Pipeline system is one of the most economic and efficient methods for transporting fluids around the world. The document review shows that several robotic solutions have been developed to navigate inside or outside pipelines. But, most of these solutions are limited to specific scenarios. Based on the survey, this paper undergoes with the characteristics, application and challenges for development of pipe robots. A comprehensive categorization of pipe robots mainly focusing on modular design, bio-inspired and soft structure are addressed. The survey results show that existing out-pipe robotic solutions require more flexibility to adapt to such confined staggered environments and further research is necessary.