维修 所有采用焊接操作的维修和对焊接的维修必须使用符合ASME第IX节标准要求的焊工和焊接工艺。所有焊接包括对焊口的维修都应采用低氢焊接工艺。焊接维修应按照经过批准的工艺进行，对主要焊口的维修则需要经过拥有人的同意。 对铸件的焊接维修应放在生产热处理之前完成。焊接维修或是对焊口的维修必须要在任何消除金属应力的热处理工艺之前完成。对于在铸件上的维修需要进行硬度试验，因为会出现跨越焊口、热影响区和母材的微小硬度横移。采用500克负荷进行测量的最高维氏硬度值应为310 HV。 对于全部维修过的疵点应采用原先用来检测疵点的相同NDE方法，并按相同标准进行检测。 焊接之前，应使用合适的工具对准备焊接的位置进行清理，去除泥土或金属碎屑。对于深度达到被修物体厚度20%以上的疵点，不得进行维修。 安 装 只要地点允许，阀门应尽量保持接近基准面。所有安装在高于地面、操作平台或其它易于接触位置2100毫米或更高的工作阀门都应能够让人锤击到其工作的皮带轮。锤击皮带轮应装有U-型夹板，而不能是J-型螺栓夹板。阀门应既能适合于立式位置安装，也能卧式位置安装。
升降式止回阀必须卧式位置安装。如果可能的话，手动轮和阀杆应放置在操作通道之外，或者是提高到手动轮底部距离基准面2100毫米的高处。阀门不得安装的让阀杆低于水平位置。
如果需要的话，隔断阀应安装在压力容器喷嘴处，或是安装在连接喷嘴的管道上，以便人们能从基准面位置或操作平台位置进行操作。如果出现以下情况时，设备能够被隔断开：
不用该设备依然可以继续操作。
为相连设备降压会推迟在设备上的维修。 闸式阀和球阀应在旁通管道上配有平衡用球心阀和球阀/旋塞阀，NPS 2 （DN 50）阀门的最小规格如 ASME 150级- NPS 12 (DN 300) 及以上规格 ASME 300 级及以上规格- NPS 8 (DN 200) 及以上规格 所有阀门都应留有足够空间，以便于拆卸阀帽、旋塞和内部器件。 repairs All repairs made by welding and repairs to welds shall be carried out using welders and procedures qualified in accordance with ASME Section IX. All welds including repair welds shall use a low hydrogen process. Repairs welding shall be performed in accordance with an approved procedure and major welds repair shall be approved by the OWNER. Repairs by welding to castings shall be made prior to production heat treatment. All repairs by welding or repairs to welds shall be made prior to any stress relief heat treatment. Repairs made to castings shall be subjected to hardness testing that include micro hardness traverses across the weld, heat affected zones and parent metal. The maximum measured Vickers hardness shall be 310 HV using a 500 gram load. All repaired defects shall be re-inspected with the same NDE method that revealed the original defect, using the same acceptance criteria. Before welding, the area involved shall be properly cleaned with suitable tools to eliminate ant trace of earth or slugs. Defects higher than 20% of thickness cannot be repaired. installation Wherever possible, valves should be kept near grade level. All operating valves installed 2100 mm or more above floor, platform or other point of easy access shall be hammer blow chain wheel operated. Hammer blow chain wheels shall have U-bolt clamps, not J- bolt clamps. Valves shall be suitable for installation in vertical as well as horizontal positions. Lift check valves shall be installed horizontally. Hand wheels and stems shall be kept out of operating aisles, where practical, otherwise elevated to 2100 mm from grade to bottom of hand wheel. Valves shall not be installed with stems below a horizontal position. Block valves, when required, shall be installed at nozzles of pressure vessels or in lines connected to nozzles to permit operating valves from grade or a platform. Equipment shall be capable of being isolated if: Operations can continue without it. De- pressuring associated facilities will delay maintenance on the equipment. Gate and ball valves shall be provided with an equalizing globe and ball/plug valve on the bypass inline, with a minimum size of NPS 2 (DN 50) for the following: ASME Class 150 - NPS 12 (DN 300) and larger ASME Class 300 and greater - NPS 8 (DN 200) and larger All valves shall have sufficient clearance to facilitate removal of the bonnets, plugs and internals. |
