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Archive for March, 2011

A Good Find

March 16, 2011 1 comment

 

Component: Dragline Bullgear

Detected with Eddy Current, confirmed with Magnetic Particle.

Note: Eddy Current commonly used to negate the requirement of detailed cleaning. Inspection is done straight through the grease.

Cause: Cracked joining bolts.

 

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Categories: Eddy Current Tags: ,

Occupational Exposure to Black Lights

March 15, 2011 1 comment

 The Occupational Exposure to Ultraviolet Radiation (2006), Radiation Protection Series No 12, sets out guidelines for the exposure limits to ultraviolet radiation.

The exposure limit values in this standard refer to ultraviolet radiation in the spectral region between 180nm and 400nm and represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect.

 For the near-ultraviolet UV-A spectral region (315-400 nm), the total radiant exposure incident upon the unprotected eye should not exceed 1.0 J cm-2 (10 kJ m-2) within an 8-h period and the total 8-h radiant exposure incident upon the unprotected skin should not exceed 2.7×105 J/m-2 (Wavelength 365nm, mercury discharge spectrum).

The minimum output required by numerous Australian Standards for Non Destructive Testing is10w/m-2 @38cm.

 This is equivalent to 10 Joules/second   (1 Joule = 1 watt/second)

  •  For Unprotected Eye, exposure limit would occur in 16.66 minutes.
  •  For Unprotected Skin, exposure limit would occur in 7.5 hours.

 Numerous systems with outputs above 60w/m2 @ 38cm are currently available.

 This is equivalent to 60 Joules/second          

  •  For Unprotected Eye, exposure limit would occur in 2.7 minutes.
  •  For Unprotected Skin, exposure limit would occur in 1.25 hours.

 (Note: Times are based on the figures and a distance of 38cm , variations in exposure distance will vary output and times accordingly.)

Safety Precautions:

  •  Never look directly at a lamp whilst it is operating.
  •  Never operate a lamp with a cracked or damaged filter.
  •  Glasses specifically designed to filter black light should be worn, however the transmission curves of the glasses should be checked against the emission curve of the fluorescent material under inspection.
  •  Wear opaque gloves and protective clothing during inspections to protect from possible UV irritation.
  •  Ensure black light source is placed  to minimize direct exposure to operators.
Categories: Safety Tags:

Film Viewer Intensity in Accordance with AS2177

March 15, 2011 Leave a comment

AS2177- 2006 requires that the output of a film viewer be such that brightness of an illuminated radiograph shall not be less then 30 cd/m2 and shall preferably be greater than 100 cd/m2.

Since the density of a film directly effects the transmission of light it is important to understand the relationship between Film Density and Viewer Brightness. Refer to Table 1.

To calculate density the formula is:

Density = Log10 (Intensity of Incident Light / Intensity of Transmitted Light)

Example 1:     What would be the maximum film density viewable, with a viewer with an output of 48000 cd/m2.

         Density = Log10 (48000/30)               

         Maximum Density Viewable = 3.2

Example 2:     What would be the recommended maximum film density viewable, with a viewer with an output of 48000 cd/m2.

          Density = Log10 (48000/100)            

          Recommended Maximum Density Viewable = 2.68

Film Density MinimumOutput cd/m2 RecommendedOutput cd/m2
2.0 3000 10000
2.5 9487 31623
3.0 30000 100000
3.5 94868 316228
4.0 300000 1000000

Table 1 – Density Vs Viewer Output

Advertised Density Capability

As most viewers are manufactured overseas, they are commonly supplied with specification sheets with nominated density capabilities that refer to other international standards. The requirements vary from standard to standard, it is therefore important to determine the correct output based on cd/m2.

For example a viewer rated to D3.6 to EN25580, has a maximum density of D3.1 to AS2177.

Measurement of Output

Confirmation of output is required annually and can be performed in a variety of ways including:

a)         Direct reading from calibrated luminous intensity meter.

b)         Conversion from illuminance (lux) to luminous intensity (cd/m2)

Categories: Radiography

R is for ?

March 15, 2011 Leave a comment

Reject , Recycle or Both

Categories: Ultrasonics Tags:

Urban Legends – The Mythical Panoramic Colimator

March 15, 2011 2 comments

Categories: Radiography

Interesting Indications In A Shaft

March 15, 2011 Leave a comment

Interesting indications detected in a shaft using Florescent Magnetic Particle.

 

 

 

Categories: Magnetic Particle Tags: