Advantages of the T5 Hytec Probe

Dave Brown VM Products, Inc.

The Problem

1) Detection of Flaws in roll transitions is problematic without a complex test 2) Tube Supports distort flaw signals 3) Circumferential cracking is difficult to detect with bobbin probes 4) Fins, internal enhancements, land areas and transitions to the land areas make flaws difficult to distinguish in air conditioner tubing

A Solution

The T5 coil set:

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An Array with the speed and simplicity of a differential bobbin probe Overlapping coils, full circumferential coverage, no dead spots Detects axial cracks Detects circumferential cracks Detects pitting, not as well as bobbin coils, but may allow sizing of ID pits more accurately Suppresses tube sheet expansion signal Suppresses Tube support signal Suppresses fin noise, both external and internal Suppresses signals from landed areas and transitions Suppresses pilger noise Suppresses some dent signals Suppresses 360 degree grooves and 4 x 20% flat bottom holes on the ASME standard

A Solution

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The T5 Hytec probe consists of a T5 coil set integrated in the same probe with VM Products’ proprietary wide bandwidth bobbin coils

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Signal Coverage

The T5 coil coils are arrayed around the probe covering 90 degree sectors and overlapping to eliminate any dead zones. Typical signals from a 60% pit are shown in the following diagram:

Signal Coverage

Due to the subtraction of one coil set from the other, signals of exactly 180 degree extent or 360 degree extent are suppressed. This provides suppression of expansions, transitions, support plates, fins, dents, etc. This also suppresses the 4 20% flat bottom holes and the OD groove of the ASME standard and the signal from a 360 degree crack which has no axial component. To account for this, the T5 coils may also be operated in an absolute mode with a remote reference probe (or autobalance) in the same way as a bobbin probe.

The bobbin coils allow for a simultaneous, conventional bobbin test.

The T5 coil sets attaches to the instrument and sets up as a standard differential bobbin probe.

Setup

The following picture illustrates the MIZ 27ET setup for testing 5/8” OD x 0.065” wall thickness, 304 stainless using a .480 T5 Hytec probe with a second probe as remote reference:

Operational Description

The following pictures illustrate some of the signals from an ASME standard. Note that the coil spacing between the bobbin and T5 coils is the same as the spacing between the holes of the standard, so that, for example, a window will show the 80% flat bottom hole with the bobbin at the same time as the 100% through wall hole with the T5 coils: Channels 1 & 3 show the bobbin signal from the 80% flat bottom hole and channels 5 & 7 show the through wall hole passing directly under one of the T5 coils. **We have changed the coil spacing since this data was taken**

Operational Description

The following picture shows the same through wall hole passing directly under an area where the coils overlap:

Operational Description

The following picture illustrates the bobbin passing under the 20% flat bottom hole as the T5 passes under the 40% flat bottom hole:

Operational Description

The following picture illustrates the suppression of the OD groove on the standard. The window has been opened enough to show both bobbin and T5 coils within the window. The very small signal on the T5 channel is from a very small volume, 40% edm circ notch:

Operational Description

Note that the 20% flat bottom holes signal is visible on the T5 coils in these pictures. This is because this particular standard was machined with only two 20% holes so that they could be seen by the T5 coils in order to set up the cal curve (a Navy requirement):

Features, Advantages and Benefits

Features

Detect circumferential and axial cracking

Advantages

Simple, high speed probe

Benefits

Increased testing and damage verification Suppress transitions See flaws without a rotating probe or array Suppress Tube Support Signal Simple setup and operation See flaws without mix NDI technician with minimal additional training Hybrid T5 and differential bobbin Highly durable probe design Combined inspection Long operational life Increased testing and damage verification - good screening tool Increased detection and accuracy No special equipment or specialized training required Increased testing and damage verification High value to test company

Current State of Development

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Integral and detachable head probes

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4 frequency ranges covering 2 kHz to 800 kHz

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Durable design has proved itself well

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2 years of field experience, some good, some not so good, looking for experienced users to advance the application

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Has been used on MIZ-27ET, MIZ-27SI, OMNI-100, TC-5800

Field Successes

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Rave reviews from Air conditioning customers

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Good success with detection of circ cracks in roll transitions in stainless heat exchangers – including multi-week job with no probe changes

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Detection of circumferential cracking in free span of Titanium tube heat exchangers

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Used on a couple of jobs as a screening tool for TTS roll transitions prior to rotating test

Summary

The ability to see circumferential cracking while suppressing circumferential noise sources Simple probe with array probe functionality Continuously improving the design – looking for feedback VM Products, Inc.

Specialists in Eddy Current Probes, Instruments, Reference Standards, Applications, Research & Development

Contact Information

Dave Brown

VM Products, Inc.

[email protected]

Tel: (253) 841-2939 Fax: (253) 841-3016 www.vmproducts.net

Gene Auville

T5 Hytec Industries [email protected]

Tel: (800) 488-2884 Fax: (623) 386-7899 www.best-test.com

VM Products, Inc.

Specialists in Eddy Current Probes, Instruments, Reference Standards, Applications, Research & Development