Procedure for PT inspection (penetration inspection) of pipe fittings
Under the action of capillarity, penetrant penetrates into the surface opening defect; After removing the excess penetrant on the surface,the penetrant in the defect is absorbed through the capillary action of the imaging agent, forming traces and showing the existence of defects. This methor is PT inspection (penetration inspection).
What are the specific operating procedures for pipe fittings to do P.T testing?
Drying, the method is clean cloth drying, compressed air drying, hot air drying, hot air circulation drying device drying ,etc. The drying temperature of the surface should be controlled within the range of no more than 52℃.
Before penetration inspection, surface cleaning and pre-cleaning must be carried out on the pipe fittings to remove all contaminants on the surface of the inspected parts. The scope of preparation work shall extend 25 mm outwards around the inspection site. cleaning method is mechanical methods ，chemical methods and solvent removal methods.
Imaging, using the imaging agent to adsorb the permeable liquid at the defect to the surface of the part to produce a clear and visible defect image. The developing time should not be too long and the developing agent should not be too thick, otherwise the defect display will be blurred. The imaging time is 10 ~ 30 minutes, and the thickness of the imaging agent is 0.05 ~ 0.07 mm.
Removal, except for particularly difficult to remove occasions, generally use dipped in cleaning agent cloth and paper to wipe; Do not wipe back and forth, do not soak the inspected part in the cleaning agent or use the cleaning agent excessively; In water spray cleaning, water pipe pressure 0.21mpa is appropriate, water pressure shall not be greater than 0.34mpa, water temperature shall not exceed 43℃.
Penetration,based on the size, shape, number and inspection parts, choose spraying, brush coating, pouring coating and dip coating methods. The length of time and temperature range in the penetration process have great influence on the sensitivity of crack detection. When the penetration temperature ranges from 15 ℃ to 50℃, the penetration time is generally divided into 5 ~ 10 minutes. When the osmotic temperature is reduced to 3 ~ 15℃, the osmotic time should be appropriately increased according to the temperature.
Inspection,the observed trace should be carried out within 7 ~ 30 minutes after the application of the developer, if the size of the trace displayed does not change significantly, it can be longer than the above time. To ensure that minor defects are checked, the illumination on the inspected part is at least 350 lux. After the inspection, the imaging agent should be removed if necessary in order to avoid the corrosion of the surface of the tested object or to affect its use. The cleaning method can be brush, air, water, cloth or paper erasing.