PT Liquid Penetrant Explained in English
Citation information
By Amado Garcia
www.Aqualified.com
Please note this is a free PT liquid penetrant review for a non-technical look at the method in reference to nondestructive testing. Some terms in this article might not be industry appropriate and other things are simply skipped. For a true liquid penetrant course per SNT-TC-1A or NAS-410 or CP-189 contact a training facility and schedule your training, something we can easily accomplish for you. (shameless plug). We are always open to onsite university, convention and seminar appearances.
Liquid penetrant also known as dye penetrant and Magnaflux Zyglo check are essentially the same thing . Except that Magnaflux Zyglo and Spotcheck are name brands.
www.Magnaflux.com
So what is liquid penetrant? A fluid usually used to find small openings at the surface of a material that is nonporous. The two key components: open to the surface and nonporous. If the material has a finish like a sponge it will absorb the dye penetrant making the part permanently fluorescent something you definitely do not want to happen.
Application of a liquid to a surface does not seem like an inspection method to most, but think back to observing someone inflating a bike tire or an inner tube. They use spit or water to see if there was a leak. The atmosphere of the room in which you are performing an inspection has a set pressure and the void or crack in the metal has a different pressure. This pressure is like the air in the tire.
If you cover the metal with liquid penetrant by dipping, spraying or brushing the part and allow the chemical to sit on the part (dwell) for 30 minutes, you can use the atmospheric-to-flaw pressure for flaw detection. The 30 minutes or time is important in allowing the penetrant to enter the flaws. With an inner tube the psi is high. When thinking about the atmosphere verses the part you must think of the psi as being low; hence time is necessary.
The next step is the removal of the penetrant, to clean off the penetrant by wiping with a towel or rinsing it off with water. This removal then causes the liquid penetrant in the crack to slowly return to the surface. The term for this effect is capillary action. The easiest way to visualize the process of penetrant coming out of the flaw and to remember the benefits of capillary action is to think of a tree. How is it that a large tree gets water from the roots to the leaves at the top? The simple answer is capillary action.
So what is liquid penetrant? A fluid usually used to find small openings at the surface of a material that is nonporous. The two key components: open to the surface and nonporous. If the material has a finish like a sponge it will absorb the dye penetrant making the part permanently fluorescent something you definitely do not want to happen.
Application of a liquid to a surface does not seem like an inspection method to most, but think back to observing someone inflating a bike tire or an inner tube. They use spit or water to see if there was a leak. The atmosphere of the room in which you are performing an inspection has a set pressure and the void or crack in the metal has a different pressure. This pressure is like the air in the tire.
If you cover the metal with liquid penetrant by dipping, spraying or brushing the part and allow the chemical to sit on the part (dwell) for 30 minutes, you can use the atmospheric-to-flaw pressure for flaw detection. The 30 minutes or time is important in allowing the penetrant to enter the flaws. With an inner tube the psi is high. When thinking about the atmosphere verses the part you must think of the psi as being low; hence time is necessary.
The next step is the removal of the penetrant, to clean off the penetrant by wiping with a towel or rinsing it off with water. This removal then causes the liquid penetrant in the crack to slowly return to the surface. The term for this effect is capillary action. The easiest way to visualize the process of penetrant coming out of the flaw and to remember the benefits of capillary action is to think of a tree. How is it that a large tree gets water from the roots to the leaves at the top? The simple answer is capillary action.