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

Most pipeline corrosion is invisible. The wall thins, pits form, and insulation traps moisture against warm steel — but from the outside, the pipe looks fine. By the time a leak appears, the damage is often severe and repair costs are measured in hundreds of thousands of dollars. The PICA Bracelet Probe is built to find that damage before it reaches that point.

The Bracelet Probe is an external electromagnetic (EM) scanning tool for targeted, spot-inspection of metallic pipelines. It wraps around the outside of the pipe and uses a low-frequency electromagnetic field to measure wall thickness, identify pits, and detect corrosion — including corrosion forming under pipe insulation. It comes in three versions: one for bare or coated pipe accessed from outside, one for dewatered pipe inspected from inside, and one for insulated pipe that requires no insulation removal at all.

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What Is the PICA Bracelet Probe?

The Bracelet Probe sits within PICA’s Intermediate NDT service tier — portable electromagnetic tools used for localized inspection at specific sites of concern. It is not a full-pipeline in-line tool. It is deployed at excavated pipe sections, exposed pipe under bridges, industrial plant piping, or locations flagged by earlier pre-screening.

PICA developed the Bracelet Probe in collaboration with Russell NDE Systems Inc., whose electromagnetic research has driven PICA’s inspection technology since 1972. PICA Corp has deployed these tools across North America and in more than 20 countries since its founding in 2008. The formal product designation for the external version is the BP2 (Bare Pipe Bracelet Probe). The insulated-pipe version is marketed as the CUI Bracelet. All three versions feed data into PICA’s Ferroscope instrument, which records and displays electromagnetic field measurements in real time during inspection.

Where Remote Field Testing (RFT) tools cover hundreds of feet of pipe wall continuously in a single in-line run, the Bracelet Probe targets the sections that matter most after pre-screening has already narrowed the field. The two approaches are designed to work together in sequence.

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How the Bracelet Probe Works

The probe generates a low-frequency electromagnetic field using a transmitter coil. That field passes through the pipe wall. A receiver array on the other side measures how the field changed in transit. A pipe wall at full design thickness produces a predictable signal. Where the wall has thinned — through corrosion, pitting, or graphitization — the field strength and phase shift deviate in measurable ways.

The Bracelet Probe carries sixteen high-resolution sensors in a flexible frame that conforms to the pipe surface. On the external version, those sensors cover a 10-inch-wide (25 cm) scan path. The probe reaches full scan speed of 12 feet per minute, and a complete scan of a pipe cross-section’s full circumference takes only a few quadrant repositions. The internal version uses a wider 24-inch (61 cm) array suited to the inside of larger-diameter pipe.

All data feeds into PICA’s Ferroscope instrument in real time. The Ferroscope displays 3D color maps, strip charts, and voltage plane views — three different representations of where wall thickness has deviated from baseline. PICA analysts can save screen snapshots during inspection, creating an immediate visual record of each scan quadrant. The crew knows what they are dealing with on the day the pipe is exposed, without waiting for off-site data processing — a practical advantage when an excavation is open and a decision needs to be made that day.

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Three Versions, Three Inspection Problems

External Bracelet Probe — Bare and Coated Pipe

The external version is applied at excavated pipe sections and inspects bare, coated, or wrapped pipe for internal and external corrosion from outside the pipe wall. This is the most commonly deployed version: it covers situations where a buried section has been dug up for investigation, repair, or follow-up on a pre-screening anomaly using the PICA Navigator (especially force mains where gas accumulations are typically H2S gas).

It is particularly effective at detecting internal diameter (ID) corrosion caused by hydrogen sulfide (H2S) in force mains and wastewater pipelines. H2S gas accumulates above the waterline in sewage lines and generates sulfuric acid that attacks the pipe crown from inside. This damage is invisible from outside and is often missed by CCTV if the pipe is not fully dewatered or the damage is in an early stage. The Bracelet Probe detects the wall thinning electromagnetically, through the pipe wall, from outside — without anyone entering the pipe.

Internal Bracelet Probe — Inside Dewatered Pipelines

The internal version is deployed inside the pipe after dewatering. Its wider 24-inch sensor array covers more wall area per pass than the external version, making it suited to characterizing damage zones in larger-diameter pipe where higher spatial resolution is needed. This version is typically used as a targeted follow-up tool at specific locations identified during a full in-line inspection run. Where PICA’s NFT or RFT in-line tools flag a cluster of anomalies, the internal Bracelet Probe characterizes that damage more precisely before the utility commits to a rehabilitation decision.

CUI Bracelet Probe — Corrosion Under Insulation

CUI forms when moisture penetrates pipe insulation and collects against the warm metal surface. Condensation cycles, rain ingress, and weathered jacketing all contribute. Because the insulation hides the pipe surface, corrosion can advance for years before discovery. According to AMPP (formerly NACE International), CUI accounts for a significant portion of external corrosion in process industry piping and is among the leading cost drivers in insulated steel pipe maintenance programs.

Traditional detection means stripping insulation, inspecting visually, then re-insulating — an expensive process that only shows what is visible at that moment. The CUI Bracelet Probe bypasses that entirely. Its electromagnetic field penetrates through insulation up to 4-5 inches (up to 12.7 cm) thick, scanning the pipe wall beneath without removal. The probe wraps around the insulation exterior and rides along it on integrated wheels. The Ferroscope records wall condition continuously as the crew walks the pipe run, and sections with meaningful wall loss appear in the data immediately.

PICA has deployed the CUI Bracelet in oil and gas plant settings, power generation facilities, and petrochemical environments. PICA’s electromagnetic inspection work with Shell Canada, detailed in a published case study, illustrates how these tools apply in upstream and industrial contexts where CUI is a persistent operational risk.

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Pipe Types and Compatible Materials

The Bracelet Probe targets metallic pipe — materials that have a steel or iron wall for the electromagnetic field to interact with. It is designed for:

• Cast iron (CI) — gray cast iron distribution mains, particularly vulnerable to graphitic corrosion where the iron matrix leaches away, leaving a structurally weakened graphite shell
• Ductile iron (DI) — the standard for modern pressure water mains and force mains
• Carbon Steel pipe — bare carbon steel, coated or lined steel, and FBE-coated steel in industrial and oil and gas applications
• PCCP (Prestressed Concrete Cylinder Pipe) — where the Bracelet Probe targets the embedded steel cylinder
• Bar-wrapped concrete cylinder pipe (BWP) — similar electromagnetic interaction via the steel cylinder component

The probe’s flexible frame adjusts from 6 inches in diameter and up with no practical upper limit on the external version, since it wraps around the outside of the pipe. For a complete map of pipe types and which inspection tiers apply to each, see PICA’s service applications overview.

The Bracelet Probe does not work on pure plastic pipe (PVC, HDPE, FRP) or asbestos cement pipe without a metallic reinforcing component. For those materials, CCTV and laser profiling are the appropriate tools.

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What the Bracelet Probe Detects

The electromagnetic scanning resolves several categories of pipe wall damage that visual inspection cannot see and that most portable tools cannot access without opening the pipe:

• Wall thickness reductions — continuous quantitative measurement of remaining wall thickness, not a pass/fail flag
• Individual pits — localized corrosion pits on the ID or OD surface, characterized by depth and spatial extent
• Graphitic corrosion — the cast iron failure mode where the iron matrix leaches away while the graphite skeleton remains, leaving a pipe that looks intact but has lost most of its structural strength
• Erosion — wall loss from abrasive flow conditions, common in slurry, sludge, and high-velocity water service
• Corrosion under insulation — external pipe wall corrosion only hidden by insulating material, accessible only via the CUI version. CUI version cannot detect ID corrosion like the 2 other versions.

All outputs are quantitative. PICA analysts can determine how much wall remains, whether the damage is localized or distributed over a wider zone, and whether the pattern is consistent with internal H2S attack, external soil corrosion, or CUI. This feeds directly into the rehabilitation decision: repair now, replace the section, or schedule re-inspection at a defined interval.

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Where the Bracelet Probe Is Deployed

In a large-diameter water main or PCCP inspection program, the typical first step is deploying the NAVIGATOR acoustic sphere in-service to flag anomaly locations while the pipeline stays pressurized. NAVIGATOR does not measure wall thickness — it identifies where to look. Those sections are excavated, and the external Bracelet Probe measures actual wall condition before the utility decides whether to authorize a full dewatered in-line program. This staged sequence avoids shutting down an entire transmission main based on pre-screening data alone.

For pipelines under bridges or on aerial structures and in processing plants, the Bracelet Probe covers exposed sections that in-line tools cannot reach without specialized setups. Field crews walk the pipe run, apply the probe at support points and mid-span, and scan without any pipeline shutdown. For industrial settings, the CUI version screens long insulated runs in plant piping — cooling water headers, fire suppression mains, process lines — as part of a planned maintenance program rather than a reactive response to failures. For teams building in-house programs, eddy current, RFT, and Bracelet Probe training is available. For force main applications, the internal version scans the crown and upper quadrants of dewatered pipe for H2S-related wall thinning. See PICA’s water and wastewater inspection services for the full picture by pipe type.

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Why Spot Inspection Needs a Full Program Behind It

The Bracelet Probe delivers precise data at the locations it is applied — not across the rest of the pipeline. A section that shows serious wall loss at one excavated window may have identical damage at ten other locations that were never opened. Spot inspection alone produces an incomplete picture.

This is why PICA structures programs around a combination of methods: pre-screening to cover the full network, Bracelet Probe validation at specific sites, and full in-line inspection where the data justifies it. The Advanced NDT tools — including the HydraSnake for 6- and 8-inch water mains and the EMIT and RAFT tools for large-diameter PCCP from 36 to 96 inches — cover the full pipe wall continuously along the entire run. The Near Field Testing (NFT) tools at PICA’s Standard NDT tier quantify broken wires in concrete pressure pipe. For an overview of how all these methods connect, see PICA’s pipeline condition assessment page.

The Bracelet Probe is what you need when you have a pipe section exposed, or insulated piping in service, and you need quantitative wall condition data before making a repair or rehabilitation call. It is fast, portable, and non-destructive — and it answers the severity question on the day the pipe is accessible, not weeks later.

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Frequently Asked Questions

What is the PICA Bracelet Probe used for?

The PICA Bracelet Probe is an electromagnetic NDT tool for localized, spot-inspection of metallic or concrete pipelines. It detects wall loss, pitting, graphitic corrosion, and erosion in cast iron, ductile iron, and steel pipe from 6 inches in diameter and up. The CUI version detects corrosion under insulation through up to 5 inches of insulating material without requiring insulation removal.

How does the Bracelet Probe detect corrosion under insulation?

The CUI version uses low-frequency electromagnetic fields that penetrate through insulation up to 5 inches thick. The probe wraps around the outside of the insulated pipe and rides along it on integrated wheels. Variations in the electromagnetic field reveal where the underlying pipe wall has lost thickness due to trapped moisture and external corrosion. No insulation removal is needed, making it faster and less disruptive than strip-and-inspect methods.

What pipe materials is the Bracelet Probe compatible with?

The Bracelet Probe works on cast iron, ductile iron, steel, PCCP, and bar-wrapped concrete cylinder pipe. It handles bare, coated, and insulated pipe depending on which version is selected. Pure plastic or non-metallic pipe without embedded steel components is not compatible, as those materials do not produce the electromagnetic interaction the probe requires.

What is the minimum pipe size the Bracelet Probe can inspect?

The Bracelet Probe inspects pipe starting at 6 inches in diameter. Its flexible, adjustable frame conforms to a wide range of pipe sizes. There is no practical upper limit on the external version since it wraps around the outside of the pipe. For pipelines below 6 inches, PICA’s handheld EM and UT probes cover that range.

How fast can the Bracelet Probe scan pipe?

The Bracelet Probe scans at up to 12 feet per minute. Its 16 sensors cover a 10-inch-wide scan path on the external version. Full circumferential coverage of a pipe cross-section requires only a few quadrant scans, which keeps field time short at each excavated location. A typical 20-foot excavated window can be executed in ½ a day pending pipe diameter. The larger the pipe diameter the longer the inspection takes.

Can the Bracelet Probe inspect pipe without excavation?

The external and internal versions require physical access to the pipe surface, so excavation is typically needed for buried pipe. The CUI version can be applied to aboveground insulated pipe without any excavation. For continuous full-pipeline assessment without excavation, PICA’s in-line RFT and NFT tools cover the entire pipe run from inside. The HydraSnake and SeeSnake tools enter the pipe without excavation for in-service deployment.

How does Bracelet Probe inspection fit into a larger pipeline program?

The Bracelet Probe fills the targeted follow-up role in a staged sequence. The NAVIGATOR acoustic sphere screens the full pipeline in-service, flagging anomaly locations. Those sections are excavated, and the Bracelet Probe measures wall condition at those specific sites before committing to a full dewatered in-line run. This avoids unnecessary pipeline shutdowns while confirming whether anomalies justify the cost of a full inspection program.