Process Industry is incomplete without use of pipes and tubes. However , Both Pipes and tubes are different items , they are used interchangeably for each other . Let us have a look on how Pipes and tubes are different.
Difference in terms of Size definition
Pipe size get mentioned in terms of Nominal Bore (NB) size or Nominal Pipe size (NPS) or Nominal Diameter (ND). However tube size is defined in terms of mm (millimeter) dia or in Inch. This is a key to identify the pipe or tube if just size is mentioned in material take off (MTO).
Tubes outer diameter (OD) is always same for a specific size . Pipes outer diameter (OD) is different from NPS till 12 inch of size as listed below.
|NPS/ND size in Inch||1″||2″||3″||4″||6″||8″||10″||12″|
|OD in Inch||1.315″||2.375″||3.5″||4.5″||6.625″||8.625″||10.75″||12.75″|
This is the reason that Pipes are measured by nominal dia and tubes are measured by outside dia.
Difference in terms of thickness
Pipe thickness is defined in terms of schedule (SCH) with associated numeric number i.e. S40, S60 , S80 or STD etc. Tubes thickness are defined in terms of mm (millimeter) or gauge number.
Difference in terms of Shapes
Pipe are round in shape only. However tubes are available in round, rectangular, oval , square shapes.
Difference in terms of size availability.
Pipe are available in wide range even beyond 100 Inch. However tubes are not available in higher size. Frequently used size of tubes are 16 mm , 20 mm , 25 mm .
Pipes available length are 8 m, 10 m, 12 m. Tube available length start from 6m and go up to 12 m in some case.
Difference in terms of end connection.
Pipe are mostly bevel ended (BE) or plain ended (PE) to get welded as per requirement. Tubes are threaded or grooved for easy and fast connection.
Difference in terms of material.
Pipe are available in wide range of material in different grades of carbon steel, alloy steel and stainless steel and many more. Tubes are available in Carbon steel , Stainless steel and nickel alloy .
Difference in terms of manufacturing.
Pipe could be welded or seamless as per process requirement. It is hot rolled product. Tubes are seamless only except some exception cases . It could be hot rolled as well as cold rolled.
Pipe are used for transfer of fluid either gas or liquid in process lines . Tubes are used for heat transfer purpose in Heat exchanger, Air cooler, Process Heater, Boiler, Heat tracing etc .
At last, Pipes are cheaper than tubes because tubes tolerance is very stringent.
Below is very useful pipe weight chart . It shows weight up to 48 ” Inch pipe.Pipe-weight-chart