Pipeline pigging calculator

The tool lives at pigging.integrityfieldguide.com. It is part of the Integrity Field Guide, it is free, it needs no sign-up, and nothing you type leaves your browser.

What it calculates

• Pig speed and flow rate — the flow needed for a target speed, or the speed a known flow gives you, with the bypass split and the speed window for the pig or tool selected.
• Back pressure — what to hold at the receiver over an elevation profile, staged along the route, with the choke valve Cv and the launch pressure that goes with it.
• Volume and pig tracking — line volume, volume pumped against pig position, the reverse look-up from a chainage, and the arrival time, on single or multi-diameter lines.
• Nitrogen, air and water quantities — line volume converted to standard volume at run pressure, peak inventory and total consumption.
• Equipment spread — compressors or membrane units for the duty, frac tanks, hose sizes and runs, flange ratings, nuts, gaskets and hand tools.
• Piggability and ILI checks — bends, valves, tees and bore changes against the pig chosen, and the tool windows for MFL, UT, EMAT, caliper and gauging runs.
• A run simulation — pressure, back pressure and differential along the profile, for different media and pipe sizes, downloadable as a standalone page.

How to use it

1. Pick the job type

   Cleaning, gauging, dewatering, drying, a batch pushed with nitrogen or air, or an ILI run. The job type sets sensible defaults for everything else.

2. Put in the line

   Size and wall (or a custom bore), length, temperature, and the medium behind and ahead of the pig. Multi-diameter lines are entered as sections.

3. Choose the pig and the target

   Pig or tool type and bypass, then either a target speed, a known flow rate, or the time the run has to finish in.

4. Read the panels

   Flow, tracking, profile and back pressure, medium quantities, equipment spread, ILI checks — each with a briefing explaining the number and where to find the input in the field.

The numbers behind it

Nothing in the tool is a black box. Pig speed is v = Q/A; friction is Darcy–Weisbach with the Swamee–Jain approximation for the friction factor; gas quantities use the real gas law with a Papay compressibility factor; bypass flow is orifice flow with a discharge coefficient of about 0.62; static head is ρgΔh. Pipe dimensions follow ASME B36.10M and the flange and bolting data ASME B16.5. A formulas page in the tool lists every relation it uses so the work can be checked by hand.

Flow rate for 1 m/s, by line size

A quick reference for the most common question the calculator answers:

Common questions

How do you calculate pig speed?

Pig speed is the bulk velocity of the fluid driving it: v = Q / A, where Q is the flow rate at line conditions and A is the internal cross-sectional area of the pipe. Flow through a bypass pig does not push it, so subtract the bypass flow first. On a gas line, convert standard flow to line conditions before dividing.

What is a normal pig speed?

Cleaning runs are typically 1 to 3 m/s in liquid and 2 to 5 m/s in gas; MFL inspection tools are usually 1 to 4 m/s and ultrasonic wall-loss tools 0.5 to 2 m/s. The vendor window for the specific tool always governs.

How much back pressure does a pigging run need?

Enough to keep the liquid column above its minimum pressure over every high point (about 0.098 bar per metre of rise for water), to stop the gas behind the pig expanding into a surge, and to supply the differential the pig itself needs to move, typically 0.3 to 1.5 bar.

How much nitrogen does a pipeline need for pigging?

Line volume multiplied by absolute run pressure over standard pressure. A 12-inch line 10 km long holds about 730 cubic metres, roughly 6,500 standard cubic metres of nitrogen at 8 bar g for one fill.

Is the pipeline pigging calculator free?

Yes. No sign-up, nothing uploaded, every calculation runs in your own browser. It is a planning and training aid, not a substitute for the approved procedure or the pig and ILI vendor data.