聚乙烯管材的连接方法和技术

为充分发挥聚乙烯（PE）管材的先进性，经济性和安全性，对PE管材的各种连接方法进行了广泛的研究。介绍了PE管材的热熔对接焊，电热熔焊，热熔承插焊，鞍形/侧壁熔焊，以及钢塑过渡接头连接方法和技术，并对热熔对接焊和电热熔焊作了较深入的探讨，同时进一步分析了不同塑料管材间的焊接方法。     

热熔焊接工艺参数对聚乙烯管道力学性能的影响

聚乙烯（PE）管道在天然气运输中应用广泛，热熔焊接是连接PE管道的主要方式之一，焊接工艺参数影响热熔接头以及管道整体的性能。文章以焊接温度、加热时间和焊接压力等工艺参数作为主要影响因素，设计正交试验，制备不同的热熔接头拉伸试样，对比分析其抗拉性能。通过数值模拟得到带卷边热熔接头拉伸试样的本构模型。结果表明：焊接温度、加热时间和焊接压力使PE管道的抗拉性能先增高后降低，焊接温度和加热时间对热熔接头的抗拉性能影响显著。PE管道热熔接头的抗拉性能比基材好。载荷-位移曲线与实验曲线较吻合。基于有限元分析和Kwon聚合物本构模型可得到PE管道热熔焊接接头准确的本构关系。     

PE管材焊接技术与应用

PE管材连接方法包括热熔焊接、电熔焊接;热熔焊接要求热熔焊机的操作要符合操作规范,电熔焊接要注意每个电熔焊机的电流和焊接时间,另外管件的焊接参数每个生产厂家不同,焊接参数也不同,不同PE级别的产品焊接只能电熔焊接。     

聚乙烯管材热熔对接接头抵抗慢速裂纹扩展性能评价

采用应变硬化试验(SH)对不同焊接工艺下的聚乙烯管材热熔对接接头抵抗慢速裂纹扩展（SCG）性能进行评价。通过建立焊接温度梯度（190~250 ℃）、焊接压力梯度（0.6~1.4 MPa）和吸热时间梯度（40~140 s）试验,分析在不同焊接工艺参数条件下,不同聚乙烯管材热熔对接接头耐SCG性能的变化规律,探索冷焊及过焊2种典型缺陷对管材接头耐SCG性能的影响。结果表明,焊接温度、焊接压力和吸热时间都是影响管材热熔对接接头耐SCG性能的重要工艺参数,试验测得PE100, d_n110, SDR11型管材的最佳焊接参数为焊接温度230 ℃,焊接压力1 MPa及吸热时间100 s,当焊接参数选取过高或过低时,会造成管材接头出现过焊或冷焊缺陷,降低管材接头的耐SCG性能。     

聚乙烯热熔焊制管件的生产

根据相关标准的要求、国内外企业和行业协会的相关资料，对热熔焊制管件的焊制原理；欧洲标准和美国标准中关于加热温度、焊制压力和加热／冷却时间的取值进行了介绍；对热熔焊制管件的压力折减和品质判定进行了阐述和说明。     

塑料压力管道热熔对接焊机的研制与开发

研制了基于80C196单片机控制的塑料压力管道热熔对接焊机，介绍热熔对接焊机的基本组成部分以及各部分的主要功能，分析高密度聚乙烯管道热熔对接焊接头的拉伸性能，冲击性能和抗开裂性能，并与母材和国外焊机焊接的接头性能进行了比较。     

塑料压力管道热熔对接自动焊机的研制

塑料压力管道热熔对接焊的工艺参数随管道尺寸和环境条件的不同而不同，同时还受人为因素的影响，因此笔者开发出了利用80C196单片机控制的塑料压力管道热熔对接自动焊机，提高焊接质量。本文还分析了塑料压力管道热熔对接焊的基本原理，并详细地介绍了热熔对接焊机的基本组成部分以及各部分的主要功能和实现方法。     

聚乙烯管道热熔焊接技术研究进展

简述了聚乙烯（PE）管道热熔焊接接头的影响因素,对国内外热熔接头可靠性测试方法的研究进展进行了综述。总结了焊接参数对接头质量的影响规律,并分析了接头的失效机理。焊接参数的改变能显著影响热熔接头的性能,选择最优焊接参数能提高接头乃至整个管道系统的可靠性。分别从力学性能、有限元模拟和无损检测3个方面总结了热熔接头相关研究,期待未来建立一种全面的热熔焊接接头力学性能评价标准,能减少实验时间、降低测试成本。随着材料的创新和科技手段的发展,未来有限元模拟和无损检测技术有望代替力学实验,成为热熔接头可靠性检测的主要方法。     

塑料压力管道的焊接方法及其发展动向

介绍了两种工程上广泛采用的焊接方法：热熔对接焊和电熔焊,并对两种方法的焊接过程和控制参数等进行了详细地阐述。对这两种方法的优缺点进行了比较,并分析了塑料压力管道焊接技术的发展现状以及我国在该领域的发展动向。     

PE管道泄漏修复新方法

PE管道广泛应用在各行各业,管道泄漏时有发生。PE管道连接方式为热熔连接或电熔连接,管子与管子或管子与管件熔接需要无水施工,否则无法保证焊口质量。但是PE管道一般为挖槽埋地施工,函井中的阀门在使用一段时间后,一般都无法保证严密的关闭,造成在管道发生泄漏时用在焊前处理上的时间和精力的大量浪费。在短时间内达到焊接需要的无水焊接条件,是困扰广大施工人员的一个问题。     

聚乙烯管道焊接接头抗开裂性能的研究

以最大荷载CTOD为基础，对聚乙烯管道的母材及其热熔对接焊接头在不同温度下的抗开裂性能进行了测试、比较和分析。结果表明，随着工作温度的降低，聚乙烯材料的抗开裂能力变差。而由于焊接接头的结晶度比母材的结晶度高，使得母材具有比焊接接头更好的抗开裂能力。在焊接时应采用合适的加热板温度和加热时间，在低温和风大的环境中焊接应采取保护措施。     

聚乙烯管道热熔对接焊接头性能的分析

测试和分析了聚乙烯管道热熔对接焊接头的结晶度、硬度、拉伸性能和冲击性能，并与基材的性能进行了比较。结果发现，焊接接头区域内的结晶度高于基材部分的结晶度。焊缝的拉伸强度和硬度也均高于基材，而冲击强度低于基材。     

The importance of axial misalignment on the long term strength of polyethylene pipe butt fusion joints

The importance of axial misalignment at polyethylene pipe butt fusion joints has been assessed by undertaking elevated temperature lifetime tests. Both medium and high density polyethylene pipes were fusion joined to give aligned and controlled misaligned butt joints. These were tested under either a constant or fluctuating internal pressure loading using conditions that induced failure by slow, stable crck growth. It was observed that the lifetime of a butt joined system depends upon both the internal pressure or pressure range applied and the level of misalignment at the butt fusion joint. Increasing either the internal pressure (range) or the misalignment reduced system performance. These two variables of misalignment and internal pressure (range) may be incorporated into a single parameter, the amplified axial stress (or stress range) at the butt joint. This amplified or butt joint axial stress (or stress range) may be derived by considering the additional bending stresses introduced at the butt joint by virtue of misalignment combined with the axial stress loading.     

Effects of welding procedures on mechanical and morphological properties of hot gas butt welded PE,PP, and PVC sheets

Mechanical and morphological properties of hot gas butt welds on polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) sheets for four different procedures, which are single and double V‐welds with and without a welding shoe, were investigated. Besides, weldabilities of base materials were evaluated by rheological measurements. These revealed that weldabilities of PE and PP sheets were better than that of PVC. Welding energy (E_w), which is transferred onto weld surfaces, was calculated to evaluate weld quality. The results of tensile, impact, and bending tests indicated that the weld strengths of PVC sheets were lower than those of PE and PP sheets. When the welding shoe was used, weld strength increased significantly for each material because of the presence of sufficient welding pressure and the effective heating on surfaces. The best results were attained for the double V‐welds with the welding shoe. Morphology of welded regions was evaluated by polarized light, stereo, and scanning electron microscopy. Polarized light microscopy studies indicated that the heat‐affected zone (HAZ) consisted of welding rod core, molten zone, and deformed spherulitic zone, and the welding interface was indistinguishable from the base material when the welding pressure was enough. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

聚乙烯及其复合管道安全检测与评价方法

聚乙烯及其复合管道广泛应用于油气输送、城市燃气等能源领域,其安全性至关重要。焊接接头的安全检测及评价是聚乙烯及其复合管道系统安全的关键技术。介绍了聚乙烯管道焊接接头的无损检测原理及方法、冷焊检测技术以及缺陷分类与失效模式三方面内容。对电熔和热熔焊接接头分别采用超声相控阵和耦合聚焦技术进行超声检测,并给出了缺陷剖切与检测结果的对比图。提出了物理概念清晰、工程应用方便的冷焊超声检测方法。将电熔接头中的缺陷分为熔合面缺陷、孔洞、结构畸变和过焊。分别对含不同类型和大小缺陷的电熔接头进行力学性能测试,发现电熔接头存在三种典型的失效模式,即沿电熔套筒壁贯穿裂纹失效、熔合面失效以及沿电阻丝所在平面贯穿裂纹失效。根据试验测试与理论分析结果,提出了相应的安全评定方法。所提出的方法,填补了国内外在聚乙烯管道安全检测与评价方法方面的技术空白,提高了燃气管道的本质安全性。     

Crack initiation and propagation paths for brittle failures in aligned and misaligned pipe butt fusion joints

Medium density polyethylene pipes of 63, 90, and 125mm outside diameter, together with 63mm high density polyethylene pipes, were butt fusion joined to give aligned and controlled misaligned joints. These fabricated systems were tested at elevated temperatures under constant and fluctuating internal pressure loading. For brittle failures at the butt fusion joint, a thorough examination has been made of the points of crack initiation and the crack propagation path in relation to weld microstructure, It has been observed that the butt fusion process induces the presence of a long sharp notch formed when the internal weld bead rolls towards the pipe. This notch initiates circumferential joint failures, particularly in misaligned butt joints. Points of disturbance on the inner weld bead appear capable of inducing axial cracks at the butt fusion joint but only for aligned joints. The microstructure at the butt fusion joint was seen to have little influence on the crack propagation path.