limit ignition sparks.

Features

• Three-tier screw terminal design separating signal lines, common reference points, and power paths.
• Integrated structural alignment guides supporting modular replacement of application hardware.
• Pass-through internal FlexBus connection mechanism for clean structural scaling on a single rail.
• Rugged housing geometry intended for high-vibration industrial installations.
• Front-accessible test points simplifying multimeter verification during plant commissioning.

Applications

• Explosive dust and grain elevator storage management systems.
• Offshore natural gas platform processing manifolds.
• Fuel tank farm telemetry and distribution controls.
• Hazardous chemical blending and batching facilities.

Technical Specifications

Connections/Interfaces

Installation Guidelines

DIN Rail Installation

Position the top retention hooks of the assembly over the upper tracking edge of a standard 35 mm DIN rail. Tilt the base downward until the lower metallic tension latch clicks firmly into place onto the bottom track rail.

Backplane Interconnection

Slide successive base modules laterally along the DIN rail until the female FlexBus socket of the new unit mates flush with the male pins of the preceding unit. Verify the side-locking tabs engage fully to ensure continuous power path transfer.

Wire Termination

Strip the insulation on incoming signal leads back approximately 7 mm (0.28 inches). Insert the conductor into the appropriate screw clamp terminal and torque the clamping screw to 0.56 N-m (5.0 lb-in) to prevent loose wire arcing.

Hazardous Area Precautions

Confirm all connected instrumentation satisfies intrinsically safe energy parameter limits matching the module inserted into the base. Ensure the local enclosure maintains a minimum dust and water ingress protection level appropriate for the target installation zone.

FAQ

What is the primary function of this structural component?

It serves as the physical mounting foundation and wiring termination interface for operational electronic modules within hazardous zones.

Can this unit be utilized with standard non-hazardous 1794 series modules?

No, this unit is keyed and engineered exclusively for use with intrinsically safe 1797 series hardware assemblies.

What size wire can be terminated into the screw terminals?

The terminal blocks accept solid or stranded copper wires ranging from 22 AWG up to 12 AWG.

Is it safe to slide bases apart while the system power supply is turned on?

No, isolate input power from the main source before separating base units to prevent interrupting the internal backplane bus.

Does this base include an integrated communication adapter link?

No, it is a passive wiring substrate that relies on a separate network adapter module placed at the front of the rail cluster.

How are the field signals routed into the attached control module?

The electrical pins on the back of the active module plug into the receptacle matrix built directly into the center of the base.

Are separate grounding terminal blocks required when using this unit?

The bottom tier provides dedicated chassis ground points designed to link instrument shielding without extra external terminal blocks.

What is the maximum torque specification for the termination screws?

Tighten all wire clamp screws to a maximum of 0.56 N-m or 5.0 lb-in to ensure a secure low-resistance contact.

Can an electronic module be replaced while the field wiring remains attached?

Yes, the terminal base design allows the processing module to be unplugged without disturbing any of the field termination wires.

How many signal connection points are available in total on the unit?

The unit features thirty-six distinct termination screws divided evenly across three separate horizontal rows.