Pipe Routing in Piping Design
Piping systems are utilized to transport liquids, chemicals, mixtures, gases, vapors, and solids from one location to another. They are important in many industrial settings such as paper mills, chemical plants, shipyards, machinery rooms, and houses. A functional piping system must be economical, and it should meet spatial constraints and safety regulations. Several routing algorithms have been developed to optimize pipe length and number of elbows, but relatively few methods have been designed to lay out pipes that strictly satisfy spatial constraints and safety regulations.
In piping design, the designer is responsible for a number of activities including laying out pipe dimensioned routes with the branches, valves, piping specialties, and instrumentation as specified on the P&ID. In addition, he/she must also consider interference and piping flexibility requirements (to absorb expansion and contraction due to thermal loads) during the process of laying out a piping system. This is often done in an iterative manner involving considerable back and forth between the client, engineer, and contractor until a satisfactory layout is reached.
The piping design process is complex and requires a deep understanding of the physics involved in piping systems, drafting and CAD tools, and the ability to visualize a system. Developing this knowledge can take years of experience, and it is difficult to transfer from one engineer to the next. This knowledge is acquired through reading customer standards and specs, field visits, construction work, correcting the work of others, mentoring by checkers and managers, vendor presentations, and through self-study by attending seminars.
The Importance of Pipe Routing in Piping Design
The most time consuming activity in piping design is determining the proper support locations for a piping system. This is an iterative activity in which the engineer tries to minimize the amount of pipe supports required while maintaining a safe system that meets all client and regulatory requirements. This is accomplished by analyzing the structural and seismic constraints, the pipe spans, and the location of the equipment.
Traditionally, piping stresses have been calculated after the pipe is routed, and the resulting stress is used to determine the support locations. However, this approach results in a rigid piping arrangement that can be difficult to elongate or bend without exceeding structural or seismic limitations. A more desirable and practical approach is to consider a system’s flexural requirements in the piping routing process, thereby avoiding rigid piping arrangements and minimizing the number of support locations.
This technique can be accomplished using a path-finding algorithm such as Dijkstra’s algorithm, which uses cost functions such as C(v) and p(vi-1, vi+1) to search for paths with minimum distances between adjacent vertices. Typically, the cost function is increased by the amount of an oblique angle penalty to encourage straight routes over sharp corners.
This is a much faster and more accurate method of determining the optimum piping route. In three experimental workspaces, the proposed piping-routing method was employed to lay out pipes inside an underwater vehicle, a machinery room, and a two-story house. The results show that the resulting pipes possess minimal costs, and they always satisfy spatial constraints and safety regulations.