Application of Indigenously Developed Robotic System for Remote
Visual Inspection of Boiler Headers of Thermal Power Plants
Background: Boiler header is one of the main important parts of any boiler which collects
the steam from the generating pipes. Any blockage in this header will affect generation of
power owing to a huge economic loss to the power plant. Besides that there are number of
mechanisms (such as overheating, corrosion, fatigue, oxidation, erosion and other mechanical
issues etc.) playing vital roles for header damages. It is very much necessary to inspect the
headers to prevent any sudden failure. Visual inspections are the primary, simplest, and most
reliable source of information. They generally identify areas of fouling, erosion, corrosion, or
localized overheating issues or presence of any foreign objects inside the headers.
Present Technique: The present method of visual inspection using video-imagescope has
several limitations due to its fixed length of cable; lack of proper guidance to the tip of the
video-imagescope after certain distance leading to spiralling of the cable or entrapment in the
tube-holes. Besides, the camera-tip cannot reach the entire periphery of the header and hence
wider view of the header cannot be obtained. Also the illumination along the periphery of the
header is non-uniform owing to location of the camera-tip-cum-light at the bottom.
Figure 1: Conventional Baroscopic Inspection of Headers Through Tube Cutting
Figure 2: Remote Visual Inspection of Headers Through Hand-hole Cutting
Requirement of Robotic Device: There was an urgent need to develop a robotic system for
remote inspection of the inaccessible boiler header inside for periodical maintenance to
prevent any unplanned shut down. As no such off-the-shelf technology was available in the
market, it was very much essential to develop such system on immediate basis. Realizing this
objective, a collaborative research project titled “Design and Development of Smart and
Advance Robotic System for Internal Inspection of Boiler Header” was initiated with CSIR CMERI, Durgapur.
DOC/Header Inspection/RVI/01/2020/NDE Imaging and Life Management Group, NETRA, Greater
NOIDA
Application of Indigenously Developed Robotic System for Remote
Visual Inspection of Boiler Headers of Thermal Power Plants
Technical Challenges: The design and development of such a robotic system for remote
inspection of boiler header was associated with number of technical challenges. The
associated technical challenges are mentioned as follows: Entry through very narrow
handhole (typical diameter range: 75 - 90 mm) and then expands 3.34 – 8 times (i.e. 334% 800% increase in dimension) for actual operation inside the boiler headers (typical diameter:
250-600 mm). There are very limited or no actuators that can support such large expansion in
dimensions. The diameters of the array of holes along the inside periphery of the boiler
header may create hindrance for smooth movements of the system. The restriction of entryarea limits the dimension of the battery wherein expansion of the on-board battery is not
possible and feasible and thus large power for longer duration may not be available. The low
illumination affects the quality of the image to be used for inspection. The restriction in size
may lead to development of customized components (motors/actuators, drives, specially
configured expanding wheels, high energy dense power packs, camera, cable; other
accessories including mechanical structure). Safe withdrawal in case of any break down or
malfunctioning which may require emergency additional drive system.
Development and Features of Robotic Device: All these challenges have inspired to think
of a miniaturised mobile robot which can enter the boiler header through the hand holes and
use collapsible arm to extend the height of the camera beyond the normal range to reach the
entire periphery of the boiler header. This ensured close-quarter imagery of the whole
periphery of the boiler header. Use of high-intense LED lights has enhanced the quality of
images for best visual inspection. The developed mobile robot have the capability for positive
traction to move on the scaled/ rusted/ dusty inner surface of the boiler header. The
collapsible arm holds the camera and can reach to a better height than the conventional videoimagescope. Pan-tilt and zoom facility has also been incorporated for best performance of the
system. Due to requirement of higher power to drive motors, collapsible systems, LED lights
etc., power has been fed from an external source. An additional positive mechanical means
has also been incorporated for retrieval in case of complete system failure. In conventional
robots wireless communication is always preferred to wired communication as the length of
the cable limits the operational distance as well as the weight of the cable puts hindrance for
easy movement of the system and higher power consumption. However, wireless
communication was not suitable in the present case due to presence of Ferro-magnetic
material. As a result wired communication was selected for transmitting command, image
and sensor data.
Figure 3: Headers Inspection Using Indigenously Developed Robotic System
Field Deployment: Header inspection already carried out using this indigenously developed
robotic system at Unit # 3, NPGC, Nabinagar, Unit # 2 and 3: NTECL Vallur, Unit # 1 and
2: BRBCL, Unit # 4 and 6, Ramagundam, Unit # 3: BRBCL.
DOC/Header Inspection/RVI/01/2020/NDE Imaging and Life Management Group, NETRA, Greater
NOIDA