Bridge Independent Manipulators - T - Crawler

Bridge Independent Manipulators - T- Crawler

The T-crawler family of manipulators is designed for performing inspection tasks in narrow gaps between internal components (such as jet-pumps, thermal shields etc.) and the vessel or core shroud wall. Since its initial deployment in 2004, the manipulator family has been used extensively in both BWR and PWR type reactors. 

The T-crawler is engineered for easy handling with a high degree of modularity and with its thin structure suitable for inspection on the whole reactor vessel inner surface. This equipment has the ability to “walk” along the vessel wall all the way down in a reactor. 

T-crawlers are built up of modules that can be combined to create a customized scanner for a specific object.

Depending on object geometry and obstacles, different extensions can be added to allow access to very narrow gaps.

The manipulator consists of a horizontal curved beam, a straight vertical beam, a hinge unit and a scan unit. The curved horizontal beam has a trolley that holds and moves the vertical beam. The manipulator modules are attached to the vessel wall near the inspection area by means of four suction cups assemblies.

Compared to other vessel inspection systems;
the T-crawler system has several advantages:

  • Lightweight; does not require a crane or lifting device
  • Easy to handle; demands only a small crew
  • The system allows for parallel activities in the RPV during the inspection
  • Modular design, easily exchangeable end-effectors and probe set-ups
  • Uses qualified control system and software
  • Compatible with a number of different NDE systems (i.e. Z-Scan, PARAGON, IntraPhase, DynaRay, TC-5700, Ectane etc.)

The RPV type T-Crawler is adaptable for a large number of vessel dimensions; current configurations are designed for vessel diameters in the range of between
4 – 6 meters. Several types of extensions are available for hard-to-reach welds/areas as well as Core Shroud / Shroud Support inspections.

A unique design of the T-Crawler has also been used for Core Barrel ultrasonic inspections, both on Core Barrels with and without thermal shield.

In 2009 the first GE-designed BWR Reactor Pressure Vessel was inspected with the T-Crawler and since then the system has been used for both GE BWR RPV and GE BWR Core Shroud inspections.


Depending on object geometry and obstacles, different extensions can be added to allow access to very narrow gaps