Everything that goes into a pigging run other than the pipeline itself: the pig bodies and what each one is actually good at, the trap hardware around them, the signalling and tracking kit that tells you where the pig is, and the consumables that get consumed. At the bottom is a directory of companies that make and run this equipment — and a form for adding your own.
Utility pigs come in three bodies — foam, solid cast and mandrel — and the choice is mostly about how much work the pig has to do and whether you need it back in one piece. Everything after that is a specialist. Sizes below are the common commercial range, not a limit.
| Pig | What it is | Use it for | Watch out for |
|---|---|---|---|
| Foam pig2–60" | Open-cell polyurethane foam bullet, bare or coated with a criss-cross polyurethane strip, silicon carbide, or wire brush. Density from light (~2 lb/ft³) to heavy (~10 lb/ft³). | Swabbing, drying, proving a new line, soaking up residual liquid, getting through reduced bore, short-radius bends, unbarred tees and plug valves where nothing rigid will pass. | Disposable — it comes out shredded and that is normal. Light densities shred early in long or dirty lines; buy by the box. Fragments can block strainers downstream. |
| Solid cast pig2–48" | One-piece moulded polyurethane with cups, discs or a bi-directional profile cast in. No bolts, no spares. | General cleaning, batching between products, dewatering and proving. The default workhorse on distribution and plant lines. | When the sealing profile wears, the whole pig is scrap. Check the hardness (durometer) suits the service temperature — polyurethane softens and loses seal when hot. |
| Mandrel pig4–56" | Steel body with bolt-on polyurethane cups or discs, plus optional brushes, scraper blades, magnets, gauge plates and bypass ports. Rebuildable between runs. | Long runs, heavy deposit removal, anything needing configurable aggression or a known bypass. Carries transmitters and loggers. | Heavy and awkward to load — plan the lift. Every bolted part is a part that can come off in the line; torque and record. More expensive per run unless you actually rebuild it. |
| Element | How it behaves | Typical choice |
|---|---|---|
| Cup | Lip seals against the wall in one direction only. Tolerates some wear while still sealing; rides over small restrictions. | Unidirectional cleaning and dewatering where high differential is expected. |
| Disc | Flat disc, seals both ways, higher contact pressure and a cleaner wipe than a cup, less forgiving of wear. | Batching, product separation, final dewatering. |
| Bi-directional (bi-di) | Symmetrical discs so the pig drives and seals in either direction. | Hydrotest and pre-commissioning, where the pig may have to come back the way it went in. |
| Conical / guide disc | Undersized support disc that centres the body and takes wear without sealing. | Keeping heavy mandrel bodies off the invert on long runs. |
| Wire brush | Carbon or stainless bristles set in a block or circular ring; removes adherent rust and hard scale. | Construction debris, mill scale, hard deposits ahead of inspection. |
| Scraper blade | Spring-loaded steel blade that cuts into deposits a brush rides over. | Wax and hard paraffin in crude lines. |
| Magnet assembly | Permanent magnets, usually on sprung arms, that lift ferrous debris off the wall and hold it to the pig. | Post-construction clean-up and recovering lost welding consumables and swarf. |
| Pig | What it does | Notes for planning |
|---|---|---|
| Gauge pig | Carries a soft aluminium or mild steel gauging plate, typically 90–95 % of nominal ID, that bends if it meets a restriction. | The standard proof run before an ILI tool. Photograph and measure the plate on arrival — the deformation is the record. |
| Bypass pig | Ported body that lets a set fraction of the flow pass through it, so the pig travels slower than the fluid and the jet keeps debris in suspension ahead of it. | The main speed-control method in gas lines. Bypass area is sized against the target speed — the calculator does this. Open the calculator. |
| Dual-diameter pig | Sprung or hinged sealing elements that collapse to pass the smaller bore and expand in the larger one. | For lines built in two sizes, or a loop tied into a bigger trunk. Confirm the tool's stated bore range covers both sizes and the reducer type. |
| Sphere | Inflatable or solid elastomer ball, seals in all orientations. | Liquid holdup control in wet gas lines and long loops; passes bends a rigid body will not. |
| Gel pig | A viscous chemical slug run between two mechanical pigs, or alone. Carries debris, separates products and can be dosed with inhibitor or biocide. | No mechanical parts to shred or jam, so it is the fallback for lines that will not pass a solid pig. Disposal of the returned gel needs planning before the run, not after. |
| Dummy / plug pig | A deliberately simple body used to prove the trap, the signallers and the launch sequence. | Cheap insurance on a trap nobody has used for a while. |
| MFL tool | Magnetic flux leakage in-line inspection — detects and sizes metal loss. Axial, transverse or spiral field. | Speed window usually 1–4 m/s; data quality degrades outside it. Needs a clean, gauged line. |
| UT wall-loss tool | Ultrasonic thickness measurement; higher accuracy than MFL on general wall loss. | Needs a liquid couplant, so gas lines require a batched liquid slug. Slower window, often 0.5–2 m/s. |
| UT crack / EMAT tool | Detects planar, crack-like flaws and SCC that metal-loss tools miss. | The tightest speed and cleanliness requirements of any tool. More on SCC detection. |
| Caliper / geometry tool | Mechanical or electromagnetic arms measuring bore, dents, ovality and bend radius. | Often run with an IMU to produce a pipeline centreline. Cheaper and more tolerant than a metal-loss run — use it to qualify the line first. |
| Tethered / self-propelled crawler | Robotic inspection for lines that cannot be pigged conventionally — no traps, no flow, or too short. | The answer for "unpiggable" lines, at a cost and access penalty. ILI tool types compared. |
The trap is where most of the risk sits, because it is the only part of the system that gets opened to atmosphere while the line is live next door. Everything in this list exists either to get the pig in and out or to stop the barrel being opened under pressure.
| Item | Function | Field notes |
|---|---|---|
| Launcher barrel | Oversized section — usually one or two sizes up from the line — holding the pig before launch, with an eccentric reducer onto the line so the pig's invert stays continuous. | Barrel length should take the longest tool you plan to run plus the pusher, not just today's foam pig. |
| Receiver barrel | Same arrangement reversed, usually longer, because it has to hold the pig and everything the pig pushed ahead of it. | Undersized receivers are the classic cause of debris carryover into the plant. |
| Quick-opening closure | Clamp, bayonet or swing-bolt door giving tool-free access to the barrel. Carries a pressure-warning device and, on modern designs, an interlock that will not release while the barrel holds pressure. | The single most safety-critical item on the trap. Check the warning port is clear and the interlock actually works before the run, not during it. |
| Main line valve | Full-bore valve in the line at the trap tee. | Must be genuinely full-bore and through-conduit. A reduced-bore or non-piggable valve here stops the run dead. |
| Trap / kicker isolation valve | Full-bore valve between the barrel and the line, taking the pig through it. | Same full-bore requirement. Verify the seat pockets will not trap a disc. |
| Kicker line and kicker valve | Small-bore line injecting flow behind the pig to push it out of the barrel into the main line. | Kicker sizing sets how controllably the pig launches. Too big and it fires; too small and it will not leave the barrel. |
| Vent, drain and relief | Depressurising and draining the barrel before the closure is opened, plus thermal relief. | Route vent and drain somewhere safe and known — this is where product and gas actually leave the system. |
| Barrel pressure gauge | Local indication that the barrel is at zero before the door is touched. | Independent of the warning device on the closure. Two indications, not one. |
| Pig stop / retainer | Holds the pig in the loading position until launch, or stops it over-running in the receiver. | Removable types get left in. Log them in and out. |
| Loading tray, davit and handling gear | Trays, rollers, davit arms and slings for getting a heavy tool into a barrel at waist height. | Match the davit rating to the heaviest ILI tool, not the pig. |
| Debris basket, filter or catch tank | Captures what arrives with the pig before it reaches rotating equipment or a separator. | Specify the disposal route with the waste contractor before mobilising. |
| Item | Requirement |
|---|---|
| Barred tees | Every branch of a significant fraction of the run diameter needs bars or a sphere/pig bar, or the pig will take the branch. Bar spacing is set by the shortest sealing element in the train. |
| Bend radius | Conventional tools want 3D minimum, many prefer 5D. Mitred and short-radius bends are a hard stop for rigid bodies — foam or a specially articulated tool only. |
| Full-bore valves | Through-conduit ball or gate valves throughout, locked or verified fully open before launch. Partially open valves shear sealing elements. |
| Wall thickness / bore changes | Each change is a step the sealing elements must survive. Internal weld protrusion and heavy-wall sections reduce effective bore — size the gauge plate on the smallest, not the nominal. |
| Dead legs and injection points | Protruding quills and thermowells catch pigs. Dead legs and injection points. |
| Minimum bend and bore survey | If the as-built records are incomplete, a caliper or foam geometry run is cheaper than a stuck inspection tool. Piggability checks. |
You need two independent answers to "where is the pig" — a calculated position from volume pumped, and a physical confirmation. These are the devices that give you the second one.
| Device | How it works | Strengths / limits |
|---|---|---|
| Intrusive pig signaller | A trigger protrudes into the bore; the passing pig deflects it, moving a flag, a switch or both. | Positive and unambiguous. The trigger is in the flow path, so it can be damaged and it is a potential leak path. Usually fitted with an isolation valve so it can be retracted. |
| Non-intrusive signaller | Detects the pig's magnet or mass through the wall — nothing enters the bore. | No penetration, no leak path, retro-fittable. Needs the pig to carry a magnet, and is less certain on heavy wall. |
| Magnetic locator | Hand-held receiver picking up a permanent magnet set in the pig body, held over the line as the pig passes. | Cheap, batteryless on the pig side, works indefinitely. Needs a crew standing at the right place at roughly the right time, and shallow enough cover. |
| Electromagnetic transmitter (ELF/VLF) and receiver | A battery transmitter in the pig pulses at low frequency; surface receivers pick it up through soil, water and concrete. | The standard for long cross-country and subsea runs. Battery life sets the maximum run duration — size it against the slowest credible run, not the planned one. |
| Acoustic / ultrasonic detector | Listens for the pig passing a known feature such as a weld or bend. | Needs no modification to the pig. Noisy environments and buried lines degrade it. |
| Radioactive tracer / gamma detector | A sealed source in the pig located with a surface scintillation detector. | Penetrates where magnetics will not. Licensing, transport and personnel requirements make it a specialist service. |
| Above-ground marker (AGM) | Recorder left at a surveyed point that timestamps the inspection tool passing it, used to tie ILI data to real chainage. | Mandatory for locating defects accurately. Plan the marker positions and their survey before the tool run. |
| Pig-mounted data logger | Records pressure, temperature, speed and stoppages through the run. | Turns "it took longer than expected" into a diagnosable event. Cheap to add to a mandrel body. |
What arrives on site on a truck. Sizing it is the part of pre-planning that most often goes wrong, because the propelling medium — not the pig — sets the schedule.
| Item | Purpose | Sizing driver |
|---|---|---|
| Air compressor | Propelling medium for dewatering and drying runs. | Line volume at run pressure, divided by the target run duration. Delivery falls with altitude and ambient temperature — derate. |
| Nitrogen: liquid tanker, pump and vaporiser | Inert propelling and purging medium where air is not permitted. | Line volume × absolute run pressure ÷ standard pressure, plus purge allowance. Nitrogen volume for pigging. |
| Nitrogen membrane or PSA unit | On-site nitrogen generation where trucking liquid is impractical. | Purity against flow — the two trade off directly. State the required purity before quoting flow. |
| Water pump / fill pump | Hydrotest fill, flushing and water-driven pigging. | Flow for target pig speed (v = Q/A), head for static lift plus friction. |
| Air dryer (desiccant or refrigerant) | Achieving a dew point specification after dewatering. | The dew point spec and the line's internal area, not just the flow. |
| Back-pressure / choke assembly | Holds the pig against the line, stops gas expansion running away and controls arrival. | The highest elevation on the profile and the pig's own differential. Back pressure explained. |
| Flow meter and totaliser | Volume pumped — the input to the position calculation. | Must be totalising and logged. A rate-only reading is not enough to track a pig. |
| Pressure and temperature instruments | Trap and line conditions, logged through the run. | Range to cover launch transient, not just steady state. |
| Filtration and separation | Protecting downstream plant from what the pig brings. | Expected debris mass from the first run, which is always more than the estimate. |
| Temporary tankage | Holding returned water, product and gel for disposal. | Full line volume unless there is a confirmed route to drain or process. |
The list that decides whether a problem costs an hour or a day.
| Group | Items |
|---|---|
| Sealing elements | Spare cups and discs in the running size, one full change-out set per mandrel body, correct hardness for the temperature. |
| Cleaning elements | Spare brush blocks or circular brushes, scraper blades and springs, magnet assemblies and keeper plates. |
| Gauge plates | Aluminium plates at the planned percentage of ID, plus a spare set — a deformed plate is a result, not a reusable part. |
| Bypass hardware | Blanking plugs and bypass orifice plates in a range of sizes so bypass can be retuned between runs. |
| Fasteners | Nose and tail bolts, washers and locking hardware for the mandrel body, plus a calibrated torque wrench. |
| Closure spares | Door seal or O-ring for every closure on the job, thread grease, and the pressure-warning device spare. |
| Tracking | Spare transmitter batteries, spare magnets, receiver batteries, and a second receiver. |
| Foam | More foam pigs than planned, in at least two densities — the cheapest contingency on the truck. |
| Chemicals | Gel, inhibitor, biocide and surfactant with their data sheets, plus the disposal paperwork. |
| Recording | Pig log sheets, camera, tape measure and calipers for the arrival inspection, and sample containers for debris. |
Companies that manufacture pigging equipment or run pigging operations. Entries record what each company supplies and where it is based — nothing more. No ranking, no endorsement, no payment, and no opinion on quality: the listing order is alphabetical and that is deliberate.
Free, and open to manufacturers, fabricators, service providers and inspection companies working in pipeline pigging. Submissions are reviewed by a person before they appear, usually within a few days. Keep the description factual — what you supply, not why you are the best at it; marketing copy gets edited down or rejected.
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