1.1 本规程建立了聚乙烯管中对接熔合接头的超声波检测（UT）程序。虽然高密度聚乙烯（HDPE）和中密度聚乙烯（MDPE）材料是最常用的材料，但所述程序可能适用于其他类型的聚乙烯。 注1: 本规程中的注释仅供参考，不应视为本规范的一部分。 注2: 本规程参考了规范中定义的管道应用中的HDPE和MDPE D3350 . 1.2 本规程不涉及电熔接头（耦合接头）、承插接头或鞍座的超声波检查。 1.3 本规程提供了两种超声波检查程序。每种方法都有其自身的优点和审查要求，并应根据合同文件中的约定进行选择。 1.3.1 检查程序A，飞行时间衍射（TOFD）， 使用一对探头，一个发射，另一个接收。该程序通常（尽管不一定）需要从一个表面进入接头的两侧。如果使用位置编码，该过程可以通过半自动或自动方式进行，以提供重新编码的成像。 1.3.2 检查程序B，相控阵超声检测（PAUT）， 使用低速折射楔或水隙产生角度压缩模式脉冲。该程序可应用于仅从一个表面进入接头一侧的情况。如果使用位置编码，该过程可以通过半自动或自动方式进行，以提供重新编码的成像。 1.4 本规程旨在用于9至60 mm[0.375至2.4 in]的厚度直径100毫米[4英寸]更大。如果可以证明该技术能够在相同壁厚和几何形状的实体模型上提供足够的检测，则可以使用本标准惯例测试较大和较小的厚度和较小的直径。 1.5 本规程未规定验收标准。 1.6 单位- 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值不一定是精确的等价物；因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 本规程主要用于聚乙烯管道系统施工中使用的对接熔合接头的自动或半自动超声波检测。 5.2 聚乙烯管道因其可靠性、耐腐蚀和侵蚀，已在石化、电力、水、天然气配送和采矿行业中取代钢合金。 最近，聚乙烯管也被用于核安全相关的冷却水应用。 5.3 两种超声波技术已被证明可用于检查融合接头的完整性；超声飞行时间衍射（TOFD）和相控阵超声检测（PAUT）。这些技术通常被认为是互补的，但可以相互独立使用。所用技术的选择可能取决于各种参数，包括直径、厚度、表面访问、表面附近的检测能力和所需的质量水平。 5.4 连接过程可能存在各种缺陷，包括但不限于:未熔合、颗粒污染、夹杂物和空洞。 5.5 聚乙烯材料可能具有一系列声学特性，使对接接头检查困难。 该材料的声速与通常用于超声楔形材料的声速相似，因此很难使用这些材料在界面处实现声音的适当折射。聚乙烯材料具有高衰减性，这通常限制了更高超声波频率的使用。它还表现出自然的高频滤波效果。声学特性范围示例见 表1 . 该表记录了文献中报告的各种声速。这使得参考块必须由相同的单元分类组成 6. 正如所考察的那样。这应通过测量实践中所述被检查管道的声速来确认 E494年 . 对比试块的声速应在被检查管道材料的±50 m/s范围内。 （A） 文献中已注意到一系列速度和衰减值 ( 1- 9 ) . 括号中的黑体数字指本标准末尾的参考文献列表。 5.6 据报道，聚乙烯的剪切速度为987 m/s。然而，由于剪切模式下的衰减极高（在2 MHz时约为5 dB/mm[127 dB/in]），因此没有使用剪切模式进行实际检查 ( 6. ) . 7. 5.7 由于应用范围广泛，聚乙烯管的接头验收标准通常是特定于项目的。 5.8 聚乙烯管中的典型对接熔合接头具有明显的珠状轮廓，如图所示 图1 其中，焊道显示在管道的外表面和内表面上。 图1 聚乙烯对接熔合接头的典型焊道轮廓 5.9 在聚乙烯上使用TOFD时，由于剪切模式的高衰减，模式转换信号几乎被消除，因此简化了TOFD。然而，如果确定与TOFD相关的近表面和远表面死区超出检测要求，则可能会被视为限制。例如，对于相对较薄壁厚的应用< 15 毫米[0.6 英寸。]，可以考虑单侧TOFD（或准弦技术）来帮助减少这些死区的范围。看见 附件A2 有关此选项的详细信息。 5.10 PAUT可用于解决TOFD出现的近表面死区。

1.1 This practice establishes procedures for ultrasonic testing (UT) of butt fusion joints in polyethylene pipe. Although high density polyethylene (HDPE) and medium density polyethylene (MDPE) materials are most commonly used, the procedures described may apply to other types of polyethylene. Note 1: The notes in this practice are for information only and shall not be considered part of this specification. Note 2: This practice references HDPE and MDPE for pipe applications as defined by Specification D3350 . 1.2 This practice does not address ultrasonic examination of electrofusion joints (coupling joints), socket joints, or saddles. 1.3 This practice provides two ultrasonic examination procedures. Each has its own merits and requirements for examination and shall be selected as agreed upon in a contractual document. 1.3.1 Examination Procedure A, Time of Flight Diffraction (TOFD), uses a pair of probes, one transmitting and the other receiving. The procedure usually, although not necessarily, requires access to both sides of the joint from one surface. Provided that position encoding is used, the procedure can be conducted by semi-automated or automated means that provide recoded imaging. 1.3.2 Examination Procedure B, Phased Array Ultrasonic Testing (PAUT), uses low velocity refracting wedges or water gaps to produce angled compression mode pulses. The procedure can be applied where access is limited to one side of the joint from one surface. Provided that position encoding is used, the procedure can be conducted by semi-automated or automated means that provide recoded imaging. 1.4 The practice is intended to be used on thicknesses of 9 to 60 mm [0.375 to 2.4 in.] and diameters 100 mm [4 in.] and greater. Greater and lesser thicknesses and lesser diameters may be tested using this standard practice if the technique can be demonstrated to provide adequate detection on mockups of the same wall thickness and geometry. 1.5 This practice does not specify acceptance criteria. 1.6 Units— The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 This practice is intended primarily for the automated or semi-automated ultrasonic examination of butt fusion joints used in the construction of polyethylene piping systems. 5.2 Polyethylene piping has been used in lieu of steel alloys in the petrochemical, power, water, gas distribution and mining industries due to its reliability and resistance to corrosion and erosion. Recently, polyethylene pipe has also been used for nuclear safety-related cooling water applications. 5.3 Two ultrasonic techniques have proven useful to provide examination of fusion joint integrity; Ultrasonic time-of-flight-diffraction (TOFD) and phased array ultrasonic testing (PAUT). These techniques are often considered complementary but may be used independently of each other. The choice of the technique used may depend on a variety of parameters including diameter, thickness, surface access, detection capabilities near surfaces, and quality level required. 5.4 The joining process can be subject to a variety of flaws including, but not limited to: lack of fusion, particulate contamination, inclusions, and voids. 5.5 Polyethylene material can have a range of acoustic characteristics that make butt joint examination difficult. Acoustic velocity of the material is similar to that commonly used for ultrasound wedge materials, making it difficult to use these materials to achieve appropriate refraction of sound at the interface. Polyethylene materials are highly attenuative, which often limits the use of higher ultrasonic frequencies. It also exhibits a natural high frequency filtering effect. An example of the range of acoustic characteristics is provided in Table 1 . The table notes the wide range of acoustic velocities reported in the literature. This makes it essential that the reference blocks are made of the same cell classification 6 as that examined. This shall be confirmed by measuring the acoustic velocity of the pipe being examined as described in Practice E494 . The acoustic velocity of the reference block shall be within ±50 m/s of the examined pipe material being examined. (A) A range of velocity and attenuation values have been noted in the literature ( 1- 9 ) . The boldface numbers in parentheses refer to the list of references at the end of this standard. 5.6 Polyethylene is reported to have a shear velocity of 987 m/s. However, due to extremely high attenuation in shear mode (on the order of 5 dB/mm [127 dB/inch] at 2 MHz) no practical examinations are carried out using shear mode ( 6 ) . 7 5.7 Due to the wide range of applications, joint acceptance criteria for polyethylene pipe are usually project-specific. 5.8 A typical butt fusion joint in polyethylene pipe has a pronounced bead profile similar to that illustrated in Fig. 1 where the bead is shown on the outer and inner surface of the pipe. FIG. 1 Typical Bead Profile for Polyethylene Butt Fusion Joint 5.9 TOFD, when used on polyethylene, is simplified in that mode-converted signals are virtually eliminated due to the high attenuation of the shear mode. However, the near surface and far surface dead zones associated with TOFD may be considered limitations if determined to be excessive for the detection requirements. For applications on relatively thin wall thickness, for example, < 15 mm [0.6 in.], one-sided TOFD (or the quasi-chord technique) may be considered to help reduce the extent of these dead zones. See Annex A2 for details on this option. 5.10 PAUT can be used to address the near surface dead zone that occurs with TOFD.