3. Flange Design Considerations
3. 凸缘设计注意事项
Most designers fight a space limitation, particularly in the vicinity of the gasketed seam. Complex fasteners are often required to make the junctions more compact.
绝大多数设计人员都要面临空间限制的问题，特别是在垫片接缝的邻近区域。通常会需要复杂的紧固件，以使得接合更加紧密。
The ideal flange includes a groove for limiting the deflection of a gasket. The screw or bolt fasteners are mounted outboard of the gasket to eliminate the need for providing gaskets under the fasteners. A machined flange and its recommended groove dimensions are shown in Figure 1. The gasket may be an “O” or “D”-shaped gasket, either solid or hollow.
理想的凸缘包含有一个开槽，以限制垫片变形。螺钉或螺栓紧固件均安装于垫片的外侧，以避免紧固件下面需要使用的垫片。机加工凸缘及开槽的建议尺寸见图 1 所示。垫片可为 “O” 或 “D” 型的实心或空心垫片。
Figure 1. Machined Flange with Gasket Groove
图 1 带垫片安装槽的机加工凸缘
Solid conductive O-rings are normally limited to a deflection of 25 percent. Therefore, the minimum compressed height of the O-ring (also the groove depth) is related to the uncompressed height (or diameter) by the expression H = 0.75 W, where W is the uncompressed diameter. The width of the groove, G, should be equal to 1.1 W. Allow sufficient void in the groove area to provide for a maximum gasket fill of 97 percent. Conductive elastomer gaskets may be thought of as “incompressible fluids.” For this reason, sufficient groove cross sectional area must be allowed for the largest cross-sectional area of the gasket when tolerances are taken into account. Never allow groove and gasket tolerance accumulations to cause an “over-filled” groove (see gasket tolerances in section which follows).
对于实心导电 O 型密封圈而言，其变形量一般限制为 25%。因此，O 型密封圈压紧后的最小高度（即槽深）与未压紧前高度（或直径）之间的关系表达式为 H = 0.75 W，其中 W 是未压紧时的直径。槽宽 G 应等于 1.1 W。开槽区域内应具有足够的空间，以使垫片最高填充率为 97％。导电橡胶垫片可被视为“不可压缩的液体”。为此，必须按垫片的最大截面积（在考虑了公差时）确定开槽的截面积。开槽和垫片公差的组合不得导致开槽被“过度填实”（见下面一章中的垫片公差）。
When a seal is used to isolate pressure environments in addition to EMI, the bottom of the gasket groove should have a surface finish of 32-64 μin. (RMS) to minimize leakage along the grooves. Avoid machining methods that produce longitudinal (circumferential) scratches or chatter marks. Conversely, a surface that is too smooth will cause the gasket to “roll over” or twist in its groove.
当密封件除用于 EMI 外，还用于隔离压力环境时，开槽的底部表面处理应至少厚32-64 μin (RMS) ，以最大限度地降低开槽周围的泄漏可能。应避免使用可能导致纵向（圆周）划痕或颤痕的机加工方法。而反过来，如果表面过于光滑，又会导致垫片在槽内“翻转”或扭曲。
The minimum distance from the edge of the groove to the nearest terminal edge, whether this terminal be the edge of a casting, a change in cross section, or a fastening device, should be equal to the groove width, G.
槽边与最近终边之间的最小距离应等于槽宽 G，无论此终边是外壳的边缘、截面变化边或是紧固装置的边缘。
Bolts should be located a minimum distance, E (equal to one-half the diameter of the washer used under the head of the bolt) from the edge of the flange.
螺栓的安装方式应保证其凸缘边之间距离不小于 E（等于螺栓头下所使用垫圈直径的一半）。
Square or rectangular cross section gaskets can be used in the same groove provided sufficient void is allowed for displacement of the elastomer. A good design practice is not to allow the height of the gasket to exceed the base width. A better, or a more optimum ratio is a height-to-width ratio of one-half. Tall gaskets tend to roll over when loaded.
如果槽口内具有足够的橡胶移动空间，则同一槽内可安装截面为方形或矩形的垫片。常用设计规程中不允许垫片高度大于底宽。而更好的高宽比为1／2。垫片过高会在加载时发生翻滚。
The thickness of a flange is governed by the stiffness required to prevent excessive bowing between fastener points. Fewer, but larger bolts, require a thicker flange to prevent excessive deflections. For calculations of elastic deformation, refer to pages 61 to 63.
凸缘的厚度由其刚度确定，以防止紧固件安装点发生翘曲。螺栓用量越少、尺寸越大，则要求凸缘越厚，以防止发生过度变形。弹性变形计算，请参见 61 至 63 页。
O-shaped and D-shaped gaskets may also be used in sheet metal flanges. The gaskets can be retained in a U-channel or Z-retainer, and are deflection-limited by adjusting the channel or retainer dimensions with respect to gasket height. Suggested retainer configurations are shown in Figures 2a and 2b.
O 型或 D 型垫片还可在板金凸缘内使用。垫片可保持于 U 型槽或 Z 型护圈中，同时，可根据垫片高度，通过调节 U 型槽或护圈尺寸，限制变形量。建议的护圈形状如图 2a 和 2b 所示。
A basic difference between flanges constructed from sheet metal and those which are machined from castings is that the bolts cannot be located as close to the edge of the part when the flange is made of sheet metal. Note, in Figure 2a, F is recommended to be 1.5 D, where D is the diameter of the washer.
板金结构凸缘与铸件机加工凸缘之间的基本差别是对于板金加工而成的凸缘，螺栓无法尽可能地近地靠近部件边缘安装。注意，在图 2a 中，建议 F 为 1.5 D，其中 D 是垫圈的直径。
Figure 2a. Shaped Sheet Metal Container
图 2a.成型板金外壳
Figure 2b. Z-Retainer Forms Gasket Cavity
图2b.由 Z 型护圈形成的垫片安装空间
Flat gaskets are ordinarily used with sheet metal or machined flanges as typically illustrated in Figure 3. Bolt holes in the flanges should be located at least 1.5 times the bolt diameter from the edge of the flange to prevent tearing when the metal is punched.
平垫片在板金或机加工凸缘上的使用方法通常如图 3 所示。凸缘内螺栓孔与凸缘边之间的距离应至少螺栓直径的 1.5 倍，以防止金属穿孔时发生撕裂。
Figure 3. Flat Gasket on Sheet Metal Flange
图 3 平垫圈在板金凸缘上的使用方法
If the holes are drilled, the position of the holes should be not less than the thickness of the gasket material from the edge of the flange. If holes must be placed closer to the edge than the recommended values, ears or slots should be considered as shown in Figure 4. Holes in flat gaskets should be treated in a similar manner.
如果采用钻孔方式，则该孔与凸缘边之间的距离应不小于垫片材料的厚度。如孔与凸缘边之间的距离必须小于建议值，应按图 4 中所示，考虑采用耳形孔或开槽。应采用相同方式，对平垫片内的孔进行处理
Figure 4. Ears or Slots in Sheet Metal Flanges or Flat Gaskets
图 4 板金凸缘或凸缘垫片内的耳形孔或开槽
4. Dimensional Tolerances
4. 尺寸公差
Grooves should be held to a machined tolerance of ±0.002 in. Holes drilled into machined parts should be held to within ±0.005 in. with respect to hole location. Location of punched holes should be within ±0.010 in. Sheet metal bends should be held to +0.030 and –0.000 in. Gasket tolerances are given in the “Selection of Seal Cross Section,” later in this guide.
开槽的机加工公差应为 ±0.002 in。对机加工件内的钻孔，其公差相对孔位置应保持在 ±0.005 in 以内。冲孔的位置公差应保持在 ±0.010 in 以内。板金弯曲公差应保持在 +0.030 和 –0.000 in。垫片公差见本指南后面的“密封件截面积选择”一章。 |
