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管道压力容器HIC抗氢致开裂性能评价的试验方法

发布时间:2022-07-14 访问量:470次 来源:隐石检测

管道、压力容器HIC抗氢致开裂性能评价的试验方法

抗氢致开裂性能检测方法主要依据NACE协会的TM0284标准进行试验检测,隐石检测腐蚀实验室从试验方法的发展历史和新版(2016版)标准两个方面做一个简介。


压力容器HIC试验

1、发展历史

氢致开裂最早被描述于一篇1949年发表的关于探讨酸性服役压力容器的裂纹和鼓泡的文章,在管线方面的报道最早在1958年。不过直到二十世纪七十年代,发生了几次比较严重的管线失效,如1972年英国石油公司的海上管线的失效,德国一酸性服役的管线失效及阿美石油公司的三起酸性气体输送管线失效,最终促使人们去研究检测管线抗氢致开裂性能的试验方法。先驱是英国石油公司,基于他们海上失效的案例,制定了一个介质为合成海水溶液的检测方法。

由于BP试验流程不是很明确,试验控制不充分,导致试验结果差异较大,重复性差。促使成立了T-1F-20工作组,由该工作组研究制定标准化的检测方法。从各相关方收集到的9种试验方法中最终选择了一个,经过一系列的试验室内部和试验室间的测试比较,于1980年发表了推荐性标准化试验流程,经过多次的修订,标准NACE TM0284最终形成于1984年,1987年进行了很小的修订。

1984年一场灾难性氨吸收装置的失效促使炼化行业重视了硫化氢引起的失效,进行了大范围的检查,于2147个容器中发现25%的受检对象有裂纹。于是在1990年NACE TM0284修订中增加了压力容器、电阻焊管、薄壁和小直径管线。另外增加了溶液A,即将NACE TM0177中的A溶液(最早用于应力腐蚀检测)引入进来。1996、2003年进行了很小的修订,如试样不允许展平等。2011年又增加了酸性服役环境下的相关附件的检测,最新版本为2016版,将在第二部分重点讲述。

从名称的转变看对该损伤认识的提高:早期氢致开裂被称为阶梯状裂纹(Stepwise Cracking)损伤,由日本学者最先提出,可见其是以裂纹的形貌特点来命名这种损伤,随着逐步深入的研究,发现这种损伤起源于氢进入材料基体,在氢陷阱处聚集形成氢分子,局部压力增大,形成了裂纹,因此,学术界开始使用了氢致开裂(Hydrogen Induced Cracking)来命名这种损伤,NACE标准从1990版开始采用。

最大裂纹率值规定的来源:一些产品标准中(如API 5L、NACE MR0175、ISO-15156),要求CLR≤15%、CTR≤5%、CSR≤2%,这些值是通过大量全尺寸试验(Full Scale Tests)和试验室试验(Laboratory Tests)结果的比较作为基础,从而确定的。即考虑全尺寸试验无裂纹下,试验室试验会检出裂纹。(参考文献-Review of the HIC test requirements for line pipe over the years 1975 to 2000)

2、新版(2016版)标准简介

本部分以修订章节为线进行介绍。

2.1 1.3 In Fitness-for-Purpose testing, the test environment and partial pressures of gases appropriate to the intended application are selected. 对于适用性试验,要选择目标实际环境和实际气体分压。注:即相当于模拟实际生产工况。

2.2 1.5 For additional information, the presence or absence of HIC in the exposed specimens may be evaluated by automated ultrasonic testing prior to metallographic sectioning and examination. A procedure is provided in Appendix A (nonmandatory). 金相分析前使用超声探伤检查HIC裂纹作为附加信息列于本标准中。试验流程见附录A(非强制性)。注:从此前生产检测过程的遇到的情况来看,只有道达尔和泰国石油明确了超声探伤试验方法,而其他公司虽也有超声探伤要求,但没有具体试验流程。现标准中列出,则今后客户或监制就可以据此提出意见,目前我们还需解决一些问题。

2.3 NOTE: In Fitness-for-Purpose HIC testing, a homogeneous test solution is required to facilitate pH control. In large test vessels, this may be achieved by continuous stirring of the test solution throughout the test. For Fitness-for-Purpose tests where buffering is less strong, stirring of the solution may also limit an increase in pH local to the corroding steel surface. 在HIC适用性试验中,需要一个均质的溶液来方便控制酸碱度,在大试验容器中试验可通过搅拌来实现。由于适用性试验所用溶液的酸碱度缓冲能力低,同样需要对溶液进行搅拌来防止钢铁腐蚀表面局部酸碱度的升高。注:酸碱度作为一个重要影响因素,在试验过程必须得以很好的控制,此处给出了如何控制的方法之-试验过程搅拌溶液,使溶液处于均质的状态下。

2.4 4.3.4 Small-diameter, thin-wall ERW and seamless pipe test specimens shall have all mill scale removed from the internal and external surfaces. Each test specimen shall be either machined and/or ground (wet or dry) to an equivalent 320 grit paper finish, or grit blasted to a uniform near-white metal finish in accordance with NACE No. 2/SSPC(4)-SP 109 or ISO 8501-1, Grade Sa 2½. For machining, the last two passes shall be such that a maximum of 0.05 mm (0.002 in) of material is removed. 或喷砂,使其达到近白亮金属表面,参照标准NACE No. 2/SSPC(4)-SP 109 or ISO 8501-1,级别Sa 2½。注:即增加了小尺寸管试样表面处理要求,给出了具体的参照标准。

If Test Solution A or B is used, the ratio of the volume of test solution to the total surface area of the test specimens shall be a minimum of 3 mL/cm2. If Test Solution C is used, the ratio of the volume of test solution to the total surface area of the test specimens shall be a minimum of 5 mL/cm2. As long as the specified ratio of volume of test solution to test specimen surface area is maintained, as many test specimens as will fit in the test vessel fully submerged and without touching may be exposed at one time. 如果使用溶液C,溶液体积与试样面积比最低为5毫升每平方厘米。

2.6 NOTE: For Test Solution C, a ratio of the volume of test solution to the total surface area of the test specimens higher than 5 mL/cm2 should be used for tests at pH levels below to reduce the frequency of re-adjustment of pH to the target pH (see

Paragraph 8.3.1). The use of an alternate test solution with greater pH stability may also be appropriate (see Paragraph 8.1.5). 注:本条解释了的要求的原因,即溶液C在酸碱度低于时,通过增加溶液体积与试样面积比来减少试验过程中调节酸碱度的频次。

2.7 8.1.5 If Test Solution C is used, the oxygen concentration in the test solution shall be maintained below 50 ppb. The laboratory shall have a demonstrated and documented procedure for solution deaeration validating that the methodology adopted achieves the required concentration of oxygen. The test solution shall consist of 5.0 wt% NaCl and 0.40 wt% CH3COONa in distilled or deionized water (i.e. 50.0 g of NaCl and 0 g of CH3COONa dissolved in 946 g of distilled or deionized water). The initial pH shall be adjusted to the target pH ± pH units by addition of HCl or NaOH before saturation with the H2S/CO2 gas mixture for the test to be valid. All reagents added to the test solution shall be measured to ± 1.0% of the quantities specified. 如果使用溶液C,则溶液中含氧量要维持在50个ppb以下,实验室需证明所采取的措施能达到这个要求。溶液C的成分为5%氯化钠、的醋酸钠来组成。起始酸碱度可以通过添加氢氧化钠或盐酸来调至目标值,控制在± 范围内。

2.8 NOTE: The oxygen concentration in the test vessel may be monitored directly or in a separate test carried out using the same apparatus and procedure, but with an oxygen concentration monitor, to demonstrate that the methodology adopted achieves the required concentration of oxygen. 氧浓度可氧浓度检测器来进行测量,可在试验容器上直接进行测量,或在相同的装置和流程下单独试验测量,以证明除氧方法有效。

2.9 NOTE: For tests requiring greater pH stability, NACE TM0177 Solution B (0.47 N total acetate) adjusted to the selected test pH value by addition of HCl or NaOH may be more appropriate. Where this solution is selected, it shall be reported as "NACE TM0177 Solution B" quoting the adjusted test pH. An alternate solution with strong buffering capacity proposed by the Iron and Steel Institute of Japan (ISIJ) high-strength line pipe (HLP) research committee, including high CH3COOH /CH3COONa (0.93 N total acetate), may also be appropriate. Where this solution is selected, it shall be reported as "HLP

solution pH x.x". 注:本部分推荐了俩个缓冲能力更强、酸碱度更稳定的溶液,即NACE TM0177中的B溶液和日本用于高强钢试验中的溶液。此处可能有一个小错误,可能应该是。

2.10 8.2.4 If Test Solution C is used; after purging, the H2S/CO2 gas mixture shall be bubbled through the test solution. The rate of bubbling should be 200 mL/min per liter of test solution for at least one hour; thereafter, a constant flow of test gas shall be maintained at a sufficient flow rate to ensure that the test solution remains saturated with the test gas for the duration of the test. The concentration of H2S in the test solution shall be measured by iodometric titration at the start (after saturation) and at the end of the test, and shall be of the minimum value as calculated from Equation (1), dependent on the mole fraction of H2S in the test gas. An acceptable iodometric titration procedure is detailed in Appendix D (nonmandatory). 注:本部分增加了溶液C的控制,类似,但硫化氢浓度要根据实际情况进行滴定溶液的选择。

2.11 If Test Solution C is used, the test duration shall be in accordance with Table, dependent on the partial pressure of H2S in the test gas.

NOTE: The test parameters given in Table for HIC tests in Solution C have been chosen in accordance with literature data to ensure HIC cracking of susceptible steels. Test durations shorter than those given in Table for HIC tests in Solution C may not lead to HIC cracking in steels susceptible to HIC under the selected test conditions of Table.

NOTE: The test durations given in Table are also appropriate for Fitness-for-Purpose testing in alternate test solutions. 注:如果使用溶液C,试验的周期将根据硫化氢的浓度来确定,这部分要求已通过敏感性材料试验得以确定。

2.12 A1.2 The procedure is not applicable to curved specimens or to small fittings tested as complete components. 超声探伤不适用于弧形和小试件试样。

2.13 A1.3 The procedure provides a method for determining the Crack Area Ratio (CAR). 超声探伤需要报出裂纹面积比。注:裂纹面积比为超声检出的伤面积除以受检面积。

2.14 D8 Calculate the H2S concentration (mg/L) using Equation (D1):

H2S concentration (mg/L) =(A − B) x 17.04/C

硫化氢浓度计算公式如上。注:此处有修改,红色字体部分老版为,其实际上是将硫化氢分子量进行了修正,由36改为38.。

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References

3.1 History of NACE TM0284 Development;

3.2 Review of the HIC Test Requirements for Line Pipe Over The Years 1975 to 2000;

3.3 NACE TM0284-2016;

3.4 NACE TM0284-2011.

2.9 NOTE: For tests requiring greater pH stability, NACE TM0177 Solution B (0.47 N total acetate) adjusted to the selected test pH value by addition of HCl or NaOH may be more appropriate. Where this solution is selected, it shall be reported as "NACE TM0177 Solution B" quoting the adjusted test pH. An alternate solution with strong buffering capacity proposed by the Iron and Steel Institute of Japan (ISIJ) high-strength line pipe (HLP) research committee, including high CH3COOH /CH3COONa (0.93 N total acetate), may also be appropriate. Where this solution is selected, it shall be reported as "HLP

solution pH x.x". 注:本部分推荐了俩个缓冲能力更强、酸碱度更稳定的溶液,即NACE TM0177中的B溶液和日本用于高强钢试验中的溶液。


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