Pipeline Pigging FAQ — Frequently Asked Questions

Pipeline pigging is the process of inserting a device called a ‘pig’ into a pipeline and propelling it through the bore — using the existing product flow or an external medium such as water, nitrogen, or air — to clean, dewater, dry, batch, or inspect the line. The process does not require the pipeline to be shut down.
Pigging is needed at every stage of a pipeline’s life. During pre-commissioning and commissioning, it removes construction debris, dewaters the line after hydrostatic pressure testing, and dries the bore before gas or product introduction. During operation, it removes deposits that reduce flow efficiency and cause corrosion. Before inline inspection, it cleans the bore to the standard required by the inspection tool.

Read more: What Is Pipeline Pigging? The Complete Australian Guide

If any of the following apply to your pipeline, you need pigging:

Depending on the pig type used, pipeline pigging performs one or more of the following functions:

Read more: What Is Pipeline Pigging? The Complete Australian Guide

Yes — one of the key advantages of pipeline pigging is that operations do not need to stop. The pig travels with the existing product flow. The launcher and receiver are fitted with isolation valves that allow safe pig loading and retrieval without interrupting pipeline operations. This is why pigging is the preferred method for routine maintenance cleaning of operational gas, water, and oil pipelines.

Pipeline pigs fall into two main categories — utility pigs (which perform physical work) and inspection pigs (which collect data). The main utility pig types are:

Read more: Types of Pipeline Pigs Explained: The Complete Guide

Pig selection requires seven key inputs: pipeline internal diameter (measured, not nominal), product type, pipeline geometry (bend radii, valve types, bore changes), debris type and volume, operating pressure and flow rate, distance of the run, and the pigging objective. Getting any one of these wrong is the most common cause of stuck pigs and failed pig runs.
As a starting rule: always begin with a low density bare foam pig (LD-BR) as the first pig run in any new or unknown pipeline to confirm the bore is clear before escalating to more aggressive pigs.

Read more: How to Select the Right Pipeline Pig: A Practical Guide

Foam pig density (kg/m3) determines how hard the pig presses against the pipe wall. Low density (LD, 16-32 kg/m3) pigs are soft and flexible — used for line proving, drying, and initial dewatering. Medium density (MD, 80-96 kg/m3) pigs are firm — used for general cleaning and progressive dewatering. High density (HD, 128-160 kg/m3) pigs are very firm — used for heavy scale and corrosion removal in confirmed clear pipelines.
Golden rule: always start lighter than you think you need. It is far easier to run a second, more aggressive pig than to recover a stuck pig.

Read more: Foam Pig Density Explained: LD, ID, MD and HD

A foam pig is a solid object that physically sweeps and pushes debris through the pipeline bore. A gel pig is a viscous liquid slug pumped between two foam pigs that encapsulates and carries fine debris particles, and can deliver chemical treatments (corrosion inhibitors, biocides) to the full pipe bore surface. They are complementary — gel pigs capture what foam pigs dislodge but cannot carry. For most commissioning applications, foam pigs alone are sufficient. For heavy construction contamination, pre-ILI cleaning, or chemical treatment, a combined foam-and-gel sequence is recommended.

Read more: Gel Pigging vs Foam Pigs: When to Use Each

Yes — foam pigs can navigate pipelines that are not ‘fully piggable’, including pipelines with non-full-bore valves, tight bends (down to 1D minimum bend radius for low density foam pigs), weld bead intrusions, and gradual diameter changes. If the pipeline has not previously been pigged, always run a low density bare foam pig first to confirm piggability before using mechanical pigs (disc pigs or cup pigs), which require a fully piggable bore.

The standard pigging process has six steps: (1) pig selection — choosing the right type, density, and coating; (2) pig insertion into the launcher barrel; (3) launching — pressurising the launcher to propel the pig into the bore; (4) tracking — pig signalers at key points confirm the pig has passed; (5) receiving — the pig is captured in the pig receiver at the far end of the pipeline; (6) post-run assessment — the pig is inspected, water volume is recorded, and debris is assessed to determine if additional runs are required.

Read more: What Is Pipeline Pigging? The Complete Australian Guide

A minimum of 3-5 pig runs is required for a standard dewatering sequence after hydrostatic pressure testing. The sequence is: LD-BR (bulk water removal x 1-2 runs), MD-BR (progressive dewatering), MD-XX (combined cleaning and dewatering), LD-FC (final drying pass). Never declare dewatering complete based on a single dry pig run — at minimum, two consecutive dry pig arrivals at the receiver are required before the pipeline is declared dry.

Read more: Pipeline Dewatering After Hydrostatic Testing: Best Practices

The complete commissioning sequence for a new Australian gas pipeline has 10 steps: (1) gauge plate run to confirm bore clear, (2) flood pig ahead of hydrotest water, (3) hydrostatic pressure test — no pig, (4) dewatering pass 1 with LD-BR, (5) dewatering pass 2 with MD-BR, (6) cleaning pass with MD-XX, (7) repeat cleaning until pig arrives clean, (8) drying pass 1 with LD-FC, (9) drying pass 2 with LD-FC, (10) gas or product introduction.

Read more: Pipeline Commissioning: The Complete Pigging Sequence

Yes — a pig launcher (at the start of the pipeline section) and a pig receiver (at the end) are required. These are oversized barrel sections of pipe fitted with closure doors, isolation valves, vent valves, drain valves, and kicker line connections. For tracking pig progress along the pipeline, pig signalers are installed at key points. Royal Poly Products supplies pig signalers (both intrusive and non-intrusive types) to complement its pig range. Launchers and receivers are typically supplied by the pipeline contractor or a specialist pigging equipment supplier.

A stuck pig is one of the most serious operational incidents in pipeline pigging, but it is preventable with correct pig selection and pre-run planning. The most common causes are: pig oversized for an undetected bore restriction, incorrect density for the operating conditions, non-full-bore valve not identified before the run, or pig disintegration. Prevention: always run a gauge plate pig on unknown pipelines before commissioning, start with low density bare foam pigs, verify all valves are full-bore and open before launching. If a pig does become stuck, Royal Poly Products can design and supply retrieval pigs and bypass pigs for recovery.

Yes — when performed by qualified operators following established procedures. Key safety requirements include: correct pig selection for the pipeline conditions, pressure monitoring during pig launch and travel, pig signalers to track pig position, trained launcher and receiver operators, and a documented emergency pig retrieval plan. Royal Poly Products’ technical team provides pig selection guidance that minimises stuck pig risk as part of the standard ordering process.

Correctly specified pigs do not damage pipelines. Risks arise from incorrect pig selection — specifically, using pigs that are too aggressive (wire brush or silicon carbide coatings) in pipelines with unknown bore condition or internal coatings, or using pigs that are significantly oversized for the bore. For coated pipelines (FBE lined, cement mortar lined, HDPE lined), always specify the lining type when ordering pigs — Royal Poly Products will specify a non-metallic, coating-compatible pig configuration.

Pipeline pig costs depend on the pig type, diameter, density, and coating. For indicative pricing: low density bare foam pigs (LD-BR) range from a few hundred to a few thousand dollars per pig depending on diameter. Medium density criss-cross pigs (MD-XX) are typically 20-40% more than bare foam equivalents. High density wire brush pigs are at the upper end of the range. For a specific project, the cost comparison that matters is total cost of ownership — including freight, lead time, and the cost of any commissioning delay caused by pig availability issues. Royal Poly Products provides transparent quotes at royalpolyproducts.com/get-a-quote.

Three critical advantages: (1) Lead time — Royal Poly Products delivers pigs in 3-10 business days vs 6-16 weeks for imported equivalents. On a critical-path commissioning project, a 12-week import lead time can cost far more in standby costs and penalties than any unit price saving. (2) Technical support — direct access to Australian engineers who know AS 2885, local pipeline configurations, and Australian climate conditions. (3) Supply chain resilience — no international shipping dependency, no customs delays, no vulnerability to global shipping disruptions.

Read more: Australian-Made Pipeline Pigs: Why Local Manufacturing Matters

Yes. Royal Poly Products is an Australian manufacturer based in Jandakot, Western Australia. Its products qualify as Australian-made content under the Australian Government’s Australian Industry Participation (AIP) framework, the Western Australian Buy Local Policy, and project-specific Local Industry Participation Plans (LIPPs). Documentation to support local content submissions is available on request.

Contact Royal Poly Products at royalpolyproducts.com/get-a-quote or call +61 08 6117 9204 with the following information: pipeline nominal pipe size and measured internal diameter, pipeline length, product type (gas, water, oil, chemical), pipeline geometry (minimum bend radius, valve types, any bore changes), operating pressure and flow rate available during the pig run, and the pigging objective (commissioning, maintenance cleaning, pre-ILI, dewatering, or other). The technical team will recommend the correct pig type, density, and coating and provide a project-specific quote.

The required pigging frequency is specified in the pipeline’s Pipeline Integrity Management Plan (PIMP) and is based on the threat assessment for that specific pipeline. Typical frequencies: gas transmission pipelines — every 1-5 years for cleaning, every 5-10 years for inline inspection. Crude oil pipelines — every 6-12 months for cleaning (wax deposition rate dependent). Water transmission mains — every 1-5 years. Mining process pipelines — every 3-12 months. The actual frequency for any specific pipeline must be determined by a qualified pipeline engineer based on the AS 2885.3 threat assessment.

Read more: Pipeline Integrity Management in Australia: What Operators Need to Know

A Pipeline Integrity Management Plan (PIMP) is a documented plan required under AS 2885.3 for Australian gas and liquid petroleum pipelines. It identifies all credible threats to pipeline integrity, assesses the risk of each threat, and specifies the inspection, monitoring, and maintenance activities the operator will carry out to manage those threats. Pigging — both maintenance cleaning and inline inspection — is central to most Australian PIMPs. The PIMP must be reviewed and updated at regular intervals and maintained as a current document throughout the pipeline’s operational life.

Read more: Pipeline Integrity Management in Australia: What Operators Need to Know

Pre-ILI cleaning is the pigging sequence performed before deploying an inline inspection (smart pig) tool. ILI tools require a clean bore to function accurately — debris, scale, and wax deposits on the pipe wall interfere with sensor signals, reduce data quality, and can physically damage the inspection tool. A typical pre-ILI cleaning sequence uses 2-4 medium density criss-cross foam pigs (MD-XX), potentially escalating to silicon carbide pigs (MD-SC) for hard scale, followed by a gauging pig to confirm bore clearance before the ILI tool is deployed. Inadequate pre-ILI cleaning is the most common cause of aborted ILI campaigns and repeat runs in Australian pipeline operations.

Read more: Pipeline Integrity Management in Australia: What Operators Need to Know