QUESTIONNAIRE FOR HOT SURFACE CRACK DETECTION  Click here to print this document
GENERAL 
Company
Contact
Street
Zip code
City
Country
E-mail
Aim of interest


CASTING PRACTISE
Number of strands
Strand section (W x H, mm) W H
Distance between strands (c/c):
Type of material / alloy:
Maximum casting speed (mm/s):
Available space for rotating sensors and manipulators:
Other important information:


STRAND SURFACE
Electrical conductivity, > Curie temp.:
Maximum depth of oscillation marks (mm):
Average depth of oscillation marks (mm):
Average distance between oscillation marks (mm):
Maximum allowed surface structure (e g max Ra):
Minimum surface temperature (C°):
Maximum recesses in the strand surface (mm):
Maximum bulges in/on the strand surface (mm):
Presence and types of scales:
Maximum scales thickness:


DETECTION
 
Types of defects / cracks:
Orientation of cracks (e g transversal, longitudinal, etc):
Location of defects / cracks (e g > 5 mm from corner, etc):


DEMANDS UPON,
Minimum detectable crack depth (mm):
Minimum detectable crack length (mm):
Minimum detectable surface hole diam (mm):
Minimum detectable surface hole depth (mm):
Maximum signal execution time / crack (ms):
Surface scanning speed (e g square metres / s):


EQUIPMENT
 
Stationary or mobile equipment: Stationary
Mobile
Manual or automatic inspection: Manual
Automatic
Desired way of crack identification and presentation:
Estimated length of cabling from DELTATEST sensors (strand) to cabinet in electric room (m):
   

Note
Minimum surface temperature, at hot inspection, must be > Curie-temp (approx. 765 C° for steel).

Crack detection using eddy current technique is based on the fact that cracks disturb the eddy current distribution in the surface of the test object. It is therefore easy to understand that other electrical conductive phenomena could also disturb the eddy current distribution and consequently disturb the measurment. Scales on the slag surface is in the "hot stage" only elecrical conductive to a minor extent.
During certain casting conditions, larger volumes of scales can be produced with local areas of low temperature scales ( below Curie-temperature). In this status however, the scales have developed a magnetic permeability which can disturb the measurement very much. Therefor, in DELTATEST hot-slab-applications, a high pressure water descaling unit always must be used.
The descaling unit is not included in the DELTATEST system.