Traditional Techniques Archives | Apex

Vacuum Box

apex_dev — Sun, 25 Feb 2024 16:09:11 +0000

Vacuum box testing is an effective leak testing technique used to inspect welding joints. This is a relatively fast test and one that can be conducted without interfering with other fabrication operations. The test uses a box fitted with rubber seals around its open bottom and a plexiglass top cover. The weld section to be inspected is coated with a soap-like solution and a light vacuum, usually under 69 kPa (10 psi) is applied to the box. The formation of bubbles on the soaped weld indicates the location of a leak.

Advantages of Vacuum Box Testing Method

Provides an immediate indication of any leaks present produced directly on the tested surface
Easy to use
Large areas can be inspected rapidly and at low cost
Can detect small leaks within a given area
Requires only access to one side of the tested surface
The method is relatively clean does not require comprehensive cleaning after the test

Disadvantages of Vacuum Box Testing Method

Can only detect leaks, other welding defects including surface imperfactions are not identified
Surface preparation before testing including cleaning, de-greasing, rust and slag removal can be time consuming
The method should not be applied to painted objects
Size and orientation of any leaks will have to be analyzed with a secondary NDT method
For standard testing surface temperature must be between 5°C and 50°C. Otherwise, a procedure effective at non-standard temperature range must be demonstrated

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Holiday Testing

apex_dev — Sun, 25 Feb 2024 15:58:06 +0000

A holiday test is an inspection method used to detect discontinuities in painted/coated surfaces using specialized tools and equipment. These tools, called holiday detectors, are portable devices that are swept across the coated surface.
Holidays tests work on the concept of electrical conductivity. Metal substrates are excellent conductors of electricity, and therefore allow current to flow through them. On the other hand, many coatings are poor conductors of electricity and resist the flow of electricity. Using this principle, holiday tests use instruments to locate flaws in anticorrosive paints and coatings.

During holiday testing, a ground wire and probing electrode are attached to the same power source. The ground wire is clamped to the specimen being tested while the probe is swept across the surface of the metal substrate. If the probe comes into contact with a coating discontinuity, the exposed metal completes the electrical circuit between the electrode and the grounding wire, resulting in a flow of electricity. This electricity shows up on an indicator, alerting the equipment operator of the defect.
While holiday tests are effective, they do possess limitations. Because these tests depend on the coating being non-conductive, they are not effective on conductive metallic coatings, such as zinc-rich primers.
A holiday test is also known as a continuity test.

The technique detects but does not discriminate between corrosion on inner or outer surfaces of the pipe.
This technique provides qualitative not quantitative information on the severity of the corrosion.
Technique is dependent on formation of ferromagnetic layer for efficient transmission of ultrasound.
The technique can be used with elevated temperature applications (up to 650 ºC).

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D F T Inspection

apex_dev — Sun, 25 Feb 2024 15:42:49 +0000

Many things contribute to a quality painting, coating or lining project. When quality control is mentioned in regard to an industrial coating application, people tend to focus in on the field quality control inspection as the only key to success. Let's not forget the need for proper specifications, the proper material selection, quality made materials and realistic schedules that allow for everything to come together in sequence.
LRUT is performed using a system which is made up of a low frequency flaw detector, a pulser receiver unit, some transducer rings, and a laptop computer which contains the software that controls the system.

COATING APPLICATION

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EMAT

apex_dev — Sun, 25 Feb 2024 15:34:27 +0000

The EMAT is an ultrasonic transducer, which operates without the application of liquid couplant. The EMAT transducer generates the ultrasound in the material being tested. As with piezo electric transducers, different modes of ultrasound can be generated in the material to be tested by varying the design of the EMAT transducer. A further advantage of this type of transducer is that it can be designed to operate at elevated temperatures.
The equipment is normally housed in a trailer, which is located within a few hundred feet from the test location. The instrumentation consists of a pulsar-receiver unit with a computer to monitor the inspection. The test signal is displayed on a computer monitor. The output signals can be printed in color for insertion in the field report. An umbilical cable connects the instrumentation to the test robot, which is used to scan the test area.
Once the equipment is connected, the transducers have to be calibrated on a representative sample of pipe.

The robot has two EMAT transducers mounted such that the transducers are closer than a diameter apart. The transducers introduce sound to the material; the sound is transmitted circumstantially in both directions The inspection can be performed on horizontal or vertical runs of pipe and is used to detect areas of localized corrosion.
The equipment records data from various signal frequency modes. An analogue output is supplied that provides a record of the condition of the pipe or pipe support. By applying this technology to pipe systems, we can perform a fast global inspection of the circumference of the pipe. By monitoring the time of flight of the sound, the operator can differentiate between the area immediately between the probes to inspect areas associated with pipe supports and the remaining area on the upper region of the pipe. Large linear sections of pipes can be scanned for corrosion. The system is also used successfully for the inspection of pipe supports and corrosion associated with the pipe supports.

The technique detects but does not discriminate between corrosion on inner or outer surfaces of the pipe.
This technique provides qualitative not quantitative information on the severity of the corrosion.
Technique is dependent on formation of ferromagnetic layer for efficient transmission of ultrasound.
The technique can be used with elevated temperature applications (up to 650 ºC).

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Hardness

apex_dev — Sun, 25 Feb 2024 15:25:07 +0000

Hardness testing makes it possible to determine material characteristics such as strength, ductility and wear resistance. It also shows whether the heat treatment process has been carried out properly. These properties can be critical for the intended application of a material.
Hardness tests are typically performed by pressing a specifically dimensioned object (indenter) into the surface of the material. The hardness is determined by measuring the depth of indenter penetration or by measuring the size of the impression left by the indenter.
Based on the used method, the measured hardness is expressed in Rockwell (HRC), Vickers (HV) or Brinell (HBW) values. If required, the test result can be translated to another scale using conversion tables. Hardness tests can be carried out on location using portable equipment or with stationary equipment in our Mechanical Laboratory.

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PMI

apex_dev — Sun, 25 Feb 2024 15:20:30 +0000

PMI Positive Material Identification : Advanced NDT Solutions personnel have extensive experience in PMI Positive Material Identification. Our experienced Inspection Engineers are certified to ASME and EN non destructive testing codes.
Positive Material Identification is a quick non-intrusive means of identifying the grade of material. PMI uses x-ray diffraction to identify the elements present in a material and the percentage of each element present. This gives a quick and easy analysis of the material grade.
So if you are unsure of the material you have in your plant and machinery our inspection engineers can carry out this quick test to identify what you have

The PMI unit is placed in contact with the material to be identified. The x rays are beamed into the material and the analyser in the unit identifies the material.
If replacement parts for a machine are required but the material is unknown this quick and non destructive inspection method is ideal.
All components on a piece of equipment can be identified quickly and easily with PMI. The only requirement is that the item to be identified is clean and free of dirt and grease which will affect the accuracy of the measurement.
PMI can be used on hot surfaces so plant does not have to be switched off for the analysis to be carried out. This is ideal where items have to be identified prior to a plant shutdown so that replacement materials of the proper grade can be made available.

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RT

apex_dev — Sun, 25 Feb 2024 15:05:57 +0000

Industrial Radiographic Testing (RT) makes use of X-ray or gamma radiation to create images that can show defects hidden inside the material. This technology is widely used to ascertain material integrity of welds, castings, piping, machined parts, pressure vessels and other objects.
The method is fully non-destructive and surface preparation of the test piece usually isn't necessary. In many cases, RT can also be used to inspect industrial installations that are in operation.
X-ray testing is possible for materials with a maximum thickness of 50 millimetres and gamma ray testing is possible for materials with a thickness varying from 10 to 120 millimetres.

Radiography advantages:

Virtually no surface preparation is required
Volumetric: both surface and sub-surface indications can be found
Suitable for inspection of assembled components
Suitable for in site and on-stream inspections
Suitable for many different material types
Permanent record deliverables (film or digital file)

Radiography limitations:

Hazardous ionising radiation requires creation of safety perimeter
Relatively expensive equipment
Relatively slow inspection process
Sensitive to flaw orientation
Usualy not possible to determine depth of indications
Two-sided access to test object is required

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UT

apex_dev — Sun, 25 Feb 2024 14:55:07 +0000

Ultrasonic Testing is a volumetric Non-Destructive Testing (NDT) method. Unlike surface inspection methods, UT makes it possible to find flaws inside the material. Highfrequency sound waves are sent into the material with an ultrasonic transducer. The ultrasound that reflects off defects in the material is made visible in a graph. Ultrasonic Testing gives insight in the depth, size, nature and orientation of the detected indications. The thickness of the material, such as wall thickness of pipes, can also be measured.

Advantages of Ultrasonic Testing:

High penetrating power
High sensitivity
Usually only one surface needs to be accessible
Insight in size, orientation, shape and nature of defectsYf
Non-hazardous to operations or nearby personnel
Portable equipment
Can be used in automated setup
Immediate test results

Limitations of Ultrasonic Testing:

Surface must be accessible to transmit ultrasound
Usually a couplant (gel or oil) is needed to enable interference-free transfer of the ultrasound
Objects that have a rough surface or are very small, thin or not homogenous are difficult to inspect
Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise
Linear flaws oriented parallel to the direction of the sound beam may go undetected
Reference standards are required for equipment calibration and for the characterization of flaws

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MT

apex_dev — Sun, 25 Feb 2024 12:25:54 +0000

ADVANTAGES

1. Flaws are highly visible
2. The equipment is:
Portable and can be battery powered
Light enough to take easily onto scaffolding
Non-hazardous to operations or other nearby personnel
Has no effect on equipment or materials in the vicinity
Very good sensitivity to fatigue cracking, tight fusion, HIC and SCC

LIMITATIONS

Surface must be accessible and must be clean and free from oil, grease, scale, etc
Cannot detect deep subsurface flaws
Instrumentation and aircraft components require demagnetization after being inspected; residual magnetization may cause them to malfunction
May require a power supply that is not intrinsically safe

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PT

apex_dev — Sun, 25 Feb 2024 12:13:36 +0000

Dye Penetrant Testing (PT) is used to find surface breaking defects. PT inspection is suitable for a wide variety of materials, but it is mainly used on non-ferrous metals. This method makes use of the capillary action principle. A liquid dye with low viscosity is applied to the test piece. Due to its low viscosity, it gets sucked into surface-breaking discontinuities. After allowing adequate penetration time, the excess penetrant liquid is rinsed off. After drying, a chalk-like developer is applied. The developer draws the penetrant dye from defects making a visible indication that can be interpreted by the inspector.

PT advantages:

High sensitivity to small surface discontinuities
Suitable for large range of materials: metallic and non-metallic, magnetic and non magnetic, and conductive and non-conductive
Large surface areas and large volumes parts can be inspected rapidly and at low cost
Parts with complex geometry can be tested without changing the inspection procedure
Indications are produced directly on the surface of the part
Aerosol spray cans make penetrant materials very portable
Required materials and equipment are relatively inexpensive

PT limitations:

Only surface breaking defects can be detected
Only materials with relatively nonporous surface can be inspected
Precleaning is critical
Metal smearing from machining, grinding, and grit or vapor blasting must be removed prior to inspection.
Surface finish and roughness can affect inspection sensitivity
Multiple process operations must be performed with waiting intervals
Post cleaning of acceptable parts or materials is required
Handling and proper disposal of chemicals is required

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