Inside Diameter (ID) Size Control

Inside Diameter (ID) Controlled Pipe:  Inside Diameter (ID) controlled pipe is manufactured based on required / specified Inside Diameter (ID). Therefore, it is certain that for the same Nominal Pipe Size (NPS), Outside Diameter (OD) of pipes is different for different pipe wall thicknesses. This is in sharp contrast w.r.t. ASME B36.10M & ASME B36.19M, which designates a unique pipe Outside Diameter (OD) value for each Nominal Pipe Size (NPS). Outside Diameter (OD) Controlled Pipe follows ASME B36.10M & ASME B36.19M. Merits and demerits of ID Controlled Pipe are indicated below, for ease of decision making.

Merits:

1. ID Controlled Pipe gives adequate freedom of specifying optimum pipe wall thickness rather than selecting a standard pipe wall thickness, as per ASME B36.10M / ASME B36.19M. For critical piping (viz. high pressure and high temperature superheated steam), this often results in considerable savings in pipe materials (weight basis).
2. ID Controlled Pipe is relatively lighter than OD Controlled Pipe, due to absence of redundant margin on pipe wall thickness. For critical piping, this often results in lesser design load for pipe supports hardware and lesser induced load on structures, at support points.
3. ID Controlled Pipe helps in reducing nozzle loads of sensitive equipment like turbines, compressors and boilers.
4. Velocity and pressure drop values can be predicted or simulated accurately for ID Controlled Pipe.
5. For a very high value of pipe wall thickness (beyond the coverage of ASME B36.10M & ASME B36.19M), ID Controlled Pipe may be specified, justified and recommended, based on calculated gain on piping material cost over complete piping hardware cost.

Demerits:

1. For the same specification (size and wall thickness) of pipe, two (2) different pipe manufacturers’ produced pipe ODs may be slightly different, based on different quality tolerance margins of two (2) manufacturers. At site, a visible step is sometimes seen at the weld points of ID Controlled Pipes from different manufacturers.
2. Enhanced cost and time is often encountered due to welding, construction & erection of non-standard or custom-made pipes & pipe fittings (viz. elbows, tees, reducers, flanges etc.), owing to non-standard pipe OD w.r.t. ASME B36.10M & ASME B36.19M.
3. On similar note, enhanced cost and time is often encountered due to non-standard or custom-made pipe supports hardware (viz. clamps, clamped shoes, saddle type shoes, wear plates), owing to non-standard pipe OD w.r.t. ASME B36.10M & ASME B36.19M.
4. ID Controlled pipes, pipe fittings and pipe supports hardware are NOT readily available on shelf.
5. Very few manufacturers agree to manufacture ID Controlled Pipe and components, due to custom-made manufacturing set up, jigs and fixtures, in contrast w.r.t. ASME B36.10M & ASME B36.19M, which specifies a unique pipe OD value for each Nominal Pipe Size (NPS).
6. ID Controlled Pipe needs to be manufactured with sufficient care and precision, as any slightest reduction in Inside Diameter (ID) affects the actual value of system pressure drop, squeezing allowable pressure drop value.

References:

http://bibekbhattacharyya.blogspot.com/2014/07/implications-of-id-controlled-pipe.html