Pipeline Pigging Guide
Foam Pig Density Explained: The Complete Australian Guide
Quick Answer
Foam pigs are available in four standard densities: low density (16–32 kg/m³) for line proving and drying, intermediate density (40–56 kg/m³) for light cleaning and batching, medium density (80–96 kg/m³) for general cleaning and debris removal, and high density (128–160 kg/m³) for heavy scale and aggressive cleaning. 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.
Published by Royal Poly Products
Jandakot, Western Australia
Contents
1. What is foam pig density?
2. The four standard densities explained
3. Density vs coating — what's the difference?
4. All coating options and their applications
5. How to choose the right density for your application
6. The standard commissioning sequence
7. Common density selection mistakes
8. Royal Poly Products foam pig series reference
9. Frequently asked questions
1. What Is Foam Pig Density?
Foam pig density refers to the mass per unit volume of the polyurethane foam used to manufacture the pig — expressed in kilograms per cubic metre (kg/m³). Density directly determines how firm the foam is, how much it compresses against the pipe wall, and how much differential pressure the pig can generate and sustain during a pig run.
A low density foam pig is soft and highly compressible — it generates relatively low contact force against the pipe wall, making it gentle on the pipeline but limited in its cleaning capability.
A high density foam pig is firm and resistant to compression — it generates high contact force and differential pressure, making it highly effective for aggressive cleaning but requiring a clear, well-documented pipeline bore to avoid getting stuck.
Density is the most fundamental selection decision for any foam pig application. It is determined before the coating is chosen, because the density defines the pig's mechanical behaviour in the
pipeline while the coating determines its cleaning mechanism.
| Density (kg/m³) | Series code | Typical use | Pipeline type | Do not use when |
|---|---|---|---|---|
| Low density 16–32 | LD Series | Line proving, drying, initial dewatering | New pipelines, gas lines | Heavy debris present — pig will compress past it |
| Intermediate density 40–56 | ID Series | Light cleaning, batching, dewatering | Water mains, product lines | High differential pressure — pig may bypass |
| Medium density 80–96 | MD Series | General cleaning, silt and wax removal | Oil, gas, water pipelines | First run on unknown pipeline — start lighter |
| High density 128–160 | HD Series | Heavy scale, corrosion, aggressive cleaning | High-pressure oil and gas | Bore restrictions present — high risk of stuck pig |
2. The Four Standard Densities Explained
Low Density — 16–32 kg/m³ (LD Series)
Low density foam pigs are the softest and most compressible foam pigs in the Royal Poly Products range. Their high compressibility allows them to squeeze through restrictions that would stop a firmer pig — making them the correct choice for any first run in a pipeline where the internal condition has not been verified, and for all drying and line-proving applications.
• Generates relatively low differential pressure — insufficient for heavy cleaning but ideal for liquid sweeping and drying
• Can negotiate tight bends down to approximately 1D (one pipe diameter radius)
• The lowest risk pig to run in any pipeline — if it gets stuck, differential pressure is low enough to retrieve it without excavation in most cases
• Standard first pig in any commissioning sequence — confirms the bore is clear before more aggressive pigs are run
LD Series tip
For gas pipeline drying after dewatering, run a low density fully coated pig (LD-FC) rather than bare foam. The solid polyurethane shell provides a better liquid seal and carries more residual
moisture to the receiver, resulting in a drier pipeline in fewer runs.
Intermediate Density — 40–56 kg/m³ (ID Series)
Intermediate density foam pigs sit between low and medium density — firmer than LD pigs but still highly flexible. They are the standard choice for water main cleaning and dewatering operations, batching applications in product pipelines, and any application where LD pigs are insufficient but the pipeline condition does not support the full contact force of an MD pig.
• More effective liquid seal than LD pigs — better suited to dewatering passes where complete liquid removal is required
• Suitable for light cleaning of soft deposits — silt, biofilm, and light wax in water and product pipelines
• Good choice for product batching in multi-product pipelines where a firm seal is needed without the risk associated with higher density pigs
• Often used as the second pig in a commissioning dewatering sequence, following an LD line-proving run
Medium Density — 80–96 kg/m³ (MD Series)
Medium density foam pigs are the most versatile and commonly used foam pig density in Australian pipeline operations. They generate sufficient differential pressure for effective
cleaning across most pipeline conditions, while remaining flexible enough to negotiate bends and minor bore anomalies.
The Royal Poly Products MD Series has the widest range of coating options — from bare and criss-cross through to carbon steel, stainless steel, nylon, and total wire brush configurations — making medium density the default specification for routine operational cleaning of gas, oil, and water pipelines.
• Available in the full coating range — BR, XX, FC, SC, NW, CW, SW, and TW
• Standard choice for pre-ILI cleaning sequences where the pipeline bore is known and clear
• Can be run in progressive sequences from MD-BR (general cleaning) through MD-CW (aggressive scale removal)
★ MD Series most popular specification
The MD Criss-cross coated pig (MD-XX) is the most widely specified foam pig in Royal Poly Products' Australian sales — used for routine cleaning and maintenance pigging across gas
transmission, water distribution, and oil product pipelines. The criss-cross polyurethane pattern provides effective wiping action across the full bore without the restriction risk associated with wire brush pigs.
High Density — 128–160 kg/m³ (HD Series)
High density foam pigs are the firmest and most aggressive foam pig in the Royal Poly Products range. They generate high contact force and differential pressure, making them highly effective for removing hard scale, heavy corrosion products, and mill scale from new pipelines. However,
their firmness means they have significantly less tolerance for bore restrictions — using an HD pig in a pipeline with unverified internal condition is one of the leading causes of stuck pigs in Australia.
• High differential pressure capability — suitable for high-pressure gas and oil transmission pipelines
• Limited flexibility — requires a well-documented, clear pipeline bore before use
• Only run HD pigs after the pipeline bore has been confirmed clear by LD and MD pig runs
• Available in bare, criss-cross, fully coated, carbon steel brush, stainless steel brush, nylon brush, and total wire brush configurations
★ HD pig warning
Never run a high density pig as the first pig in an unknown pipeline. Hard scale and weld splatter that an LD or MD pig would compress past will stop an HD pig dead. Always use the progressive density sequence — LD then MD then HD — and only escalate to HD when lower density pigs have confirmed the bore is clear and the cleaning objective has not been achieved.
3. Density vs Coating — What's the Difference?
Density and coating are two independent but complementary selection decisions that together define the pig's complete specification:
Density determines the pig's mechanical behaviour — how firmly it contacts the pipe wall, how much differential pressure it generates, how compressible it is, and how it responds to bore restrictions. Density is the foundation of the specification.
Coating determines the pig's cleaning mechanism — how it interacts with the pipe wall surface, what types of deposits it can remove, and what level of sealing it provides. Coating is applied on top of the density decision.
The same density can be combined with different coatings to achieve very different results. For example, a medium density pig can be specified as MD-BR (bare, for general cleaning), MD-XX
(criss-cross, for wiping action), MD-SC (silicon carbide, for abrasive scale removal), or MD-CW (carbon steel wire brush, for aggressive mechanical cleaning). The density remains 80–96
kg/m³ in all cases — only the surface interaction changes.
How to read a Royal Poly series code
Series codes follow the format: [Density]-[Coating]. For example, MD-XX = Medium Density, Criss-cross coated. HD-CW = High Density, Carbon steel Wire brush. LD-BR = Low Density, Bare foam. This system covers the full range from LD-BR (softest, gentlest) to HD-TW (firmest, most aggressive).
4. All Coating Options and Their Applications
Royal Poly Products manufactures foam pigs in eight coating configurations. The table below covers every coating, its cleaning mechanism, its best application, and which density/series combinations are available:
| Coating Code | Mechanism | Best application | Royal Poly series available |
|---|---|---|---|
| Bare foam (BR) | Open-cell foam contact — gentle, low friction | Line proving, drying, first runs in unknown pipeline | LD-BR, ID-BR, MD-BR, HD-BR |
| Criss-cross coated (XX) | Spiral PU pattern — continuous wiping action | General cleaning, routine maintenance, dewatering | LD-XX, ID-XX, MD-XX, HD-XX |
| Fully coated (FC) | Solid PU shell — maximum liquid seal | Drying passes, abrasive conditions, extended life | LD-FC, ID-FC, MD-FC, HD-FC |
| Silicon carbide (SC) | Abrasive grit bonded to foam — grinding action | Heavy scale, mill scale, hard corrosion product | LD-SC, ID-SC, MD-SC, HD-SC |
| Nylon wire brush (NW) | Nylon filaments — light mechanical cleaning | Classified areas, potable water, SS pipelines | LD-NW, ID-NW, MD-NW |
| Carbon steel brush (CW) | Steel wire — aggressive mechanical cleaning | Heavy scale, hard deposits, gas transmission | MD-CW, HD-CW |
| Stainless steel brush (SW) | SS wire — no carbon contamination | Food grade, pharmaceutical, SS lined pipelines | MD-SW, HD-SW |
| Total wire brush (TW) | Full-body wire coverage — maximum aggression | Severely fouled pipelines, pre-ILI cleaning | MD-TW, HD-TW |
5. How to Choose the Right Density for Your Application
Use these decision rules to select the correct foam pig density for your specific application:
If you are commissioning a new pipeline
Always start with Low Density (LD). The pipeline bore has never been verified by a pig run, and construction debris, weld splatter, and temporary plugs may be present. A low density bare foam pig will pass through most restrictions without getting stuck, allowing you to confirm the bore is clear before running more aggressive pigs.
If you are dewatering after hydrostatic pressure testing
Start with Low Density (LD) for the initial bulk water removal runs, then progress to Medium Density (MD) for the residual liquid removal pass, and finish with a Low Density Fully Coated (LD-FC) pig for the drying pass. Do not start dewatering with an MD or HD pig — use the
progressive sequence.
If you are cleaning a water main or distribution pipeline
Specify Intermediate Density (ID) or Medium Density (MD) depending on the known debris load. For routine maintenance cleaning of a regularly pigged water main, ID-XX or MD-XX is
appropriate. For a water main that has not been pigged for many years with known silt and scale accumulation, start with MD-XX and escalate to MD-SC or MD-CW if the objective is not achieved.
If you are cleaning a gas transmission pipeline
Specify Medium Density (MD) as the standard operational cleaning pig. MD-XX for wax and light scale, MD-CW for heavy scale in known, clear pipelines. For pre-ILI cleaning where high cleanliness is required, a sequence from MD-XX through to HD-CW may be specified by the ILI tool operator.
If you are cleaning an oil or product pipeline
Specify Medium Density (MD) for general wax and paraffin removal — MD-XX is the standard specification. For heavy wax or asphaltene deposits, MD-SC or HD-SC may be appropriate. Always confirm the pipeline bore is clear before running silicon carbide or wire brush pigs — their abrasive action will lock them against any restriction they encounter.
If the pipeline has not been pigged before or pigging history is unknown
Always start with Low Density Bare (LD-BR), regardless of what the pipeline drawings say. Confirm the bore is clear, then escalate progressively. The cost of a second pig run is a fraction of the cost of recovering a stuck pig.
6. The Standard Commissioning Sequence
The following pig run sequence is the standard Royal Poly Products recommendation for commissioning a new pipeline — covering line proving, dewatering, and drying. This sequence
is used on gas, water, and oil pipelines across Australia:
| Run | Pig | Density | Coating | Objective | Pass criteria |
|---|---|---|---|---|---|
| 1 | Foam pig | Low density | Bare (BR) | Line proving — confirm bore clear | Pig arrives intact, gauge plate undamaged |
| 2 | Foam pig | Low density | Bare (BR) | Dewatering pass 1 — bulk water removal | Significant water volume at receiver |
| 3 | Foam pig | Medium density | Bare (BR) | Dewatering pass 2 — residual water | Reduced water volume, pig arrives wet |
| 4 | Foam pig | Low density | Fully coated (FC) | Drying pass — remove residual moisture | Pig arrives dry or near-dry |
| 5 (if req.) | Foam pig | Low density | Fully coated (FC) | Final drying confirmation | Pig arrives completely dry |
This sequence can be compressed or expanded depending on the pipeline's specific commissioning requirements, the line profile (number of low points), and the volume of water to
be removed. Royal Poly Products can provide a custom commissioning sequence recommendation for any pipeline project — contact the technical team via
royalpolyproducts.com/get-a-quote.
7. Common Density Selection Mistakes
Starting too high — running MD or HD pigs before the bore is confirmed
This is the most common cause of stuck pigs in Australian pipeline commissioning operations. A medium or high density pig that encounters a weld bead intrusion, a construction debris item, or a partially closed valve will lock in position and require costly retrieval. Always run LD-BR first.
Using the same density for every run regardless of objective
A single density does not cover all stages of commissioning. Low density for line proving and drying, intermediate to medium for dewatering, medium to high for cleaning — each stage requires a different density. Running MD pigs for the drying pass, for example, increases the risk of residual moisture being left in the pipeline because the MD pig does not compress and conform to the bore as effectively as an LD-FC.
Escalating to HD without progressive runs
Some operators skip from LD directly to HD in an attempt to reduce the number of pig runs. This dramatically increases the risk of a stuck pig. The progressive sequence (LD → MD → HD) is not excessive caution — each run confirms the bore is clear and removes the material that the next, more aggressive pig will encounter.
Specifying HD pigs in pipelines with unverified bore condition
High density pigs are less compressible and have a significantly higher stuck pig risk than LD or MD pigs. They should never be specified for a pipeline where the internal bore has not been verified by previous pig runs, recent inline inspection, or a pig qualification trial.
Selecting density based on nominal pipe size only
Density selection must consider operating pressure, flow rate, pipeline geometry, and pigging objective — not just pipe size. A 12" low-pressure water main and a 12" high-pressure gas
pipeline require entirely different density specifications despite having the same nominal bore. Always factor in operating conditions when selecting density.
8. Royal Poly Products Foam Pig Series Reference
The following is the complete Royal Poly Products foam pig series matrix — every density and coating combination available. Series codes are used when ordering to specify the exact pig configuration required:
Low Density (LD Series) — 16–32 kg/m³:
• LD-XX — Low density criss-cross coated
• LD-FC — Low density fully coated
• LD-SC — Low density silicon carbide
• LD-NW — Low density nylon wire brush
Intermediate Density (ID Series) — 40–56 kg/m³:
• ID-XX — Intermediate density criss-cross coated
• ID-FC — Intermediate density fully coated
• ID-SC — Intermediate density silicon carbide
• ID-NW — Intermediate density nylon wire brush
Medium Density (MD Series) — 80–96 kg/m³:
• MD-XX — Medium density criss-cross coated
• MD-FC — Medium density fully coated
• MD-SC — Medium density silicon carbide
• MD-NW — Medium density nylon wire brush
• MD-CW — Medium density carbon steel wire brush
• MD-SW — Medium density stainless steel wire brush
• MD-TW — Medium density total wire brush
High Density (HD Series) — 128–160 kg/m³:
Frequently Asked Questions
What is the most commonly used foam pig density in Australia?
Medium density (MD Series, 80–96 kg/m³) is the most commonly specified foam pig density in Australian pipeline operations. The MD Criss-cross coated pig (MD-XX) is Royal Poly Products' best-selling product, used for routine cleaning and maintenance pigging across gas transmission, water distribution, and oil product pipelines. Low density (LD) pigs are the most commonly used density for commissioning operations.
Can I use a high density pig for dewatering after hydrostatic testing?
A medium density pig is appropriate for the residual water removal pass in a dewatering sequence, but the sequence should start with low density bare foam pigs for the initial bulk water removal runs. High density pigs are not recommended for dewatering — they are specified for aggressive cleaning of hard scale and corrosion products, not liquid removal. The final drying pass should always use a low density fully coated pig.
What happens if I choose too high a density?
A foam pig that is too dense for the pipeline conditions risks becoming stuck. High density pigs have less compressibility and will lock against bore restrictions — weld bead intrusions, partially closed valves, and construction debris — that a low or medium density pig would compress past. A stuck pig requires costly retrieval operations that may involve pipeline excavation. Always start lighter than you think you need.
What is the difference between LD-XX and MD-XX?
Both are criss-cross coated foam pigs — the coating and cleaning mechanism are identical. The difference is the foam density: LD-XX uses 16–32 kg/m³ foam (soft, highly compressible, lower
differential pressure) while MD-XX uses 80–96 kg/m³ foam (firmer, less compressible, higher differential pressure and cleaning force). LD-XX is used for light cleaning and dewatering in non-
piggable or unknown pipelines. MD-XX is used for routine operational cleaning in verified, clear pipelines.
How many pig runs does a commissioning dewatering sequence require?
A standard commissioning dewatering and drying sequence requires 3–5 pig runs: one or two LD-BR runs for line proving and bulk water removal, one MD-BR run for residual water removal,
and one LD-FC run for the drying pass. A fifth LD-FC run may be added if the pipeline has many low points or if the drying pass pig arrives wet. The exact number depends on pipeline length,
profile, and the volume of water to be removed.
Can foam pig density affect product quality in a product pipeline?
The pig foam and coating materials must be compatible with the pipeline product. Royal Poly Products uses polyurethane foam and elastomer materials that are compatible with most gas, water, and hydrocarbon products. For specialist product pipelines — food grade, pharmaceutical, or aggressive chemical service — advise the product type when ordering so the correct materials can be confirmed. Incompatible materials can cause pig degradation and
product contamination.
Need Help Selecting the Right Foam Pig Density?
Royal Poly Products manufactures all four foam pig densities — low, intermediate, medium, and high — in every coating configuration, from its facility in Jandakot, Western Australia. ISO 9001 certified. Australian made.
About Royal Poly Products
Royal Poly Products is an Australian manufacturer of pipeline pigs and pigging solutions based in Jandakot, Western Australia. The company manufactures the full Royal Poly foam pig range — LD, ID, MD, and HD Series in bare, criss-cross, fully coated, silicon carbide, nylon wire brush, carbon steel wire brush, stainless steel wire brush, and total wire brush configurations — along with bi-directional disc pigs, cup pigs, solid cast pigs, dual diameter pigs, and pipeline gels.
ISO 9001:2015 certified and recipient of the Western Australian Export Award (Emerging Exporter 2025) and the Australian Export Award, Royal Poly Products supports pipeline operators across Australia and internationally.
Website: royalpolyproducts.com
Phone: +61 08 6117 9204
Address: Unit 5/41 Biscayne Way, Jandakot WA 6164, Australia
Email: sales@royalmechgroup.com