2016 International Conference on Applied Mechanics, Mechanical and Materials Engineering (AMMME 2016) ISBN: 978-1-60595-409-7

Behavior Research and Application on Defect Examination of High Sensitivity Penetrating Materials under High Ambient Temperature Hao-yang DU 1,2,*, Jian YANG 3, Dong-yun SHI 2, Yong ZHAO 3, Yu ZHANG 4 and Zhen-an REN 1 1College of Mat. Sci. & Eng., University, , Jilin, 130022, 2State Grid Jilin Elec. Power Research Inst., No.4433 Renmin Str. Changchun, Jilin 130021, China 3Northeast Test &Research Inst. of Datang Electric Power Research Institute, No.3195 Weishan Road Gaoxin , Changchun, Jilin,130031,China 4Guodian Jilin Longhua No.1 Changchun Thermal Power Station, No. 6789 Xiaochengzi Street Kuancheng District, Changchun, Jilin,130114,China *Corresponding author

Keywords: Penetrating material, High ambient temperature, Wetting phenomena, Surface tension.

Abstract. Penetrating agents for penetrating test include penetrant, remover and developer. The capillarity abilities of the penetrant and developer are influenced by ambient temperature, which may affect the probability of defect detection. The behavior of penetrant agent under high ambient temperature has been researched and improved PT procedure has been made and performed based on ASME and related codes and according the features of the units. Some potential defects were detected subsequently.

Introduction Penetrating test is a widely used non-destructive testing method for the surface open defects of non-porous metal and non-metal materials[1]. According to ASME V Non-destructive testing, the penetrating agent includes penetrant, remover and developer. And the Standard testing temperature scope is from 5 ℃ to 52 ℃.When temperature increases, the activity of the penetrant increases, which will influences the behavior of penetrating into small defects. In Apr. 2007, we had undertaken a non-destructive testing of power station in Mehardeh, Syria. The last NDT work has been performed by another non-destructive testing company .Un-acceptable defect has not been found in the final test report. Leakages have been found during the commissioning. With the consideration of the leaking position, defect type, fuel type and the high temperature in the middle east area, the reason of leakage has been analyzed and an improved testing procedure has been made. The No.2 generation unit was manufactured by Alston Company, France and the turbine and generator were manufactured by SIMENS Company, Germany. The commissioning date of the unit is Dec. 7, 1979. The main parameters of the unit is as following, rating power of the unit 150MW, nominal rating 465T/h, main steam pressure 13.1MPa, reheating steam pressure 3.1MPa, reheating steam temperature 543 ℃, fuel heavy oil or gas, commissioning fuel diesel or gas. The operation parameters are as follow, operation time 133633 hours, commission time 786, generation capacity 13456401 MWh and the maximum load is 115MW. When survey the non-destructive testing report of the last examination, it has been noticed that the liquid penetrating test omitted the fuel of the unit is oil and no consideration on the high ambient temperature .So the examination sensitivity has decreased and leakage occurred in the examined part during operation .

Influence of High Temperature and Contaminant Environment on Penetrating Efficiency Code and examination scope of liquid penetrating test. It has been agreed to abide by vol. V Nondestructive Examination subsection A Nondestructive methods of examination Article 6 Liquid

Penetrant Examination test and subsection B Article 24 Liquid Penetrant Standards SE-165 (ASTM E165-02) Standard Test Method for Liquid Penetrant Examination [2]. The examination scope is as following, the circumferential weld and longitude weld of the drum, the fillet weld of header and the convex surface of the back arc of pipes and the valves in the turbine side. High sensitivity has been selected. Determination of liquid penetrating method. With the consideration of .the examination sensitivity, water source and power source, solvent removal method has been selected for examination. Selection of liquid Penetrant. According to ASME Vol. V SE-165(ASTM E165-02) Standard Test Method for Liquid Penetrant Examination, the penetrant in solvent removal method include the following, solvent removal penetrant, solvent removal remover and non aqueous developer. DPT serial is often applied in domestic examination. Ely Chemical Company Limited penetrating materials manufactured in Great Britain are available. Different properties could be found compared with domestic materials after comparison. Table 1 shows the parameters of solvent removal materials of Ely Chemical Company. Table 1. Comaprision of Ely Penetrating Materials. Lowest Viscosity Density[g/ Water Application Title Flashing Pack. Co.[40 ℃] cm 3,50℃] holding cap. Scope point[℃] can 5lt Not Suitable Checkmor 200 Water 100 4.40 0.860 min10% 25lt for water washing type 200lt washing type pe Can Suitable for net Checkmor 222 Solvent 5lt 100 3.90 0.850 - solvent ran removal remover 25lt removal type t 200lt Not Suitable Checkmor 200 Gel 100 -- 0.900 - 500ml for water Water washing type washing type Suitable for Can5lt S72 Solvent removal solvent 30 -- 0.759 - 25lt remover removal 200lt remover Can Suitable for S71ASolvent removal Not 5lt solvent -- 1.450 - remover flammable 25lt removal 200lt remover Solvent Can removal Re S76 Solvent removal 5lt <0 -- 0.713 - remover with mo remover 25lt low flashing ver 200lt point Need 5lt preparing H91A Condensed 100 15.00 1.000 No limitation 25lt solvent, not 200lt suitable N/A Lowest to 5lt temperature SC High Temperature 200 27.00 0.985 10% 25lt scope, not suitable Can LD3 non aqueous 12 -- 0.900 - suitable 5lt De LDW alcohol vel 44 -- 1.100 - 5lt suitable suspending op LD5 non aqueous 18 -- 0.820 - Can suitable er None LD2 (M)non aqueous -- 1.310 - Can suitable flammable

Determination of Penetrating Procedure under Non Standard Temperature Temperature requirements according to ASME Code. The day time temperature in middle east area is high. The boiler and main pipes are under open air, the surface temperature often reaches 52 ℃ and higher. According to ASME T-652, as a standard method, the temperature of the being examined part and the penetrant should not be lower than10 ℃ or higher than 52 ℃ during examination. Partial heating and cooling is allowed but the surface temperature of the part should be in the scope of 10-52 ℃. If the temperature exceeds the scope, determination should be made according to the rules in T-653. So the examination parameters under higher than 52 ℃ has been made. Preparation of calibration block. No merchandised blocks are available for the future penetrating test. According to the rules in ASME VT653.2, 2024 type aluminum alloy from ASTM B209 Standard specification for Aluminum and aluminum-alloy sheet and plate. The specification of 2024 aluminum alloy sheet is 52×76×9.5mm. A circle area with diameter25mm in the central part of the sheet has been marked and heated to 510-524 ℃ by gas blast burner. Put the heated sheet into cold water. Quenching cracks formed in the surface of the block. Reheating the block to 149 ℃, drying and separated from the middle . One half marked A and the other half marked B. Part A is used for the evaluation under-standard temperature and part B for the evaluation under non Standard temperature. It should be noticed that the cracks in part A and B are asymmetrical, while not in the central area of part A or B. That means the area for evaluation is in the central of the block before separation while not making cracks after separation. Penetrating procedure determination beyond 52 ℃℃℃.According to the measurement, when the ambient temperature is beyond 52 ℃, the surface temperature of the examining part is between 52-58 ℃.So procedures evaluation have been performed under four temperatures 52 ℃, 54 ℃,56 ℃, 58 ℃. During qualification, part A of calibration block has been examined under 35 ℃, then qualifiedly under the above four temperatures. According to the requirements of ASME V A chapter 6 T653.3, test and recording have been performed and the parameters under high temperature have been performed. The procedures under 52 ℃ and 58 ℃ show no big difference for the similar sensitivity. For an example, the penetrating time from 230-260 seconds obtains similar result. So the procedures between 52 ℃ and 58 ℃ are identical.

Application of the Penetrating Procedure after Qualification Preparation before examination. Necessary scaffolds have been prepared and sufficient illumination is required. When enters enclosed spaces such as drum or vessels, ventilation and outside supervision are required. Power resources must also meet the safety requirements. Surface pretreatment. The fuel of the unit is heavy oil and serviced for long time, also arranged under open air, so oil black is ease to deposit on the surface of the part due to in sufficient burning. And no protection measures have been adopted for the parts under open air during raining season, rusts deposited in the surface of the parts. Pre-grinding is applied to remove the oil deposit and rust till the metal exposed. Pretreatment. With the consideration of the possible oil mud may block the tiny open of tiny cracks, S72 Penetrant Remover has been used to clean the oil mud. Nature drying has been used due to the high ambient temperature. For the parts in the turbine side, S72 Penetrant Remover is directly used for cleaning and drying. Imposing of penetrant. The penetrate is imposed by spraying and the penetrating time under ambient temperature beyond 52 ℃ is about 240 seconds with the consideration of increased activity and not too dry to effect the next step. During penetrating the whole surface should keep wet and covered by the penetrate. Removing of the penetrate. S72 Penetrant Remover has been used as remover. According to the requirements of ASME V A chapter 6 T673.3, the redundant penetrate should be removed by cotton cloth and over cleaning should be avoided. Drying after removing. Drying time is determined by ambient temperature. Nature-drying has been adopted due to the high ambient temperature.

Imposing of developer.LD-3 Liquid Developer is used for developing. Thin and even developer film are required and developing time should not exceed 7 minutes. Observation. Observation should be performed under the environment with not less than 1000lx. Evaluation. Elevation should follow ASTM E433-71(2003) Liquid penetrating test reference pictures and ASTM A 903/A 903MSteel casting MT and PT Acceptance Standard. Post treatment. Necessary post treatment is required for cleaning and future usage of the part.

Defects Found under the Improved Procedure Lots of defects have been found under the improved examination procedure for high temperature. Figure 1a shows a crack in a governor valve and 1b shows a crack in the repair weld in the inner wall of the drum.

a. cracks found in governor valve b. crack found in the inner side of the drum Figure 1. Defects found.

Summary 1. The qualification of procedure of liquid penetrating procedure should consider the fuel, ambient temperature of the part. When temperature exceeds the standard scope of ASME, it should be qualified and applied in the examination 2. The improved procedure reduced the penetrating time based on standard temperature and more defects have been found.

References [1] Hu Xuezhi. Penetrating Test. China Labor and Social Security Pressing House (Edition 2).1997. [2] 2010 ASME Boiler &Pressure Code V Nondestructive Examination. American Society of Mechanical Engineering.