ADVANCE ULTRASONIC INSPECTION

DACON INSPECTION SERVICES VISUAL TESTING

Who we are

Conventional and Advanced NDT and Inspection Services

Oil and Gas, Refinery, Petrochemical, Heavy Industry, Mining

Over 400 personnel including more than 300 inspectors

Thailand headquarters with International expertise since 1979

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• Oldest and most widely used inspection Method

• Often eyes of inspector used is the only inspection equipment used

• Direct visual testing: When access allows eyes to be within 25 inch of surface to be examined and within an angle not less than 30 degrees to the inspection surface

• Remote visual inspection: For inspection of restricted access area’s

Visual Testing

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

For direct visual testing here are a variety of optical aids available: • Magnifiers • Inspection mirrors (when eye cannot be put in recommended viewing range) • Microscope • Telescopes • Camera’s

In addition to this some other equipment is often part of visual testing: • Vernier calipers • Micrometer • Pit gauge • Scraper • Digital camera

Visual Testing

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

Visual Testing

Important factors in Visual inspection:

Visual acuity of the inspector • Near distance acuity , reading a chart at certain distance • Color blindness, Ishihara test charts

Lighting conditions • Measure the light intensity • Amount of light between 350-1000 Lux depending

on code requirements • Use of artificial light (flashlights) • Use of sunlight (mirrors)

Cleanliness of surface • Normally a clean surface is required to detect discontinuities • Remove • Scale • Paint • Debris

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

Visual Testing

Important factors in Visual inspection:

Visual angle and distance • Eyes to be within 25 inch of surface to be examined • Eyes to be within an angle not less than 30 degrees to the inspection surface

Perception • Length of arrows?

Reflectance and back ground • The amount of light that is reflected from a background is of great influence

Temperature (heat wave distortion) • Heat waves coming off from item distorting the view

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Visual Testing

Important factors in Visual inspection:

Physical comfort Can be of great influence (applicable for every inspection and NDT examination)

• Comfortable arrangement for inspector will result in greater attention to detail

• Inspection from awkward position may result in missed indications Inspector may hurry examination in order to get back into comfortable position

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Visual Testing

Remote Visual Testing (RVI) For inspection of inaccessible area’s • Small bored pipes or tubes • Pressure vessels or tanks which cannot be

entered (not gas free etc)

Typical equipment to be used: • Bore scopes

Rigid bore scopes (lens-optic)

• Contains a train of lenses • Light source at the end of scope to illuminate area of interest

Fiber scopes (fiber-optic)

• Uses a glass fiber bundle • Light is transmitted to the inspection area via glass fiber • The light reflected of the object is send back to

viewing end via the glass fiber

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

Visual Testing

Remote Visual Testing (RVI) Typical equipment to be used (continued): Camera’s (Video scopes) Fiber camera • Light is transported to area of interest by

fiber optic bundle

• Light waves form the object pass through a lens and will hit a CCD (charged coupled device)

• CCD converts the waves into electronic signals which are transmitted to a CCU

• CCU processes received signals to produce a “picture” on a video screen

• Limitation to the length the fiber bundles can be manufactured

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Remote Visual Testing (RVI) Typical equipment to be used (continued): Mini camera’s

• Light source is placed at the area of interest via electrical wire

• Bigger size required because a ring of light will have to be placed at the tip.

• Length can be bigger than Fiber camera

• Variation the Fiber is transported to area of interest by fiber optic bundle

• Principle of operation similar to fiber camera with CCD

Visual Testing

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

Visual Testing

Remote Visual Testing (RVI) Typical equipment to be used (continued): Camera’s with Pan, Tilt , Zoom lens

• Are available with long cable and reach (up to hundreds of meters)

• Bigger size, requires: Motor controls for remote operation of lens Motor controls for panning and tilting More light (need to cover several zones for longer viewing distance and for close up)

• Panning and tilting allows the camera to be positioned in almost every position

DACON INSPECTION SERVICES F O R A L L Y O U R I N S P E C T I O N N E E D S

Visual Testing

Remote Visual Testing (RVI) Typical equipment to be used (continued): Remote operated vehicles (ROV)

• The term ROV is most often used for Remotely operated underwater vehicles

Self propelled sub marine like vehicles that contain a camera and can be

remotely operated

Crawler, tractors