Piping
Threaded fittings
In short
G, R, Rp, Rc and NPT: recognise, measure, never mix.
Families
GParallel BSP ISO 228-1 (BSPP)55° thread. The thread does not seal: flat gasket, O-ring or seat.
R · Rp · RcTaper BSP ISO 7-1 / EN 10226 (BSPT)R taper male, Rp parallel female, Rc taper female. The thread seals, with paste or tape.
NPTAmerican taper ASME B1.20.160° thread, 1-in-16 taper on diameter. Does not mate properly with BSP.
Identifying a thread
Measure the Ø across the crests and count threads over 1 inch (25.4 mm). 19 threads: BSP. 18 or 27: NPT. The inch size is not the measured Ø: a 1/2 is 20.96 mm in BSP and 21.34 mm in NPT.
BSP: G (ISO 228-1) and R (ISO 7-1)
| Size | DN | Threads per inch | Pitch (mm) | Major Ø (mm) |
|---|---|---|---|---|
| 1/8 | 6 | 28 | 0.907 | 9.728 |
| 1/4 | 8 | 19 | 1.337 | 13.157 |
| 3/8 | 10 | 19 | 1.337 | 16.662 |
| 1/2 | 15 | 14 | 1.814 | 20.955 |
| 5/8 | — | 14 | 1.814 | 22.911 |
| 3/4 | 20 | 14 | 1.814 | 26.441 |
| 1 | 25 | 11 | 2.309 | 33.249 |
| 1 1/4 | 32 | 11 | 2.309 | 41.910 |
| 1 1/2 | 40 | 11 | 2.309 | 47.803 |
| 2 | 50 | 11 | 2.309 | 59.614 |
5/8: G only.
NPT (ASME B1.20.1)
| Size | Threads per inch | Pitch (mm) | OD (mm) |
|---|---|---|---|
| 1/16 | 27 | 0.941 | 7.95 |
| 1/8 | 27 | 0.941 | 10.29 |
| 1/4 | 18 | 1.411 | 13.72 |
| 3/8 | 18 | 1.411 | 17.15 |
| 1/2 | 14 | 1.814 | 21.34 |
| 3/4 | 14 | 1.814 | 26.67 |
| 1 | 11.50 | 2.209 | 33.40 |
| 1 1/4 | 11.50 | 2.209 | 42.16 |
| 1 1/2 | 11.50 | 2.209 | 48.26 |
| 2 | 11.50 | 2.209 | 60.33 |
| 2 1/2 | 8 | 3.175 | 73.02 |
| 3 | 8 | 3.175 | 88.90 |
| 3 1/2 | 8 | 3.175 | 101.60 |
| 4 | 8 | 3.175 | 114.30 |
OD = OD of the ASME pipe of the same size. Pitch = 25.4 / TPI.
Sources
- Bollin : filetages gaz ISO 228 et ISO 7-1 : Tableaux G 1/8 à G 2, R 1/8 à R 2 (link)
- IndFastPro : dimensions BSPP / BSPT : ISO 228 et ISO 7, recoupement (link)
- RoyMech : filetages de tuyauterie : G, R, Rp, Rc ; EN 10226 (link)
- Engineering ToolBox : filetages NPT : Filets au pouce, Ø extérieur, conicité 1/16 (link)
- ISO Hydraulic : tableau NPT : Recoupement, NPT ≠ BSP (link)
Tools · Piping
Isometric planLine entered item by item: dimensioned isometric, 3D, spool cut list, bill of materials, welds, PDF.Pipe offsetOffset a line with two elbows: cut length, angle from the spool or the run, elbow cut layout.Rolling offsetOffset both up and sideways with two elbows: true offset, cut length, elbow roll.Parallel pipe offsetSeveral parallel lines through the same offset: start shift of each line, cut length.Branch on pipeSaddle cut for a square, angled or offset branch: generator lengths and full-size wrap-around template.Branch on elbowSaddle cut for a branch at the middle of an elbow (outer side or flank): generators and full-size template.Mitre bendSegmented elbow: cut angle, outside / centreline / inside length of each piece, cutting template.Cut-down elbowCut a 90° or 45° elbow down to any angle: lengths at the back, side and belly, marks and cutting template.Tee + elbowTake-out of an elbow fitted on an equal tee, direct or with a spool; spool to cut for a given dimension.Swept teeBranch made from an elbow laid on the header: elbow cut, height-gauge marks, full-size header hole.ReducerConcentric or eccentric reducer: angle, taper and flat pattern to mark out on plate.Pipe bendingCut length, bend marks from the end, gain and approximate wall thinning.Standard fittingsTake-out of buttweld elbows, tees, reducers and caps (ASME B16.9, EN 10253-2).Flanges and boltingDrilling, bolts, studs and wrench size of an EN 1092-1 (PN) or ASME B16.5 (class) flange.Flange gasketDimensions of EN 1514-1 and ASME B16.21 flat gaskets and ASME B16.20 spiral wound gaskets (rings included).Jacketed pipePipe in a pipe: gap, spacers (height, count, positions), volumes, weight and gap in the elbows.Line weightWeight of a pipe run per metre and in total: pipe, water, insulation.Hydrostatic testIndicative test pressure (PED / EN 13480-5 or ASME B31.3) and gauge range.