Radiography (X-Ray)
X-rays are used by Score to inspect the internal body (Sub surface) of steels and most other materials. Steel thickness up to 80mm can be x-rayed (Single wall).
X-rays produce better quality results compared to Gamma radiography. While x-ray is more expensive and difficult to carry out, it is preferred by clients and certifying authorities. X-rays produce a graph that can be reviewed and verified ensuring that the weld/valve, process/material, is correct. The x-ray graph is a permanent record that can be reviewed at anytime.
Ultrasonic Inspection:-
Ultrasonic is one method used by Score to inspect the internals (Sub surface) of steels for defective areas. This is done by sending a sound wave through the steel and when it hits either a void or the opposite external surface of the tested part, it returns to the probe that sent the signal and the operator can determine both how deep and what size the flaw is.
Thickness Surveys (Using a Type of Ultrasonic)
As above but using a digital ‘D’ meter or thickness gauge.
Dye Penetrant Inspection ( Water Washable, Fluorescent & Visible)
Dye Penetrant is a technique which can be used to detect flaws on the surface of most materials, i.e. glass, plastics, steels, etc.
Normally used for stainless steels, where you cannot use Magnetic Particle Inspection due to the material being non-magnetic, it can be used on carbon steels as well. The types used at Score’s Glenugie site are Water Washable, Fluorescent & Visible.
Visible, which is the most commonly used, is normally red in colour. After the part has been cleaned, the dye is applied by brush, spray, pouring or dipping. It is then left to dwell (soak) for 15 – 30 min, then wiped off with lint free cloths or paper towels till no dye remains. A light, even coating of developer is applied from a distance of approx 12”, the part is then inspected for any red indications appearing in the white developer. The developer is left for a further 15 – 30 minutes and then re-inspected for additional red indications. Fluorescent penetrant follows the same method, but is more sensitive than the visible penetrant, and an Ultraviolet (black) light is used to see the fluorescent penetrant. Score also operate two fluorescent water washable penetrant lines, used primarily to inspect fuel nozzles and turbine parts, but these can be used for other items.
Magnetic Particle Inspection (Fluorescent & Visible)
Magnetic Particle inspection is used to inspect the surface of carbon steels. The part to be inspected is magnetised using an electromagnet. A medium of iron powder particles suspended in a carrier fluid is sprayed on to the part between the poles of the electromagnet and the area inspected for any black indications formed by the iron powder. A white contrast paint may be applied if required prior to the application of the ink, this is to aid interpretation on some surface finishes. Fluorescent is used in the same way - no white contrast paint is required but an ultraviolet (black) light is.
Ferrite Inspection
Ferrite testing is carried out mainly on Duplex material. The ferrillium count is measured by the means of a small probe utilising the magnetic induction test method. This is where the ferrite content is obtained from the magnetic permeability. The measurement is displayed as a percentage and has to fall between 40% to 60% to be acceptable. If the reading is between either 30 to 40% or 60 to 70% then it is referred to Score’s Engineering Department for a decision. If it falls below 30% or is above 70% then the material is deemed unacceptable.
Hardness Testing
Hardness testing is carried out by means of a portable hardness testing unit. The unit measures the (L) EEB value and then converts it into a recognised hardness value such as HV, HB, HRC or HRB. This method leaves a very slight mark on the surface, barely visible to the naked eye. Rockwell Bench hardness testers are also used but are restricted due to size.
Positive Material Identification (PMI)
PMI is carried out using a 45 kV x-ray tube which converts the information gathered and returned to the PMI unit into a chemical symbol for the different chemical elements contained within the steel and can also confirm what the steel is, for example:- Zeron 100.
The advantage of this unit is that it is battery operated, hand held, making it extremely portable, leaves no arc strike on the part which means that seal areas can be tested without ill-effect. Swarf or filings can be tested without melting them into a block.
Water Testing
Samples of water used for hydrostatic testing and samples taken from the nitrogen testing tanks are analysed for chloride (30 ppm maximum), fluoride (30 ppm maximum) and Ph (6 – 8) values. These tests are carried out by using a digital analyser. These checks are necessary as too high a percentage of these elements can induce cracking in Duplex steels.