NPS Pipe Size

 

NPS Pipe Size

Silently transporting everything from gas and water to chemicals and oil, pipes are the hidden heroes of modern infrastructure. Knowing the size of a pipe is essential for engineers, entrepreneurs, and anybody else involved in an industrial or plumbing project. Although it seems simple, pipe sizing can sometimes be a little confusing, especially when terms such as Nominal Pipe Size (NPS) are used. The purpose of this article is to dispel some misconceptions about NPS and provide a clear understanding of how pipe sizes are specified and calculated. Let’s get into it!

What is it? Nominal Pipe Size (NPS)

A standard set of diameters for pipes used in a variety of applications is known as nominal pipe sizes (NPS). It's important to realize that the NPS does not directly measure the pipe inside or outside diameter.Rather, it's an identification number that corresponds to the pipe's size. Consider it the pipe's "name," which thereafter denotes a particular collection of measurements. This seemingly perplexing methodology has a historical basis: the internal diameter, which changes depending on the pipe wall's thickness, was the basis for pipe size in the past.

A new approach was required as wall thicknesses became standardized and manufacturing techniques improved. While maintaining some of the capabilities of the previous system, NPS was created to make things simpler.

How is Pipe Size Specified?

Pipe size is typically specified using two numbers: NPS and Schedule. We have already discussed NPS. the pipe's wall thickness is referred as 'Schedule". If the schedule number is bigger/ high then that indicates a thick wall.

For example, let's assume a pipe might be specified as "NPS 4, Schedule 40." This tells us the nominal size is 4, and the wall thickness corresponds to Schedule 40.

It's crucial to specify both NPS and Schedule because pipes of the same NPS can have different wall thicknesses and thus different internal diameters. Pipe's capacity of handling pressure, pipe's weight and flow is affected by this difference.

What are Standard Pipe Sizes?

While there's a wide range of NPS values, some are more common than others. Standard sizes vary depending on the application.

Larger NPS are seen in industrial setting while the smaller NPS are encountered in resident plumbing. With range of  6”, 8”,  12” and ½”, ¾”, and 1” respectively.

It's important to consult pipe dimension charts or standards documents to find the exact dimensions (outside diameter, inside diameter, and wall thickness) for a given NPS and Schedule. These resources will give you the exact measurements required for installation and design. You can look for such information on manufacturer catalogs or engineering websites.

How to Calculate the NPS of a Pipe?

Because NPS is not a direct measurement, you can't just measure a pipe and know its NPS. You have to use standard tables instead. The tables provide the equivalent outside diameter (OD) for every NPS and Schedule.

Here's a general strategy:

Measure the Outside Diameter (OD): Measure the outside diameter of the pipe with precision.

Use an Official Pipe Dimension Chart: Obtain a reliable pipe dimension chart or standard (such as ASME B36.10 or ASME B36.19) to determine the NPS value corresponding to measured OD. Recognize that OD may not have the exact same table value but will be reasonably close.

Determine the Schedule: If you have the wall thickness, you can refer to the chart to verify the Schedule. If you do not know the schedule, you will have to make an educated estimate based on the application or assume a typical schedule.

NPS is necessary for several reasons.

Standardization: It ensures everyone is on the same page by providing a common terminology for pipe size designations.

Interchangeability: Through the use of NPS, pipes and fittings from different manufacturers are assured to be compatible.

Design Calculations: To find pressure drop, flow rates, and other significant factors, engineers use NPS and Schedule.

Procurement: Purchasing and ordering pipes is simplified by using NPS and Schedule.

Anyone who works with piping systems must know NPS. Although it might seem confusing at first, a bit of research clarifies the system. Remember that NPS is not a measurement but a designation. To find the exact dimensions for a specific NPS and Schedule, always refer to standard pipe size tables. You can ensure your plumbing projects succeed by understanding how NPS, schedule, and actual dimensions are related to each other.