Penetrant testing is one of the most commonly utilised non destructive testing methods used in all industries. This can largely be attributed to its relatively low cost and high adaptability meaning it can be applied in all manor of ways without dramatically affecting its sensitivity.
The one application method however which is believed to marginally increase the sensitivity of a penetrant inspection is the electrostatic penetrant application method.
When penetrant is applied via electrostatic spray application there several benefits including:
- Reduced consumption of penetrant
- Ability to test large components
- Ability to test complex geometry
- Increase in sensitivity attributed to electrostatic attraction
- Reduced in service tests on consumables
One of the easiest advantages to quantify is the reduced cost of consumables that occurs, to immersion test a large component with dimensions of 1000mm x 1000mm x 200mm would require hundreds of litres of penetrant in a dip tank to ensure adequate penetrant to cover the parts, this could cost thousands of pounds. Electrostatic penetrant application allows a small singe 25 litre barrel to be used and apply via spray which can vastly reduce initial outlay costs.
Another easy to see advantage is the reduction of in service tests that are required when using electrostatic penetrant application. When using immersion methods, the penetrant is classified as re used, as a result there are checks to be carried out including daily contamination checks, monthly water content checks and quarterly fluorescent intensity checks. As electrostatic application is classified as a spray to waste system, this negates the need to have these checks performed. Not only does this reduce the amount of work to be carried out by the operator but also removes the chance of any of these tests constituting in a failure which could subsequently lead to down time on the penetrant line.
The final and possibly most important advantage of electrostatic penetrant application is the slight increase in sensitivity when using electrostatic penetrant application. Penetrant naturally is “drawn” into surface breaking defects by capillary action, when using the electrostatic spray method this action is further aided by the electrostatic effect which further draws penetrant to the surface of the part. As such it is believed that this application method increases the overall sensitivity of the penetrant inspection.