Both Piping and Pipeline are originated from Mechanical Engineering and many a time, share common activities. For example, both have piping materials, piping expansion, stress, and support problems. So, both piping and pipelines need Stress and Material engineers. Both piping and pipelines are used to transport fluids. On a broad scale, ASME B 31.3/ASME B 31.1 deals with piping engineering and ASME B 31.4/ ASME B 31.8 deals with pipeline engineering. Refer to Figure 1, which shows the piping and pipeline demarcation for a typical plant. Through this article we will try to find out a few other differences that piping and pipeline systems have in general sense:
Piping and Pipelines are normally demarcated by a boundary or fence. Outside the fence comes under pipeline scope and inside boundary falls under the piping scope. Generally, pipeline travels a long distance (across villages or countries) whereas the length of single piping is short (equipment to equipment or pipeline to equipment).
Physical Personality or Action Performed
Piping is normally connected with various equipments and carry fluids inside a complex network that will be processed in that equipment. Whereas Pipelines supply the feed for further processing or deliver the processed fluid or end product and they normally run straight. No of equipment connections in the pipeline is very less as compared to piping.
Pipelines travel aboveground, underground or sub-sea with the maximum part being buried. Whereas, piping systems are mostly aboveground.
Pipe Diameter and Fitting Types
In piping systems, pipe size is normally less (the majority of lines in the Process or the power piping systems are less than 36 inches) but the number of the fittings used is very high. On the contrary, pipeline diameters are large and the number of fittings is comparatively much less.
Type of Pipe and valves:
In most of the cases Line Pipes i.e, API 5L code is used for pipeline material and API 6D is used for pipeline valves whereas piping material uses ASTM, BS, API 5L, or various other codes and standards and piping valves are from BS or API standard.
In most of the cases, fluid design temperature for pipelines is normally less than 230 deg C, whereas piping systems carry fluids with different design temperatures.
For the piping system, the hydro test pressure is calculated by multiplying design pressure with 1.5 and a temperature factor whereas pipeline design pressure is 1.25 times the design pressure for liquid pipelines and (1.25 to 1.5) times design pressure for gas pipelines. Also, pressure holding time for pipelines is normally 24 hours whereas for piping the same is generally, 2 to 6 hrs.
While routing of pipelines large-diameter elbows (Normally, Hot bends up to 6D and Cold Bend up to 60D) are used whereas piping systems, in general, do not find such large diameter bends.
The construction drawings in case of pipeline systems are termed as alignment sheets, but the same for piping systems are termed as isometric drawing.
Various technical surveys like Topographical survey, Soil-resistivity survey, Cadastral Survey, Hydrological Survey, Geo-technical investigation, etc are performed to collect various data during pipeline design. On the contrary, Only wind and seismic profile studies are performed for piping systems.
Long pipelines are cleaned or inspected used pigs whereas piping systems are cleaned with steam or nitrogen.
- Pipelines are normally preserved using inert gas or corrosion inhibited water.
- Cathodic protection systems are involved with pipelines.
- Corrosion protection coating is normally applied for pipelines whereas piping systems are painted.
- The pipeline runs across rivers, below railroads, highways, etc. Hence, special design and constructional considerations are required.