Design of an inspection robot for inspection of small diameter gas distribution mains

No part of this work may be reproduced by print, photocopy or any other means without the permission in writing from the publisher. All pictures in this thesis have been reproduced with permission of the respective copyright holders. Summary The gas distribution network in the Netherlands has a length of roughly 100 000 km in urban areas. This network needs to be monitored constantly and segments need to be replaced when the risks of leaks increase. Since replacement is expensive it is important to know how long a segment of the network is still expected to offer reliable service. In this thesis a solution for the lack of 'inside information' is explored: the realisa-tion of a swarm of autonomous robots that move constantly through the network, while collecting and storing data. The robots surface now and then for maintenance and exchange of data with the network operators. This project can be seen as a feasibility study of a part of this goal: Is it possible to design a robot which can move (autonomously) through the gas distribution network? Five partial questions need to be answered: • What is the best mechanism for propulsion for the system? • What is the best way of providing energy to the system? • Which sensing methods can be used for assessing the quality of the pipes? • What is the best method for communication with the system? • How to control the designed mechanism? Which steps are necessary for autonomous or operator-based control? In order to answer these questions, three prototypes have been realised. The design of a propulsion mechanism depends strongly on the layout of the gas distribution network. Based on data available on a number of representative urban distribution networks a description has been made of the environment in which the robot has to operate. The most important aspects are long stretches of pipe (tens of metres), a diameter range of 63 mm to 125 mm, (mitre) bends, T-joints and inclinations up to 30 •. The most demanding requirement is that in 63 mm pipes with thick walls the robot has to move through an inner diameter as small as 51.5 mm. Most of the design requirements follow directly from the given network environment. The design which is the basis of all of the realised prototypes is a wheeled robot 'snake' consisting of a number of modules which can be used as …