Refinery & Petrochemical

Refinery & Petrochemical

Valve leak detection

MISTRAS Group has the instrument to correctly detect through valve leaks, the VPAC™. The VPAC™ is an acoustic emission instrument that has been the through valve leak detection standard for over 15 years. Based on over 10 years of research, the VPAC™ can estimate the quantity of material leaking through the valve using the accompanying proprietary software. With over 400 systems currently in use, the VPAC™ is the instrument of choice for through valve leak detection.

The VPAC™II unit is a handheld digital AE leak detector. It has been designed to replace the very successful VPAC™ and includes several improvements that are now possible with new technology advancements.

The user interface is simple and intuitive, and the unit retains all settings even when powered down. The instrument is powered by four rechargeable AA batteries which will last several weeks in typical use. Battery replacement and charging is quick and easy, so downtime is minimized.

Ultrasonic Phased Array and TOFD inspection in lieu of radiography

It would not be an overstatement to describe phased array as one of the great technological advances of recent centuries. In a world now dominated by industries that constantly push the frontiers of scientific capability, complex structures and reliance on new and traditional materials, an NDT process that probes and scrutinizes to exacting tolerances is as an essential a tool as the materials it tests.

A simple definition is 'an electronic method of generating, receiving and displaying an ultrasound signal'. The process uses a conventional probe cut into many segments which are individually 'excited'. It does not change the physics of ultrasonics but can be accurately manipulated to provide precise data about the materials under test. Sophisticated technology allows multiple elements to steer, angle, multi-focus and scan beams using a single transducer assembly. The principles of ultrasonic technology have been known for many years but it is only in the last 50 or so that knowledge been harnessed to great and diverse effect where surface and depth of any description needs to be tested and inspected. Phased array is also extensively utilised in the food processing, medical, biological, agricultural and pharmaceutical sectors for the same purposes as every other division - the gathering of vital data essential for product performance, health & safety, research and development.

MONPAC - Acoustic Emission Pressure Vessel Testing

MONPAC is an Acoustic Emission based expert system for evaluating the structural integrity of metallic pressure vessels, spheres, columns and tanks. MONPAC consists of AE test procedures and evaluation criteria and enables 100% inspection of the vessel during one pressure test.

The MONPAC technology package is the result of a strategic cooperative development by Physical Acoustics Corporation (PAC), Software & Systems Division of MISTRAS Group, and Monsanto Chemical Company (MON). An acoustic emission 'expert system' for evaluating the condition of metal pressure systems and tanks, based on experience from over 5,000 tests, MONPAC procedures are now widely used in the oil and chemical industries.

MONPAC can be applied during:

  • First Hydrotest of a new Pressure Vessel according to ASME-V Part 12
  • Requalification Hydrotest of a used Pressure Vessel
  • On-line Pressurization (in-service with working fluid)

The method utilizes's PAC's multichannel Acoustic Emission systems and sensors that detect the high-frequency signals resulting from deterioration in the structure when subject to stress. The systems have sufficient speed and resolution to ensure real-time, on- screen indications of the development of any defects.

The signals may result from local over-stressed areas, crack growth, and/or corrosion products de-cohesion. According to evaluation criteria, developed after thousands of tests, MONPAC gives 'color coding' for severity of emission and complete associated recommendations.

MONPAC testing requires Acoustic Emission Instrument Training and Certification. Only experienced AE practitioners qualify for the MONPAC license, so the market is well identified, being limited to those companies that regularly practice the technology.

Benefits of the method are largely seen in the reduced inspection costs and reduced downtime resulting from improved information about plant condition. MONPAC is particularly effective on spheres and columns, and for tank shell integrity testing. It is also used on complete process systems. The method provides a 'color coding' for severity of emission, complete with associated recommendations.

Key Advantages

  • Rapid Inspection (e.g. a 15m sphere is tested in approx. 3 days)
  • Global Monitoring (100% inspection, including welds, repairs, base metal etc...)
  • On-line Testing (can be tested with service product)
  • Minor Insulation Disturbance (insulation not removed, only few holes cut locally)
  • Reduction in Inspection costs
  • Reduction in downtime resulting from improved information about plant condition
  • The AE test is performed in accordance with ASME-Section V, Article 12
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