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首页Home＞美国热塑性塑料阀门及附件 Thermoplastic Valves & Accessories＞正文Text
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Page 119		 螺纹连接
THREADED CONNECTIONS
美国斯毕尔公司
 
　　如果管道系统偶尔需要清洗或者预期要进行更新，则就可能需要用到螺纹连接。由于螺纹减少了管道的有效壁厚，则管道的压力等级与采用液状粘固剂连接的非螺纹管道相比将会减少一半。但是，阀门有自身的压力等级，与管道的压力等级实际上并不相同。因此，并不需要由于螺纹连接而减少阀门特有的压力等级。螺纹系统应该只能采用管道壁厚标准Schedule 80管道，按照美国国家标准协会的标准，用于一般用途的螺纹应该是锥管螺纹（NPT）。管道壁厚Schedule 40管道不应该用于螺纹连接。
　　Threaded joints are used where piping system dismantling for occasional cleaning or modification is anticipated. Since threading reduces the effective wall thickness of pipe, pressure ratings of the pipe are reduced to one-half that of unthreaded pipe using solvent cement welded joints. Valves, however, have individual pressure ratings substantially different from that of pipe. As a result, no reduction in the valve's specified pressure rating is necessary for threaded connections. Threaded systems should be made with Schedule 80 pipe only, threaded with an ANSI general purpose tapered pipe thread (NPT). Schedule 40 pipe should not be threaded.
     

常规操作程序概述
General Procedure Outline

步骤1：
Step 1:

涂敷连接密封剂
Apply Joint Sealant
　　螺纹连接需要涂敷优质螺纹密封剂，对连接组装部位进行密封。
　　Threaded connections require application of a quality grade thread sealant to seal joint assembly.
　　警告：有些管道连接化合物或Teflon®粘贴物可能包含会导致热塑性塑料应力断裂的物质。美国斯毕尔制造公司建议采用美国斯毕尔公司BLUE 75™螺纹密封剂，这种密封剂已经通过测试证明能够与美国斯毕尔公司产品相兼容。请遵循密封剂制造商的涂敷和安装说明书。是否选择与上列不同的密封剂取决于用户自身。
　　 WARNING: SOME PIPE JOINT COMPOUNDS OR TEFLONG® PASTES MAY CONTAIN SUBSTANCES THAT COULD CAUSE STRESS CRACKING IN THERMOPLASTIC MATERIALS. Spears® Manufacturing Company recommends the use of Spears® BLUE 75™ thread sealant which has been tested for compatibility with Spears® products. Please follow the sealant manufacturers' application / installation instructions. Choice of an appropriate thread sealant other than those listed above is at the discretion of the installer.
步骤2：
Step 2:		 手工进行组装连接
Assemble Joint by Hand
　　螺纹管道和阀门或管件首先应该进行“手指紧固”组装（螺纹之间完全啮合没有间隙就足够了）。
　　Threaded pipe and valves or fittings should be initially assembled "finger tight" (just enough to fully engage thread clearance).
 
步骤3：
Step 3:

开始用扳手进一步紧固
Start Wrench Make-up
　　螺纹塑料管道和相应的部件总要采用市面上销售的带式扳手进行安装。不要使用常规管道扳手以免损坏塑料管道。
　　Threaded plastic pipe and fitting components should always be installed using commercially available strap wrenches. Do not use conventional pipe wrenches which can damage plastic piping materials.
　　警告：螺纹连接失败最常见的原因是过分紧固。锥管螺纹在内螺纹内会产生径向应力。如果过分紧固可能会超过热塑性材料的应力极限，导致连接件断裂。
　　WARNING: THE SINGLE MOST COMMON CAUSE OF THREADED JOINT FAILURE IS OVER TIGHTENING. Tapered pipe threads produce radial stress in female fittings. Over tightening can exceed the stress limits of thermoplastic materials, resulting in split fittings.
　　在手指旋转使螺纹啮合无间隙后，再用带式扳手旋转不要超过一至两圈。旋转到最后位置要小心，避免产生用扳手往回倒退旋转的需要。
　　Apply strap wrench make-up of no more than one to two turns beyong finger tight thread engagement. Care should be taken in final positioning so as to avoid the need to "back-up" the wrenched assembly.
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