Process piping plays a critical role in the operation of all process plants. Failure to design and fabricate pipelines correctly can lead to significant production problems and higher costs due to increased pump workloads.
In this short blog, we outline three design considerations for single phase pipes, carrying either gas or liquid.
1. Pressure Drop – Pressure decreases as a fluid flows along a pipeline due to friction with pipe walls. Other restrictions in the pipe like valves, flanges and instruments will also lead to a drop in pressure. In general, the longer the pipeline, the greater the pressure drop. Pressure in a pipeline will also be affected by elevation changes.
Pipelines must be designed for an allowable pressure drop that is dictated by process requirements, as well as other factors like economics and safety. When sizing piping, a balance must be struck between pipeline cost and pump operating costs.
2. Process Parameters – The temperature and pressure of the product to be transported must be taken into account. When handling a fluid under high pressure, design should follow recommended standards, like the ASME B31, Code for Pressure Piping.
Fluid velocity is also a factor that must be considered in design calculations when transporting liquids. If a liquid carries suspended solids, the velocity must be sufficient to avoid settling of solids in the pipeline.
3. Fluid Properties – Fluid properties will impact the selection of piping material. High temperature and corrosive substances require the selection of a suitable material that can withstand these effects in order to eliminate pipe corrosion.
Pipe sizing and fabrication must take all these factors into consideration. Process parameters, fluid characteristics, allowable pressure drop and acceptable fluid velocity must all be factored into calculations for pipe diameter. This is also influenced by viscosity and whether the product is compressible, like a gas, or non-compressible in the case of liquids.