Piping Design (part 01)

Monday, June 29, 2009

First of all, i'd like to make a clear understanding in determining between pipeline and piping. Pipeline has long distance in transporting fluids, it can be a hundreds miles away from the upstream to downstream. Meanwhile, piping just to transport the fluids in a short distance within the plant area. Pipeline used to be has large bore of nominal pipe size, above 20". meanwhile piping has smaller bore of nominal pipe size, under 18".
Now we've understood the main discrepancies between pipeline and piping, since i'd like to discuss about the design process for piping only, in the next paragraph.

Many aspects should be considered while design a piping system. As we've discussed in previous article, regarding the discrepancy between pipeline and piping. So, in this article we talk about piping design consideration, instead of pipeline. Although the items to be considered are mostly same, but i'd like to focus in piping.
In design stage, there are three main aspect which cover the overall detail aspects. The first aspect is related with the piping system's performance to transport the fluids. Based on "Inspeksi Teknik-Buku3" wrote by Sri Widharto, the parameters should be considered are as follow :

* Design temperature, is the temperature of pipe's material which is simulated in the most critical condition. In this case, critical condition means a condition that demand the maximum specification of the piping's material, including it's fittings. I divide the piping for two condition, un-insulated and insulated.

1. For un-insulated piping system, if the fluid temperature <>= 100 deg F (38 deg C), then the piping system's temperature (including the valves, flat face flange, welded joint fittings, and other components which have equal rating with the pipe's wall thickness, may not less then 95% of fluid's temperature. For flange's temperature (unless flat face flange) may not less then 90% of fluid's temperature. And for the fastener's temperature may not less then 80% of fluid's temperature.
2. For an insulated piping system, the piping system's temperature is designed to be equal with the fluid's temperature. Unless, based on previous experienced operation that make the design temperature should be considered to follow the existing data.

* Design pressure, is the pressure which may not less then a combined pressure from internal and external pressure in maximum and or minimum temperature which may occur in operating condition. A design pressure have to be able to throw out an over pressure that could be occur while in operating condition. Over pressure caused by a fluctuative pressure, incorrect operating, or even failure of equipment's function. Therefore, a pressure relieving device always installed in a piping system.

That is all i can describe about design process for piping system which is related with it's performance. We are going to have a long discussion regarding with design process related with the piping routing and mechanically consideration, in the next part of this article