Selecting a low-strength bolt to be used with a Class 600 flange joint with proper gasketing will require the bolts to be torqued beyond their yield point, or, at the very least, beyond their elastic range, To explain this briefly, bolts act as springs when they are installed and loaded properly. In order for the flange joint to maintain a gasket seal, it requires dynamic loading. Dynamic loading of flange bolts allows expansion and contraction movement in and around the joint while maintaining a seal. This is achieved by applying sufficient stress to the bolt to take it into the material’s elastic range.
If the bolts are not stressed sufficiently into their elastic range, any relaxation in the gasket could reduce the sealing ability of the joint. To the other extreme, if the bolts were stressed beyond their elastic range and into the plastic range of their material of construction the same issue would apply; they would lose their dynamic load on the gasket. In that case, if they did not shear, they would take a set. Any relaxation in the gasket will then result in the reduction or elimination of the joints sealing ability.
The nut should be selected to complement the bolt. The bolt material specification will steer you, either partially or completely, into the proper nut selection.
ASME A307, a material standard for bolts in the low-strength category, states that the proper grade for bolts to be used for pipe flange applications is Grade B. The standard goes further to state that when used for pipe flanges, Grade B bolts require a Heavy Hex Grade A nut under ASTM A563. In writing a pipe specification that included the A307 bolt, you would not need to specify the nut, since it is already defined in A307.
However, ASTM A193, alloy and stainless-steel bolts, goes only so far when it states that nuts shall conform to ASTM A194—there are several grades of A194 nuts to select among. This is an example of where the matching nut is not always explicitly called out in the ASTM standard. Because the ASTM standards are inconsistent in that regard, the specification writer must make sure that the nut is covered in a specification.
In summary, all four components—flanges, bolts, nuts and gaskets—have to be selected in conjunction with one another in order for the joint assembly to perform in a way that it is expected to for a given application.
选择低强度螺栓可用于一类600法兰接头与适当的gasketing将需要螺栓要扭转超出其屈服点，或在最低限度，超出其弹性范围，解释这简单，螺栓作为弹簧，当他们安装并加载适当的。在为了使法兰接头，以维持一个垫片密封，它需要动态加载。动态加载法兰螺栓，使膨胀和收缩运动和周围的联合，同时保持密封。要实现这个目标，运用足够的压力，螺栓考虑到材料的弹性范围内。
如果螺栓不强调，充分考虑到他们的弹性范围内，任何放宽，在垫片可以减少密封能力的联合。到了另一个极端，如果螺栓被强调，超出其弹性范围，并纳入塑胶一系列的物质建设的同时，问题将适用于他们将失去他们的动态负载对垫片。在这种情况下，如果他们不剪，他们会采取一套。任何放松，在垫片，然后将结果在减少或消除关节的密封能力。
螺帽应选择，以配合螺栓。螺栓材料的规格，将引导您，无论是部分或完全，到适当的螺母的选择。
对ASME a307 ，材料标准，螺栓，在低强度类别，国家适当职螺栓可用于管道法兰申请一级乙标准更进一步说明，当用于管道法兰， B级螺栓的要求一个沉重的Hex A级螺母下，美国ASTM a563 。在写作的管道规格，其中包括a307螺栓，你不会需要指定螺母，因为这是已经确定的a307 。
不过，美国ASTM a193 ，合金及不锈钢螺栓，云只有这样，到目前为止，当它指出，坚果应符合美国ASTM a194 -有几个等级， a194坚果选择之间。这是一个例子，那里的配套螺帽并不总是明确要求指出，在ASTM标准。因为ASTM标准不一致在这方面，规格，作家必须确保螺帽是涵盖在一个规格。
总括来说，所有四个组成部分-法兰，螺栓，螺帽和垫圈-要选定在联同另1 ，以便为联合大会在执行的方式，这是预期某一特定的应用。