By the PICA Corp Engineering Team  |  Updated June 2026  |  Est. reading time: 7 min

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What Is the PICA SeeSnake?

The PICA SeeSnake is an in-line pipeline inspection tool that uses Remote Field Technology (RFT) — a through-transmission electromagnetic technique — to measure pipe wall condition from inside the line while it operates. Unlike conventional magnetic flux leakage (MFL) tools, the SeeSnake and other Advanced NDT tool families based on pipeline size requires no contact with the pipe wall, contains no magnets, and delivers reliable measurements through internal liners, scale, wax, and sand deposits. It travels with the product flow or on compressed air, inspecting 360 degrees of pipe wall continuously as it moves.

The tool belongs to PICA’s Advanced NDT service tier, which delivers the highest-resolution pipe wall data available through in-line inspection. It is part of a broader Advanced NDT product family engineered specifically for lined, coated, and deposit-heavy pipelines where MFL tools cannot perform reliably.

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Why MFL Falls Short in Lined and Deposit-Heavy Pipelines

Magnetic flux leakage is the dominant in-line inspection technology for clean-bore steel pipelines. For that application, it works well. The problems appear the moment you introduce a liner, a coating, or internal product deposits. In industrial, oil and gas, and municipal water pipelines, those conditions are the rule rather than the exception.

The contact requirement creates liner damage risk

MFL tools need intimate contact with the steel pipe wall to generate a measurable flux leakage signal at defect sites. In an unlined pipe, this is straightforward: the tool’s magnets press against bare metal and read the disturbance in the magnetic field where wall loss exists. In a cement-mortar-lined or HDPE-lined pipe, the same close contact becomes a problem. The tool drags against the liner. Over a long run, that abrasion damages the very asset protection layer the pipeline operator installed to control internal corrosion. Inspecting the line risks undermining the protection system.

Deposits and non-magnetic liners disrupt the MFL signal

Even in pipelines without a formal liner, internal deposits create the same problem. Wax in crude oil pipelines, sand and scale in produced water lines, and mineral deposits in water mains all stand between the MFL sensor and the steel wall. Each deposit layer attenuates the flux signal. The result: partial or unreliable data on pipeline condition, precisely in the areas where deposits concentrate, which are often the same areas where corrosion is most active. The pipeline owner gets a report that looks complete but has gaps in the most critical zones.

Non-magnetic liners such as cement mortar, epoxy, or polyethylene do not carry a magnetic field at all. MFL tools effectively cannot see through them. This leaves operators of internally-lined pipelines with two bad options: run an MFL tool and accept incomplete data, or dewater and pig the line to bare steel or remove the liner before running the tool, an expensive and disruptive process that removes the liner protection for the duration of the inspection campaign.

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How Remote Field Technology Gives SeeSnake Its Edge

Remote Field Technology is an electromagnetic inspection method based on through-transmission of an alternating current signal rather than the flux leakage principle. The SeeSnake and other Advanced NDT tool families use RFT’s through-wall signal path to sidestep all of the liner and deposit limitations that constrain MFL.

Through-wall sensing from inside the pipe

A transmitter coil inside the Advanced NDT tools excites an alternating current that propagates through the pipe wall — outward through the steel and back in. The receiver coils, positioned at a distance from the transmitter that places them in the “remote field zone,” detect this signal after it has completed a full through-wall transit. Because the signal travels through the wall rather than along its surface, it passes through any non-magnetic liner and through scale, wax, or deposit layers without interference. The SeeSnake maintains a minimum 0.25-inch clearance from the pipe wall throughout the run, which means it never contacts the liner or deposits at all.

Equal sensitivity to ID and OD flaws

Because the RFT signal passes through the full pipe wall cross-section on each cycle, the SeeSnake measures both the inside-diameter (ID) and outside-diameter (OD) surfaces with equal sensitivity. An external corrosion pit and an internal corrosion pit of the same depth produce the same signal magnitude. This is a significant operational advantage. Pipeline operators do not need to guess which side of the pipe wall their corrosion is on; the SeeSnake reports both simultaneously. For pipelines with cathodic protection on the outside and liner protection on the inside, this gives a complete picture of where each system is or is not performing.

The tool simultaneously measures remaining wall thickness and the surface area of each detected defect (length and width) with accuracy that competitors using single-measurement approaches cannot match. This is the data that drives fitness-for-service assessments and repair prioritization decisions.

Stress detection through magnetic permeability variation

Steel under mechanical stress shows localized changes in magnetic permeability. The SeeSnake’s multi-channel sensor array detects these changes as it passes through areas where the pipeline is under external loading. Soil movement, inadequate bedding support, bridging across a void, rippling from thermal expansion, and denting from third-party impact all produce measurable permeability signatures. The SeeSnake flags these locations in the report so operators can investigate the external condition at specific pipe segments, often before the stress has caused visible wall damage. This capability has no analog in MFL inspection.

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SeeSnake Technical Specifications

Pipe size range and tool configurations

SeeSnake and Chimera tools cover pipe diameters from 2 inches (75 mm) to 36 inches (914 mm). For in-service inspection in larger pipes up to 36 inches, PICA’s extended in-service RFT tool lineup provides coverage. Each SeeSnake is built for a specific pipe diameter range, carrying one sensor channel per half-inch of pipe circumference. A 12-inch tool, for example, carries 24 channels covering the full 360 degrees continuously as the tool travels.

The tool body is approximately 7 feet (213 cm) long in total. It is flexible enough to negotiate a 90-degree long-radius welded elbow in pipes 6 inches and larger. For tighter geometry or smaller pipe sizes, PICA’s engineering team specifies the appropriate configuration based on the pipeline survey information provided before mobilization.

Specification	Value
Pipe diameter range	3″ – 30″ (75 mm – 762 mm)
Cast iron wall thickness detection	Up to 1″ (25.4 mm)
Steel wall thickness detection	Up to 0.5″ (12.7 mm)
Inspection speed	1–2 km/hr
Minimum tool clearance	0.250″ (6.3 mm) from pipe wall
Sensor density	1 channel per 0.5″ of pipe circumference
Run time	Minimum 5 hours (scalable)
Frequency range	5 Hz – 200 Hz (user-selectable)
Onboard memory	64 Kb – 2 Gb per channel (scalable for long runs)
Min. elbow radius	90° long-radius welded elbow (6″ tools and larger)
Data interface	USB or Bluetooth download post-run
Propulsion requirement	Product flow or compressed air/nitrogen; as low as 25 psi

Data output formats

The SeeSnake produces four complementary representations of the same dataset: color maps, strip-chart logs, 3D views, and voltage planes. Color maps give the analyst and the client a quick spatial picture of where wall loss concentrates along the pipeline. Strip charts show the signal amplitude channel-by-channel as a function of distance, which is how individual pits and defect zones are sized. Voltage plane plots allow the analyst to distinguish pit signatures from geometrical features like welds and tees. The reporting module is built into the analysis software, so report generation runs in parallel with data analysis rather than as a separate step.

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How SeeSnake Inspection Is Deployed

A SeeSnake survey requires fewer access preparations than MFL inspection because there is no need to clean the pipe to bare metal and no need to manage the large driving force that MFL’s magnets require. The main requirements are a launch point, a retrieval point, and sufficient flow or air pressure to propel the tool at inspection speed.

Access and launch options

The SeeSnake can be introduced to the pipeline through any of the following access points: a standard pig launcher, a stuffing box at a cut pipe end, a riser, a flange. In oil and gas applications, most transmission lines have pigging facilities already installed, which makes launch straightforward. In water and industrial applications where pig launchers are less common, a hot-tap or flange provides access without cutting out a section of pipe.

Once inside, the tool travels with the product flow that is not compressible. Because the SeeSnake contains no magnets, it requires much less driving force than MFL tools; 25 psi is often sufficient for fluid based deployments. At the far end of the inspection run, the tool is either trapped at a standard pig trap or winched back and forth on a winchlines for out of service deploments. For in-service pipelines carrying hazardous products, the winchline retrieval option means the pipeline needs to be accessible at both ends of the target inspection length.

For smaller-diameter water mains, PICA’s HydraSnake is the deployment-optimized variant for 6-inch and 8-inch cast iron and ductile iron mains, entering through a fire hydrant or tee adapter with no excavation required. For pipes above 36 inches requiring out-of-service RFT inspection, PICA’s EMIT and RAFT tools cover that range and require 18″ or greater maintenance hole access or pipe segment or feature like a valve to be removed for tool access.

Tool tracking from the surface

One practical limitation of many in-line tools is that tracking their position inside the pipeline requires a separate transmitter pig running ahead of the inspection tool. The SeeSnake eliminates this. Its RFT signal travels through the pipe wall and up through the soil to the surface, where it is detectable with above ground markers (AGM). Field crews can track the tool’s progress in real time and locate it precisely if it stalls, without needing an additional pig run or a separate tracking system. This simplifies depth-of-cover logging and makes it straightforward to correlate the inspection data to GPS or survey coordinates for the final report.

Data analysis and reporting timeline

All inspection data is stored on the SeeSnake’s onboard flash memory and downloaded via USB or Bluetooth after retrieval. The built-in reporting module produces a structured report in parallel with data analysis. PICA’s preliminary analysis is typically completed within approximately one week of the inspection run and final formal reporting 8 to 12 weeks after. Complex pipelines go through additional off-site quality-control processing before the final report is issued.

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Compatible Pipe Types and Industry Applications

The SeeSnake, as part of PICA’s Advanced NDT RFT service, is compatible with metallic pipe: steel (lined and unlined), cast iron, and ductile iron. It is not suited for pipelines with no metallic reinforcement. Pure plastic pipe and asbestos cement without a steel cylinder are outside its range because the RFT signal requires a conductive metallic path through the pipe wall.

Within the compatible pipe types, the SeeSnake serves a wide range of industries:

In oil and gas, the SeeSnake handles lined transmission and gathering lines with cement mortar, epoxy, FBE, or polyethylene or HDPE coating on the inside. It is also the right tool after a pipeline failure, used to inspect several kilometers on each side of the repair point and establish whether the same corrosion mechanism has affected adjacent pipe.

In water and raw water systems, it inspects cast iron and ductile iron transmission mains, particularly where graphitic corrosion or external pitting is suspected. For 6-inch and 8-inch water mains, the HydraSnake variant enters through a fire hydrant with no excavation required.

In wastewater, the SeeSnake covers metallic force mains carrying sewage under pressure, where external corrosion or internal erosion is an ongoing concern. For concrete pressure pipe types such as PCCP or bar-wrapped pipe, see PICA’s NFT and RFT tool comparison for guidance on which electromagnetic method applies.

Industrial and mining applications include cooling water loops, fire suppression systems, slurry lines, and process water piping where operational continuity makes out-of-service inspection costly. Power generation uses the SeeSnake for cooling water intake and discharge piping at nuclear and thermal plants, where inspection precision matters and extended shutdown is not an option.

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When SeeSnake Is Part of a Broader Inspection Program

The SeeSnake is most effective when combined with supporting inspection tiers rather than deployed as a standalone tool. A typical sequence for an industrial or oil and gas pipeline program:

PICA’s Navigator acoustic sphere runs first, in-service, to identify leak and gas/air pocket locations and priority anomaly zones. This pre-screening pass defines where to focus resources. The SeeSnake then runs in those priority zones to deliver wall-thickness data and defect sizing. Where the SeeSnake identifies high-severity locations, PICA’s Intermediate NDT Bracelet Probe provides targeted handheld verification at excavated pipe sections.

For pipelines with PCCP or bar-wrapped concrete sections alongside metallic pipe, PICA’s PCCP inspection services using EMIT and RAFT tools handle those segments separately. The combined program data maps to a single water main inspection report, giving operators a unified risk picture across mixed-material systems. For background on how RFT and NFT are applied across pipe types, see PICA’s NFT and RFT tool comparison or the TRWD RFT case study.

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Frequently Asked Questions

What does the PICA SeeSnake detect in a pipeline?

The SeeSnake detects internal and external wall loss simultaneously, measuring remaining wall thickness and the surface area (length and width) of each corrosion pit. It also identifies stress concentrations from soil movement, bridging, inadequate support, and denting by measuring local variations in magnetic permeability. Because it uses Remote Field Technology, it has equal sensitivity to flaws on the inside and outside of the pipe wall. Results are delivered as color maps, strip-chart logs, 3D views, and voltage planes.

What pipe sizes does the SeeSnake inspect?

SeeSnake and Chimera tools cover pipe diameters from 2 inches (50 mm) to 36 inches (914 mm) for in service deployments, with PICA’s broader out of service RFT lineup extending to 96 inches. Each tool carries one sensor channel per 0.5 inches of pipe circumference for full 360-degree coverage. The 0.25-inch minimum clearance from the pipe wall allows the tool to pass weld roots, deposits, and minor protrusions without stalling.

Can the SeeSnake inspect lined pipelines without damaging the lining?

Yes. The SeeSnake never contacts the pipe wall during inspection. Its 0.25-inch minimum clearance keeps it clear of cement mortar, epoxy, polyethylene, and any other internal lining throughout the run. The Remote Field Technology signal passes through the liner and through scale, wax, or sand deposits to read the steel wall directly. MFL tools require close contact with the steel surface and can abrade or damage liners. The SeeSnake eliminates that risk entirely.

How does the SeeSnake compare to MFL tools for pipeline inspection?

MFL tools need close contact with the steel pipe wall and cannot measure through non-magnetic liners or internal deposits. The SeeSnake needs no contact and reads through any non-magnetic liner or deposit layer. MFL tools also carry large magnets requiring substantial driving force; the SeeSnake contains no magnets and moves on as little as 25 psi of air. Both cover 360 degrees continuously, but only the SeeSnake delivers reliable results in lined, scaled, or waxy pipelines.

How is a SeeSnake inspection deployed in the field?

The SeeSnake enters the pipeline through a pig launcher, stuffing box, riser, flanges. It travels through the line propelled by non compressible fluid flow. At the far end, the tool is trapped at a pig trap or winched back and forth on a winchlines for out of service deploments. It is self-contained with onboard batteries and flash memory, requiring no umbilical cable. After retrieval, data is downloaded via USB or Bluetooth. The tool’s RFT signal is detectable from the surface, so field crews can track its position and locate it immediately if it stalls, without a separate transmitter pig.

What industries and pipe types does the SeeSnake serve?

The SeeSnake inspects steel, cast iron, and ductile iron pipes. It is used in oil and gas (lined transmission and gathering lines), water and raw water systems, wastewater force mains, industrial cooling and fire water loops, mining water supply, and power plant cooling water piping. It is not suited for pipelines made entirely of plastic or asbestos cement without a steel cylinder. For pipes below 36 inches in diameter carrying any of these fluids, the SeeSnake & Chimera is typically the most practical in-service RFT inspection option.

How quickly are SeeSnake inspection results delivered?

Data is downloaded immediately after tool retrieval, and PICA’s reporting module produces the report in parallel with data analysis. Preliminary analysis is typically completed within approximately one week of the inspection run and the final reporting typically in 8-12 weeks. Complex pipelines requiring additional quality-control checks go through off-site processing before final findings are issued. The SeeSnake’s surface-detectable signal allows depth-of-cover logging during the run, which speeds report finalization.

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