By the PICA Corp Engineering Team  |  Updated July 2026  |  Est. reading time: 8 min

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What is remote field technology for inline pipeline inspection?

Remote field technology, or RFT, is an electromagnetic inspection method that sends alternating current through a transmitter coil inside a pipe. That signal travels outward, penetrates the pipe wall completely, and wraps around the outside before returning inward — picked up by receiver coils positioned at least two pipe diameters downstream. Because the signal passes entirely through the pipe wall in both directions, the receiver captures changes in wall condition from inside and outside the pipe at the same time.

The physics here explain why RFT is replacing MFL in a growing range of applications. MFL saturates the pipe wall with a powerful permanent magnet, then looks for magnetic flux escaping through metal that has been lost to corrosion. It works very well in clean, bare-metal steel pipelines with consistent geometry. The tool needs a clear, direct relationship between its sensors and the pipe wall. RFT generates its own electromagnetic field and has no such requirement. The signal passes through cement mortar lining, epoxy coatings, wax deposits, mineral scale, and internal tuberculation without losing its ability to detect wall loss on the surfaces underneath.

The result is continuous wall thickness data along the full pipe run, with quantified wall loss mapped to both inner and outer surfaces — regardless of what coats or fills the pipe between inspection runs.

For concrete pressure pipes including PCCP and bar-wrapped transmission mains, PICA’s RFT technology goes further still. In addition to measuring steel cylinder wall thickness, it detects broken prestressing wires or broken bars and characterizes whether individual pipe segments have lost their compressive pre-load condition. No other single in-line electromagnetic technique covers all three failure indicators in one deployment.

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Why MFL tools fall short — and where RFT fills the gap

MFL has been the standard for in-line inspection of unlined steel pipelines for half a century. It remains the right tool for many applications. But four conditions make MFL unreliable or impractical — and these conditions are common in the pipeline types that are aging fastest and carrying the highest risk.

Internal scale, deposits, and tuberculation

Water and sewer pipelines accumulate scale, biofilm, mineral deposits, and in cast iron mains, iron tubercles that can reduce internal diameter by 30 percent or more in older pipes. MFL tools depend on direct or near-direct contact between their sensor array and the pipe wall. Heavy scale breaks that relationship. Readings become unreliable, and in severe cases the tool cannot pass through at all.

RFT does not require sensor contact. The electromagnetic field bridges the gap between the tool body and the pipe wall, reading through scale, sludge, sand, wax, and biofilm without degradation in sensitivity. In water distribution and transmission mains where internal tuberculation is a given on older cast iron pipe, this capability is what makes inspection possible at all without excavating for cleaning.

Liners, coatings, and concrete pressure pipe

Many transmission pipelines are lined internally with cement mortar, epoxy, or polyethylene to slow corrosion or protect water quality. FBE (fusion-bonded epoxy) coating is standard on gas gathering lines and many oil and gas flowlines. For MFL, these liners are an obstacle. The sensors need bare metal or near-bare metal to read accurately.

RFT transmits through liners of any practical thickness. The electromagnetic signal detects the steel cylinder or pipe wall beneath without the liner being removed, thinned, or even interrupted. This is especially significant for PCCP and concrete cylinder pipe inspection, where an internal cement-mortar lining is standard construction and cannot be removed for inspection purposes. RFT handles it without preparation beyond removing loose debris.

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The industries driving RFT adoption

Municipal water and transmission mains

Municipal water utilities operate some of the most challenging pipelines for conventional inspection. Cast iron mains installed in the early 20th century are heavily tuberculated. Concrete pressure pipes carry internal cement liners. Aging large-diameter transmission mains were built without pigging ports. And operating pressures make dewatering disruptive and expensive — most utilities cannot take a major transmission main offline for inspection without contingency planning that takes months.

AWWA’s 2026 State of the Water Industry report identifies infrastructure renewal and replacement as the top challenge facing water sector professionals. That pressure is pushing utilities toward inspection approaches that work within tighter operational constraints. In-service RFT inspection through hydrants — which does not require dewatering for pipes 6 & 8 inches — directly addresses this constraint.

These small-diameter water mains, PICA’s HydraSnake inserts through a fire hydrant or tee adapter for 6″ and 8″ cast iron and ductile iron mains. No excavation. Limited service interruption beyond a flow reduction to manage tool speed. The tool is retrieved downstream and the data downloaded for analysis. For municipalities with hundreds of miles of older cast iron distribution pipe and limited capital budgets, this provides inspection access that would otherwise be impractical.

Oil and gas production pipelines

In oil and gas, MFL has dominated integrity programs on main trunk lines for decades. But some lined production pipelines and lined gathering systems operate under conditions that defeat standard MFL tools. Low flow rates in many production and gathering lines mean there is not enough velocity to drive an MFL pig reliably. Crude with significant wax content deposits on the pipe wall, filling the gap between sensor and metal. Lined steel pipelines — common in gas gathering, where FBE coating protects against internal corrosion — block MFL sensor arrays.

RFT tools handle all three conditions. Tethered deployment removes flow-velocity dependency. The electromagnetic signal reads through wax and hydrocarbon deposits. And coated pipe interiors are not an obstacle. In the Shell Canada application, RFT inspection provided accurate condition data on lined pipelines that conventional tools could not assess. That case helped establish RFT’s track record in oil and gas applications beyond the water sector.

Industrial, mining, and power generation

Fire suppression loops, cooling water headers, slurry lines, and brine service pipes present the same inspection problem as aging water mains but in a different operating environment. Mining operations run a range of pipe materials — carbon steel, ductile iron, HDPE-lined steel — that no single MFL tool covers. Industrial facilities have tight physical access around pipe runs, limited shutdown windows, and the full mix of lined and unlined metallic pipe found in older water systems.

RFT’s applicability across cast iron, ductile iron, steel, and concrete pressure pipe types gives maintenance teams a single inspection methodology that works across a mixed-material inventory. PICA’s inspection applications extend from municipal water to wastewater, industrial water, mining, power generation, and oil and gas — covering this full range of operating environments.

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What RFT actually measures in a single inline run

Every RFT deployment produces a continuous log of wall condition data mapped to the pipeline’s linear distance. The tool moves through the pipe at controlled speed, taking measurements across multiple electromagnetic channels simultaneously.

In metallic pipe, the primary outputs are remaining wall thickness and the location and extent of wall loss. The through-transmission signal sees loss on the ID surface (internal corrosion, erosion, pitting) and OD surface (external corrosion from aggressive soils or stray current) without differentiation. In cast iron mains, graphitic corrosion — where iron leaches out of the wall while a graphite skeleton remains — shows as a distinct signal pattern that PICA analysts identify and quantify separately from conventional pitting.

RFT also captures anomalies associated with stress concentrators: cracks, local deformation, and features linked to fatigue or stress corrosion cracking mechanisms. In oil and gas pipelines where stress corrosion cracking is a known failure mode, this capability expands the value of a single inspection run beyond simple wall thickness measurement.

In concrete pressure pipe, the output is more extensive. PICA’s Advanced NDT RFT tools provide three simultaneous outputs for PCCP and bar-wrapped transmission mains:

• Broken prestressing wires or bars (count and cluster density per pipe segment)
• Steel cylinder wall loss (graphitic corrosion, pitting, through-wall damage)
• Pre-load characterization (whether individual pipe segments retain compressive pre-load or have lost it)

That third output is what separates RFT from the Standard NDT approach using Near Field Testing (NFT). NFT accurately detects clusters of five or more adjacent broken wires — and nothing else. It cannot measure wall thickness. It cannot determine whether wire breaks have caused the steel cylinder to lose its pre-load condition. For PCCP operators making rehabilitation or replacement decisions, knowing only the wire break count is not enough. Pre-load loss is the structural consequence that determines whether a pipe segment is at risk of catastrophic failure under operating pressure.

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Why one inspection method is rarely enough

RFT inline inspection produces a structural picture of the pipe wall across the full pipe run. What it cannot show is what the interior looks like: whether the cement liner is intact, whether joints are separating, or whether a previous repair has held. That information requires visual inspection.

For most practical pipeline condition assessments on aging transmission mains, combining RFT with CCTV and Lidar produces a complete dataset. RFT identifies where wall loss or structural deterioration exists. Visual inspection confirms liner condition, documents joint status, and flags anything the electromagnetic data alone cannot resolve. The two technologies are complementary, not competing.

On smaller-diameter pipelines in reasonably good condition, RFT alone may be sufficient to prioritize maintenance and rehabilitation spending. On large-diameter concrete pressure mains approaching or past their design service life, both datasets together give the asset manager a defensible, auditable basis for capital program decisions.

Where RFT cannot be deployed — for example, very large-diameter concrete pressure pipe in situations where time or access constraints prevent a full out-of-service program — NFT is available as a fallback method that provides at minimum a wire break count. But NFT’s output is more limited: wire break count only, no wall thickness, no pre-load characterization. It is an alternative for situations where RFT cannot run, not an equivalent substitute.

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What an undetected pipeline failure actually costs

Inline inspection is a capital expenditure. The resistance to spending is understandable. The cost comparison is not complicated.

PICA’s RFT-based inspection programs for large-diameter mains typically run $100,000 to $200,000 per mile, depending on pipe diameter, access complexity, linear footage, and program scope. An unplanned large-diameter pipeline failure typically costs $200,000 to $1.5 million per event, according to AWWA failure cost data. In urban corridors where emergency excavation must cut through roads, divert traffic, and restore pavement, that number climbs higher still. That range covers direct repair costs only — it excludes regulatory response, customer service penalties, liability exposure from property damage, and the reputational cost of a public main break making local news.

The inspection-to-failure cost ratio typically runs 10 to 50 times in favor of inspection. That framing applies across water utilities, oil and gas operators, and industrial facility managers. The question is not whether inspection costs money. It is whether the consequence of not inspecting is acceptable when a failure finally happens.

For a detailed look at how RFT inspection data changed maintenance decision-making for a major water authority, see the TRWD case study — one of the most documented RFT inspection programs in the public record.

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How PICA deploys RFT tools for inline inspection

PICA’s RFT tool lineup runs from 2″ to 96″ pipe diameter, with tool selection depending on pipe size, material, access geometry, operating pressure, and what is inside the pipe.

For pipes up to 36″ operating under pressure, in-service deployment is standard. Flow must be reduced to maintain tool speeds in the 5 to 20 feet per minute range — enough to get reliable data without the tool moving too fast for the sensor acquisition system. Full isolation and dewatering are not required. PICA’s SeeSnake and Chimera tools cover the smaller diameter range in this configuration. The HydraSnake handles 6″ and 8″ cast iron and ductile iron water mains through fire hydrant access.

For large-diameter pipelines from 36″ to 96″ — including PCCP and bar-wrapped transmission mains — the pipe is taken out of service and dewatered. PICA’s RAFT tool handles the 36″ to 48″ range with a collapsible design that inserts through standard manway-sized access. The EMIT tool covers 48″ to 96″ and assembles inside the pipe through a standard maintenance hole. Both tools are autonomous and tethered, running at approximately 20 feet per minute through the dewatered main.

Preliminary analysis is typically available within approximately one week of the field run. Complex programs covering multiple pipe sections or requiring additional QC go through off-site processing before final findings are issued. PICA analysts then review findings with each utility’s engineering team — pipe segment by pipe segment — with risk ratings, priority flags, and response timeline recommendations.

PICA Corp has been running RFT inline inspection programs across North America and more than 20 countries since 2008, with tool technology developed by Russell NDE Systems Inc. going back to 1972. The full technical basis for RFT inline inspection is documented in PICA’s technical paper on increased use of remote field technology, which presents the comparative analysis of RFT and MFL across multiple case studies and pipeline types.

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Frequently asked questions

Why are pipeline operators switching from MFL to remote field technology for inline inspection?

MFL tools require close contact with the pipe wall and magnetic saturation of the steel. Where internal scale, heavy deposits, liners, or complex pipe geometry interfere with that relationship, MFL produces unreliable data or cannot run at all. RFT uses electromagnetic induction rather than permanent magnets, so it passes through coatings, liners, scale, and wax deposits without losing sensitivity. Operators in water, wastewater, oil and gas, and industrial sectors have adopted RFT specifically because it handles conditions that stop MFL from running reliably.

What types of pipelines cannot be inspected with magnetic flux leakage (MFL) tools?

MFL tools have difficulty in three situations: internally scaled or tuberculated water mains where mineral deposits break sensor-to-wall contact; lined or coated pipelines where cement mortar, epoxy, or FBE liners interfere with the sensor array; pipelines carrying wax-laden crude or operating at low flow rates where there is not enough velocity to drive the tool. All three conditions are common in aging municipal water systems and in production-stage oil and gas pipelines.

Can RFT inspect pipelines with heavy internal scale or deposits without cleaning?

Yes. RFT’s through-transmission electromagnetic signal crosses the gap between the tool and the pipe wall without requiring direct contact. It reads through scale, biofilm, sludge, sand, wax, and mineral deposits, accurately measuring wall thickness on both inner and outer surfaces. Line preparation for RFT typically means removing loose tubercles and verifying the pipe is clear of obstructions large enough to trap the tool — not cleaning to bare metal, which is an expensive and time-consuming prerequisite for MFL and many other inspection methods.

How does RFT measure wall loss in lined or coated pipelines?

RFT uses alternating current in a transmitter coil to generate an electromagnetic field that penetrates completely through the pipe wall regardless of what is coating the inside. Receiver coils positioned two or more pipe diameters downstream detect changes in that signal as it re-enters through the outer wall. Wall loss from ID pitting, OD external corrosion, or graphitic corrosion in cast iron shows as changes in signal amplitude and phase that PICA analysts quantify and map to specific pipe locations. The liner or coating does not absorb or distort the signal in a way that hides wall defects beneath it.

Can inline RFT inspection run while a pipeline is still in service?

For pipe diameters up to 36 inches, yes. PICA’s in-service RFT tools run through pressurized pipelines without requiring full isolation or dewatering. Flow must be reduced to maintain tool speeds in the 5 to 20 feet per minute range, which does require a temporary operational adjustment but avoids the cost and disruption of a full shutdown. For pipelines 36 inches and larger — including most large-diameter PCCP and bar-wrapped transmission mains — the pipe must be taken out of service and dewatered before RFT tools can be deployed.

Which industries use remote field technology for in-line pipeline inspection?

RFT inline inspection is used across six industries. Municipal water utilities use it for cast iron, ductile iron, and concrete pressure transmission mains where scale, liners, or in-service constraints make conventional tools impractical. Oil and gas producers use it in lined flowlines, wax-affected gathering pipelines production systems. Industrial facilities inspect cooling water headers, fire suppression loops, and process piping. Mining operations inspect slurry and brine lines. Power generation facilities rely on it for cooling water and fire suppression pipe. Wastewater utilities use it for pressurized force mains where CCTV alone cannot assess wall condition.

Can RFT detect stress in pipelines in addition to wall thickness and corrosion?

RFT can identify stress concentrators and local anomalies in metallic pipelines — features associated with fatigue cracking and stress corrosion cracking. The electromagnetic signal responds to changes in material properties caused by residual stress and localized cracking, showing as a distinct pattern in the data. This capability is one reason RFT has expanded beyond simple wall thickness surveys in oil and gas applications, where stress corrosion cracking in production and gathering pipelines is a known failure mechanism that wall thickness measurement alone does not capture.

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