Design Tools

ARIavCAD 2009, a software program for the sizing and location of air valves

A.R.I. has developed a program, which will assist engineers in selecting the most important locations to place their air valves on the pipeline. In addition, it will also specify which model in the A.R.I.series will best suit the applications as well as the most appropriate sizing.

The program, known as ARIavCAD is user friendly and simple to understand and is designed so that the end user can clearly and rapidly define his needs as far as air valves on the pipeline is concerned. This ARIavCAD software contains many refinements and improvements, and provides an analysis for air valve sizing and location for most applications. Additionally, the software can be used in conjunction with applications, such as AutoCAD and Microsoft Excel.

With the new version of ARIavCAD, a simple import operation followed by a click on the mouse, and the entire pipeline profile, with much of the required data, is ready for entry of remaining data and analysis that will determine air valve recommendations by location, model, size and quantity.

The savings in time, cost and effort that this technology offers is considerable and A.R.I. is proud to offer the service of running analyses to our customers.

Instructions

NPS (Nominal Pipe Size)

Nominal Pipe Size (NPS) is a set of standard pipe sizes used for pressure piping in North America. The same pipe dimensions are used with different names in Europe.

Pipe size is specified with two non-dimensional numbers: a Nominal Pipe Size (NPS) and a schedule (SCH). The relationship of these numbers to the actual pipe dimensions is a bit strange. The NPS is very loosely related to the inside diameter in inches, but only for NPS 1/8 to NPS 12. For NPS 14 and larger, the NPS is equal to the outside diameter (OD) in inches. For a given NPS, the OD stays constant and the wall thickness increases with larger SCH. For a given SCH, the OD increases with increasing NPS while the wall thickness increases or stays constant. Pipe sizes are documented by a number of standards, including API 5L, ANSI/ASME B36.10M in the US, BS 1600 and BS EN 10255 in the United Kingdom and Europe, and ISO 65 internationally.

For NPS of 5 and larger, the DN is equal to the NPS multiplied by 25 (not 25.4).

The most commonly used schedules today are 40, 80, and 160. There is a commonly held belief that the schedule number is an indicator of the service pressure that the pipe can take. For example, the McGraw Hill Piping Handbook says the schedule number can be converted to pressure by dividing the schedule by 1000 and multiplying by the allowable stress of the material. However, this is not true Pressure rating actually goes down with increasing NPS and constant schedule.

The various standards for pipe schedule are not identical. Frequently some sizes—or even entire schedules—are present in some standards but not others. When different standards do overlap, they usually have the same dimensions. For this reason, the source of the schedules is not distinguished in the table below. Beyond NPS 8, however, there are differing version of schedules 5, 10, 40, and 80. One variation is the presence or absence of an ‘S’ suffix after the schedule number. Generally, ‘S’ indicates Stainless Steel Schedule.

Some specifications use pipe schedules called Standard Wall (STD), Extra Strong (XS), and Double Extra Strong (XXS), although these actually belong to an older system called Iron Pipe Size (IPS). The IPS number is the same as the NPS number.

STD is identical to SCH 40S, and 40S is identical to 40 for NPS 1/8 to NPS 10, inclusive. XS is identical to SCH 80S, and 80S is identical to 80 for NPS 1/8 to NPS 8, inclusive. Different definitions exist for XXS, but it is generally thicker than schedule 160.

8 to NPS 3-1/2