Piping Engineering Guides

Worked calculations and selection guidance — sizing, wall thickness, test pressure, bolt torque and material choice, each with the formula and a full example.

What these guides are for

The dimension tables on this site say what a component measures. They do not say which component to pick. These guides cover that second question: how a flow rate becomes a line size, how a design pressure becomes a wall thickness and then a schedule, and how a pressure class is read off at the design temperature.

Each guide gives the formula, says where it comes from, and then works one example through to a result using the pipe and flange data published here. The example figures are calculated when the site is built, so the answer in the text is the answer the data gives. Where a guide depends on a value that a code fixes, such as an allowable stress, the value used is stated so that it can be replaced with the one that applies to your job.

Start here: how pipe is designated

Pipe is ordered by a nominal size and a schedule, and neither of them is a measurement. These guides explain what the designations mean, which is the background every table on the site assumes.

What a Pipe Schedule Actually IsWall series · fixed ODWhy a schedule is a wall series and not a thickness.NPS vs DN ExplainedDesignators · not measurementsTwo designators for one pipe, and why neither is a measurement.Pipe End ConnectionsBevel · plain · threadedBevelled, plain and threaded ends, and where each is used.

Sizing a line and its wall

The usual order of work is to size the bore for the flow, then find the wall the pressure needs, then pick the schedule that provides it, and finally choose the material. The guides follow that order and each carries a worked example with the arithmetic shown.

Pipe Sizing by Flow Rate and VelocityVelocity limits · gpm capacityTurn a flow rate into a line size using velocity limits.Pipe Wall Thickness CalculationBarlow · B31.3 · worked exampleBarlow and ASME B31.3, corrosion allowance and mill tolerance.Pipe Material SelectionA53 · A106 · A312 · A335A53, A106, A312 and A335: which grade suits which duty.

Flanged joints

A flange is chosen by pressure class at the design temperature, given a facing to suit the gasket, and made up to a bolt load. These guides cover each of those steps.

Pressure-Temperature DeratingReading P-T tables · interpolationReading a P-T table and interpolating between temperatures.Choosing a Flange Face TypeRF · FF · RTJ selectionRaised face, flat face or ring-type joint, by service.Flange Bolt TorqueT = K·F·d · all B16.5 bolt sizesTarget torque from bolt stress, for every B16.5 bolt size.

Testing

What a finished line is pressure tested to, and how the flange class limits the test.

Hydrostatic Test PressureTest limit · B31.3 · by classWhat a line is tested at, and what its flanges allow.

What the guides leave out

A pressure design calculation is one check among several. A real line also has to carry its own weight between supports, absorb thermal expansion, and withstand wind, earthquake and relief valve reaction where those apply. The guides stay with the calculations that lead directly to a size, a schedule or a class, because those are the ones the tables on this site can answer. For comparisons between two specific options, see the comparison pages.

These guides explain method, not code compliance. Every calculation here is a worked illustration. Confirm the governing equations, allowable stresses and acceptance criteria against a current copy of the applicable ASME, ASTM or API document before using them in design.