Development and Drying (3)

Question 1

What is a developer?

Answer 1

• fine powder that absorbs the dye
• provides contrast
• “bleed out” action
• enhances “see ability”

Question 2

How does developer enhance the visibility of indications?

Answer 2

• blots dye bringing more back to surface
• spreads dye making indications appear larger
• contrast

Question 3

What is a Developer time?

Answer 3

time it takes the developer to blot the penetrant (reverse capillary action)
ASTM E165 = 10 minutes

Question 4

Describe development times

Answer 4

dwell times 20min or greater, development time is = 1/2 dwell time

• maximum time for aqueous developers is 2 hours
• maximum time for non-aqueous = 1 hour

Question 5

Types of developers

Answer 5

A - dry powder
B - water soluble
C - water suspendible
D - wet non aqueous

Question 6

Dry powder devloper

Answer 6

• as sensitive as water soluble
• same job as water based
• article must be dry
• drying time and temp must be controlled, do not overheat
• air soluble
• air suspendible

Question 7

Application of dry developers

Answer 7

• dusting
• dust chamber
• dipping
• spraying

Question 8

Water based developers

Answer 8

• suspendible (mix with water but don’t dissolve)
• soluble (particles dissolve)
• time needed for water to evaporate
• forced air ovens, but do not overheat
• require proper storage

Question 9

Application of Water based developers

Answer 9

• dipping
• pouring
• spraying

done in production line or lab
applied after washing stage (emulsified or water wash)

Question 10

Wet Non-Aqueous Developers

Answer 10

• powder held in suspension with a non aqueous fluid
• often an alcohol base
• alcohol thins penetrant viscosity and speeds up blotting effect thus increasing sensitivity
• most sensitive
• solvent action brings more penetrant to surface
• often used with solvent removable

Question 11

Application of Wet Non-aqueous developers

Answer 11

• applied to dry surface
• even, light coats
• white light
• time for alcohol to evaporate and apply another coat

Question 12

Properties required of developers

Answer 12

• absorb penetrant
• disperse dye to make indications bigger
• fine grainer to retain sharp definition
• mask background discontinuities
• provide contrast
• easily applied
• must not fluoresce
• easily removable
• not harm part
• not harm inspector

Question 13

Drying in LPI

Answer 13

• blast of cold air (remove water only)
• ambient air temperature
• forced hot or cold air

Question 14

Drying oven requirements

Answer 14

• thermostatically controlled
• air no >71°C
• part no > 10°C to 38°C (fluorescent)
• part no >10°C to 52°C (visible)

Per ASTM E165