Pipelines have a widely spread applications in industry. Water, sewage, flammable liquid, high pressure gasses and oil are transported using pipelines. These pipelines are long, interconnected and may be constructed underground or underwater. This makes their monitoring, periodic maintenance and repair a hard job when done by human operators. Hence, a robot system capable of carrying out these complicated operations in pipelines is extremely requested.in this papers a mechanical design and a prototype of an in-pipe robot system for cleaning 0.5 m inner diameter water pipes is presented. The proposed robot system is designed to perform cleaning operations for straight horizontal water pipes based on abrasion concept. The in-pipe robot system have three modules; forward and backward motion module, two identical cleaning modules which can move in rotational motion and radial motion (in and out) module. These three modules are designed to have the robot's two main positions: open position (for cleaning) and closed position (while entering and getting out of the pipe). A 3D model has been built using Solid works software, then a finite element analysis was carried out on robot's frame using two materials: Steel and Aluminium. However, the Steel material has been selected due to its high rigidity. The robot control system was done using Adriano software. Robot dynamics were simulated in Simulink environment. The real time robot testing and measurements showed that the proposed robot mechanism can complete the cleaning operations effectively. The developed robot is expected to minimize maintenance time, effort, and cost.