For pipe sizes less than NPS 14 inch , both methods give a nominal value for the OD that is rounded off and is not the same as the actual OD. For example, NPS 2 inch and DN 50 are the same pipe, but the actual OD is 2.375 inches or 60.33 millimetres. The only way to obtain the actual OD is to look it up in a reference table.
The IPS number is the same as the NPS number, but the schedules were limited to Standard Wall , Extra Strong , and Double Extra Strong . Different definitions exist for XXS, glass pipes however it is never the same as SCH 160. XXS is in fact thicker than SCH 160 for NPS 1/8″ to 6″ inclusive, whereas SCH 160 is thicker than XXS for NPS 8″ and larger.
A broad variety of standardized pipe fittings are available; they are generally broken down into either a tee, an elbow, a branch, a reducer/enlarger, or a wye. The piping and plumbing fittings and valves articles discuss them further. Mechanical grooved couplings or Victaulic joints are also frequently used for frequent disassembly and assembly. Developed in the 1920s, these mechanical grooved couplings can operate up to 120 pounds per square inch working pressures and available in materials to match the pipe grade.
Typically the pipe wall thickness is the controlled variable, and the Inside Diameter (I.D.) is allowed to vary. The pipe wall thickness has a variance of approximately 12.5 percent. There are two water pipes common methods for designating pipe outside diameter . The North American method is called NPS (“Nominal Pipe Size”) and is based on inches (also frequently referred to as NB (“Nominal Bore”)).
Our pipe systems and treatment plants are old and in need of replacement. Some of the equipment and materials are reaching 100 years old. The annual cost to repair broken pipes has reached $20 million.