Each of the materials used in the dye penetrant test is crucial from a respective functionality point of view. In previous blogs, we discussed the penetrant types and their uses. Here, we will see the different types of developers and how they impact the dye penetrant test.
This is an essential topic in the oil and gas courses for mechanical engineers.
Why are developers used?
Developers facilitate the visibility of penetrant indications – by pulling penetrant to the surface for inspection from an open discontinuity and subsequently spreading the penetrant through the developer coating on the sample surface.
The penetrant indication sometimes appears more prominent than its actual size as the penetrant spreads through the developer over time.
As per specifications, the developer shall be applied as soon as possible after penetrant removal.
In any online course for piping engineering, the dye penetrant test information is of utmost importance.
Type of developers
Dry powder developer: Dry powder developers are loose fluffy white powders that may be applied manually with powder spray bulbs or spray guns or by dipping and dragging parts in the dry powder developer.
The dry developer usually has high absorbing properties. A dry developer shall be applied evenly in a thin layer on the surface only when the test surface is completely dry.
The different types under this category are-
Water-soluble developers: These are available in powdered form and are mixed with water according to the manufacturer’s directions. The supplied powder will dissolve in water and only requires stirring during the solution preparation. Water-soluble developers go only with fluorescent penetrants.
Water Suspendable Developers: Similar to the previous type, these are available in powdered form and are mixed with water according to the manufacturer’s directions. But, the water suspendable developers do not dissolve in water. Instead, they form a developer suspension.
The developer suspension must be continuously stirred to form a consistent developer concentration.
Other categories of developers
Non-aqueous developer: Nonaqueous developers are available in ready-to-use form. Nonaqueous developers are mostly white powders suspended in volatile solvents and require thorough mixing before use. The solvent evaporates when applied by spray and leaves a dry white developer coating on the part surface. Application of the same is made by spraying in aerosol cans.
Non-aqueous wet developer: This type of developer is prepared by suspending the absorptive white powder in a solvent. It is applied by using a pressurized spray can such as a paint spray gun. The developer is carefully applied to form a thin white coating on the specimen without soaking the test surface. A non-aqueous wet developer is the best choice when you want to determine fine discontinuities.
To know more about similar interesting topics as a part of oil and gas training courses online, check our piping engineering course.