Pipe Schedule Chart for Your Application To Choose Right Pipe Size

Pipes are essential components in a wide range of mechanical engineering applications, from oil and gas rigs to home water networks. Made of metal or plastic, pipes have two key geometrical features: outer diameter (OD) and inner diameter (ID). In the past, there has been some confusion about which diameter should be used to define the nominal pipe size (NPS). This has led to inconsistencies in the industry.

Pipe Schedule Chart  And Their Dimensions

In order to keep consistency with the pipe fitting sections, we have nowadays decided to relate the outer diameter with the “nominal pipe size” classification, so when we’re dealing with a one-inch pipe we can consult data tables and figure out its specific “outer diameter”. Next, there is the “wall thickness” of the pipe that is used by engineers to determine whether a pipe section is suitable to handle the designated pressures or not, categorized in “schedules”. The pipe’s wall thickness practically determines the strength of the pipe but it also helps us derive the “inner diameter” of the pipe. Based on the aforementioned consideration, we can simply calculate the inner diameter of a pipe by subtracting the pipe wall thickness twice from the number that corresponds to the outer diameter. This consideration is important for engineers since the inner diameter is what determines the flow velocity and rate. For example, a pipe that has an outer diameter of 60.3 mm and a wall thickness of 2.8, has an internal diameter of 60.3 – (2.8 x 2) = 54.7 mm.

Different Dimensioning Standards

Considering how widely these elements are applied in practical engineering, it is very important to be able to ensure coherence between them (fitting and connecting/welding sections) as well as to predict their performance from the perspective of fluid flow, and thus pipe sizes are fully standardized. Usually, engineers use a term called “nominal bore” which corresponds to a certain outer diameter measured in inches, or the “nominal diameter” which corresponds to an outer diameter measured in millimetres. These sizes are based on an approximation and are not characteristic of the exact diameter of the pipe. For example, the actual diameter of a pipe that has a nominal bore of two inches isn’t exactly two inches or 50.8 millimetres, but 2.37″ or 60.3 mm. This means that there is always a standard corresponding value for each nominal bore category, indicating the pipe’s outer diameter. Engineers can find that value in data tables and never try to follow a “data reduction” approach as this won’t work in this case.

As per the ANSI/ASME, ISO, ACPA, EN, BS, and DIN standards, all pipes are classified as per their “nominal bore” or “nominal diameter” and their “schedule”. Based on that, the internal diameter is given through tables. There are also other standards such as the IPS, the JIS, the DIPS, and the PIP, but those are limited, obsolete, and/or too specialized. Obviously, there are many pipe sizes to address every possible need, but I will provide a data table covering the sizes that are most commonly used in the industry starting from a half-inch diameter and up to eight inches. The schedule rating categories that indicate the wall thickness range from 5 to 160, indicating an increasing thickness value. It is also important to note that for practical reasons, the edge of pipes are often coloured according to their schedule rating and this is also standardized. Green corresponds to extra light thickness, yellow corresponds to light thickness, blue to medium, red to heavy, and white to extra heavy wall thickness. To relate these with the schedule ratings, the medium is the schedule – 40, and the heavy is the schedule – 80. Of course, the higher the thickness the higher the weight, and this very important consideration can also be attained by data tables provided by the pipe manufacturer.

Pipe Schedule Chart (1/8″ – 24″ Nominal Bores)

Pipe Schedule Chart (26″ -48″ Nominal Bores)